Chapter 12- Forces of Evolutionary Change

Question 1

What is evolution?

Answer 1

Simple definition: Evolution is descent with modification (coined by Darwin)

Precise definition: evolution is genetic change in a population over multiple generations

It is detectable by examining a population’s gene pool- the entire collection of genes and their alleles. Evolution is a change in allele frequencies. The allele frequencies of each gene determine the characteristicss of a population.

Question 2

Natural selection

Answer 2

When individuals with certain genotypes- that are best suited to the environment- have greater reproductive success than other individuals.

Question 3

Artificial selection

Answer 3

A selective breeding strategy in which humans only allow organisms with desired traits to reproduce

Question 4

Modern evolutionary synthesis

Answer 4

Suggests that genetic mutations create heritable variations, and that this variation is the raw material upon which nature selection acts upon

Question 5

Mutations

Answer 5

changes in DNA sequence (randomly!)

Question 6

Adaptions

Answer 6

heritable traits that give a selective advantage for organisms’s ability to survive and reproduce

Question 7

Phenotype

Answer 7

observable traits (caused by environmental + genes)

Question 8

Fitness

Answer 8

refers to an organisms’s genetic contribution to the next generations (succesful reproduction) even if that means they die right after they do it!)

Question 9

What is the study of population genetics

Answer 9

Relationship between allele frequencies and genotype frequencies

Question 10

Hardy-Weinberg equilibrium

Answer 10

HIGHLY UNLIKELY situation in which allele frequencies and genotype frequencies do not change generation to generation.

It occurs in populations that meet following assumptions:
(1) Natural Selection does not occur
(2) Mutations do not occur, so no new alleles arise
(3) Population is infinitely large (or large enough to eliminate random changes in allele frequencies)
(4) Individuals mate at random
(5) Individuals do not migrate in and out of population.

• Helps figure out whether evolution occurred, infer characteristics about a population, estimate genotype frequencies in a population

Question 11

Natural Selection can shape populations in three main ways

Answer 11

Directional selection: one extreme phenotype is fittest, and the environment selects against the others

Disruptive selection: two or more extreme phenotypes are fitter than the intermediate phenotypes

Stabilizing selection: extreme phenotypes are less fit than the optimal intermediate phenotype (more common in stable, unchanging environments)

Question 12

Why do harmful alleles persist in a population?

Answer 12

Individuals with two different alleles for a gene (heterozygote) have greater fitness than those whose two alleles are identical (homozygote). Heterozygotes can maintain a harmful recessive allele in a population through reproduction (a 25% chance of giving birth to a homozygous)

Question 13

Sexual dimorphism

Answer 13

Difference in appearance between males and females. Sometimes these traits are highly visible and dangerous, but its sexual selection (a type of natural selction resulting from variation in the ability to attract mates).

Question 14

Sexual selection

Answer 14

A type of natural selction resulting from variation in the ability to attract mates

Ways to do so:
(1) Members of one sex compete with each other for access to the other sex
(2) Members of one sex (typically female who invest a lot to reproduce), choose males from among mutiple individuals within the other sex