Download B20 C4 notes Mechanisms of Population Change p

B20 Ch4 Mechanisms of Population Change p. 112
Inquiry Question: Why are there so many species? So much diversity? So much variation
within and between species? (4.1-4.2 pg. 114 – 133)
In the 1700s - 1800s scientists were exploring the world and curious about a great variety of
patterns they were finding around the world. They began to question the belief from ancient
Greek times that life had all been created perfectly and has remained unchanged ever since. Lots
of evidence was piling up that indicated that life had changed over time.
FOSSILS:
A. Why are there fossils of organisms that are not modern day species? What had become of
them? Where had the modern day species come from?
B. Why are fossils found in the oldest rock strata so different from present day species, and the
fossils in the youngest rock strata so similar to modern day species?
C. Why are there transitional fossils (1/2 one type of animal and ½ like another) - like
Archaeopteryx – ½ way between dinosaurs and birds?
D. Why don’t all the animal groups appear in the fossil record at the same time?
A.
B.
D.
C.
BIOGEOGRAPHY:
A. Why do geographically close environments (i.e. forests, deserts) have related or similar
species, and forests or deserts that are widely separate like the deserts of Africa and
Australia don’t. Cacti are only found in North, Central, and South American deserts, not in
Australian and African deserts.
B. Why do species found on islands usually resemble species found on the closest mainland,
but not farther away?
C. Why are the same species found on the neighboring coastlines of continents?
A. cactus distribution
B.
C.
ANATOMY:
A. Why are there homologous structures in different species – structures that have different
functions, but have the same bone structure - for example a human arm, frog leg, bat wing,
horse leg, porpoise fin.
B. Why are there analogous structures in different species – body structures that perform the
same function but are not of similar underlying bone structure?
C. Why are their vestigial organs in different animals – i.e. appendix in humans
A.
B.
C.
EMBRYOLOGY:
Why do embryos of different but related
organisms (i.e vertebrates) show similar
stages of embryonic development?
MODERN DAY SCIENCE also provides evidence that life changes over time:
•
•
MOLECULAR BIOLOGY (DNA and PROTEINS)
GENETICS (HOW TRAITS ARE INHERITED, MUTATIONS).
2 THEORIES OF EVOLUTION WERE PROPOSED:
LAMARCK’S: the theory of INHERITANCE OF ACQUIRED CHARACTERISTICS
DARWIN’S: the theory of EVOLUTION BY NATURAL SELECTION
A comparison of the 2 theories
Larmarck
Darwin
Use and disuse determines evolution
Variation
Characteristics acquired during an
organism’s lifetime could be passed on to
offspring.
Inheritance
Evolve from primitive to complex to perfect
Differential survival
No extinction
Extinction

Crash Course : How Darwin’s theory of evolution explains lots of what we have observed.
https://www.youtube.com/watch?v=P3GagfbA2vo
Darwin’s Theory of Evolution: Evolution by Natural Selection
Darwin’s theory needed 4 conditions to work. All of these conditions are present in every
natural population studied so far:
1) All populations must have
individual variation
2) Some of these variations must be
heritable so they can be selected
3) Populations must be greater than
the available resources so there is a
struggle for survival
4) Adaptations are variations in the
population that allow individuals to
survive in the struggle for limited
resources, reach reproductive age
and reproduce, passing on their
genes to the next generation.
Variation in a population is caused by 1) mutation (permanent changes in a cell’s DNA),
and 2) genetic recombination (recombining of traits owing to sexual reproduction). If any
of these variations cause increased survival, they are called adaptations.
DEFINITIONS:
Mutation: permanent changes in a cell’s DNA; includes changes in nucleotide sequences,
alteration of gene position, gene loss, or duplication and insertion of foreign sequences. An
inheritable mutation has the potential to affect an entire gene pool. Mutations can be
advantageous, disadvantageous or neutral. They can happen owing to 1) meiosis (the
reproducing of DNA to make sperm and egg), and 2) to environmental factors.
