6.3 Evolution.

Question 1

What is evolution?

Answer 1

A change in allele frequency.

Question 2

How does evolution occur?

Answer 2

Natural Selection

Question 3

What are the steps of natural selection?

Answer 3

1. Selection Pressure.
2. Individuals with an advantageous allele survive.
3. These survivors reproduce, and pass on advantageous allele.
4. Over time frequency of this allele increases.

Question 4

What is Stabilizing Selection?

Answer 4

When environment is stable, individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce.

Question 5

What is Directional Selection?

Answer 5

When there is a change in the environment, individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce.

Question 6

What is genetic drift, and how does it work?

Answer 6

Individuals in a population show variation in genotypes.
By chance the allele for 1 genotype is passed onto the offspring more often than others.
Number on individuals with the allele increase.
If by chance the same allele is passed on more often again and again, it can lead to evolution.

Question 7

Does genetic drift have a greater effect on larger or smaller populations?

Answer 7

Smaller populations.
It has a greater influence

In larger populations any chance variations in allele frequency tend to even out across the whole population.

Question 8

What is a genetic bottleneck?

Answer 8

An event that causes a big reduction in a populations size, leading to a reduction in gene pool.
(A natural disaster)

Question 9

What’s the founder effect?

Answer 9

Describes what happens when just a few organisms from a population start a new population. There are only a small number of different alleles in the initial gene pool.

Question 10

What is the Hardy - Weinberg Principle?

Answer 10

It predicts that the frequencies of alleles in a population won’t change from 1 generation to the next.

Question 11

What conditions are required for Hardy - Weinberg principle to be true?

Answer 11

Large population
No immigration or emigration
No mutations
No natural selection
Random mating.

Question 12

What is the Hardy - Weinberg Equation to predict Allele Frequency?

Answer 12

p + q = 1

p: Frequency of dominant allele
q : Frequency of recessive allele

Question 13

What is the Hardy Weinberg equation to predict Genotype frequency.

Answer 13

p^2 +2pq + q^2 = 1

p^2: frequency of homozygous dominant genotype
2pq: Frequency of heterozygous genotype
q^2: Frequency of homozygous recessive genotype.

Question 14

What is Artificial Selection?

Answer 14

Breeding individuals with desirable traits.

Question 15

What are the benefits of artificial selection?

Answer 15

Offspring produced which have desirable traits.

Question 16

Negatives of Artificial selection?

Answer 16

Reduces gene pool:
As a result lower chance Alleles could be resistant to a disease.
Potentially useful alleles are accidentally lost.

Question 17

What is Speciation?

Answer 17

The development of a New Species.

Question 18

How does allopatric speciation occur?

Answer 18

1. A physical barrier separates a population, and stops interbreeding between populations.
2. Populations adapt to new environments (Natural selection)
3. Allele and phenotype frequency change leading to the development of new species.

Question 19

How can reproductive isolation occur?

Answer 19

Seasonal changes - Develop different mating seasons.
Mechanical Changes - Changes in genitalia prevent successful mating.
Behavioral Changes - Group of individuals develop courtship rituals that aren’t attractive to the main population.

Question 20

What is allopatric speciation.

Answer 20

Speciation caused by a physical barrier.

Question 21

What is sympatric speciation.

Answer 21

Speciation which occurs without a physical barrier.
Much less common than allopatric speciation.