Download adaptations, genetic variation and natural selection

ADAPTATIONS, GENETIC VARIATION
AND NATURAL SELECTION
Seventh Grade
Piloted at West Hawaii Explorations
Academy
(WHEA)
By:
Leayne Patch-Highfill and Jessica Schwarz
PRISM UHH GK-12 Program
ADAPTATIONS, GENETIC VARIATION AND NATURAL SELECTION
GRADE LEVEL: Seventh Grade
PURPOSE:
This curriculum was designed to communicate concepts about evolutionary processes to
seventh grade students. Hawaii is home to many endemic species that exhibit different
genetic variations. These unique species are excellent examples to utilize to help students
understand evolution.
STANDARDS/BENCHMARKS:
Standard 1: The Scientific Process: SCIENTIFIC INVESTIGATION: Discover,
invent, and investigate using the skills necessary to engage in the scientific process
Benchmark SC.7.1.1 Design and safely conduct a scientific investigation to answer a
question or test a hypothesis
Benchmark SC.7.1.2 Explain the importance of replicable trials
Benchmark SC.7.1.3 Explain the need to revise conclusions and explanations based on
new scientific evidence
Standard 3: Life and Environmental Sciences: ORGANISMS AND THE
ENVIRONMENT: Understand the unity, diversity, and interrelationships of
organisms, including their relationship to cycles of matter and energy in the
environment
Benchmark SC.7.3.2 Explain the interaction and dependence of organisms on one
another
Standard 5: Life and Environmental Sciences: DIVERSITY, GENETICS, AND
EVOLUTION: Understand genetics and biological evolution and their impact on
the unity and diversity of organisms
Benchmark SC.7.5.2 Describe how an inherited trait can be determined by one or more
genes which are found on chromosomes
Benchmark SC.7.5.3 Explain that small differences between parents and offspring could
produce descendants that look very different from their ancestors
Benchmark SC.7.5.4 Analyze how organisms' body structures contribute to their ability
to survive and reproduce
Benchmark SC.7.5.6 Explain why variation(s) in a species' gene pool contributes to its
survival in a constantly changing environment
RATIONALE:
The Hawaiian Island chain is the most isolated archipelago on the planet. This isolation
has limited the number of animal and plant species that have arrived here naturally.
When organisms do colonize the islands successfully, their populations must change over
time in order to suit the conditions of their new environment. As a result of millions of
years of evolution in isolation, the Hawaiian Islands are home to many fascinating
endemic species, such as Hawaiian honeycreepers, Happy-face spiders, and Ohia trees.
This curriculum focuses on examples of Hawaii’s native flora and fauna to understand
evolutionary concepts, including genetic variation, natural selection, and adaptation.
Additional reading material developed by Full Option Science System (FOSS) at the
Lawrence Hall of Science is included for each topic. Background information is included
at the beginning of each lesson, but more detailed information with added examples from
FOSS is included for added teacher support. This unit can be used as supplemental
teaching materials with the FOSS Populations and Ecosystems Course, lessons
Adaptations, Genetic Variation and Natural Selection.
LESSONS PLAN:
This unit was designed to last from 8-9 weeks, depending on the total number of field
trips taken or how long it takes to complete “Build a Hawaiian Bird”. Most lessons can
be completed within a 45-minute class period, but some lessons need several weeks to be
completed. Lessons that include a field trip take the entire school day. Depending on
the number of science classes taught each week, the duration of this unit will vary. Due to
complex topics, students may need extra time to review concepts before starting lessons,
which will also affect the duration of this unit.
Although the topics are introduced in a particular order and the unit is designed to flow
well, the lessons can be used out of context or used individually to address specific
concepts.
All lesson plans start with a summary of the lesson and a list of objectives students will
learn. Lessons also include detailed materials lists as well as instructions for teacher
preparation at the beginning of each lesson. The instructor should scan these lists prior to
beginning of each lesson since materials must be purchased (some ordered), hand-outs
should be Xeroxed, and field trips must be organized. Background information is also
included with each lesson for the instructor and vocabulary words that can be used for
vocabulary or spelling lessons are introduced here as well.
Week 1: Students are introduced to the concepts of adaptations, (founder species,
endemism, adaptive radiation, Hawaiian honeycreepers, Hawaii as an archipelago, etc.)
and a verbal pre-assessment of what the students already know about the topic is
conducted. Students can be given background information on Adaptations before the
start of the first lesson and this could also be discussed.
The students then learn about particular adaptations Hawaiian birds have in order to
survive and study a poster of different bird bills. They then engage in a hands-on
Hawaiian Bird Beak Adaptation Lab to simulate how birds have particular beak shapes to
acquire different food sources.
Week 2: If applicable, students will explore different bird habitats on a field trip. In this
unit, students visited Puu waa waa Forest Bird Sanctuary. Other ideas for field trips
could be Hawaii Volcanoes National Park, Kaloko-Honokohau National Park or Kipuka
21 on Saddle Road. Students will observe different adaptations birds have in order to
survive in their respective habitat. If a field trip is not possible, a classroom simulation of
a bird habitat could be created. After the field trip, students will write a paper about a
Native Hawaiian Forest Bird.
Week 3-4 (could last to week 5): Students get creative and apply what they have learned
in prior weeks with “Build a Hawaiian Bird”. They first develop a bird from paper cutouts provided. After the model is completed, the bird is then constructed using papier
mache. The actual building of the birds can take several weeks depending how detailed
the birds become. After the birds are completed, students write a paper describing their
bird and its specific adaptations. Each bird should also be presented to the class.
Week 5: Students are introduced to the subject of Genetic Variation. Genetics can be a
confusing concept for students, having students read the background material provided
helps with complex vocabulary. After discussing the reading material, students play
Vocabulary Bingo to get more comfortable with the topic. If more review is needed, a
vocabulary review is also provided. Students then study human traits in the lesson,
“Exploring Human Traits” where they survey their own traits.
Week 6: Students will learn how genes are passed from generation to the next by
studying Happy-Face Spiders. They will act as captive breeders and choose traits to
breed that are beneficial for survival. Punnet squares will also be introduced.
Week 7: After students have a solid understanding of adaptations and genetic variation
they are introduced to the topic of Natural Selection. They participate in a natural
selection simulation in which they create and modify “paper airplanes” over several
generations to see how favorable heritable traits are passed on.
Week 8: Students get another chance to get out of the classroom with a field trip to the
Ohia Common Garden in Volcano. Ohia from different elevations have morphological
differences and students get a chance to observe this phenomenon. After the trip to the
garden, students write a reflection about their field trip.
CONCEPT MAP:
FORMATIVE ASSESSMENT:
The level at which the students understand the topic will assessed throughout the lessons.
Each lesson will begin by asking the students what they already know or recall about the
topic. At the end of each lesson the students are asked to come up with three concepts
they learned during the lesson. At the beginning of the next lesson the previously learned
concepts will be re-visited. After the Hawaiian Bird Beak Adaptation lab, students will
take a field trip to different bird habitats to see how birds use their adaptations in the
wild. After this field trip, students write a scientific report on a Hawaiian bird of their
choice. Students will be given background reading material on genetic variation for
homework in order to discuss the topic. The next lesson will begin answering questions
about the reading material and vocabulary will be assessed with vocabulary bingo. Prior
to visiting the Ohia Common Garden, the students will be introduced the concept of
Natural Selection by talking about Ohia and phenotypic plasticity. Before meeting with
the guest speakers, students were able to ask questions to clear up any misconceptions.
The students will then write a reflection about their visit to the garden.
SUMMATIVE ASSESSMENT:
These students will not have one final assessment project; rather they will have
summative assessments at the end of each topic. They will be assessed of their
knowledge of adaptations with the activity “Build a Hawaiian Bird”. They choose
adaptations that will be beneficial for the birds’ survival and reproduction. Students
follow with written reports explaining the scientific name given to the birds, the adaptive
advantages of their features, and how the birds are adapted to their environments.
Finally, students improve their communication skills by giving oral presentations on their
project.
After learning about genetic variation of Happy-face spiders, students will choose the
color of spider they would use to breed so the spider can survive in the wild. They then
color a picture of a Happy-face spider using the colors they chose to breed. They will
continue to improve on communication by presenting their pictures to the class and
defending their selection. Finally, after studying natural selection, the student will write a
reflection about their trip to the Ohia Common Garden and Hawaii Volcanoes National
Park.
This unit was developed and piloted by Leayne Patch-Highfill and Jessica Schwarz
at West Hawaii Explorations Academy (WHEA).
PRISM UHH GK-12
ADAPTATIONS
Concepts Kkjkjkj
Endemic Hawaiian
birds are unique to
Hawaii because they
are only found here.
Founder species that
came to Hawaii were
isolated for millions of
years, and they had to
physically adapt in
order to survive in
their new
environments. Many
Hawaiian birds, such
as Hawaiian
honeycreepers have
different beak length
and sizes in order to
obtain food in their
habitats.
Standards addressed
7.1.1, 7.1.2, 7.5.4
Duration
60 minutes
Vocabulary
Endemic
Founder species
Hawaiian
honeycreepers
Adaptive radiation
Source Material
Adapted from
sciencenetlinks.com &
www.eduref.org
Hawaiian Bird Beak Adaptation Lab
Summary
Students will be introduced to the different types of bird beaks that Hawaiian
birds have developed as adaptations to the different habitats in which they live.
They will use tools that represent different beaks to learn which beak is better
adapted to collect different food types in a certain amount of time.
Objectives
• Students will examine the relationship between a bird’s beak and its
ability to find food and survive in a particular habitat.
• They will understand that Hawaiian birds have adapted physically to
their food sources.
• Students will learn about different Hawaiian birds.
• Students will explore which beaks are more efficient for collecting foods
by experimenting with different tools representing different beak types.
• Students will represent their data using bar graphs.
• Students will recognize the importance of multiple trials.
Materials
Plastic cups to represent bird stomach-will need one for each student
Beak materials:
5-6 sets of chopsticks, 1 turkey baster, 1 nut cracker, 2 pliers, 4 tweezers, 2
medicine droppers, 1 Clothes pin, 2 rulers, 3 plastic spoons, 1 slotted spoon,1
long snapping hair clip, 1 small hand strainer, and 3-4 straws to hold
marshmallows and one straw for nectar
Food Materials:
Gummy worms, sunflower seeds, rice, small berries or sweet tart candies,
marshmallows, Swedish gummy fish, oreo/graham cracker cookie crumbs (to
represent soil), small twigs, water colored with food dye (can use clear if easier).
Three plastic graduated cylinders
2 Cookie Sheets or pans for sunflower seeds and rice
Plastic container to hold “soil” and worms
Bowls for holding water
Pictures of Birds
Bird Beaks Record Sheet (see below)
Challenge cards for each station (see below)
Teacher Prep for Activity
• Make challenge cards (cut and paste from list below) to put at each
station-can be made on card stock and laminated, so they can used again.
The challenge cards state the scenario for each station.
• Xerox “Adaptations” reading and data sheet provided
• Set up 8 work stations: 1 for each type of food source represented. Place
the 3 different types of tools for each station.
 Station #1: Bird: Ae’o
Food Source: Gummy worms buried in cookie crumbs
Tools: chopsticks, turkey baster, nut cracker
 Station #2: Bird: Palila
Food Source: String beans and sunflower seeds scattered on
cookie sheet
Tools: pliers, chopsticks, tweezers
 Station #3: Bird: I’iwi
Food Source: Colored water in a graduated cylinder (one for each student)
Tools: Medicine dropper, straw (don’t suck up, use finger to stop the liquid), pliers
 Station #4: Bird: Elepaio
Food Source: Rice spread out on cookie sheet (to represent insects)
Tools: Tweezers, clothes pin, medicine dropper
 Station #5: Bird: Nene
Food Source: Small berries and grass (round sweet tarts work well too)
Ggh Tools: 2 rulers held together, chopsticks, spoon
 Station #6: Bird: Albatross
Food Source: Swedish gummy fish
Tools: Chopsticks, long snapping hair clip, spoon
 Station #7: Bird: Koloa or Hawaiian Duck
Food Source: Small twigs in a bowl of water
Tools: Slotted spoon, tweezers, hand strainer
 Station #8: Bird: ‘Io or Hawaiian Hawk
Food Source: Marshmallows (skewered on a straw)
Tools: Chopsticks, tweezers, spoon
• Place each challenge card and picture of corresponding bird at every station
Background
Over time, animals change in order to fit the needs of their environment. The Hawaiian Islands are the most
isolated archipelago on the planet, and due to millions of years of isolation, only a small amount of animals and
plants have arrived here. Species arrived on the islands by only three modes of transportation: wind, waves, and
wings (the “three Ws”). All plant and animal species that are native or endemic to Hawaii descended from a
small community of founder species. Hawaiian rain forests are home to several endemic species, such as
Hawaiian birds and these species are unique to the islands. Most endemic forest birds belong to a group of birds
known as Hawaiian honeycreepers. Scientists think all the honeycreepers evolved from a single finch species
that colonized the islands 15 million years ago. Hawaiian endemic birds evolved and radiated into new species
after they arrived to the islands from somewhere else. This is a process called adaptive radiation, which has
resulted in many different honeycreepers adapted to various environments. One characteristic that can distinguish
Hawaiian honeycreepers apart are their diverse bill shapes and lengths. There are also non-honeycreepers, such as
a species of Flycatcher (the Elepaio) and a species of Hawk (the ‘Io) that are also endemic to Hawaii.
All birds have different beak shapes and sizes depending on what the bird eats and where that food is found. A
bird’s beak is basically a lightweight, bony extension of the skull. Bird beaks are multi-functional tools used to
gather and capture food, build nests, groom feathers and attack competitors.
Procedure
1) First have students read background information about Adaptations (Information follows)-this can be done in
class or have students read the information for homework or the instructor can lecture on the material.
2). After students have completed the readings, ask the students what they know about adaptations. Explain that
Hawaii is the most isolated archipelago in the world and how animal and plant species arrived here. Be sure the
students understand species, such as Hawaiian honeycreepers filled different niches throughout Hawaii and
adapted to their specialized habitats. Have them explain what it means if a species is endemic or indigenous. Pick
at least three concepts that you will want the students to really remember such as; What is adaptive radiation?
