Chapter 8 - Evolution

Question 1

On which level does evolution operate?

Answer 1

On populations, NOT on individuals

Question 2

What is evolution?

Answer 2

When the allele frequency in a population change

Question 3

What are the 4 main points or Darwin’s theory of evolution?

Answer 3

• Organisms change over time
• Some organisms have gone extinct
• The Earth is 6000+ yrs old
• The geology of Earth is not constant, but always changing

Question 4

What are the 4 mechanisms that can give rise to evolution?

Answer 4

1-Mutation
2-Genetic drift
3-Migration
4-Natural Selection

Question 5

What are 2 ways to alter a population?

Answer 5

Breeding (selective or not)

Immigration (adding/removing individuals)

Question 6

What is a mutation?

Answer 6

A direct change in the DNA sequence of an individual - it is the ultimate source of genetic variation

• We can’t predict which individuals will have mutations
• We cant predict what are going to be the consequences of the mutations

Question 7

What is genetic drift?

Answer 7

A random change in allele frequencies in the population over time (neither allele have better success than the other)

Question 8

What is fixation?

Answer 8

When an allele’s frequency becomes 100% in a population

Question 9

Name and explain 2 ways that genetic drift can occur

Answer 9

1- Founder effect: A small number of individuals may leave a population and become the founding members of a new, isolated population, and bring with them their specific genetic variation (not the same as the original pop variation)
2. Bottleneck effect: catastrophy (famine, disease, environmental change) causes the death of a large number of individuals, and the new population has different alleles than the original population

Question 10

What is migration?

Answer 10

Gene flow in or out of a population may change allele frequencies

Question 11

What are the 3 factors required for natural selection to happen?

Answer 11

1. There must be variation for the trait within a population
2. That variation must be inheritable (inheritance/heritability)
3. *Individuals with 1 version of the trait must produce more offspring than those with a different version of the trait (differential reproductive success)

Question 12

What are the 2 formulas of the Hardy-Weinberg Law?

Answer 12

p = dominant allele A
q = recessive allele a
p+q=1
(pp) = homozygous dominants (AA)
(qq) = homozygous recessives (aa)
2pq = heterozygotes (Aa)

Question 13

What are the conditions required for the Hardy-Weinberg equilibrium (when allele frequency proportions stay the same)?

Answer 13

• No natural selection
• No mutations
• No migration
• No genetic drift
• Random mating

Question 14

What is fitness?

Answer 14

A measure of the relative amount of reproduction of an individual with a particular phenotype, compared with the reproductive output of individuals of the same species with alternative phenotypes

Question 15

What are the 3 important elements of fitness?

Answer 15

1. An individual’s fitness is measured relative to other genotypes or phenotypes in the pop.
2. Fitness depends on the specific environment in which the organism lives
3. Fitness depends on a organism’s reproductive success compared to other members of the population

Question 16

What is adaptation?

Answer 16

The process by which organisms become better matched to their environment and the specific features that make an organism more fit (environment has to be considered when considering fitness)

Question 17

What is artificial selection?

Answer 17

A case of natural selection where humans decide which traits are successful rather than nature

Question 18

What is trait categorization?

Answer 18

traits can be specific (yellow or white) or continuous (height)

Question 19

What is directional selection?

Answer 19

selecting a trait in one specific direction (ex: poultry with increasing breast size)

Question 20

What is stabilizing selection?

Answer 20

individuals with intermediate phenotypes are the most fit

Question 21

What is disruptive selection?

Answer 21

Individuals with extreme phenotypes experience the most fitness, and those with intermeditate phenotypes have the lowest

Question 22

What are the 4 ways in which natural selection can change the traits in a population?

Answer 22

1- trait categorization
2- Directional selection
3- Stabilizing selection
4- Disruptive selection

Question 23

What are the 5 primary lines of evidence for evolution?

Answer 23

1- Fossil record (using radiometric dating)
2- Geographic patterns of species distribution reflect specie’s evolutionnary history (biogeography)
3- Comparative anatomy reveal common evolutionnary origins
4- Molecular biology reveals that common genetic sequences link all life forms
5-Laboratory and field experiments enable us to watch evolution in progress

Question 24

What is convergent evolution?

Answer 24

different types of organisms evolve to have similar traits because their environment is very similar (even though they are geographically separated)

Question 25

What are homologous structures?

Answer 25

Similar structures present in many different species

Question 26

What are vestigial structures?

Answer 26

No longer useful structures but still there (ex: wisdom teeth)