Evolution Part 2

Question 1

Explain the statement “selection acts on individuals, but populations evolve.”

Answer 1

1 individuals do not change during the process, only the succeeding population change in allele frequency
2 natural selection acts on individuals by favoring reproduction of some, but the evolutionary change occurs in the frequency of certain genetic traits of the population over time.
3 changes in genes are random/selection driven, not progressive
4 environmental changes are random, and selection favors individuals that are more “fit”
5 this produces a “tree of life” randomly.

Question 2

Explain why evolution applies to populations and species, not individuals.

Answer 2

Evolution is defined as changes in allele frequencies in a population over time.

Question 3

Explain why genes and mutations are the source of evolution.

Answer 3

1 genotype (genetic alleles for traits) determines phenotype (observable traits, both physical and behavioral)
2 mutations create changes in DNA such that new alleles appear
3 mutations in DNA are the raw material of natural selection and evolution
4 “Mutation proposes, selection disposes.”

Question 4

Define mircoevolution

Answer 4

a change in allele frequencies in a population over a relatively short period of time

Question 5

Define macroevolution

Answer 5

evolution that results in the formation of new species or other groupings of living things.

Question 6

Define Darwinian fitness

Answer 6

The ability of an individual to pass on its alleles to offspring relative to other individuals in the population

Question 7

Define selective adaptation

Answer 7

A heritable trait that increases the fitness of an individual in a particular environment, relative to individuals lacking the trait.
-Adaptations increase fitness—the ability to produce offspring
(Malaria and sickle cell example)

Question 8

What are the four postulates that make up the process of natural selection?

Answer 8

• VARIATION in traits exists among the individuals in a population.
• The variable traits are HERITABLE, or genetically based.
• An environmental factor reduces survival and reproduction in a portion the population (VARIABLE REPRODUCTION)
• The subset of the population that survives better and reproduces more is NOT A RANDOM sample.

Question 9

Define population bottleneck evolution.

Answer 9

Population bottleneck is an evolutionary event in which a significant proportion of a population is dies or does not reproduce.
population bottlenecks reduce genetic variation in a population and alter frequency of alleles present.
genetic traits selected for in a bottlenecked population can increase quickly and therefore, bottlenecked populations can undergo relatively rapid evolutionary change

Question 10

Define Founder Event Evolution

Answer 10

Founder event is an evolutionary event when a new colony is started by a few members of the original population.

Question 11

Which of the following mechanisms does not change allele frequencies in populations?
A Founder event
B Population bottleneck
C Natural Selection
D Mutation
E All of the above change allele frequencies in the population

Answer 11

E

Question 12

Define stabilizing natural selection

Answer 12

stabilizing section favors intermediate (or selects against extreme phenotypes)
over time, a population will become closer to the average for any particular trait being selected

Question 13

Define directional natural selection

Answer 13

directional selection favors one of the extremes

over time, a population will approach one of the more extreme phenotypes

Question 14

Define disruptive natural selection

Answer 14

Disruptive selection selects against the intermediate phenotype (or in favor of both extreme phenotypes)

Over time, a population will have mostly two different phenotypes