What will happen if a species will not adapt to environment? or What will happen if a habitat changes?
3). Divide students into groups of three (one tool per student). If there are more students, add another station, or
divide groups into four and have one of the students be responsible for timing the other students and writing down
data. Have the students repeat what they did, but have the student who was the scorekeeper trade out with another
student. Also, each student will keep the same beak throughout the lab. They should improve as they go along.
4). Have students go to their assigned station and have them read their challenge card.
5). Pass out record sheet.
6). Have each student write down a prediction on the worksheet provided.
7). Each student will be given 20 seconds to gather as much food as they can with the “beak” (tool) they
have. They will put the food into their “stomach” (cup).
8). When fff
the teacher says “Stop”, students empty their stomachs and count the number of items they
collected. Record this amount on the Bird Beaks Record Sheet.
9). Repeat the trial 3 times and be sure students empty their stomachs after each round and record amount
on their worksheet.
10). Students calculate the average amounts for each beak type and have each group construct a bar
graph of their averages for each station. The three different bird beaks should be on the X axis and the
average amount of food collected should be on the Y axis. (See sample bar graph below).
Amount of
Food
Beak 1
Beak 2
Beak 3
Teacher Resources for this activity
Challenge Cards:
Challenge #1-You have been given gummy worms (to represent worms) as your food source. You have
also been given sample beaks: 1) Chopsticks, 2) Turkey Baster, and 3) Nut cracker. Your challenge is to
obtain as many gummy worms as you can that are buried in the soil within 20 seconds. Put your food in
your stomach (cup). Repeat each trial 3 times and record the amount of food after each trial on your
worksheet.
Challenge #2-Your have been given sunflower seeds (to represent seeds) as your food source. You have
also been given sample beaks: 1)Pliers, 2) Chopsticks, and 3) Tweezers. Your challenge is to use each
beak to crack the shell and remove the seed inside within 20 seconds. Put your food in your stomach
(cup). Repeat each trial 3 times and record the amount of food after each trial on your worksheet.
Challenge #3-You have been given colored water (to represent nectar) in a graduated cylinder. You have
also been given sample beaks: 1) Medicine dropper, 2) Straw, and 3) Pliers. Your challenge is use each
beak to see how much water you can transfer to your stomach in 20 seconds. Repeat each trial 3 times
and record the amount of food after each trial on your worksheet.
Challenge #4-You have been given rice (to represent insects) as your food source. You have also been
given sample beaks: 1) Tweezers, 2) Clothes Pin, and 3) Medicine Dropper. Your challenge is to use
each beak and transfer as many pieces of rice to your stomach in 20 seconds. Repeat each trial 3 times
and record the amount of food after each trial on your worksheet.
Challenge #5-You have been given small berries or sweet tart candies that llok like berries as your food
source. You have also been given sample beaks: 1) 2 rulers held together, 2) Chopsticks, and 3) Spoon.
Your challenge is to use each beak and transfer as many berries to your stomach in 20 seconds. Repeat
each trial 3 times and record the amount of food after each trial on your worksheet.
Challenge #6-You have been given Swedish gummy fish (to represent fish) as your food source. You
have also been given sample beaks: 1) Chopsticks, 2) Long snapping hair clip, and 3) spoon. Your
challenge is to use each beak and transfer as many fish to your stomach in 20 seconds. Repeat each trial 3
times and record the amount of food after each trial on your worksheet.
Challenge #7-You have been given small twigs (to represent small invertebrates) in water as your food
source. You have also been given sample beaks: 1) Slotted spoon, 2) Tweezers, and 3) Small hand
strainer. Your challenge is to use each beak and transfer as many twigs to your stomach in 20 seconds.
Repeat each trial 3 times and record the amount of food after each trial on your worksheet.
Challenge #8-You have been given Marshmallows on a straw (to represent small mammal) as your food
source. You have also been given sample beaks: 1) Chopsticks, 2) Tweezers, and 3) Spoon. Your
challenge Kl;
is break apart the marshmallows and transfer as many marshmallows to your stomach in 20
seconds. Repeat each trial 3 times and record the amount of food after each trial on your worksheet.
Assessments
Journal writing
Bird Beak Data Sheet
Build a Hawaiian Bird Lesson
Extensions
If time prevails, students can switch stations after the first 3 trials and learn about different beak
adaptations. If this is the case, then the worksheet should be extended to add more columns.
Also, take students on a field trip to different habitats where native birds might be found. For example,
students could visit a rain forest such as Volcanoes National Park to see native birds such as the ‘Omao,
Apapane and Hawaii Amakihi. Students could also visit a mesic forest like Pu’u Wa’a Wa’a Forest Bird
Sanctuary and observe birds like Akepa and Elepaio and in the Dry Land Forest of Pu’u Wa’a Wa’a
students may see Nene. If time prevails, take students on another field trip to a habitat that is completely
different from the first one they visited. A second field trip could be to the coastline, such as KalokoHonokohau National Historical Park for example. Students may see Ae’o and the Hawaiian Coot. It
would be ideal if students had binoculars and field guides to see the birds up close. Discuss with students
why birds live in different habitats (be sure to notice different food sources within each habitat). Ask
what adaptations the birds have in order to survive in each of the habitats. This would be a good time to
get the students thinking about what types of questions they could ask in order to conduct a scientific
investigation in the feild. For example, “How many invertebrates does an Ae’o collect in a certain
amount of time”? How would they set that experiment up and how would they conduct it? They can
write about it in a journal entry.
If a field trip is not possible, create a class simulation of a field trip. Before the students come to class,
transform your classroom into a natural habitat. Get pictures of birds and plants that represent a particular
habitat and hang on wall or an area of your choice. When the students come to class, explain to them
which habitat they just encountered and have them walk around to see the different bird and plant
pictures. Audio with bird songs could help improve this simulation. For ideas about forest habitats, the
following website is a good start (pgs 7-11):
http://www.state.hi.us/dlnr/dofaw/kids/teach/forest%20activity%20guide.pdf
They can still use field guides and come up with questions that would be suitable for field research.
Great field guides to use as references on bird watching and plant identification are:
A pocket guide to Hawaii’s birds, H.D. Pratt and J. Jeffrey (~$9.00)
A pocket guide to Hawaii’s trees and shrubs, H.D. Pratt (~$10.00)
Resources
http://www.eduref.org/cgi-bin/printlessons.cgi/Virtual/Lessons/Science/Animals/ANM0016.html
www.sciencenetlinks.com/pdfs/birdbeaks_actsheet.pdf
http://www.hear.org/hoike/
http://www.esi.utexas.edu/outreach/gk12/docs/lessons/birdBeak.pdf
Foss-Populations and Ecosystems
Bird Beaks Record Sheet
ll
Name:_________________________
My Food Source is ___________________________________________________.
My Bird is __________________________________________________________.
Prediction: I think that ________________________________________________
___________________________________________________________________
___________________________________________________________________
Data Table
Beak 1:
Beak 2:
Beak 3:
rere
Trial 1
Trial 2
Trial 3
Average
(Total/3)
Draw a bar graph that shows the average amount of food gathered by the three
types of beaks.
Amount
of
Food
Beak 1
Beak 2
Beak 3
A
e
`o
Photo: en.wikipedia.org/wiki/RecAurvirostridae
Hawaiian Black-necked Stilt
P
a
l
i
l
a
Photo: J. Jeffrey
`I
`i
w
i
Photo: J. Jeffrey
`E
l
e
p
a
i
o
Photo: P. Latourrette
N
e
n
e
Photo: www.americanparknetwork.com
Hawaiian Goose
M
o
l
i
Photo: www.pbase.com/jpkln/image/54126096
Laysan Albatross
K
o
l
o
a
Hawaiian Duck
`I
o
Photo: R. Decker
Hawaiian Hawk
Challenge # 1-You have been given gummy worms (to represent worms)
as your food source. You have also been given sample beaks: 1)
Chopsticks, 2) Turkey Baster, and 3) Nut cracker. Your challenge is to
obtain as many gummy worms as you can that are buried in the soil
within 20 seconds. Put your food in your stomach (cup). Repeat each
trial 3 times and record the amount of food after each trial on your
worksheet.
Challenge #2-Your have been given sunflower seeds (to represent seeds)
as your food source. You have also been given sample beaks: l)Pliers, 2)
Chopsticks, and 3) Tweezers. Your challenge is to use each beak to
crack the shell and remove the seed inside within 20 seconds. Put your
food in your stomach (cup). Repeat each trial 3 times and record the
amount of food after each trial on your worksheet.
Challenge #5-You have been given small berries as your food source.
You have also been given sample beaks: 1) 2 rulers held together, 2)
Chopsticks, and 3) Spoon. Your challenge is to use each beak and
transfer as many berries to your stomach in 20 seconds. Repeat each trial
3 times and record the amount of food after each trial on your worksheet.
Challenge #6-You have been given Swedish gummy fish (to represent
fish) as your food source. You have also been given sample beaks: 1)
Chopsticks, 2) Long snapping hair clip, and 3) spoon. Your challenge is
to use each beak and transfer as many fish to your stomach in 20
seconds. Repeat each trial 3 times and record the amount of food after
each trial on your worksheet.
Extensions
Take students on a field trip to different habitats where native birds might be found. Students can observe
birds in the wild and they can also record what birds they will see in different environments. For
example, if you live on the Big Island, students could visit a rain forest such as Volcanoes National Park
to see native birds such as the ‘Omao, Apapane and Hawaii Amakihi. Students could also visit a mesic
forest like Pu’u Wa’a Wa’a Forest Bird Sanctuary and observe birds like Akepa and Elepaio and in the
Dry Land Forest of Pu’u Wa’a Wa’a students may see Nene. If time prevails, take students on another
field trip to a habitat that is completely different from the first one they visited. A second field trip (on
the Big Island) could be to the coastline, such as Kaloko-Honokohau National Historical Park for
example. Students may see Ae’o and the Hawaiian Coot. It would be ideal if students had binoculars and
field guides to see the birds up close. If you live on neighboring islands, bird habitats are accessible as
well. On Maui, native forest birds can be found at Hosmer Grove in HaIeakala National Park and water
birds can be found at Kealia National Wildlife Refuge. On Oahu, seabirds can be seen around Makapu’u
Point and some native forest birds might be seen near Lyon Arboretum. On Kauai, Kokee State Park is a
great place to see native forest birds and Kilauea Point National Wildlife Refuge is a great environment
to see different species of seabirds and Nene. If you don’t have the opportunity to visit a habitat that has
native birds, students can observe non-native birds just about anywhere. All birds use certain adaptations
to survive so observing any type of bird will be beneficial.
Discuss with students why birds live in different habitats (be sure to notice different food sources within
each habitat). Ask what adaptations the birds have in order to survive in each of the habitats. This would
be a good time to get the students thinking about what types of questions they could ask in order to
conduct a scientific investigation in the field. For example, “How many invertebrates does an Ae’o
collect in a certain amount of time”? How would they set that experiment up and how would they
conduct it? They can write about it in a journal entry.
If a field trip is not possible, create a class simulation of a field trip. Before the students come to class,
transform your classroom into a natural habitat. Get pictures of birds and plants that represent a particular
habitat and hang on wall or an area of your choice. When the students come to class, explain to them
which habitat they just encountered and have them walk around to see the different bird and plant
pictures. Audio with bird songs could help improve this simulation.
For ideas about forest habitats, the following website is a good start (pgs 7-11):
http://www.state.hi.us/dlnr/dofaw/kids/teach/forest%20activity%20guide.pdf
They can still use field guides and come up with questions that would be suitable for field research.
Great field guides to use as references on bird watching and plant identification are:
A pocket guide to Hawaii’s birds, H.D. Pratt and J. Jeffrey (~$9.00)
A pocket guide to Hawaii’s trees and shrubs, H.D. Pratt (~$10.00)
Resources
http://www.hawaiiaudubon.com/birding/
FOSS-Populations and Ecosystems
West Hawaii Explorations Academy
Public Charter School
Developing an Outline
Title: Short Description of what the paper is about.. .not Topic Paper!
Topic: Native Hawaiian Forest Birds
Major Point 1 : Description of Organism (including scientific name and significant
adaptations)
Major Point 2: Description of Habitat
Major Point 3 : Description of Negativepositive Human Impact (Origin and nature
of threats to organism/habitat/efforts to preserve/conserve organisrnlhabitat)
Conclusion: Summarize three main points, state opinion and importance of this
topic.
Topic sentence:
Opening Paragraph:
Major Point 1 :
*
Rev. 411 012007
West Hawaii Explorations Academy
Public Charter School
Major Point 2:
Major Point 3:
Bibliography : Must be in proper format (separated by type, alphabetized and including the
necessary information) and include three sources where you found the information cited in the
body. Do Not Use .corn, unless previously approved by advisor. Paper will not be accepted if
this section is not completed or is incomplete.
Example of a source cited within the body of the paper:
The use of enriched food will increase the growth rate of the Omilu (Vencent,1999).
0r
According to Vencent (1999) the use of enriched food will increase the growth rate of Omilu.
Or
"During this study, the use of enriched food in the diet of Omilu resulted in a 22% increase in
growth rate over a four month trial period," (Vencent, 1999).
Example of a source cited within a bibliography:
Bibliography
Magazine
Vencent, Amanda. 1999."Raising Omilu." National Geographic,
Available at: www.national~eographicmagazine.com.
Author's last name, first name. (or name of organization) date. "Title(of article)." Title (of book
or magazine). Place Published: Publisher. (or web address)
Book
Vencent, Amanda. 1999. Aquaculture Techniques. Honolulu, Hi: Bess Press.
Website
Vencent, Amanda. 1999. Enriching Food for Aquaculture.
http//www.pbs.orgiwnetlenrichingfoodforaqua/
Rev. 411 0!2007
1,
A POCKET GUIDE T r l
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HAWA
TREES
SHWUR:?
,
A Pocket Guide to Hawai'i's Trees and Shrubs is
mo-t ,plete guide available to both native and naturalized treps, s h r i , i , ,,
and large vines in the Hawaiian Islands.