Genetic recombination: through sexual reproduction parents pass on genes to their offspring.
The number of possible combinations that can be passed on to offspring results in great variation
in individual characteristics in populations.
Adaptation: characteristics that make an organism better suited for survival in different
environmental conditions.
 There are 3 types of adaptations. Choose an animal/plant of interest and complete the
following table:
Organism: _______________________________________
Adaptation
Structural (morphological)
Behavioral
Physiological
Examples
Selective Pressure: environmental condition(s) that select for some characteristics of
individuals and select against other characteristics.
 Test your understanding of the above definitions by completing online BLM:
Adaptations, Variation, Mutations and Natural Selection Quiz
 Read Thought Lab 4.2 Pg. 120 and answer Analysis questions 1 and 2.
INDIVIDUALS DON’T EVOLVE – they either survive or they don’t. POPULATIONS EVOLVE,
CHANGING THE GENETIC COMPOSITION OF THE ENTIRE POPULATION.
Evidence for Natural Selection in present time: Evolution of Antibiotic Resistance in Bacterial
Populations (ex. MRSA – multiple resistance Staphylococcus aureus, superbugs) and Pesticide
Resistance in disease pest (i.e. insects carrying
malaria, plague) and agricultural pest (insects,
weeds, fungus) populations.
What can we do to stop this serious problem
of superbugs?
1. use of antibiotics only when necessary
2. Take full course of antibiotics prescribed
3. Use Purell or similar hand sanitizers – they
use alcohol which dehydrates and kills
bacteria, instead of antibacterial soaps
4. Practice good sanitation – wash hands with
soap, cough into elbow, etc.
Learning Check: Read Thought Lab 4.1 Evolving “Superbugs” pg. 119. Answer Procedure
question #1, Analysis #1, Analysis #2, 1st bullet – just think about it and come up with some ideas.
(no research).
Learning Check! – Read pg. 115 – 118. Defend your answers!
1.
2.
3.
4.
5.
Do all variations become adaptations?
How does sexual reproduction lead to variation in a population?
How do mutations arise?
How do mutations lead to genetic variation?
Why are mutations especially important in changing environments? (explain using either of
the following examples: DDT in houseflies, rattlesnake venom factor in squirrel blood).
6. Are mutations always advantageous or disadvantageous? Defend your position.
7. Pg. 121: Answer # 2, 4a,b; 6, 7
8. Take online 4.2 Practice Quiz
Inquiry Questions: How do species form? How do scientists know this? What lines of
evidence do they use to determine evolutionary relationships?
https://www.youtube.com/watch?v=lIEoO5KdPvg (Evolution Stated Clearly). What is the
evidence scientists use to determine whale evolution?
 Check your understanding of the evidence scientists use to determine the evolution of
species. Complete the following questions:
1. Thought Lab 4.4 pg. 131 – answer Analysis #1 (just think, discuss with partners – no
research)
2. Pg. 133: #3 (see pg. 130 – 132), #4a, b, c (see pg. 126), #5 (see pg. 130 – 132) , #6,
#7 (see pg. 128 - 129), #8 (see pg. 129 – 130), #10 (see pg. 132).
3. Pg. 144 - 5 #1, 7, 9
Burgess Shale and the Cambrian explosion: an amazing evolutionary experiment of body
plans: https://www.youtube.com/watch?v=qNtQwUO9ff8
What is a species?
A species consists of populations that can
interbreed and produce viable offspring, and
the offspring can also reproduce. So, mules
and ligers are NOT species.
A new species can arise by 2 pathways: Transformation and Divergence
1) Transformation: a new species
gradually develops as a result of mutation
and adaptation to changing environmental
conditions, and the old species is gradually
replaced. This DOES NOT result in
increased species diversity.
Ex. mammoths.
