Download Environment Pt 2

Unit: Evolution and
Classification
Objectives:
1. Define and describe natural selection.
2. Explain how adaptations and genetic changes lead to
speciation over time.
2/15 Bell Work
Rearrange the letters in the phrase below to discover what
they detect.
the detectives
2/15 Schedule
 Grade sheets and letters home due THURSDAY
 Notes Online Evolution Pt 2
 Finish Notes Ch 16.3 -17.1 “Genetic Variation”
 Answer the two “Mutations Brainstorm” questions at the
end in your notebook.
Assignments:
1. Dir Rdg Ch 16 “Evolution” due THURSDAY
2. Natural Selection Simulation – LATE
3. Signed Letter and Grade Sheet – THURSDAY
4. Dir Rdg Ch 17 “Genetic Variation - TBA
Studying Evolution at All
Scales
Patterns of Macroevolution
 Gradualism
Many small changes to build up gradually over a long
period of time.
Gradualism
Studying Evolution at All
Scales
Patterns of Macroevolution
 Punctuated Equilibrium
Species may remain stable for long periods until the
environment changes. Then, many new species may
“suddenly” appear.
Punctuated
Equilibrium
Ch 17.1 “Genetic
Variation”
Objectives
1. Describe how microevolution is studied.
2. Describe how phenotypic variation, genetic variation,
and genetic change are measured.
1. Review where phenotypic variation originates.
Breeding “Improved”
Goats
Imagine that you are in charge of a goat ranch. The cost of
fencing is really high, so you must implement a breeding
program that will produce shorter-legged goats within the
next 20 years. Write down how you would meet this goal.
Population Genetics
Microevolution : evolution of populations at the genetic level
 Studying changes in numbers and types of alleles is
population genetics.
Phenotype Variation and
Change
Gene Pools: particular combination of alleles in a
population at any one point in time.
 Variation and change are measured in terms of the
frequency of alleles.
 A frequency is the proportion of a group that is of one type,
can be tracked over time.
Phenotypic Variation
Phenotype variation: traits have a variety of “looks”
Depends on how many genes affect it, and the type of
dominance.
 1 gene “R” and “r”
 Complete dominance = Red flowers and white flowers
 Codominnce = Red and white spotted flowers
 Incomplete dominance = Red flowers, pink flowers, and
white flowers
Phenotypic Variation
Pheotype variation: traits have a variety of “looks”
 Polygenic characters are influenced by several genes.
Examples include human eye color and height.
 Study by measuring each individual and then analyzing
the distribution.
Phenotype Variation
 Examples
Phenotypic Variation
 A distribution is an overview of the relative frequency and
range of a set of values.
 A normal distribution, or bell curve, is one that tends to
cluster around an average value in the center of the
range.
Genotype Frequencies Vs.
Allele Frequencies
Sources of Genetic
Variation
Evolution cannot proceed with no variation. The major
source of new alleles is mutation in germ cells.
 New alleles appear slowly.
 Only mutations in egg and sperm are passed on to
offspring.
Mutation Brainstorm
Put these in your notebook.
1. Give an example of a beneficial and a harmful mutation.
2. Discuss how the two mutations would most likely be
affected by natural selection.
2/16 Bell Work
A professional fisherman caught 30 fish during a 5 day
tournament. Each day, he caught 3 more fish than the day
before.
 How many fish did he catch on the first day?
2/16 Schedule
 Grade sheets and letters home?
 Check “Mutations Brainstorm” questions.
 Notes Ch 17.2 “Genetic Change”
Assignments:
1. Dir Rdg Ch 16 “Evolution” due TODAY
2. Natural Selection Simulation – LATE
3. Signed Letter and Grade Sheet – TODAY
4. Dir Rdg Ch 17 “Genetic Variation - TBA
Ch 17.2 “Genetic
Change”
Objectives
1. Describe the the Hardy-Weinberg principle.
2. Explain how sexual reproduction effects evolution.
3. Identify the importance of population size on survival.
4. Describe the limits and patterns of natural selection.
Equilibrium and Change
Stability vs Change
 Genetic equilibrium: no genetic change
 Changes can be measured in genotype or allele
frequency
Equilibrium
Equilibrium
Change
Equilibrium and Change
Hardy-Weinberg Principle
 Predicts frequencies of alleles and genotypes will not
change unless at least one of five forces acts.