Included are photos of all the spectes Innst. t i k e l ~to b p or,cnuqtered by residents and visitors al~ke.Smqll nr,ougt~far a backpacK,
but complete enough to be a valuable Dljokshelf rpferenca, this
book is the perfect addition to any nafursltst's f~braryAlthrdugh t
.photographs will be valuable to boton~rits,the text 1s writfert.for t
?wa3,:
J M g d c W o o k provrdes a vlsub~,,
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ttor;,
obvious f~elcicharacters that can be '!id-o
resorting to a hand-lens.
The plants are arranged by liab~tatso that tlro reader will gain
a thorough overview of Hawaiion ecolarly arid an appreciation fo
the uniqueness of these beaut~fulislarirlc; No na'turslist and natur
lover in Hawai'i should bo r ~ i t h o ~tl ht l ~{jlll(k.
~,n+iw
~ U B C .~RRY'J%Q~
Dr. H Douglas Pratt Iias decade6 of experlencc ?s
a f~eldnatural~st,scholar, wildl~feartrs: ph6tor)re~ahnr.
an!
ecotour leader In Hawal'~Me I,: best hnown ~ U hi9
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tech
nlcal and popular works on Hawailall btrds duch as h13
popular gu~deboolc Enjoyrng t31rds kt ilawFta, bhwat'l
Beautiful Wrds, and A Pocket F~ltdoto klitn~a~'r's
Birds.
Is
TREES
SHRUBS
Aloha! Welcome to the Ahupua'a of Pu'u Wa'awa'a. The Division of Forestry & Wildlife and the Pu'u Wa'awa'a Volunteer
Program are pleased to offer these trails for your enjoyment. Please observe the following guidelines so that these hails not only
stay open, but so that the system may expand!
There is no trail maintenance staff. Please kokua to keep this trail clean and safe. If you encounter any litter, please pick
it up. If you see any loose rocks on the trail surface, please toss them aside - mahalo!
Dogs are
allowed on the trail at this time. This is for your safety as well as your pet. We are working to expand the
trail to include some areas for dogs on leashes.
r
Please stay on the trails as indicated on the map. Absolutely NO ENTRY into the quarry area.
Keep the pedestrian gate closed at Tamaki Paddock --this area remains an active cattle ranch.
Please be courteous to hikers, residents and ranchers.
For more information about Pu'u Wa'awa'a and Volul~teerProgram, call 937-2501.
PRISM UHH GK-12
ADAPTATIONS
Concepts
Different bird species,
such as Hawaiian
honeycreepers are
endemic to Hawaii
and they have adapted
to the diverse habitats
found only aaaadfgfa
within
these ecosystems. The
beak structures, leg
and facial muscles of
honeycreepers all give
insight into their diets
and how they forage
for food.
Standards Addressed
7.1.3, 7.3.2, 7.5.4
Duration
40-50 minutes to
construct paper bird.
(2) 40-50 minute class
periods to construct
papier mache bird.
40-50 minutes for
student presentations.
Source Material
Adapted from Project
Wild
Build a Hawaiian Bird
Summary
After students have completed the Bird Beak Adaptation Lab and study different
habitats to see how birds are adapted to different habitats in the wild, students will
create imaginary birds using papier mache´.
Objectives
• Students will identify and describe the advantages of bird adaptations and
evaluate the importance of adaptations to birds.
• Students consider different bird adaptations required for a specific habitat.
• Students will present their constructed bird to the class and will defend why
they chose their specific adaptations.
Materials
Paper bird parts (cut-out worksheet)
DLNR free posters to as habitat reference
Adaptations and advantages for bird worksheet (For teacher)
Elmer’s papier-mache glue (powder form)
Newspaper
Glue, Scissors, Paint
String to display birds
Teacher Prep for Activity
• Elmer’s papier-mache art paste was used for this lesson. The paste was
ordered from the following website:
http://www.enasco.com/ProductDetail.do?sku=8100197J, each box costs
about $2.50/box and make 4 quarts. Approximately 3-4 boxes were used for
15 large birds.
• Make Xerox copies of bird cut-outs and outline for Topic Paper
• Collect newspaper
• Request free bird habitat posters from DLNR:
http://www.state.hi.us/dlnr/dofaw/kids/teach/forest%20bird%20poster2.jpg
Background
All life forms have adaptations that allow them to survive and maintain populations.
Wildlife species are adapted to the environments in which they live. Birds have
many different adaptations, including beaks, feet, legs, coloration and bone type.
Beaks allow different birds to acquire specific foods and their feet allow them to
grasp branches or prey, or wade in water. In order for birds to be better suited to
their environment, these adaptations have evolved.
Many different Hawaiian forest birds have different adaptations that allow them to
survive in such a unique environment. Some forest birds are known as
honeycreepers and many of the honeycreepers have beaks that are shaped in order to
gather food from specialized sources. For example, the ‘I’iwi has a long, curved bill
that is designed to consume nectar from long, tubular, curved flowers. Also, the
Palila, another honeycreeper, has a short, thick bill used to rip open mamame pods
to obtain the mamane seeds inside. The `Io or Hawaiian Hawk has talons in order to
grasp food items such as small birds and a sharp bill to eat its prey. The ‘Ae’o or
Hawaiian Stilt has long legs so it can wade in mudflats or shallow coastal wetlands.
The way that a bird looks, obtains food, or travels are all advantages for a species to
physically adapt to its environment.
Procedure
1).Discuss with students the different adaptations that bird’s exhibit-explain the different adaptation paper cutouts that will be given to the students and the benefits of these adaptations. Students could also help with what
cut-outs will be used. Days prior to this starting this activity ask the students to brainstorm about different
adaptations that they may have already learned from the previous lessons or bring in pictures of birds. A
worksheet with bird cut out will be provided, but the class could make other cut-outs. Each student should
create their own bird using the paper cut-outs, but student’s can pair up to create a single bird. Our students
worked together in pairs and integrated their different adaptations to create one bird. (Examples are included at
the end of the lesson. We learned that the larger the size of the balloon used for the body form, the larger the
bird.)
2). The teacher can either assign a specific habitat that the student will create the bird for or the students can
choose the habitat themselves. For this lesson, the habitats will be the coastline and the rainforest. Students can
choose adaptations from either one of the habitats or a combination of both. Inform students that they will
later have to explain in a presentation why they chose certain adaptations and the benefits for those
adaptations. Explain to the students that they will have a chance to design their own original bird that is
adapted to a Hawaiian habitat (e.i. rain forests, dry forests, wetlands, shoreline, etc). Each student should
decide: The name of their bird (they should come up with a scientific name that is representative of their
created bird), what the bird will eat (nectar, insects, small mammals, invertebrates, etc.), how it moves (fly or
non-flyer), it’s gender (coloration), range (does it have to travel far for food), where does it nest (in the trees,
ground, burrows) and any other characteristics they may want to add. As they create their birds, they should be
writing in a journal or notebook why they are choosing the specific traits since they will have to present their
bird at a later time and write a paper. An outline is provided for a paper the students will write after they have
completed their bird. This paper should include all the information about the bird the students think is
applicable.
3). Have the students choose from the cut-outs presented to them to construct a preliminary paper bird. Have
the students glue their different parts to a blank piece of paper. As they are selecting the parts they are going to
use, they should be taking notes about why they chose the particular traits. They should also color their bird,
since coloration in birds is important adaptation for camouflage and courtship. This might take a full class
period; since it may take students time to decide which adaptations they will use.
4). Once the paper bird is constructed, they will then have the opportunity to create their paper bird using
papier mache. This could also be done in other artistic techniques, such as drawing or clay.
5). Students will then be asked to present their bird to the class. They should include the name of their bird, its
food sources, lifestyle, etc. They will have to describe why they chose the adaptations they used and the
advantages provided by the adaptations for the habitat of the bird.
6). Once students have presented their birds, hang them from the ceiling to display their creations.
Assessments
Designed Bird with appropriate adaptations
Written paper about their bird.
Presentation
Resources
Project Wild-K-12 Curriculum & Activity Guide. 2002
http://www.hear.org/hoike/
http://www.state.hi.us/dlnr/dofaw/kids/teach/index.htm
http://www.state.hi.us/dlnr/dofaw/kids/teach/forest%20bird%20poster2.jpg (for free posters)
FOSS-Populations and Ecosytems
Teacher Resources
Adaptations and advantages worksheet for teacher:
Beaks:
Advantage:
Pouch-Like
Can hold the fish it eats
Long-thin
Can probe in mud or shallow water for insects
Pointed
Can probe into bark of trees for insects, like grubs
Curved
Can tear solid tissue for the meat it eats
Short, stout
Can crack the seeds and nuts it eats
Slender, long
Can probe the flowers for nectar it eats
Feet:
Grasping
Long toes
Clawed
Webbed
Advantage:
Aids in sitting on branches, roosting, and protection
Aids in walking on mud
Can grasp food when hunting prey
Aids in walking on mud
Legs:
Long, slender
Powerful muscles
Long, powerful
Flexor tendons
Advantage:
Aids wading
Aids lifting, carrying prey
Aids running
Aids in perching, grasping
Wings:
Large
Advantage:
Aids in flying with prey, soaring while hunting
Coloration:
Bright plumage
Dull plumage
Change of plumagewith seasons
Advantage:
Usually male birds, attraction in courtship, mating rituals
Usually female birds, aids in camouflage while nesting
Provides camouflage protection-brown in summer, white
in winter.
Bone structure:
Fused bones
Hollow bones
Advantage:
Ground bird, does not fly
Can fly
EXAMPLES OF STUDENT WORK
Build a Bird Kit-"Cut Out" Sheets
BUILD A BIRD KIT
Body Forms To Be Used For All
Birds:
Heads:
ESl,
Small ~nvwkkrcrcfc~
e
Small insc&
Tails:
West Hawaii Explorations Academy
Public Charter School
Developing an Outline
Title: Short Description of what the paper is about.. .not Topic Paper!
.Topic: Forest Bird Adaptations
Introduction: introdwe main points
Major Point 1 : Description of Scientific name and reason for choosing name
(Genus and species)
Major Point 2: Description of each body part and what the evolutionary purpose
Major Point 3: Explain what habitat this bird would be most successful in, give
details.
Conclusion: Summarize main points
Major Point 1:
Major Point 2:
*
Major Point 3 :
*
Rev. 4/4/2007
INVESTIGATION 8:
GOAL
Adaptatir
duces students t o .the conce?ptof ad;
.
an organism that helps it survive and reproduce.
..
1,
any struc
OBJECTIVES
TENT
ldaptatlon is any trait of an orgarusm that enhances its chances of surviving and reproduc~ngm
nvironrnt?nt.
ahue is a structure:, characteristic, or behavior of an organism, such as eye color, fur pattern, or
-- - L -:-rration.
lit is the w,ay a fea hue is e,cpressed in an individual organism, such as brown eyes, small spots, or
r migratior1.
.... .-:--.- < .
Variation is the range
of expression
or a feature within a population, such as all the different eye
colors, all the different fur patt~
ems, andI all the dates on which migration starts.
CONDUCTING INVESTIGATION!S
Use a multimedia simulation to investigate the adaptive value of protective coloration.
Conduct simulated predator/ prey interactions over multiple generations to investigate the effect of
protective coloration on the color characteristics of a population of walkingsticks.
BUILDING EXPLANATIONS
Explain how adaptations help organisms survive in an environment.
Describe how a population can change over time in response to environmental factors.
SCIENTIFIC AND HISTORICAL BACKGROUND
Life is incredibly robust and indomitable.
At the same time, however, it is sensitive
and vulnerable. This apparent
contradiction is one of the many aspects of
life that makes its study so intriguing.
What makes life simultaneously durable
and fragile?
Life resides in individual organisms. Life
continues as long as the basic needs of an
organism are met. These include energy,
water, gases, nutrients, space, and
protection. The exact measure of each
requirement and the medium in which it is
provided vary for each kind of organism.
If the resources needed by a given
organism are plentiful--optimum
conditions-the organism will thrive. If
the resources are marginal-just at the
threshold-the organism will survive. If
any of the resources falls below the level
needed by the organism, it will die. In this
regard life is tenuous, dependent upon
uninterrupted access to the requirements
for life.
The resources for life originate in an
organism's environment. The relationship
bemeen an organism and its environment
is, therefore, critically important.
Environments are notoriously dynamic.
When an environment changes, organisms
that interact with it are influenced. A
change in the environment might improve
for a given organismto
the
survive. On the other hand, a change
might decrease its survival potential.
Furthermore, a change in the environment
might enhance one organism's ability to
survive and reproduce more offspring
while it decreases the chances of another
organism.
ADAPTATIONS
Organisms have adaptations that allow
them to live in an environment. Sea otters
live in the sea, desert tortoises live in the
desert, and mountain heather lives in the
mountains, The sea otter will die in the
desert or mountains as surely as the
tortoise and heather will die in the sea.
Every kind of organism has a unique set of
adaptations to live in its environment.
Adaptations are physiological attributes
(structures and functions) or behaviors
that enhance an organism,s opportunity to
live and reproduce in its environment.
The hawk's talons, the shark's broad tail,
the toad's long, sticky tongue, and the
clam,s hard shell are examples of
structural adaptations. The trout's ability
to extract oxygen from water, the skunk,s
ability to produce and spray disgusting
defensive chemicals, the beers ability to
transform nectar into honey, and the
ability to reason are examples of
functional adaptations. The squirrel's
propensity for storing nuts, the black
bear's long winter hbernation, the
herring's habit of schooling, the crayfish's
active territorial defense, and the arctic
tern's long annual migration are examples
of behavioral adaptations.
The particular combination of adaptations
expressed by an individual definesthe
lifestyle that that organism will lead and
the environment in which it can survive.
VARIATION WITHIN A SPECIES
Organisms of the same kind are all
members of the same species. All
members of a species have similar
adaptations and, therefore, the ability to
live in the same environment. The
members of a species that are living
together and interacting constitute a
population. All members of a population
do not, however, have identical traits.
Within a population there is variation.
Variation is the amount of difference in
physiological and/or behavioral attributes
exhibited by the members of a population.
Variation can show up in an organism's
structures. Some giraffes, for example,
have longer necks than others. There is
variation in neck length. Some trout have
larger, darker spots than others. There is
variation in pattern. Some sulfur
butterflies are brighter yellow than others.
