Topic Test Two: Evolution

Question 1

What are alleles?

Answer 1

Different variants of a gene

Question 2

What is required for natural selection to exist within a population?

Answer 2

Variation occurs
Variation is genetically heritable
Differential reproduction/survival is based on phenotypic variation

Question 3

Do changes caused by natural selection proceed environmental changes?

Answer 3

No. Natural selection is not forward thinking

Question 4

What is stabilizing selection?

Answer 4

Intermediate phenotypes lead to greater fitness. Decreases variation

Question 5

What is directional selection?

Answer 5

Phenotypes at one end of a spectrum lead to greater fitness. Literally shifts the direction of the distribution of traits.

Question 6

What is disruptive selection?

Answer 6

Average phenotype is favoured against. Tons of genetic variation on the extremes

Question 7

What kinds of populations face the most impact from genetic drift?

Answer 7

Small ones

Question 8

What are founder events?

Answer 8

A new population is founded by a subset of a larger population. Decreases genetic variation within this subset.

Question 9

What determines the initial frequency of many traits in new populations?

Answer 9

Random chance (so long as those traits did not cause individuals to successfully migrate)

Question 10

What is a genetic bottleneck?

Answer 10

When genetic variation within a population is lost due to random chance because of a dramatic shrink in the population. No natural selection because survival/reproduction does not depend on phenotypic traits.

Question 11

What do populations with have survived genetic bottlenecks often have less of?

Answer 11

Alleles

Question 12

What does genetic drift decrease?

Answer 12

Genetic variation

Question 13

What can genetic drift result in?

Answer 13

Alleles being lost from a population

Question 14

Which traits are most prone to genetic drift?

Answer 14

Those not being acted on by natural selection or which have weak selection

Question 15

What is allele fixation?

Answer 15

When everyone in a population is homozygous?

Question 16

How can genetic drift lead to an increase in frequency of deleterious alleles?

Answer 16

If one member of a founder event or survival of bottleneck event possesses a deleterious allele, it’s frequency will likely increase among future members of this population

Question 17

Do most mutations meaningfully affect phenotypes?

Answer 17

No. Most are silent (no change in amino acid sequence) or take place in a non-coding region

Question 18

What does allele flow do to populations?

Answer 18

Makes them more genetically similar to one another

Question 19

What is Hardy-Weinberg equilibrium

Answer 19

A null evolutionary model. Defines genotypic frequency if evolution is not happening

Question 20

What are the five assumptions made by Hardy-Weinberg?

Answer 20

Population size is infinite
Mutations are not allowed
No new individuals enter and none leave
All genotypes are equally likely to survive and reproduce
All mating is random

Question 21

How many genes does Hardy-Weinberg track at on time?

Answer 21

One gene. One allele

Question 22

How many alleles are there for every gene in a population?

Answer 22

Two (for heterozygous individuals, one allele of each type)

Question 23

What is speciation?

Answer 23

A splitting event where one species breaks off into two or more separate species.

Question 24

What commonly occurs with speciation?

Answer 24

One species rapidly evolves new allele frequencies and traits while the other does not change much.

Question 25

What does speciation create?

Answer 25

Biodiversity

Question 26

What are the two steps that precede speciation?

Answer 26

Genetic isolation Genetic divergence

Question 27

What is genetic isolation?

Answer 27

When some event or process interrupts gene flow between two populations of the same species

Question 28

How does genetic isolation lead to genetic divergence?

Answer 28

Gene flow can no longer transport alleles between two populations so they can no longer become homogenized.

Question 29

What is genetic divergence?

Answer 29

The process of genetically isolated populations diverging from one another. Evolutionary mechanisms begin to act on each population separately. The populations will become more genetically unlike over time.

Question 30

What is proximate causation?

Answer 30

The mechanisms responsible for animal behaviour. Ex: hormonal changes, muscle activity, neural circuitry, etc.

Question 31

What is ultimate causation?

Answer 31

Why animal behaviour occurs on a deeper level. It's adaptive significance.

Question 32

What is genetic determinism?

Answer 32

The false belief that certain DNA sequences lead to certain behavioural traits.

Question 33

What combination of factors determine how genes manifest in an individual?

Answer 33

Gene action Interactions between alleles that influence the trait and other alleles in the genotype Physical and social environment Learning

Question 34

What is polygenic inheritance?

Answer 34

The combined influence of many genes over a specific behavioural trait

Question 35

What are epigenetic changes?

Answer 35

Changes which determine the amount of gene product but not the gene sequence

Question 36

What are epigenetic modifications?

Answer 36

Changes which determine the amount of gene product and the gene sequence itself

Question 37

What are the two major epigenetic modifications?

Answer 37

Addition of a methyl group to a specific cytosine on a gene Addition of a acetyl group to the histones that DNA wraps around to form chromatin

Question 38

What does methylation typically lead to?

Answer 38

Prevention of transcription factors from bonding to DNA. Shuts down gene expression and reduces protein production

Question 39

What does acetylation typically lead to?

Answer 39

Neutralization of positive charge on histone proteins and prevention of +/- interaction that keeps DNA wound around histones. Promotes gene expression and increases protein production

Question 40

Are methylation and acetylation reversible

Answer 40

Yes

Question 41

What is artificial selection?

Answer 41

When humans decide which individuals will reproduce based on specific traits.

Question 42

What are the three conditions that must for a trait to have evolved over time?

Answer 42

The trait is known to have genetic variation Environmental conditions are kept as constant as possible Changes in said trait are observed over time

Question 43

What is a natural experiment?

Answer 43

When conditions in nature change and are documented before and after the change.

Question 44

What is kin selection?

Answer 44

A form of natural selection that favours a trait due to it's positive effects on the fitness of an organisms relatives, even at the cost of said organism's fitness

Question 45

What is inclusive fitness and how is it related to kin selection?

Answer 45

The theory that an organism's success is derived from altruistic and cooperative behaviour. The alleles found in an individual transfer not only through them but through their relatives

Question 46

How is the relationship between inclusive fitness and kin selection represented?

Answer 46

rb > c r= coefficient of relationship b= fitness benefit of recipient c= fitness cost to organism

Question 47

What is reciprocal altruism?

Answer 47

An exchange in fitness benefits between individuals over time

Question 48

What are the three criteria required for reciprocal altruism?

Answer 48

Individuals must be able to recognize one another Individuals must have long lifespans and live in stable groups Individuals must have high intelligence and good memories.

Question 49

What is eusociality?

Answer 49

A system of group living where a few individuals reproduce and the rest raise the offspring

Question 50

Why might eusociality have evolved?

Answer 50

Sterile workers receive indirect fitness benefits by raising their siblings