gene flow
nonrandom mating
genetic drift
mutation
natural selection
Equilibrium and Change
Gene Flow
 Gene flow occurs when genes are added
to or removed from a population.
 Can be caused by migration.
Nonrandom Mating
 Limits or preferences of mates
Equilibrium and Change
Genetic Drift
 Chance events can cause rare alleles to be lost, especially
when populations are small.
Mutation
 Mutation can add a new allele to a population.
Equilibrium and Change
Natural Selection
 Natural selection acts to eliminate individuals with certain
traits and their alleles become less common.
Sexual Reproduction &
Evolution
Benefits of Sexual Reproduction in Evolution
 Creates chances to recombine alleles and increase
variation.
 Mating patterns or behaviors can influence the gene pool.
 Females sometimes select mates based on the male’s size, color,
ability to gather food, etc.
birds of paradise
Sexual Reproduction &
Evolution
Influencing the Gene Pool
 Inbreeding: individuals either self-fertilize or mate with
others like themselves.
 Inbreeding is more likely if a population is small because
all members are likely to be closely related.
European royal families often
suffer from hemophilia.
Poodles are prone to seizures.
Population Size and
Evolution
Population Size
 Strongly affects the probability of genetic change.
 Allele frequencies are more likely to remain stable in
large populations than small.
Natural Selection and
Evolution
How Selection Acts
 Natural selection causes evolution by acting on individual
survival.
 Less “fit” individuals are less likely to pass on their
genes.
2/21 Bell Work
A cow is tied to a post in the middle of a field with a 14 ft
rope. Assume it eats 100 ft2 of grass a day.
 How many days will the cow have enough to eat?
 Hint: Need circle area formula
2/21 Schedule
 Notes Ch 17.2 “Genetic Change”
 Hardy-Weinberg Worksheet - THURSDAY
Assignments:
1. Dir Rdg Ch 16 “Evolution” LATE
2. Signed Letter and Grade Sheet – LATE
3. Dir Rdg Ch 17 “Genetic Variation – TBA
4. Hardy-Weinberg Worksheet - THURSDAY
Natural Selection and
Evolution
Results of Selection
 The result of natural selection is that each allele’s
frequency may increase or decrease depending on the
effects on survival and reproduction.
 The ENVIRONMENT does the selection.
Natural Selection and
Evolution
Natural selection is indirect
 It acts only to change the relative frequency of alleles that
exist in a population.
 It acts on genotypes by removing unsuccessful phenotypes
from a population.
Hardy-Weinberg Equation
The H-W Equation can predict frequency of alleles and
genotypes.
 Allele Frequency: p + q = 1
 Genotype Frequency:
Hardy-Weinberg Equation
Albinism is a rare homozygous recessive trait.(aa). The
characteristic symptom is a lack of pigment. The average human
frequency of albinism in North America is only about 1 in 20,000.
 The frequency of homozygous recessive individuals (aa) in a
population is q². Therefore the allele frequency is…
 q² = 1/20,000 = .00005
 q = .007 or 1 in 140 people
 Therefore the dominant allele frequency is…
 p=1–q

p = 1 - .007 p = .993
Hardy-Weinberg Practice
Rabbits can be brown or white which is recessive. The
frequency of the BB genotype is .35.
 What is the frequency of the B allele?
 What are the chances any individual rabbit is
heterozygous?
Patterns of Natural
Selection
Three major patterns affect the distribution of polygenic
characters over time.
 These patterns are:
 directional selection
 stabilizing selection
 disruptive selection
Patterns of Natural
Selection, continued
Directional Selection
 In directional selection, the “peak” of a normal
distribution moves in one direction along its range.