There is variation in color. And so it goes.
Look at individuals in the same age class
in the species Homo sapiens and you will
see a great deal of variation in size,
strength, eye color, hair color, amount of
hair, number of teeth, sensitivity to cold,
and so on.
Variation extends to behavior as well.
Some silk moths spin denser cocoons than
others. There is variation in construction.
Some red-winged blackbirds defend larger
territories than others. There is variation
in range management. Some sunflowers
bloom a few days earlier than others.
There is variation in timing. Some people
sleep later, talk louder, eat more, play more
sports, or read more than others. There is
a lot of variation in human behavior.
BIOLOGICAL IMPLICATIONS OF
VARIATION
When the environment provides abundant
resources, all members of a population
share in the bounty and survive. Optimal
conditions, however, are the exception
rather than the rule in nature. Often some
factor in the environment is in limited
supply or pushing the limits of tolerance
of the organisms. This is where variation
is essential to the survival of the species.
The individuals that have structures or
behaviors that allow them to break slightly
harder seeds, run a little faster, produce
broader leaves to capture more sunshine,
store a little more water, and so forth, will
have a survival advantage over other
members of the population when the
environment changes. As a result of
natural variation in a population, the
population may survive failure of a
primary food source, invasion by a fleet
predator, reduction in solar radiation, or
drought. It is important to note that
difierent members of the population will
have the advantage, depending on what
environmental factor imposes pressure on
the population. The result is that some
members will survive to reproduce,
ensuring the survival of the species and
the continuation of the population.
THE ORIGIN OF VARIATION
One of the big ideas in biology is the
origin of variation in organisms. The first
fully elaborated explanation of the origin
and role of adaptations in organisms was
by French naturalist Jean-Baptiste-PierreAntoine de Monet de Lamarck (1744-1829)
in his book Zoological Philosophy (1809).
His arguments were logical, but were
shown later to be wrong. Even so, it is
important to explore his reasoning, as it
might also be the reasoning of some
students.
In his work Lamarck proposed the
incorrect idea that individual organisms
change in response to pressures from the
environment in order to advance their
chances of survival. For example, Lamarck
thought that the turtle hardens its shell in
response to repeated assault by predators,
the giraffe's neck Iengthens as it reaches
for ever-hgher foliage in the trees, the redwinged blackbird enhances the amount of
red on its wings to better attract a mate,
the poppy blooms earlier in the spring to
take advantage of residual soil moisture,
and a philodendron grows larger leaves to
take advantage of the limited light filtering
down to the forest floor. Because these
modifications enhanced the survival of the
individual, and therefore its probability of
reproduction, Lamarck proposed that the
acquired characteristics were passed on to
the offspring.
The Lamarckian theory of evolution that
grew out of this explanation of the origin
of adaptations was accepted for a time, but
by the middle of the 19th century it had
been refuted. Changes in structure and
behavior that occur during an organism's
life cannot be passed to its offspring. It
just doesn't work that way. But students
often think this way, so it is important to
understand why this is incorrect.
Here's an example. The 95-lb. weakling
grows weary of having sand kicked in his
face every time he goes to the beach. He
enrolls in a bodybuilding program and
bulks up to be a magnificent 210-pound
Adonis. Later, he marries and settles
down, producing offspring in due course.
Will his male progeny be husky and
strong, reproduced in the image of their
transformed dad? Not likely. They will
have his tendency to be scrawny and
victimized, just like Dad was at birth. But
they will doubtless have mherited, like
h m , the adaptation for superior muscle
development in response to a rigorous
bodybuilding regimen.
In 1859, after more than 20 years of
fieldwork and rumination on the subjects
of adaptation, variation, and speciation,
Charles Darwin published his conclusions
called O n the Origin of Species by Means of
Natural Selection, or the Preservation of
Favoured Races i n the Struggle for Lijie,
usually referred to as T h e Origin of Species.
In it Darwin described the origin of
variation as a random occurrence that
takes place during the process of
reproduction. In this way it is possible for
offspring to vary somewhat (or
significantly) from their parents, as well as
from their siblings. Furthermore, the
variation may or m a y not contribute to the
improved survival of the individual
sporting the variation.
The adaptive value of a population's
variation manifests itself when the
environment imposes pressure on the
population. If the climate turns hot,
rabbits with thinner fur will dissipate heat
better than rabbits with thicker fur. Thin
fur in this case is a trait that gives an
advantage. On the flip side, if the climate
turns cold, thick fur is an advantageous
trait, and thin fur is a liability. If the
climate remains unchanged, fur thickness
offers neither advantage nor
disadvantage-it is just a variation.
If the climate does make a permanent shift
to cold, those rabbits that randomly
happened to have thicker fur will survive
better, and, in the long run, they will
reproduce more. As a result of the
differential reproduction, the population
will in time have thicker fur. The thicker
fur is an adaptation. The important thing
to remember is that no rabbit decided to
have thicker or thinner fur-fur variation
already existed in the population, it just
happened. The environment imposed
pressure on the rabbits, selecting those
with thicker fur to survive and reproduce.
The rock ptarmigan is a small member of
the grouse family adapted to live in arctic
regions year-round. It feeds and nests on
the ground in small family groups.
During the fall it molts its brown summer
plumage and grows a fresh set of white
feathers and a dense downy underlayer
for winter. The color and insulation
permit the small bird to survive in the
bitter arctic winter environment.
In the spring the ptarmigan again molts,
restoring its lightweight, brown summer
plumage. This elaborate process of feather
replacement could be construed as a
conscious, plamed behavior on the part of
the ptarmigan, but it is not. Just like the
giraffe's long neck, the rattlesnake's rattles,
and the redwood tree's fire-resistant bark,
the ptarmigan's dual-colored, variably
insulated coat is the result of random
change over time that resulted in an
organism adapted to live in the arctic.
Other variations may have shown up in
the ptarmigan's features along its
evolutionary path, but those that
prevented survival in the arctic
environment disappeared from the
Students will be challenged by t h s idea
that organisms don't decide how to
modify their structures and behaviors to
their advantage. They will be tempted to
adopt the logic that seduced Lamarck. It is
doubly difficult because the most
important adaptive characteristic of
humans is the evolution of the brain as a
flexible, logical, problem-solving organ.
Because brain power is such a powerful
adaptation, humans have been extremely
successful organisms on Earth. One
manifestation of brain power is that Homo
sapiens can consciously modify themselves
and their environment, effectively
changing their defensive strategies,
modifying their body covering, moving
faster, communicating effectively, and
securing food in many different ways.
Humans are adaptable, but this must not be
misunderstood as adapted. These changes
and behaviors do not get passed down to
the next generation, only the brain power
to think them up gets passed on.
ADAPTATIONS FOR SURVIVAL
One of the popular terms extracted from
Darwin's Origin of Species is "survival of
the fittest." By this Darwin meant that the
organism with adaptations that allow it to
acquire resources and reproduce more
effectively than another is the one that will
survive. The wordfittest is perhaps
misleading. This is another example of
common usage versus scientific usage of a
word. In common usage, because of the
emphasis on physical prowess and athletic
conditioning, most students will think that
the phrase means the most robust
individuals will succeed. However, in the
scientific sense of the phrase, it means the
ones best adapted to respond to the
pressures of the environment will survive.
"Survival of .the fittest" thus means the
organisms that fit best with their
surroundings will thrive and reproduce.
FEATURES AND TRAITS
Organisms have distinctive features that
make them recognizable. Perch have
scales, fins, eyes, and a mouth. Grasses
have blade leaves, fibrous roots, tiny
flowers, and lots of seeds. Snakes have
scales, color patterns, eyes, and mouths.
Pine trees have massive stems, large roots,
needle leaves, and seeds in cones. Ducks
have feathers, beaks, legs, webbed feet, and
eyes. Cats have fur, eyes, teeth, color, and
tails. Features are structures of organisms.
There is tremendous variation in features
from species to species but all individuals
of the same species have the same features.
There can, however, be variation in how
the features look within a speciesvariation from individual to individual. .
The appearance of a feature within a
species is called a trait. A trait is the
particular manner in which an organism
exhibits a feature, that is, how it looks.
Let's look at some examples. Black bears
all have the same features: four legs, short
tail, small ears, two eyes, long, coarse fur,
and a brown nose, among others. The
color of the fur can vary from jet black to
honey yellow. In this case, fur color is the
feature, and black fur is the trait for one
individual.
Larkspur is a plant that grows in moist
meadows. The plants share common
features that make them identifiable to
plant fanciers: small green leaves, tall
central stems, and clusters of distinctively
shaped flowers. The flowers, however,
can range from pale pink to deep royal
purple. Colored flowers is a feature of
larkspur; the particular color of flower is a
trait displayed by an individual plant, and
may vary from plant to plant.
A classic scientific investigation looked at
the feature of wing color in the peppered
moth of England. This little moth can
vary from almost white with dark dots on
the wings to completely black. In its
typical form it is Iight-colored. Lightcolored wings was the predominant trait
before the Industrial Revolution.
When the Industrial Revolution filled the
air with pollutants, the fragile lightcolored epiphytic lichens on tree trunks
and branches died, leaving the dark
trunks exposed. The moths with the white
color trait were easy for predators to see
on the tree trunks, and they were eaten.
Moths with the dark color trait were less
often seen by predators, so they survived
to reproduce. Moths with dark wings
tended to have offspring with the darkwing trait.
Humans have colored hair and colored
irises. Hair color and eye color are
features of humans. There is variation in
hair color from jet black to nearly white
and variation in eye color from pale blue
and green to dark brown. Hair and eye
color are features of humans; the
particular hair color and eye color of an
individual are traits of that person.
The ideas of feature and trait are discussed
in greater detail in Investigation 9, when
we introduce the fundamental mechanism
that determines traits, the gene.
WHY DO I HAVE TO LEARN THIS?
"So, people are different. I know that
already. Some people are tall and some
have freckles. It doesn't really matterwe're all people-it's just that we are
individuals. Individuals are supposed to
be different from one another. Otherwise
the world would be too boring."
It's true, we are all people, just like
goldfish are all goldfish, spotted owls are
all spotted owls, and orcas are all orcas.
Even so, there is variation in all
populations, and the variation is doubtless
perceived and factored into the way
members of a population interact. T h s is
the level of awareness that middle
schoolers will bring to the study of
variation, and it is a good place to start.
An important notion for students to start
thinking about is that variation in traits
may be present but undetected in a
population. Traits that allow an organism
to respond to changes in the environment
can be the fulcrum on which the balance
between life and death pivots. Such traits
may reveal themselves as important for
survival when conditions change. An
animal that is just a little more heat
tolerant or a plant that sets seed just a bit
earlier than others in its population could
be the one that survives to reproduce if the
environment presents a particular set of
challenges. In another instance, however,
it might just as easily be the individual
that is just a little more cold tolerant or
sets seed a bit later that survives.
Variation within a species is one way to
ensure that some members of a population
survive to continue the population line.
Many students think that adaptations, like
warm fur, sharp talons, wings,
- venom,
webs, fins, and fragrance, are the clever
devices that organisms developed to help
them survive. They tend to attribute
conscious decision and deliberate action to
the processes that produced the features
and traits, for example, the giraffe grew its
neck to reach high branches; the frog grew
webs between its toes to swim better; the
mosquito developed a proboscis to suck
blood; the monkey developed a prehensile
tail to keep it from falling out of the trees.
The idea that these and millions of other
adaptations emerged by chance or as
accidents is not intuitive to students. The
idea that the adaptations we see today are
the "happy accidents," the ones that
worked to the organism's advantage and
helped it survive, is equally difficult. The
countless unhappy accidents that did not
help an organism survive are the features
we can read about in the fossil record or
dream about, but they are not expressed by
organisms on the planet today.
Students' understanding of ecology and
natural selection hinges on the
fundamental concept of adaptation.
Carefully monitor their progress with this
difficult idea. Adaptations determine the
relationships organisms have with their
environment. An organism's
relationship
with its environment is a matter of life and
death. And remember, an organism's
environment is everything surrounding it,
physical objects and conditions as well as
all the organisms of its own kind and every
other kind.
-
~
PRISM UHH GK-12
Genetic Variation
Concepts ;;l
Within a population of
organisms, individuals
will exhibit variation or
differences among their
features.
Genes are the basic units
of heredity and they are
what make each
individual’s
characteristics, traits and
behaviors different.
Standards addressed
7.1.3, 7.5.2, 7.5.3
Duration
60 (+) minutes
Vocabulary
Genetics
Variation
Genes
DNA
Nucleic Acids
Chromosome
Alleles
Traits
Dominant
Recessive
Homozygous
Heterozygous
Source Material
Adapted from FOSS
Exploring Human Traits
Summary
Genetics can be a confusing concept for many students to understand. In order for
the class to begin to understand genetics, they will first study variation in human
traits. Students will start learning about the study of heredity by surveying their
own features. They will learn that they possess single gene traits with simple
dominance inheritance patterns such as earlobe attachment, tongue rolling, and
bent little finger. Students will work in groups, and after surveying their partners,
the data of the class will be collected and patterns of inheritance will be discussed.
Objectives
• Students will describe human traits.
• Students will distinguish which trait they possess for chosen features.
• Students will organize data, calculate percentages, and create graphs.
• Students will identify patterns and discuss conclusions for those observed
patterns.
Materials
Rulers (1 for each group of 2)
Grid for Vocabulary Bingo, or have each student take out a piece of paper and
make their own grid (5 squares down x 5 squares across).
Vocabulary Review Sheet-Can be used as transparency or a handout.
Internet access if added background material is neededTeacher Prep Activity
• Xerox “Genetic Variation” readings, grids for Vocabulary Bingo
Vocabulary Review Worksheet and Exploring Human Traits Record
Sheets for students.
• Xerox a single copy of the Human Traits that can be used for teacher.
Background
With the invention of better microscopes in the late nineteenth century, biologists
were able to discover the basic facts of cell division and sexual reproduction.
With these new discoveries, scientists began to focus genetics research to
understanding how hereditary traits are passed on from parents to their children.
