06. Evidence for evolution & mechanisms of evolution

Question 1

What is evolution?

Answer 1

Changes in the genetic make-up of populations over time, sometimes resulting in adaptation to the environment and the origin of new species.
-change in allele frequencies over time

Question 2

What are the lines of evidence for evolution?

Answer 2

1. Structural
2. Microbiology
3. Direct observation

Question 3

Homology

Answer 3

The existence of shared ancestry between a pair of structures, or genes, in different taxa.
Example: Despite modifications, all mammals
share several traits
-bone structure

Question 4

Vestigial structures

Answer 4

-genetically determined structures that are

retained despite having lost some or all of their ancestral function

Question 5

Vestigial structures in humans (4)

Answer 5

1. tail bone - makes sense if we had a tail
2. arrector pilli muscle - makes sense if we were covered in fur
3. wisdom teeth - makes sense if we had poor oral hygiene
4. appendix - makes sense if we had to digest cellulose

Question 6

Principle of faunal succession:

Answer 6

Sedimentary rock strata contain
fossilized organisms that succeed
each other vertically in a specific,
reliable order

Question 7

Microbiology evidence of evolution

Answer 7

• all life forms have DNA
• DNA is replicated, translated, and transcribed similarly across all life forms
• Genetic similarity across life forms

Question 8

Sequence homology

Answer 8

-protein or DNA sequences that are similar due to shared ancestry

Question 9

Direct observation of evolution

Answer 9

• the evidence for evolution is that we can see it taking place around us!
• Example: mosquito population evolved resistance to the pesticide

Question 10

What are the units of evolutionary change

Answer 10

Genes

Question 11

Gene pool

Answer 11

all the alleles for all loci in a population

Question 12

What happens if the allele frequency changes within the gene pool?

Answer 12

evolution has occurred

Question 13

What is a population?

Answer 13

 A localized group of individuals capable of interbreeding

and producing fertile offspring

Question 14

What is a prerequisite of evolution?

Answer 14

Variation in heritable traits

Question 15

Genetic variation

Answer 15

differences in genes or other DNA segments

Question 16

Sources of genetic variation

Answer 16

1. Mutation

2. Recombination

Question 17

Mutatations

Answer 17

• number one source of all new variation

- mutations can be neutral, deleterious, advantageous

Question 18

Recombination

Answer 18

the shuffling of existing alleles as a result of sexual reproduction

Question 19

The Hardy-Weinberg Equation

Answer 19

p^2 + 2pq + q^2 = 1
-Describes the genetic makeup we expect for a population that is not evolving
at a particular locus
-if the population meets HW expectations it is said to be in “HW equilibrium”, otherwise it may not be evolving

Question 20

What are the 5 conditions a population must meet to be considered in H.W. equilibrium?

Answer 20

1. No differences in the survival & reproductive success of individuals
2. No movement of individuals into and out of the population
3. No mutation
4. Population must be large enough to prevent sampling errors
5. All mating must be random

Question 21

What are processes that can change allele frequencies?

Answer 21

1. Natural selection
2. Genetic drift
3. Gene flow
4. Mutation

Question 22

Natural selection is an inescapable conclusion if a population has…

Answer 22

1. Variation in traits
2. relationship b/w traits and survival and/or reproduction
3. Variation can be inherited

Question 23

How does natural selection involve both chance and sorting?

Answer 23

chance - new genetic variations arise by chance

sorting - beneficial alleles are “sorted” and favored by natural selection

Question 24

Directional selection

Answer 24

Favors individuals at one extreme end of the phenotypic range

Question 25

Disruptive selection

Answer 25

Favors individuals a both extremes of the phenotypic range

Question 26

Stabilizing selection

Answer 26

favors intermediate variants and acts against extreme phenotypes

Question 27

Sexual selection

Answer 27

• selection for mating success

- can result in sexual dimorphism

Question 28

Intrasexual selection

Answer 28

-direct competition among individuals of one sex (often males) for mates of the opposite sex

Question 29

Intersexual selection

Answer 29

-occurs when individuals of one sex (usually females) are choosy in selecting their mates

Question 30

Genetic drift

Answer 30

A change in the frequency of an allele due to the random effects of finite population size.

• strongest when populations are small
• does not lead to adaptive evolution

Question 31

Bottleneck effect

Answer 31

Rapid reductions in population size associated with external

pressures on a population

Question 32

Founder effect

Answer 32

Occurs when a small number of colonizing individuals “founds” a new population in a new area

Question 33

Gene flow

Answer 33

• movement of alleles among populations

- tends to reduce variation over time