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KEY Unit 9: Evolution Unit Study Guide

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Vocabulary to know: Absolute Dating Adaptation Allele Frequency Artificial Selection Continental Drift Directional Selection Disruptive Selection Embryology Evolution Founders Effect

Fossil Gene Pool Genetic Bottleneck Genetic Drift Geologic Time Scale Homologous Structures Mass Extinction Mutation Natural Selection Plate tectonics

Polygenic Traits Scientific Theory Sexual Selection Stabilizing Selection Struggle for Existence Survival of the Fittest Variation Vestigial Structures

1. Age of the Earth a. Which gas was NOT present in large amounts in Earth's early atmosphere? Oxygen

b. What was the first form of life on Earth? Unicellular prokaryotes

c. How did the first life forms on Earth affect the atmosphere? Early life forms started photosynthesizing and releasing oxygen into the atmosphere. The oxygen in the atmosphere then reacted with the dissolved iron in the oceans and created large deposits in the Earth's crust that we can see today in the geologic record. Photosynthesizing organisms also took in a lot of Carbon Dioxide, decreasing the greenhouse gas and ultimately causing the global temperature of Earth to decrease.

d. Describe the theory of plate tectonics The surface of Earth is made of several large continental plates that move over the Earth's molten mantle. This movement causes continental drift, earthquakes, volcanoes, the creation of new ocean floor, and the recycling of older crust.

e. What type of rock are fossils generally found in? Sedimentary

f. How can the same type of plant fossil be found in South America and Africa when the two continents are separated by thousands of miles of ocean? The two continents were once part of a large supercontinent, Pangaea, which has since drifted apart.

g. How old is the Earth estimated to be? 4.6 billion years old.

h. How many mass extinctions have there been in Earth's history? There have been 5 mass extinctions in Earth's history.

i. What happens to the biodiversity of life immediately after a mass extinction? The biodiversity of life decreases dramatically after a mass extinction but does not ever

reach zero-there is always some form of life on Earth.

j. What causes the biodiversity of life to increase over time after a mass extinction? The species that survive a mass extinction have traits that allow them to adapt to the new environment and they will eventually change over time to create new species.

2. Darwin and Natural Selection a. Define evolution. A change in a species over time.

b. What is a theory? A well-supported, testable explanation of a phenomena that has occurred in the natural work.

c. Why is Charles Darwin important to evolution? The father of the Theory of Evolution by natural selection.

d. Define natural selection. The process by which organisms with variations most suited to their environment survive and leave more offspring

e. Explain the 4 requirements for natural selection. i. The struggle for existence- more individuals are produced than can survive and must compete ii. Variation- individuals vary, and some are better suited to life in an environment than others. iii. Adaptation- Any heritable characteristic that increases an organism's ability to survive and reproduce in its environment. May be physical, physiological, or behavioral. iv. Survival of the fittest-the individuals in a population that have the traits best suited to their environment will survive to reproduce and pass along the traits.

f. Explain and give an example of how natural selection occurs in nature. Examples will vary- A forest has a species of butterfly that comes in two variations- red and brown. A new predator beings to live in the forest and eat the butterflies. The red ones are easier to stop, so they are eaten more often. Over time, the population changes and there are only brown individuals in future populations.

g. Why is variation important to natural selection? Natural selection acts on the different traits of a population. Without variation there would be nothing to select for.

h. What is artificial selection? Give an example of artificial selection. Artificial selection is the intentional breeding of organisms by humans for a specific trait. An example of artificial selection is how we bred wolves for the gentler traits that allowed them to live alongside humans. Eventually, they became a new species: dogs!

3. Evolution as Genetic Change Over Time

a. Allele Frequency is the number of times an allele occurs in the gene pool compared to

the total number of alleles in that pool for the same gene.

b. Evolution, in genetic terms, involves a change in the frequency of alleles in a population

over time.

c. What are three sources of genetic variation and give an example of each.

i. Mutations: a change in the genetic materials o a cell. An example is a random

mutations that changes the color of a lizard's skin from brown to black.

ii. Genetic Recombination: independent assortment causes genes to separate

independently of each other during gamete formation and crossing-over where

paired chromosomes swap sections of DNA.

iii. Lateral Gene Transfer: the passing of genes from one individual to another that

is not their offspring. An example is bacteria trading genetic information on

plasmids.

d. What is a single gene trait? A polygenic trait?

A single gene trait is a trait that is controlled by only one gene. A polygenic trait is a trait

controlled by two or more genes.

e. Explain the different types of natural selection on polygenic traits.

What does it favor?