Genetics is the branch of science that deals with inheritance of biological
characteristics. Within a population of organisms there will be variation among
the individuals in the population and this is the reason for population change and
differences. Within a population of sexually reproducing organisms, every
individual within that population will be unique and vary in their traits, behaviors
and environmental needs. Genes are the basic units of heredity and they are what
make each individual’s characteristics, traits and behaviors different. Genes are
found along the DNA strand. DNA (deoxyribonucleic acid) is made up of nucleic
acids, which are large molecules that hold the story of life. DNA is the specific
nucleic acid that deals with determining the genetic code of each individual.
Typically, DNA molecules are quite long, approximately 5 cm long and in order to
fit within the nucleus of the cell, they are coiled and tightly wound into a structure
called a chromosome. branch of science that deals with inheritance of biological
characteristics.
Organisms have different number of chromosomes, some organisms has as few as two, while some have up to a
thousand. Humans have 23 different chromosomes and each of those has an identical partner chromosome. The
paired chromosomes that are similar are considered to be homologues and each chromosome has the same genes.
These two genes interact with each other to produce the characteristic they are assigned to and the two copies of
the genes are called alleles. When the two alleles are considered together, they make up a single gene. When a
gene is composed of two identical alleles it is considered homozygous. When the gene is composed of two
different alleles, the gene is heterozygous.
Gregor Mendel, an European monk, became known as the “father of modern genetics” for his study of inheritance
of traits in pea plants. Through selective cross-breeding of different traits (tall, short, purple flower, white flower,
smooth seed) of pea plants Mendel discovered the basic principles of heredity. Over many generations of
breeding pea plants, Mendel discovered that certain traits show up in offspring without any blending of parent
characteristics. For example, when pollen from tall plants was used to pollinate the flowers of short plants, all the
offspring were tall. There was no mixing of tall and short plants. In the previous example, the trait of “tall” which
exclusively appeared in the first generation (F1) and reappeared in the second generation (F2) was identified as the
dominant trait. The second generation also revealed the “short” trait that was absent in the F1 generation. This
trait that was absent in the F1 generation but present in the F2 generation was identified as the recessive trait.
Unfortunately, Mendel did not know about DNA, chromosomes, or genes and was unable to understand the
biological and physical processes that allowed inheritance to occur and the importance of his work was not
recognized until many years later.
Procedure
1). First have students read background information about Genetic Variation. This can either be assigned as
homework, or this can be done as a lesson during class prior to this activity. If the reading is to be assigned as
homework, be sure to take a period to go over the information since some of the vocabulary can be complex.
2). Play a round (or two) of Vocabulary Bingo and then review genetics vocabulary sheet as a class.
3). Divide students into groups of two and give each group a ruler (ruler will only be used if the traits that you
assign to survey need to be measured). First ask the students if they think there are differences among humans and
have them give examples of possible differences. Ask them if there were going to describe a person, for example,
if they needed their parents to go pick up a friend that their parents had never met, how would they describe their
friend to their parents. Hopefully they say things like “my friend has brown hair, they are tall, they have brown
eyes, etc.”. Explain to them that they just described traits about a person. They will now survey their own traits.
4). On the list of traits provided, choose up to five traits and be sure to introduce the traits and go over them with
the students. Each feature only has two traits, so each student should have one or the other trait. Let students
know that their assignment is to discover which trait they have for each of the assigned features. For example, if
the tongue trait is chosen, the student will either be able to curl their tongue or not.
5). Give the students about 10 minutes to observe each other and determine which traits they possess. Have the
students record their traits on a piece of paper. They should write which feature they have and the trait, either the
dominant or recessive trait. Dominant traits will be symbolized by 2 capital letters (TT) and recessive traits will be
symbolized by 2 lower-cased letters (tt). This actually defines the genotype of the trait.
6). Poll the class by having the students come to the board and tally their results. On the board, have each trait
written out and next to each trait, each student can make a tick or a check next to the trait.
For example:
Tongue rolling: TT ___________ “5 students”
tt ___________ “2 students”
Then determine the percentage of students in the class that have the certain trait.
The class can also be polled using a transparency, having the students raise their hands and report to the teacher
which traits they have.
7). Talk about the results. Is there variation among the students? Which traits occurred the most? Are the traits
linked? If you can roll your tongue, is your little finger always bent? Summarize the results, determining that
there is variation among the students in the classroom.
8). Have the students create a bar graph of their results on the back of their Exploring Human Traits Record
Sheet.
Teacher Resource Extensions:
FOSS Genetic Vocabulary Review Worksheet (included)
When introducing the material, students can visit the web site
http://www.dnaftb.org/dnaftb/1/concept/index.html (DNA from the beginning) and choose chapters to explain
some of these complex concepts. The animation tab for each chapter is a beneficial way to have students
engaged in the material. Chapters 1-5 can be used for the topics of inheritance.
Resources
file:///Users/universityofhawaiihilonsfprismgk-12/Desktop/GK-12%20/Human%20Traits.webarchive
http://www.dnaftb.org/dnaftb/1/concept/index.html
Foss-Populations and Ecosystems
Human Traits
1. Shape of face (probably
polygenic)
Oval dominant, square recessive
2. Cleft in chin
No cleft dominant, cleft recessive
3. Hairline
Widow peak dominant, straight hairline recessive
4. Eyebrow size
Broad dominant, slender recessive
5. Eyebrow shape
Separated dominant, joined recessive
6. Eyelash length
Long dominant, short recessive
7. Dimples
Dimples dominant, no dimples recessive
8. Earlobes
Free lobe dominant, attached recessive
9. Eye shape
Almond dominant, round recessive
10. Freckles
11. Tongue rolling
12. Tongue folding
13. Finger mid-digital hair
Freckles dominant, no freckles recessive
Roller dominant, nonroller recessive
Inability dominant, ability recessive
Hair dominant, no hair recessive
14. Hitch-hiker's thumb
Straight thumb dominant, hitch-hiker thumb recessive
15. Bent little finger
Bent dominant, straight recessive
16. Interlaced fingers
Left thumb over right dominant, right over left recessive
17. Hair on back of hand
Hair dominant, no hair recessive
Exploring Human Traits Record Sheet
Ll
Name:________________________
Use this tally sheet to keep track of the different traits that your classmates have. Under “Trait” write the different
traits that your class has decided to survey, such as Dimples or Tongue Rolling. Under “Dominant” or
“Recessive”, record the tally marks or check marks of your classmates. Then determine the percentage of students
that are either dominant or recessive for the trait.
TRAIT
Example: Dimples
____________________________:
DOMINANT
√√√√√√√√
_____________
RECESSIVE
√√√√
_____________
% (# ÷ Class total)
8 ÷ 4 = 2% Dominant
_______(D)
______(r)
= _______%
____________________________:
_____________
_____________
_______(D) ______(r)
= ________%
____________________________:
_____________
______________
_______(D) ______(r)
=________%
____________________________:
______________
______________
_______(D) _______(r)
=________%
____________________________:
_______________
______________
_______(D) _______(r)
=________%
'4
Name
-
Period
-
GENETICS VOCABULARY
*.*.*****....*....**..*.
Date
. . *...*.***.*****.
*****.***e.*e*.e
The offspring of organisms often grow up to look like one or b )thof their parents. This is
because offspring inherit info mation from their parents that directs their development.
of every cell in the organism. The
The inherited information 1 - 1 rated in the
molecule. The huge molecules are coiled into
information is coded in the 'luge
compact hot dog-shaped s. ictures called
are always
present in almost identical lirs. Locations on chromosomes that affect features of
. A gene is composed )f
organisms are called
An organism's unique combination of genes is its
by an organism's genes is its
.
Alleles that ha
. The traits produced
more influence in
alleles. Alleles that have 1: ,influence in determining
determining traits are
traits are
alleles.
1
FOSS Populations and Ecosyster
0 The Regents of the University c
Can be duplicated for classroom c
.
Zourse
alifornia
vorkshop use.
55
Investigation 9: Genetic Variation
Student Sheet
Answer Key for Genetics Vocabulary Worksheet
1). Nucleus
2). DNA (nucleic acid)
3). Chromosomes
4). Chromosomes
5). Genes
6). Bases (sequence of bases or nucleotides)
7). Genotype
8). Phenotype
9). Dominant
10). Recessive
Answers for picture of cell
First Block: Chromosome
Second Block: Gene
Third Block: Nucleus
Fourth Block: Allele
PRISM UHH GK-12
Genetic Variation
Concepts
Genes are passed on from
one generation to the next
and this is the concept of
heredity. Genes code for
what an organism will
look like and are carried
by chromosomes.
Chromosomes, which
occur in nearly identical
pairs in the nucleus of
every cell, are responsible
for passing on hereditary
information. Depending
on which alleles an
organism has will
determine how the
organism will look and
behave.
Standards addressed
7.5.2, 7.5.3, 7.5.6
Duration
1-2 60 minute class
periods
Vocabulary
Happy-face Spider
Homologous
Phenotype
Genotype
Punnet square
Probability
Homozygous
Heterozygous
Morphs
Source Material
PRISM
Happy-Face Spider Propagation
Summary
Students will act as captive breeders in order to simulate how genes are passed on
from one generation to the next. They will also observe how small differences
accumulate over time to produce descendants that look very different from their
ancestors. Students will use the Happy-face spiders (Theridion grallator), a spider
that is endemic to the Hawaiian Islands and exhibits genetic variation. Spiders on
the island of Maui follow basic Mendelian genetic patterns, so they will be useful
organisms for this lesson. This simulation will help students determine how
genetic information is transferred during breeding, and what the resulting
phenotype (how they look) will be. They will decide which traits are most
important to breed in order for better survival for the spiders. Students will also be
introduced to Punnet squares, which will be used to predict the proportion of
offspring with each trait.
Objectives
• Students will learn about a species that is endemic to Hawaii
• Students will simulate how genes are passed from one generation to the
next.
• Students will act as captive breeders and choose which traits will help the
survival of the spiders.
• Students will use Punnet squares to predict the proportion or frequency of
which genes will be passed on.
Materials
Pictures of Happy-face spiders that show variation in color.
Pink and Blue Card Stock-each group of 2 students should have a total of 12 pink
cards and 12 blue cards. (Size of playing cards). Need one set for use in explaining
concept to students.
Clear transparency to go over Punnet squares
Paper for student Punnet squares.
Hand-out of Happy-face Spider for students to color using their color choice.
Background
Happy-face spiders are found in the rainforests of the Big Island, Oahu, Maui and
Molokai. They are usually found on the underside of leaves. Happy-face spiders
have a pattern on their body that resembles a smiley face. Every spider has a
unique pattern and the body color differs from island to island. Some of the
spiders lack the pattern of the smiley face alltogether. These different morphs
(forms) are caused by the different gene versions carried by the spiders. The
combination of alleles on the homologous chromosomes (similar, paired
chromosomes) which determine a specific trait or characteristic is the organism’s
genotype. The way the information is expressed and how the spider looks is
considered its phenotype. Genotypes and phenotypes of an organism can be
determined with the use of a Punnet square which estimate the probability
(likelihood) of genetic combinations being passed on to potential offspring. A
Punnet square is created by crossing either homozygous (two identical alleles)
alleles, heterozygous alleles (two different alleles) or a combination of both on a
grid.
Researchers believe that the variation of color and pattern in Happy-face Spiders is
a possible type of camouflage against birds, their only significant natural predator.
In order for these spiders to escape predators they must be able to blend into their natural environment. If the
student is to be the captive breeder they must decide what would be the best color for the spider to survive in the
wild.
Teacher Prep for Activity
• Review background reading for Genetic Variation
• Xerox Happy-face Spider Drawing page.
• Cut out cards for the students: a group of two students will have one set of 12 blue cards and one set of
12 pink cards. Be sure to make a set to use as an example when explaining the activity to the students.
Except for the set to be used by the teacher, the other sets of cards should remain blank since the students
will be writing in the color traits that they will be using. These cards could be laminated and used year
after year, if dry erase markers that could be cleaned off were used.
• Have a clear transparency handy to go over the Punnet squares after they have finished the “card game”.
Procedure
1). Split students into groups of two and pass out drawing sheet. One student will act as the MOTHER passing
on traits to its offspring and they will receive 12 blank PINK cards. The other student will act as the FATHER
passing on traits to its offspring and they will receive 12 blank BLUE cards.
2). Before the students start working on the cards, have them draw a Punnet square (more information about
Punnet squares can be found on pg. 257 in the FOSS readings at the back of the lessons) to determine what the
probability of allele combinations will be (this can be done on the back of the drawing page). The students will
have to choose if the dominant parent will be either heterozygous (Ww) or homozygous (WW or ww). They
should work together on creating the Punnet square.
3). Ask the students to determine which color they would like to represent. Remember: this color should be
beneficial for their survival in the wild. If a student chooses fluorescent pink, they will have to explain how this
color would allow the spider to be camouflaged in the rainforest. The mother and the father should be 2 different
colors. For example: Mom=White, Dad=Yellow.
4). Next, ask the students to choose which color is going to be dominant and which is going to be recessive and
assign the correct genotype to the respective trait. Remember: the letter designated must be the same for each
color but must be represented by either a capital letter or lower cased letter. For example, if mom is considered
to be dominant for White, then her genotype would be WW or Ww (students can choose, WW x ww will only
have Ww offspring which will all be the dominant color, white in this case. If more variation is wanted in
offspring, have the dominant parent be Ww, since Ww x ww will have 50% white and 50% yellow) and
eventhough dad is yellow, his recessive genotype would be ww.
5). Ask the students to take a card and write one allele type per card. For example, for mom, each pink card
should have a W written on half (6) the cards and the other half (6) will have a lower-cased w written on them, if
you make mom heterozygous. If mom is homozygous then all her cards will have W on each one. For the blue
cards, for dad, each card should have a lower-cased w written on it, since the gene is recessive he will only be
passing the recessive gene on.
6). Now have the student with the pink cards shuffle their cards and the student with the blue cards shuffle their
cards as well. Then have the students lay all the pink cards out next to each other and below that row of cards,
lay out all the blue cards. Be sure the cards are lined up above and below each other to show how the different
genes line up.
7). Once the cards are laid out, have the students look at the frequency of the combinations of traits. Ask the
students to compare the probabilities of the allele combinations from their Punnet squares (on the back of their
drawing page) to the frequencies created from the cards they made.