2) Divergence: one or more species arise
from a parent species that continues to exist.
Ex. Hyracotherium (50mya) is thought to have
been the common ancestor of modern horses,
tapirs and rhinoceroses.
Divergence results in increased
biodiversity.
How are interbreeding populations REPRODUCTIVELY ISOLATED so they can no longer
interbreed and then become species?
If populations remain isolated long enough, speciation will eventually occur because of
changes accumulated in the population due to natural selection, which prevents
reproduction, causing new species.
Check out https://www.youtube.com/watch?v=8yvEDqrc3XE bird of paradise speciation
Reproductive Isolation occurs in 2 ways: Geographical Barriers and Biological Barriers
1) Geographical Barriers keep populations physically isolated. Ex. mountains, islands,
water, roads, human habitation isolating pockets of natural areas (Yellowstone to Yukon
Corridor). Speciation in African Cichlid Species, Darwin’s Finches, California Salamanders,
Birds of Paradise occurred this way. See pg. 137 -140.
2) Biological Barriers p populations biologically isolated
A) Temporal isolation - breed at different times of the year
B) Evolved structural differences prevent mating
C) Evolved pheromone differences prevent mating, Ex. spider pheromones
D) DNA changes prevent offspring
E) Behavioral differences- courtship rituals, bird and insect songs
F) Habitat isolation: 2 species occupy different habitats in the same area rarely
encountering each other.
Adaptive Radiation
Adaptive Radiation is the diversification of a common ancestral species into a variety of species,
all of which are differently adapted. – Ex. Darwin’s Finches on the Galapagos Islands
The Pace of Evolution by Natural Selection
There are 2 theories – they agree on the Theory of Natural Selection – but differ in the rate of
evolutionary change:
1) Gradualism – proposed by Darwin. He believed that new species result from gradual
changes that occur steadily. Big changes (such as the evolution of a new species) occur as a result
of many small changes.
2) Punctuated Equilibrium – proposed by Stephen Jay Gould (and Niles Elderidge). They
believe that evolutionary history consists of long periods of equilibrium (little or no change)
“punctuated” by periods of rapid speciation. Their evidence for this is the fossil record
(paleontology) where there is evidence of different rates of evolution, and there are periods of
rapid change (but don’t forget, not all species necessarily left fossils, and many fossils have not
yet been discovered).
There is evidence for both theories and both are still being researched.
How do scientists represent speciation over time to show evolutionary relationships?
Cladograms: https://www.youtube.com/watch?v=e4Yq41EypHc (educreations)
Cladograms show evolutionary relationships and common ancestors. The point at which a
line diverges indicates a common ancestor. The characteristic lines show when a given
characteristic developed in evolutionary time. Closely related species are closer together
in a cladogram.
Present time
Millions of years ago
 Do T. rex activity
http://www.ucmp.berkeley.edu/education/explorations/tours/Trex/index.html
 Study Summaries on pg. 141 -143.
 Complete all online practice quizzes.
Does evolution really matter? https://www.youtube.com/watch?v=hqepQGOYKZ0
 Using your favorite of the following questions (from Stated Clearly) explore the question:
“Does Evolution Really Matter?”
Why are elephant tusks shrinking?
How do invasive plants get to new islands?
Why do kakapos fail to defend against predation?
How does the flu overcome our immune defenses?
Can we speed fish growth without genetic modification?
How do new kinds of flu come about?
How can we preserve pine tree diversity?
Why are toxic animals so often brightly colored?
Why is the rough-skinned newt so toxic?
What causes antibiotic resisitance/
How do we avoid a future potato famine?
Why do animal tested meds often fail on humans?
Why are ram horns shrinking in size?
What are the risks of monoculture?
Can we prevent pesticide resistance?
Why is the western pond turtle disappearing?
Can malaria be tamed to be safe?
Can cholera be tamed to be safe?
Why are rattlesnakes losing their rattles?