Graph

Stabilizing

Individuals near the

center of the cure

Disruptive

Individuals on either end of the curve

Directional

Individuals on one end of the curve or the either

f. Explain genetic drift. A random change in allele frequency in a small population.

g. Explain a genetic bottleneck. A change in allele frequency following a dramatic reduction in the size of a population.

h. Explain the Founder Effect. A small subgroup of a population migrates resulting in a different gene pool and allele frequency than the original gene pool.

i. What is genetic equilibrium? The allele frequency in a population's gene pool is not changing.

j. A population of snails lives in a woody forest. No dark banding is the dominant trait in

snails. Fill in the table below and use it to answer the following questions.

Banding on Snails Amount

Genotype Amount Total Alleles

Totals

No Banding

7

AA=4

A= 8

A= 11

Banding

3

Aa=3

A= 3

a= 9

a= 3

Total

10

Aa=3

a= 6

Total 20

i. What is the allele frequency of the dominant no dark banding allele? 11/20 x 100% = 55%

ii. What is the allele frequency of the recessive dark banding allele? 9/20 x 100% = 45%

k. The following table is the next generation of snails. Fill in the table below and use it to

answer the following questions.

Banding on Snails Amount

Genotype Amount Total Alleles

Totals

No Banding

9

AA=4

A= 8

A= 13

Banding

1

Aa=5

A= 5

a= 7

a= 5

Total

10

Aa=1

a= 2

Total 20

i. What is the allele frequency of the dominant no dark banding allele?

13/20 x 100% = 65%

ii. What is the allele frequency of the recessive dark banding allele? 7/20 x 100 = 35%

iii. Is this population of snails evolving? Explain your answer. Yes, this population of snails is evolving. The allele frequencies of the nonbanded and banded snails is changing from generation to generation so the population is evolving.

l. Explain how the following 5 things that disturb genetic equilibrium. i. Nonrandom mating: organisms select a mate based on a heritable trait. This means that one trait is better suited to their environment. ii. Small population size: this means that variation can occur often, disrupting genetic equilibrium. iii. Immigration or Emigration: organisms introduce new alleles or alleles will leave a gene pool-changing the allele frequencies of the population. iv. Mutations: this also introduces new alleles to the population, changing the allele frequencies of the population. v. Natural Selection: different genotypes have a different fitness for an environment, therefore the allele frequencies will change over time.

m. What is the Hardy-Weinberg Principle? What do we use it for? The Hardy-Weinberg Principle states that allele frequencies in a population should remain constant unless one or more factors cause those frequencies to change. We use the Hardy-Weinberg Principle to make predictions about the allele frequencies in future generations. We can use these predictions as a comparison to see if a population is evolving over time.

n. Write the Hardy-Weinberg equations below. P2 + 2pq + q2 = 1 and p + q = 1

o. In corn, kernel color is governed by a dominant allele for white color (N) and by a recessive allele (n) for yellow color. A random sample of 100 kernals shows that 65% are white and 35% are yellow. Using the Hardy-Weinberg equations, predict the following allele frequencies: i. NN= p = 0.65 p2 = (0.65 x 0.65) = 42%

ii. Nn= 2pq = (2(0.65)(0.35)) = 46%

iii. nn= q = 0.35 q2 = (0.35)(0.35) = 12%

p. You take a random sample of corn kernels from the next generation. You collect the

following data.

Allele

Allele Frequency

NN

28%

Nn

50%

nn

22%

q. Is the population of corn evolving? Explain your answer. Yes, the population of corn is evolving. Using Hardy-Weinberg, we predicted that 42% of the next generation of corn would have the dominant NN genotype, 46% of the next generation of corn would have the heterozygous Nn genotype, and 12% of the next generation of corn would have the homozygous recessive nn genotype. Our actual data does not match these predictions; therefore, the population of corn is evolving.

4. Evidence for Evolution a. Explain and give an example of homologous structures. Similar structures that share a similar origin, but may not share a similar function Example: arm and hand bones in humans, cats, whales, and bats

b. Explain and give an example of vestigial structures. Structure present by in reduced size. They have no use or a less important function. Example: Femurs in pythons.

c. What is suggested by the fact that bats and humans have similar bone structure? They share a common ancestor.

d. If you have 3 animals with similar leg bones, but 2 of the animals use the bones for walking and the third animal uses the bone for climbing, which are likely more closely related? The two that use their bones for walking would be more closely related

e. Why is it believed that all vertebrates share similarities during early development? They share a common ancestor

f. If you looked at the DNA of organisms with similar bone structures, would you expect it to be exactly the same, similar, or different? You would expect their DNA to be similar.

g. True or False: Humans descended from chimpanzees. Explain your answer. False- they descended from a common ancestor.

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