Assessments
Journal writing and coloring picture of spider to accompany writing or defense of color choice.
Class presentation on spider color choice
Resources
http://evolution.berkeley.edu/evolibrary/article/_0/happyface_02
Google images-http://images.google.com/
Foss-Populations and Ecosystems
Name: ____________________________
Color the body of the Happy-Face Spider the color that was chosen to breed the spider for survival in the wild.
Use the extra space behind the spider to draw the habitat where this spider can be found.
UHH PRISM
Drawing by: Bobby Hsu
Bobby Hsu
Look under a leaf and find a smiling surprise. But look out, because I like to catch my prey in
a silken trap.
WHO AM I?
Color the numbered spaces to find me.
1 = red
2 = black
3 =-.-.a
fl InR.
S - h L . +C b o ~ 0 3
Unscramble the letters to find out.
1
.
P Y P A H E F A C
D E P I R S
Coloring and Activity Book
.-......- 3565 Harding Avenue Honolulu, Hawai'i 96816
-b-..--..
http://nature.berkeley.edu/~gillespi/re
search.htm
http://nature.berkeley.edu/~gillespi/research.htm
http://nature.berkeley.edu/~gillespi/research.htm
http://nature.berkeley.edu/~gillespi/research.ht
m
http://nature.berkeley.edu/~gillespi/research.htm
In Genetic Variation students learn the basic genetic mechanisms that determine the traits express1
individu
In.
SCIENC
The individuals in evt?rypopu:lation vairy from c~ n eanother in their traits.
Heredity is tlle passin g of info]nation f rom one generation to the next.
. ,.
.
Chromosomes are structures that contaln hereditary information and transfer it to the next generation;
they occur in nearly icientical F)airsin tEte nucleu.s of every cell.
Gentes are thc? basic urlits of he]redity c a:ried
~ by c:hromosabmes. Genes code for features of or$
. .
-~
.~ .
.
.. .
A l l,les
a
are vanations ot genes that d e t e r m e tralts in orgarusms; the two alleles on paired
chrolmosomes constik~ t ae gene.
Alleles can bc2 dominamt or recessive. Dominant alleles exhibit the!ir effect if they arc2 present on one
chromosome; recrsslve alleles exhibit their effect only when they are on both chromosomes.
An organism's particular combination of paired alleles is its genotype; the itraits produced by those
alleles result in the organism's phenotype.
A gene composed of two identical alleles (e.g. both dominant or both recessive) is homozygous; a
gene composed of two different alleles (i.e. one dominant and one recessive) is heterozygous.
. .
....
.
.
CONDUCTING INVESTIGATIONS
Observe vari ation in 1luman tr(aits and 1arkey traits.
Use a simula tion to dt2termine the transfer of genetic information during breeding and the traits that
result.
Use Punnett squares to predict the proportion of offspring that will have certain traits.
BUILDING EXPLANATIONS
Explain how organisms Inherit features and traits from their parents.
Describe how dominant and recessive alleles interact to produce traits in a population.
-
,-
;-,
1
SCIENTIFIC AND HISTORICAL BACKGROUND
I
,
.i
I
In their ecoscenario studies, students were
introduced to two dozen or so key
organisms that interact in a particular
ecosystem. That's quite a few organisms
to keep track of for middle schoolers, but
in fact, the handful of species presented for
study represents only a tiny fraction of the
actual number of species living and
interacting in the most diverse and robust
ecosystems.
Diversity raises questions. How can so
many different populations live in the
the
same ecosystem? And where did
different species come from in the first
place?
; In Investigation 8 students were
introduced to important concepts that get
at the first question. The simple answer is
that all organisms living in an ecosystem
have adaptations that let them get the
resources they need to live and reproduce.
Close analysis reveals that every species
has a unique suite of adaptations. This
ensures that when resources are limited,
every organism will use at least slightly
different resources, in a slightly different
way, at a slightly different time, in a
slightly different place. In this way
organisms keep out of each other's way
and avoid excessive competition for
valuable resources. In a sense an organism
is defined by its adaptations; similarly its
role in the ecosystem is defined by its
adaptations. Organisms that are not
adapted to live in a particular ecosystem
are not found there.
Why there are so many different kinds of
organisms in an ecosystem is one of the
monster questions in biology. Presumably
life started on Earth as one kind (or
possibly several) and over the last 3.5
billion years diverged into hundreds of
millions of different kinds, a small Fraction
of which are living on the planet at this
time. What process could have produced
so many kinds of organisms?
Most biologists concur that the theory of
natural selection provides the answer. The
theory stands on several tenets.
First, there is variation in a population of
organisms. The variation can be the result
of mutations and recombinations in the
genetic code, but these concepts will not
be pursued in this course. Variation in a
population may be the result of
immigration and emigration (gene flow)
or the random change in the frequencies of
alleles (genetic drift). We will accept as a
fact of life that there is variation in the
many features of individual organisms,
and they stem from natural processes.
These variations are traits.
Second, environments are dynamic,
continually presenting new and different
challenges for the organisms living in
them. The environmental change could be
the introduction of a new organism better
adapted to compete for resources, a
change in the climate, a disaster of some
kind, or any number of subtler changes.
An organism that was adapted before the
change in the environment may not be
adapted to cope after the change.
Ecologists call this changed condition a
selective pressure. The change in a very
real way selects the organisms that will
succeed and those that will fail. There is,
of course, no conscious decision to select
this organism and eliminate that one.
If the selective pressure is radical, a whole
population may succumb. If the pressure
is slight or incremental, however, the
pressure may be felt by only some
members of a population. That is to say,
some traits, such as thin fur, pale skin, or
short legs, might preclude an organism
from acquiring resources or reproducing,
so those traits will be selected against in
the population.
Other members of the
- population might continue to survive and
reproduce, perpetuating their traits. In
this way the appearance and/ or behavior
of a population as a whole can change,
sometimes in a relatively short time.
The third factor contributing to natural
selection and the evolution of new species
is isolation. As long as the members of a
population interact and breed, they will
not normally generate a new species. The
population may change over time, but will
not become a new species. If one portion
of a population is separated from the
other, either physically (isolated by
geography) or behaviorally (exploiting
different food sources), creating two
populations, new species may evolve.
When a portion of a population emigrates
or is transported to an island or new
continent, the selective pressures in the
two environments-the originating
environment and the new environmentmay favor different traits. After a period
of time, from decades to scores of
millennia, the two populations may have
diverged to such an extent that, even if
they were reunited, they would continue
to conduct their separate lives, unable to
mate and reproduce.
That's an oversimplified picture of the
origin of species, but in practice the
science of identifying the precise point in
this process when a new species has
arrived is daunting, and even a precise
definition of what constitutes a species is
illusive. We will not enter these deep
waters in this course.
MECHANISMS FOR POPULATION
CHANGE
:.
The key to population change is variation
among the individuals in the population.
In a population of sexually reproducing
organisms, each individual is unique and
therefore has ever-so-slightly different
needs, behaviors, tolerances, and
responses to stimuli from the
environment. When the environment
changes, the makeup of the population
changes in response.
-
What makes each individual unique?
Genes. The genes that direct the assembly
of molecules into organisms are different
for every individual.
1
,
This discussion
applies to organisms
that reproduce
sexually. Organisms
that reproduce by
simple division,
producing two
genetic clone
daughters, follow a
slightly different path
to achieve
population change.
The simple version of genetic transfer of
information goes like this. The story of life
is recorded in huge molecules called
nucleic acids. The specific nucleic acid
that handles the genetic code is DNA
(deoxyribonucleic acid). The long
filaments of DNA
are made of
millions of sugar
and phosphate
units bonded
together, with
organic bases
sticking out to
the side.
Picture a comb.
The sugar /
backbone sports
like tines.
9
The bases sticking out are key
to the structure of DNA. The four bases
are adenine, thymine, guanine, and
cytosine, usually represented by the
symbols A, T, G, and C. The bases can
bond with one another, but only in specific
bonding pairs. A and T can bond with one
another, and C and G can bond, but A
cannot bond with C or G, and so on. Base
pairing is specific, and there are no
exceptions.
The bases on two sugar / phosphate
strands bond and form a double DNA
strand called a double helix. The result is
a long ladder with the bonded bases
forming the rungs.
A typical DNA molecule might be 5 cm
long. To fit in the nucleus of a cell, the
huge molecule is coiled (wound into a
helix) and recoiled into a compact
structure called a chromosome.
Organisms have different numbers of
chromosomes-as few as two to well over
a thousand. Most vertebrates fall into the
20- to 80-chromosome range, and humans
have 46. Toads have 22 chromosomes, and
chickens have 78. Plants and animals that
reproduce sexually generally have an even
number of chromosomes because a set of
chromosomes is made of nearly identical
pairs. In humans, for instance, there are 23
distinctly different chromosomes, and each
of those has an almost identical partner.
The two similar chromoson~esare called
homologues.
Every cell in every plant and animal on
Earth has a complete set of chromosomes
that define the organism. 7'he
chromosomes reside in the cell's nucleus.
Every time a cell divides to produce two
daughter cells, the complete set of
chromosomes is duplicatecl. Each new cell
is provided with a full complement of
DNA-the complete set of blueprints and
operating instructions for irssembling and
managing one particular kind of organism.
The order in which the paired bases are
aligned along the length of the DNA
molecule is all important in decoding the
message to make a new organism. Just like
the 26-letter alphabet can be used to make
untold numbers of words, depending on
their sequence, the four-letter genetic code
can make untold millions of "words,"
depending on the number and sequence of
the bases. The plan for making a
mosquito, tree frog, banana plant, gila
monster, begonia, blue whale, or any other
organism is encoded in the sequence of the
same four bases distributed along the
incredibly long double helix molecule.
,
Organismsthat have
pairs of
chromosomes are
called diploid. Some
organisms have
multiple copies of
similarchr~~oso*es
and are
polyploid. We will
deal only with diploid
organisms in this
and in this
course.
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DETERMINING TRAITS
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Features, characteristics, traits, and
behaviors are determined by genes. Large
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genes.
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When alleles are identical, both forms of
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investigation), one of the alleles dominates
the other and the effect of the dominant
gene is exhibited in the organism. Such an
allele is called a dominant allele, and the
"overruled" allele is the recessive allele.
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THE DISCOVERY OF HEREDITY
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typical of their kind and unique.
There is another important piece to
understanding genes. The homologous
chromosomes (the two that are almost
identical) each have the same genes. So it
would seem that every organism has two
genes for every characteristic. This is not
entirely true because the two genes interact
to produce the characteristic. The two
copies of the gene are called alleles. The
two alleles considered together constitute a
gene.
The homologous chromosomes are usually
identical with regard to gene location, but
are not identical in sequence of bases.
Those differences in DNA structure can
result in two forms of a gene or alleles.
The pioneer work on heredity was
undertaken by the brilliant Gregor
Mendel, son of a Moravian farmer. Young
Mendel demonstrated an aptitude for
academics, but was in no ~ositionto
pursue a university career. In order to
continue his studies Mendel joined an
Augustinian monastery. There he
undertook his detailed inquiry into the
role of heredity in conveying
characteristics from one generation to the
next.
Mendel worked extensively with pea
plants. He started his long series of
experiments by developing a number of
strains of pure breeding stock. He did this
by raising several generations of selffertilized plants. The result was separate
populations of peas that produced clearly
defined and predictable characteristics,
such as tall, short, purple flower, white
flower, smooth seeds, and wrinkled seeds.
Whenever he planted seeds from his
purple-flower stock, for example, all the
experiments. He used pollen from tall
plants to pollinate the flowers on short
plants, and pollen from short plants to
pollinate the flowers on tall plants. What
Mendel discovered was that all of the
offspring were tall. This was confusing to
him.
Undaunted, Mendel collected the seed
from the tall pea plants, which he named
the first filial generation (F1) and planted
them (filial = son or daughter). Some of
the offspring that grew from the F1 seeds
(F2 generation) were tall, and some were
short. Both characteristics were present in
the offspring. The characteristic of height
had not blended to produce all mediumheight plants; the characteristics were
passed along intact, some exhibiting the
tall trait and some the short trait. He
concluded that even though all the F1
seeds came from plants that were tall,
when they grew into mature plants, some
were tall and some were short. Both traits
were present in the offspring, the F2
generation.
Mendel paid close attention to the
numbers of each growth form and
discovered that there were more tall
forms than short forms in the ratio of 3:1,
that is, 75% tall and 25% short.
At this point Mendel made his
revolutionary surmise. He reasoned that
each offspring must get half its
information about height from each
parent. Further, the influence of the
information from the two sources was not
necessarily equal. Mendel knew nothing
constructed a functional model for genetic
heredity without knowing the biochemical
and physical processes that carry the
process forward.
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Tall and short are traits. The parental trait
that appeared exclusively in the F1
generation and prevailed in the F2
generation, Mendel identified as the
dominant trait. The trait that disappeared
in the F1 generation but reappeared in the
F2 generation, he dubbed the recessive
trait. Whenever a seed acquired the
dominant trait from both parents orfrom
just one parent, the dominant trait was
expressed in the plant that grew from that
seed. If the seed acquired the recessive
traitfrom both parents, the recessive trait
was expressed by the plant that grew from
that seed.
Some 150 years after Mendel puzzled out
the probable mechanism for heredity, we
understand that dominant and recessive
traits are transmitted by genes on
chromosomes. When a gene is
represented by two dominant alleles, the
trait is that of the dominant allele (e.g.
purple flowers). Such a condition is called
homozygous (same allele) dominant.
When a gene is represented by two
recessive alleles (homozygous recessive),
the trait is that of the recessive allele (e.g.
white flowers). When a gene is
represented by one dominant allele and
one recessive allele, the organism is
heterozygous (different alleles), and the
trait is that of the dominant allele (e.g.
purple flowers).
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Here is an important point. Where purple
flowers are e h b i t e d as a result of a
heterozygous condition-the combination
of a dominant and a recessive a l l e l e t h e
recessive allele for white flowers is still
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Resources
for
diagrams of mitosis
(cell division to form
two daughter cells)
and meiosis (cell
division to form
During the production of sperm and eggs,
a process called meiosis occurs, the
homologous pairs of chromosomes
separate so that each egg or sperm cell has
only half of the usual number of
chromosomes. The two alleles that make a
gene are, therefore, separated. (Meiosis,
the mechanism for passing just one allele
from the male and one allele from the
female to the offspring, is not explored in
this course, but it is one of the most
important factors in hereditary biology.)
