Topic 8a - Evolution & Evolutionary Mechanisms

Question 1

Four postulates of Darwin & Wallace that lead to natural selection & evolutionary change are?

Answer 1

1. Variation exists among members of a population
2. At least some of this variation is due to possession of heritable traits
3. Reproductive success varies w/ individuals
4. The survival & reproductive success depends at least in part on heritable characteristics

Question 2

Define evolution. Give examples

Answer 2

descent of modern organisms, with mutation, from preexisting life forms.
All organisms are related by common ancestry & have changed over time.
Any change in genetic makeup from one generation to the next.

E.g. artificial selection by humans, pesticide resistance, natural selection, industrial melanism (peppered moth)

Question 3

Define natural selection

Answer 3

the unequal survival & reproduction of organisms with differing phenotypes, caused by environmental forces.

“Survival of the fittest”

Question 4

Evidence of evolution is shown by…?

Answer 4

Fossil record
Comparative anatomy
comparative embryology
genetic/biochemical similarity

Question 5

Comparative anatomy involves?

Answer 5

homologous structures
vestigial structures
analogous structures

Question 6

Homologous Structures have…?

Answer 6

a common origin, but may serve different functions

Question 7

Vestigial structures have…?

Answer 7

no current function in existing form; had function in ancestral form

Question 8

Analogous structures have..?

Answer 8

no evolutionary relationship, but serve similar functions

Question 9

Define gene pool

Answer 9

all of the alleles that code for a particular gene product in a given population

Question 10

Define allele frequency

Answer 10

the occurrence (on a percentage basis) of a particular allele in a gene pool

Question 11

What is the Hardy-Weinberg Equilibrium?

Answer 11

No change in allele frequency will occur if:

• mutation does not occur
• no gene flow exists
• population is very large
• mating is random
• natural selection does not occur

ONE OF THESE ALWAYS OCCURS!

Question 12

Define gene flow

Answer 12

the movement of alleles from one population to another owing to the migration of individual organisms

Question 13

Mutations are required for…?

Answer 13

evolutionary change. think genetic variation => e.g. antibiotic resistant bacteria

Question 14

What is genetic drift? What effects does this have on population?

Answer 14

A shift in genetic frequencies in small populations, results due to small proportion of pop. reproducing.
Genetic variability reduced, alleles are sometimes lost

Effects:

• founder effect
• population bottleneck

Question 15

Explain founder effect

Answer 15

Only a few members of a population arrive at a new location to produce a new population.
Consult lecture diagram

Question 16

Population bottleneck is?

Answer 16

Consult lecture diagram.
An event drastically reduces size of population. By chance, gene pool now contains a higher number of a certain allele.
After pop. regrows, this allele dominates and some alleles have disappeared

Question 17

3 natural selection mechanisms are?

Answer 17

1. directional selection
2. stabilising selection
3. disruptive selection

LECTURE DIAGRAM IS SUPER AWESOME AND EXPLANATORY!!

Question 18

Darwin’s finches are an example of?

Answer 18

Adaptive radiation

Note: do not forget about divergent & convergent evolution!