 Eliminated one extreme phenotype, making them less
common.
Patterns of Natural
Selection, continued
Stabilizing Selection
 In stabilizing selection, the bell-curve shape becomes
narrower. Both extreme phenotypes eliminated.
 Not very common in nature.
Patterns of Natural
Selection, continued
Disruptive Selection
 In disruptive selection, the bell curve is “disrupted” and
pushed apart into two peaks.
 Average phenotype eliminated.
Kinds of Selection
2/22 Bell Work
 Solve the word puzzles.
2/22 Schedule
 QL: Alleles due TODAY
 Work time
 Hardy-Weinberg Worksheet – THURSDAY
 Dir Rdg Ch 17 - TBA
Assignments:
1. Dir Rdg Ch 17 “Genetic Variation – TBA
2. QL: Alleles - TODAY
3. Hardy-Weinberg Worksheet - THURSDAY
QL: Alleles the Next
Generation
 Collect class data, lab sheet as desk groups.
 Everyone gets 2 blocks.
 Purple (P) is dominant to white (p)
 Without looking, pass one of your blocks to someone else
every generation. RANDOM “MATING”!
 Keep track of genotypes and phenotypes for 5 generations.
 Answer questions and keep for tomorrow.
2/23 Bell Work
 Solve the word puzzles.
2/23 Schedule
 Notes Ch 17.3 “Speciation”
 Start Genetic Drift Lab
Assignments:
1. Dir Rdg Ch 17 “Genetic Variation – MONDAY
2. QL: Alleles - LATE
3. Hardy-Weinberg Worksheet - TODAY
Hardy-Weinberg Practice
There are 100 students in a class. Ninety-six did well in the
course whereas four blew it totally and received a grade of F.
Sorry. In the highly unlikely event that these traits are
genetic rather than environmental, if these traits involve
dominant and recessive alleles, and if the four (4%)
represent the frequency of the homozygous recessive
condition, please calculate the following:
A. The frequency of the recessive allele.
B. The frequency of the dominant allele.
C. The frequency of heterozygous individuals.
Ch 17.3 “Speciation”
Objectives
 Define species and speciation.
 Explain why studying extinction is important in
understanding evolution.
Species?
Describe differences that let you distinguish between dogs
and cats.
Defining Species
Multiple Definitions for Species
1. Species: group of natural populations that can
interbreed and usually produce fertile offspring
 based on the biological species concept.
Defining Species
Multiple Definitions for Species
 Other definitions may be used for fossils or asexual
organisms.
 Useful characteristics:
 physical features
 ecological roles
 genetic relatedness.
Forming New Species
Divergence
 Each population of a species lives in a different place.
 Offspring that are adapted to each.
 Eventually can lead to the formation of new subspecies
and then species.
Forming New Species
Speciation: forming new species by evolution from
preexisting.
 Evolutionary forces result in a population that has
unique features and is reproductively isolated.
 Reproductive isolation: two populations can no longer
interbreed to produce future offspring.
Forming New Species
Mechanisms of Isolation
 Any of the following mechanisms may contribute to the
reproductive isolation of populations:
 Geography
 Ecological Niche
 Mating Behavior and Timing
 Polyploidy
 Hybridization
Red wolves are grey wolf-coyote
hybrids.
Extinction: The End of
Species
Extinction: a species fails to produce any more descendants.
 More than 99% of all of the species that have ever lived
become extinct.
1. Tasmanian wolf
2. Dodo bird
3. Yangtze River
Dolphin
Extinction: The End of
Species
 Many cases of extinction are the result of environmental
change.
 If a species cannot adapt fast enough to changes, the
species may be driven to extinction.
Genetic Drift Lab
How does population size affect the alleles?
 Gen 1 Allele Ratio: 2 A: 2B: 1i
 Use populations of 5, 10, and 20… how many alleles
from each “person”? ________________
 Model 4 generations in each population group.
 Generation 2-4 use the “gene pool” ratios from the
generation before.