During fertilization, one set of
chromosomes comes from the father
(sperm) and a homologous set comes from
the mother (egg). As the sperm and egg
cells fuse, the two sets of chromosomes
create new homologous pairs of
chromosomes with corresponding alleles.
The new sets of
form genes that are
unique to the offspring.
If two purple-flowered parents are both
heterozygous for flower color, it is possible
that the recessive allele for white flowers
will be passed to the offspring by both
parents. Two purple-flowered parents can
have white-flowered offspring if both
parents had a recessive gene for white
flowers, and each passed it to the
offspring. This will happen, on average, in
one out of every four offspring.
GENOTYPE AND PHENOTYPE
Geneticists refer to the genetic makeup of
an organism as its genotype. F~~
instance, in the example of the two parent
pea plants, the gene for flower color can
be represented by the letter b (bloom). An
uppercase B represents a dominant allele
for purple color, and a lowercase b
represents a recessive allele for white
color. Our two heterozygous parents
would have the following genotype for
flower color:
9
Hb
Bb
The way the genes are expressed in fur,
feather, flesh, and function is an
organism's phenotype. The simplest way
to think of phenotype is how an organism
looks-its traits. Purple flowers, tall
growth form, and wrinkled seeds are
phenotypical traits. An organism's
genotype determines its phenotype.
During sexual reproduction, each parent
contributes one allele to the genotype of
the offspring. The heterozygous flowering
peas .contribute either a B or a b. If either
parent (or both) contributes the dominant
B allele to the offspring, it will have purple
flowers. But there is a chance that both
parents will contribute the recessive b
allele, in which case the offspring will
have white flowers.
PUNNETT SQUARES
years ago ~
~punnett,
~a
*bout
Cambridge professor of genetics,
developed a simple and useful technique
for predicting the characteristics of
offspring when the dominant and
recessive traits of the parents are known.
It is known as the Punnett square. The
square is a grid, with the alleles of one
parent on the top and the alleles of the
other parent on the left. The flower-color
Punnett square looks like this.
The completed Punnett square shows the
four
~ possible
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contributed by these two parents. These
are
possibilities linked with
probability, not absolutes.
One homozygous dominant
Two heterozygous
One homozygous recessive
The heterozygous condition is always
recorded with the dominant allele first,
followed by the recessive allele.
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This Punnett square suggests that there is a
possibility that three out of four offspring
will have purple flowers, and one out of
four will have white flowers.
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It's not always that simple, however. Not
all alleles are wholly dominant or
recessive. Some are partially dominant. In
this case homozygous dominant alleles
will produce one trait, homozygous
recessive alleles will produce a second
trait, and heterozygous alleles will produce
a third trait, often a blend of the two other
traits.
Students are introduced to this when they
work with the feature of fur pattern on
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BLENDED EFFECTS
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Each grid square represents the
combination of two alleles. Transcribe
those two alleles into the squares, like this.
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PRISM UHH GK-12
PRISM UHH GK-12
Hawaiian Origami Birds
Natural Selection
Concepts
In 1859, Charles Darwin
and Aflred Russel
Wallace proposed the
theory of evolution by
natural selection. Their
theory was later combined
with Mendelian
inheritance to explain the
connection of genes (units
of evolution) and natural
selection. This theory has
become the principle
explanation for species
diversity.
Standards addressed
7.5.4, 7.5.6
Duration
1 60 minute class periods
Source Material
w w w.indiana.edu/~ensiw
eb/lessons/origami.html
Vocabulary
Natural Selection
Phenotype
Genotype
Summary
After students have a strong understanding of Adaptations and Genetic
Variation, they will be introduced to Natural Selection. They will participate in
a natural selection simulation in which they will create and modify “paper
airplanes” over several generations to visualize how favorable heritable traits are
passed on. These paper airplanes represent wild birds of a population.
Objectives
• Students will simulate how genes are passed from one generation to the
next.
• Students will understand how traits that are favorable for survival
become more common over generations.
• Students will know that both genetic variation and environmental factors
causes of evolution and species diversity.
Materials
Paper
Ruler
Tape
Straws
Scissors
Coin
Six-sided die
Background
The Hawaiian Origami Bird (Aves hawaiiensis) lives on the rugged coastline of
Hawaii Island. It feeds on Opae'ula (Halocaridina rubra) which are found in
anchialine ponds around the island. Due to high development of the coastline on
the island, alchialine pools are decreasing and becoming less common. Only
birds that can successfully fly the long distances in search of Opae'ula will live
long enough to breed successfully. This simulation will allow students to breed
several generations of the Hawaiian Origami Bird to see how phenotypes and
genotypes are affected over time.
Biological evolution, which is the gradual change to a population of species over
many generations, is the process responsible for the diversity of species. Natural
selection is the process by which favorable traits that are passed on over
generations become more common in a population of reproducing organisms.
Natural selection is also responsible for how unfavorable traits (not conducive
for survival) become less common in the population. This process acts upon the
phenotype or the morphological characteristics of an organism. Organisms that
have favorable phenotypes that allow them to survive and reproduce in the wild
are more likely to survive than organisms that have unfavorable phenotypes.
If the phenotype is based on genetics, then the genotype associated with that
favorable phenotype will increase in frequency in the next generation and
generations to follow. Natural selection also acts upon populations, not
individuals alone. The changes to the phenotype and genotype must affect the
entire populations of organisms, not just select individuals of the population.
Teacher Prep for Activity
• Prior to this lesson, the teacher can cut the paper into different sized strips. Be sure to make many strips of
each size (they will vary from the original size of 3 cm x 20 cm). The width and circumference of the
strips will increase or decrease by 1-2 cm after each generation.
• Xerox Origami Data Sheets
• The procedure section can be Xeroxed and handed out or the diagrams can be written on the board.
Procedure
1). Split students into groups of two. Each student will prepare an ancestral bird: Cut two strips of paper, each 3
cm x 20 cm. Loop one strip of paper with a 1 cm overlap and tape. Repeat for the other strip. Tape each loop 3
cm from the edge of the straw.
2). Breed offspring. Each Origami Bird lays a clutch of three eggs.
Record the dimensions of each chick and hatch the birds using these instructions:
a. The first egg has no mutations. It is a clone of the parent, this measurement will be the same as the ancestral
bird. In the interest of time you may substitute the parent when testing this chick.
b. The other two chicks have mutations.
For each chick, flip your coin and throw your die then record the results on the table.
i.) The coin flip determines where the mutation occurs: the head end or tail end of the animal.
ii). The die throw determines how the mutations affect the wing:
After you have determined where the mutation occurs, cut new strips of paper and re-build another bird with the
new measurements. You can use the strips from the original bird if able.
iii). Lethal mutations:
A mutation which results in a wing falling off of the straw, or in which the circumference
of .the wing kujkjkjkjkjkjkjkj
is smaller than the circumference of the straw, etc. is lethal. Fortunately,
Aves hawaiiensis birds are known to “double clutch” when an egg is lost. If you should get a
lethal mutation, disregard it and breed another chick.
3). Test the birds:
Release the birds with a gentle, overhand pitch. It is important to release the birds as uniformly as possible.
Test each bird twice.
4). The most successful bird is the one that can fly the farthest.
Mark which chick was the most successful on the tally sheet provided.
5). The most successful bird is the sole parent of the next generation. Use the measurements from this bird to be the
parent of the next generation. The following generation will be continuing to breed, test, and record data for as many
generations as you can in the time allotted. Use the table to record the results of your coin flips and die throws, the
dimensions of all chicks, and the most successful bird in each generation.
Extensions and assessment
You can use the following questions for discussion of the topic. These can either be turned in for credit or can be
discussed during the next class period.
1. Did your experiment result in better flying birds?
2. Evolution is the result of two processes: variation and selection.
a. How did your experiment produce variation among the offspring?
b. How did your experiment select offspring to breed the next generation?
3. Compare your youngest bird with your neighbor’s youngest bird.
a. Compare and contrast the wings of of other birds with your own.
b. Explain why some aspects of the birds are similar.
c Explain why some aspects of the birds are different.
4. Predict the appearance of your youngest bird’s descendants if:
a. the selection conditions remain the same and the longest flying bird survives to produce the
most .offspring.
b. the selection conditions change the worst flying bird survives to produce the most
offspring.
c. the selection conditions change and the bird whose color blends with its environment
survives to .produce the most offspring.
5. Predict how the Aves hawaiiensis might adapt after the alchialine pools have disappeared from over development?
Name ___________________
Date _____________________
Origami Bird Data Sheet
Flip coin, throw die, record results. Plan the baby chicks, record their dimensions,
breed the chicks.
GENERATION 0:
No Mutation
3 x 20 3 x 20
_kk
Head k
COIN
_________x _________
Tail
Head
DIE
3 cm
COIN
x
Tail
Head
DIE
3 cm
Mark the winning bird. Only the most successful bird becomes a parent of the next
generation. The “no mutation” chick in the next generation is identical to the
winning bird in the immediately preceding generation. Continue to flip and throw,
plan chicks, breed them, and test them for more generations.
Tail
PRISM UHH GK-12
Exploring the Ohia Common Garden
Natural Selection
Concepts
Changes to the
environment may affect
how an organism may
survive in the wild.
Occasionally, organisms
have the ability to activate
different phenotypes in
response to its changing
surroundings. This lesson
uses an endemic Hawaiian
tree species, Ohia, to show
how this species changes
its phenotype in response
to different habitat
requirements.
Standards addressed
7.5.4, 7.5.6
Duration
1 full day for field trip
Vocabulary
Natural selection
Phenotype
Genotype
Glabrous
Pubescent
Phenotypic plasticity
Source Material
PRISM
Summary
After students have a strong understanding of Adaptations and Genetic Variation,
they will be introduced to Natural Selection. They will visit the Ohia Common
Garden in Volcano, Hawaii to see how Ohia (Metrosideros polymorpha) from
different elevations have morphological differences.
Objectives
• Students will simulate how genes are passed from one generation to the
next.
• Students will understand how traits that are favorable for survival become
more common over generations.
• Students will know that both genetic variation and environmental factors
causes of evolution and species diversity.
Materials
Background information about Ohia to lecture students before visiting garden
Permission to visit the garden
Dr. Elizabeth Stacy-can give presentation at garden about Ohia
Background
Biological evolution, which is the gradual change to a population of species over
many generations, is the process responsible for the diversity of species. Natural
selection is the process by which favorable traits that are passed on over
generations become more common in a population of reproducing organisms.
Natural selection is also responsible for how unfavorable traits (not conducive for
survival) become less common in the population. This process acts upon the
phenotype or the morphological characteristics of an organism. Organisms that
have favorable phenotypes that allow them to survive and reproduce in the wild
are more likely to survive than organisms that have unfavorable phenotypes.
If the phenotype is based on genetics, then the genotype associated with that
favorable phenotype will increase in frequency in the next generation and
generations to follow. Natural selection also acts upon populations, not
individuals alone. The changes to the phenotype and genotype must affect the
entire populations of organisms, not just select individuals of the population.
Ohia lehua (Metrosideros polymorpha) is a Hawaiian endemic plant found in
almost all Hawaiian ecosystems. It is present on all Hawaiian islands, except
Niihau and Kahoolawe. Ohia is an extremely variable plant that ranges in
elevation from sea level to approximately 7000 feet. In order for Ohia to survive
and reproduce at such drastic environments, species at different elevations have
morphological differences. Ohia found at low elevations have larger, glabrous
(smooth with no hair) leaves while ohia at high elevations have smaller,
pubescent (with short fuzzy hair) leaves. One reason ohia at high elevations have
smaller, fuzzy leaves is because they are closer to the sun and the fuzzy hair might
protect the leaves from cold temperatures. Lower elevation Ohia are further from
the sun and need a larger surface area to collect more sunlight and they are without
fuzzy hair because they live at warmer temperatures. Ohia have a given
phenotype, but also have the ability to change its phenotype in response to
environmental changes. This phenomena is called phenotypic plasticity.
Teacher Prep for Activity
Weeks prior to the field trip, Dr. Elizabeth Stacy at the University of Hawaii, Hilo must be contacted for access
into the common garden. Dr. Stacy could possibly be available to meet with the students to discuss Ohia and
natural selection also. Her contact information is: Elizabeth Stacy, Assistant Professor Department of
Biology, University of Hawaii 200 West Kawili Street Hilo, Hawaii 96720, Email: [email protected]. Please
give yourself many weeks to months in advance to plan this field trip.
Procedure
After finalizing the plans to visit the Ohia common garden, give the students some background information on
Ohia before visiting the garden.
At the garden, Dr. Stacy will talk about Ohia and its morphological differences. After the lecture, students will be
split into groups and be asked to examine the different trees at the garden. They will be asked to collect a single
leaf from a tree from high elevation, mid elevation and low elevation. After they have collected their leaves, they
will be asked to explain why they think the leaves they collected belong to their respective habitats. After the field
trip is completed, have the students write a reflection about their trip to the garden. They could also be asked to
research another organism that displays phenotypic plasticity.
Assessment
Journal writing
Written report of another organism that displays phenotypic plasticity.
Extensions
If the class is unable to visit the common garden or a project extension is needed, a possible class simulation of
this exercise would be to grow tomato plants. Before growing the plants, ask the students if they think tomato
plants (with the same genotype) grown in sunlight would look different from tomato plants grown without
sunlight. Have them write down their predictions. Plant several plants in pots and place half the plants in direct
sunlight and place the other half in the classroom, away from any light. Water and feed both sets of plants the
same way. The plants grown in direct sunlight should grow upright, reaching for the sun while the plants grown
inside should grow low, creeping along searching for sunlight. This simulation shows that different environmental
factors can affect how an organism survives.
NATURAL SI
GOAL
Natural Selection introduces students to natural selection as the mechanism that produces change in the
genetic makeup of a population.
OBJECTIVES
SCIENCE CONTENT
Environmental factors put selective pressure on populations.
Natural seletion is the process by which the individuals best adapted to their environment tend to
survive and pass their traits to subsequent generations.
Members of a species are all the same kind of organisms and are different from all other kinds of
organisms.
CONDUCTING INVESTIGATIONS
Use a game simulation to experience change in a population, resulting from selective pressure.
Record and process information presented in a video about natural selection.
Use a multimedia simulation to explore the effects of natural selection on a population.
BUILDING EXPLANATIONS
Describe how selective pressure can affect the genetic makeup of a population.
Explain how the traits expressed by the members of a population can change naturally over time.
SCIENTIFIC AND HISTORICAL BACKGROUND
It m a y be said that natural selection is daily
and hourly scrutinizing throughout the world,
every variation, even the slightest; rejecting
that which is bad, preserving and adding u p all
that is good; silently and insensibly working,
whenever and wherever opportunity offers, at
the improver~entofeach organic being i n
relation to its organic and inorganic conditions
of lqe.
-Charles
Darwin
In 1831,22-year-old Charles Darwin
embarked on a 5-year voyage of discovery
as resident naturalist aboard the survey
ship Beagle. The impact of the incredibly
diverse and complex biota he encountered
in South America revolutionized his
perception of life on Earth. During the
voyage and the years following, Darwin
formulated a theory explaining the
uniqueness and origin of the organisms he
discovered. It was many years, however,
before he finally published his famous
book, O n the Origin of Species by Means of
Natural Selection, in 1859.
Darwin anguished over his manuscript.
He was diligent in his science, wanting
solid sources of evidence for his
sveculative ideas. But even when the
theory was clearly described and
supported to h s satisfaction, he feared the
societal response to his propositions. The
assumed affront to God, excused from the
role of creator of all nature, and the
reduced status of humanity, dismissed
from the pinnacle of creation, troubled
Darwin. But when he found out that
Alfred Wallace had reached essentially the
same conclusions about natural selection
and was preparing to publish his work,
I
Darwin brought his book to print. The
ideas disseminated quickly throughout the
scientific community, and in their wake a
new understanding of the progression of
life emerged.
NATURAL SELECTION
The idea is simple, really, and is
constructed on some fundamental
assumptions that have since been shown
to be sound.
Nature Produces Variation. During the
process of reproduction, random changes
occur in the genetic information directing
the manufacture of a new unit-an
offspring. Extreme changes are usually
lethal, and no offspring result. Those
genetic miscues are not perpetuated.
Modest changes translate into often subtle
and sometimes dramatic differences in
individuals. Individual offspring turn out
to be unique; one perhaps a little larger,
another more aggressive, and still others
darker in color, slower to respond, having
larger fins or wider teeth, on and on. The
result is variation in populations.
Life Is a Challenge. Many factors
converge to prevent organisms from
enjoying a peaceful, relaxed, successful
existence. The physical environment can
be harsh, and is often variable. Weather
and catastrophe put pressure on
organisms that can stress, weaken, and kill
them. At the same time, nature produces
many more organisms than can be
supported by the environment.
Organisms that are not adapted to
withstand environmental pressures are
doomed to fail.
Biotic factors put pressure on organisms.
Heterotrophc organisms eat other
organisms for energy and building blocks.
Organisms that fail to acquire food die.
On the other side of that equation,
organisms that are taken for food also die.
Microbes sometimes invade organisms,
causing disease. Life is always under
pressure.
Organisms in a Population Compete.
Every species has a niche in which it lives
and acquires the resources it needs for
survival. The problem is, all the other
members of an organism's species are
trying to make a living in that niche as
well. This creates competition among
members of a population for access to
limited resources. If resources are not
limited, members of the population could
coexist without complications. Those
individuals that succeed in getting
resources and that successfully reproduce
pass their genes to the next generation.
The measure of the success of an
individual organism is whether or not it
survives and reproduces. The traits that
prepared a successful organism to
complete its destiny are passed to the next
generation. Traits that resulted in
successful reproduction by their parents
are, in all likelihood, the traits that will
increase the offspring's chances of
reproducing. Successful individuals pass
the tools of success to their offspring.
As discussed earlier, however, the
perversity of the physical environment
and the pressures imposed by the biotic
community don't allow for the idea of a
perfect organism, ideally equipped to
survive. Survival has to happen in a
dynamic environment, so perfection is a
The measure of the success of a population
is its ability to withstand change in the
environment and to prevail. Nature's
hedge against complete disaster imposed
by disease, drought, or hoards of predators
is variation. When a new pressure is
imposed on a population, some
individuals may succumb. But some will
likely have adaptations that allow them to
survive and reproduce more offspring
than other individuals of that species. In
this way the population continues, but
changes.
Darwin did not have the benefit of
understanding the fundamentals of
genetics, although it was well accepted
that organisms passed the code for making
reasonably accurate reproductions of
themselves from generation to generation
through sexual processes. He was able to
observe firsthand the variation within a
population, particularly when he observed
the finches on the Galfipagos Islands. The
puzzle that Darwin pursued was how the
countless kinds of organisms came into
being. What forces created a new kind of
organism? What was the origin of species?
If a population existed in a constant,
supportive environment, natural processes
would produce variation in the
population, and the individuals would all
have reasonable chances of survival. The
success of a varied population would
perpetuate a varied population.
Pressure on the population might favor
some individuals over others because the
variations represent different adaptations,
and different adaptations affect the
potential for survival. So selective
pressure on a population will favor some
individuals, which will reproduce,
influencing the distribution of traits in the
individuals. The population changes in
response to selective pressure. (Notice,
individuals don't change in response to
selective pressure; they only survive or die.
Populations change depending on the
characteristics of the survivors.)
Over time a population may change
sufficiently for science to judge it to be a
different kind of organism than it was
before the selective pressure was brought
to bear on the original population. How
long does that take? And how different
does the "new" population have to be to
be deemed a new species?
It isn't easy to answer these questions. A
new species may emerge in an extremely
short time-a matter of days or weeks in
the case of bacteria. Or it may take
millions and millions of years for a
successful species like the white shark or
horseshoe crab to change enough to be
considered a new species.
Darwin observed the finches on the
GalApagos Islands. The 20 or so islands
are situated about 1000 km west of
Ecuador. The current islands range in age
from about 700,000 to 4 million years, but
scientists suggest that there may have been
other islands or sea mounts in the area as
long as 10 million years ago. The point is
that the GalApagos Islands are young, and
any terrestrial life had to make its way
there across the open sea or through the
air.
Some time ago a single finch species
arrived on the islands. Perhaps a small
flock was blown off course in a storm. The
birds apparently had no competitors for
resources, and they thrived. As time
passed, variation entered the population.
The most conspicuous variation was the
beak. Different subgroups within the
population were better adapted to exploit
different food sources. We can imagine
that the members of the population that
sought similar food sources would
associate, and other groups that shared
different traits would associate. Feeding
behavior isolated subgroups within the
larger population. Breeding among the
subgroup reinforced the trait that isolated
it in the first place, further separating the
subgroup.
Variation within the subgroup might have
produced other traits that also tended to
isolate the subgroup, perhaps coloration,
size, nesting habits, mating rituals, and so
forth. In time, isolation and change in
response to pressures from the
environment produced a new subspecies.
The exact time at which a splinter group is
awarded the status of species is a subject
for scientific debate. There are few
absolutes for defining a species, so the
moment at which it happens is nebulous.
Darwin concluded that speciation was a
natural outcome of ongoing life processes:
(genetic) variation in a population,
selective pressure in the environment, and
isolation of a segment of the population.
Darwin's momentous discovery is often
summarized as "survival of the fittest."
This creates a mental image of a ferocious
battle for survival, with the biggest,
strongest, most voracious individuals
always surviving to continue their kind.
This is not an accurate picture. Fittest
doesn't necessarily mean the individual in
the best condition or the one with the
biggest teeth and strongest bones. It
means the individual with the best
adaptations to survive the pressure being
imposed by the environment. Fittest
simply means the best equipped to
survive and reproduce.
Who or what determines fitness? The
selective pressure in the environment. The
pressure might come from the weather. A
return of the ice ages will select for those
individuals with adaptations for surviving
cold and select against those without
adaptations for cold. A new predator that
climbs trees will select for those treedwelling individuals that can flee or
defend against the predator, and select
against those that have no defensive
adaptations. A drought that reduces the
acorn crop may select for the smaller
members of a population that can survive
on less food and select against those that
require more food. The result of natural
selection is that the genetic makeup, and
therefore the suite of traits expressed by
the population, is constantly changing.
The change process in organisms is called
evolution. Organisms can be thought of
as work in progress; they are constantly
evolving from something into something
else.
If you follow the evolutionary process
back in time, perhaps 3.5 billion years or
so, logically you eventually arrive at the
first living organisms on Earth.
Remember, life is the Olympic flame that
burns in every organism. The flame is
handed from one organism to the next. If
it goes out, it cannot be rekindled. Life
has only one chance to carry the torch, and
every organism guards it tenaciously as
long as it can. So every organism alive
today has received the precious fire
through millions and millions of handoffs
without a fumble.
The processes of variation, natural
selection, and isolation have produced an
amazing array of organisms. There are
millions of species alive on Earth today,
and for each one there were at least a
hundred species that are now extinct. The
process of evolution has produced a
continuous parade of new species, each
adapted to the specific environments in
which it lived, and continues to do so
today.
ARTIFICIAL SELECTION
A discussion of artificial selection might
shed light on the selection process. We
humans have one adaptation (thanks to
natural selection) that makes us a
formidable organism to deal with-an
advanced brain. We can control our
environment to an unprecedented degree.
As a result we can manage food resources,
create shelter, manipulate energy, control
other organisms, and re-create the world
we live in.
One human enterprise is manipulating the
traits of organisms through artificial
selection. Think about the domestic dog.
Every breed From the skinny, shivering
Chihuahua to the robust, barrel-toting St.
Bernard, and all the retrievers, hounds,
terriers, poodles, spaniels, bulldogs, collies,
and Pomeranians in-between are the same
species. Where did all the diversity come
from? Variation, selection, and isolation.
Let's say you wanted to have a dog to
catch squid for you. Where would you get
such a dog? Because there is no such dog,
you would have to breed one. Squid live
in the water, so you need a dog that is
enthusiastic about water and swims well.
A retriever or a spaniel would be a good
breed to start with. So you get a bunch of
retrievers and spaniels and show them a
squid. Toss the squid in the water and see
whch dogs jump in to grab it. Of the
original subset of water-loving dogs, only
a few will pass the "goes for squid" test.
Breed the squidophiles and raise the pups.
Test them for squidophilia. Breed the most
promising of those.
Take the best squidders out in a boat and
see how good they are at spotting a squid
in the water. Breed those with the best
night vision. What's the best color (maybe
black) and hair length (shorter the better).
Identify those sharp-eyed squidophiles
that have the darkest, shortest fur. The
animals that have the traits that fit your
needs are the ones that you allow to
reproduce to get more offspring with their
traits.
After many generations of selective
breeding you produce a squid hound,
equal to the task you want it to perform.
And if you find you are not completely
satisfied with the dog's performance in the
future (maybe the breed shakes after
getting back into the boat after snaring a
squid), you can always continue to tinker
with the traits to make it "better" by
breeding members of the isolated
population that have the desirable trait, in
this case, stand and drip.
There is danger in this process. By
isolating a small population, you
significantly reduce the diversity in the
gene pool. If a genetic weakness, such as a
tendency to bite, kidney disease, joint
dysfunction, or shvering, shows up as a
trait in the breed, it may be difficult or
impossible to breed it out without losing
the traits you selected for in the first place.
A reduced gene pool caused by inbreeding
often introduces vulnerability and
weakness into the breed, due to lack of
variation.
Artificial selection has been used for years
to develop disease-resistant strains of
grains, higher-yielding corn, fastermaturing soybeans, square tomatoes,
seedless watermelons, and hundreds of
other agricultural plants. And, of course,
horses and livestock are selectively bred
for a variety of functions and products,
and the celebrated silk moth and the large
and exotic goldfish called koi have been
selectively bred for centuries to produce
the living products we see today.
Nahire does the same, but without
purpose, allowing some individuals with
the right stuff to produce more offspring
than others in the population. But in
nature, the selection is based on passing a
test, not possessing arbitrarily desirable
traits. And the "right stuff" is having the
traits that better prepare the offspring to
survive and reproduce, not measuring up
to a set of predetermined criteria.
You've heard the lament, "Just when I
learned the answers, they changed all the
questions." That's the way it goes out
there in the biosphere--every time an
organism "gets it right," the environment
changes the test, so the winner yesterday
may not have the right stuff to win today.
That's natural selection, and that's what
keeps life evolvkg on Earth.
WHY DO I HAVE TO LEARN THIS?
This investigation presents some sensitive
issues. The ideas of natural selection and
evolution of life on Earth can bring
scientific historical evidence and the very
essence of scientific inquiry into conflict
with deeply held beliefs concerning the
sacred origins of life. Both points of view
seek to answer the same questions, in a
and where did I
way: How did I get
come from?
Evolutionary biologists study the scientific
evidence provided by the inventory of
living organisms, and piece together the
fragments of life's prehstory, to synthesize
a credible story for the emergence and
progressive redesign of life on Earth.
According to the biologst, the 3.5-billionyear ongoing experiment has produced
Homo sapiens and the several millions of
other species living on Earth today. And
the biologist suggests that, just as it has
from the beginning, the description,
distribution, and diversity of life on Earth
today is a snapshot of a work in progress.
The evolutionary processes will continue
to reshape the image of life on Earth
indefinitely. We are here now simply as a
result of chance and natural selection, just
like every other living thng.
T h s course introduces students to the
scientific explanation for the origin of
species and, in the process, lays the
groundwork for answering the questions
of how I got here and where I came from.
It is not the intent of this course to
disparage the belief system of students.
Rather, we present the science ideas and
encourage students to engage them and
incorporate them into their growing
catalog of shared human knowledge.
For a full discussion of the issues
associated with the teaching of natural
selection, biological evolution, and the
origin of species, obtain this book or
browse it on-line: Teaching about Evolution
and the Nalure of Science. Details are in the
References chapter.