Roles
1st = On task
2nd = Hands on
3rd = Secretary
2/27 Bell Work
“Mr. Shady?” inquired Shadow. “I’m afraid I have some bad
news. Your brother-in-law’s been murdered.” “Oh no!”
replied Shady. “I just saw Sam. I’m not surprised though,
he had a lot of enemies. He just got in fight with all my
sisters’ husbands over a business deal, and he owes people a
lot of money. Then there’s my sister’s brother who just got
out of jail who’d accused Sam of framing him…”
 As Shady rambled, Shadow arrested him on suspicion of
murder. Why?
2/27 Schedule
 Hardy-Weinberg Practice
 Genetic Drift Lab
 Finish collecting data TODAY
Assignments:
1. Dir Rdg Ch 17 “Genetic Variation – TODAY
2. QL: Alleles - LATE
3. Hardy-Weinberg Worksheet - LATE
Q3 Galileo Test
• 10% of Quarter Grade
• Wednesday-Thursday
• Study!
Hardy-Weinberg Practice
After graduation, you and 19 of your closest friends (lets say
10 males and 10 females) charter a plane to go on a roundthe-world tour. Unfortunately, you all crash land (safely) on
a deserted island. No one finds you and you start a new
population totally isolated from the rest of the world. Two
of your friends have cystic fibrosis which is recessive.
 Assuming that the frequency of this allele does not
change as the population grows, what will be the
incidence of cystic fibrosis on your island? ______
Genetic Drift Lab
How does population size affect the alleles?
 Gen 1 Allele Ratio: 2 A: 2B: 1i
 Use populations of 5, 10, and 20… how many alleles
from each “person”? ________________
 Model 4 generations in each population group.
 Generation 2-4 use the “gene pool” ratios from the
generation before.
Roles
1st = On task
2nd = Hands on
3rd = Secretary
2/28 Bell Work
Draw 4 rectangles. Put 9 X’s in the four rectangles so that
there is an odd number of X’s in each.
 How is this possible?
X
X
X
X
X
X
X
X
X
 Hint: Can overlap rectangles
2/28 Schedule
 Genetic Drift Lab
 Finish collecting data today. Due WEDNESDAY
 Review
Assignments:
1. Dir Rdg Ch 17 “Genetic Variation – LATE
2. QL: Alleles - LATE
3. Hardy-Weinberg Worksheet - LATE
Q3 Galileo Test
• 10% of Quarter Grade
• Wednesday-Thursday
• Study!
“Spell of the Albino”
 What are albinos?
 Have you ever seen any? Where?
 Albinos are relatively rare in nature. Why do you think this
is?
 Do you think culture selects for certain groups of people and
against others? How? Why? Think “beauty”…
2/18 Schedule
 Exams, Grades, Etc.
 Specific questions on Ch 16-17?
 Test
 Finish Rat Island
 Due TODAY
Assignments:
1. Rat Island due TODAY, all other assignments LATE
Exams, Grades, Logistics
 Changing standards, testing, expectations – hang in there
 General grading
 Get assignments in on time, use work time, get help EARLY!
 Lose points for late assignments, not using work time, breaking
rules, EDs -- if it interferes with work, you will lose it.
 Final exams are a significant part of grades
 3rd Q – Galileo final is 10% of quarter grade
 4th Q – AIMS Sci or equivalent and Galileo final are 15% of
semester grade
Rat Island Project
 2 days in class to create a “comic book” for 6-10 year olds
AND do Hardy-Weinberg #2. DUE END OF CLASS
2/13!!
 Work in partners or by yourself.
 Follow the checklist…these are things you will be graded on!
 Draw a block from the pouch to determine your island.
Block
Island
White
A
Black
B
Blue
C
Yellow D
Adaptation Overview
 Variation - The naturally-occurring differences among
individuals in a species.
 Adaptations - naturally-occurring (and usually
genetically controlled) differences that give some
individuals advantages in their particular environment.
 The organisms with Adaptations are more likely to be
Naturally Selected and pass on their genes.