biology - 2.2a - drift and selection

Question 1

What is evolution?

Answer 1

The change over time in the
proportion of individuals in a population differing in one or more inherited traits.

Question 2

During evolution, what do changes in allele frequency occur through?

Answer 2

The non-random processes of
natural selection and sexual selection, and the random process of genetic drift.

Question 3

What does natural selection act on?

Answer 3

Genetic variation in populations.

Question 4

What does variation in traits arise as a result of?

Answer 4

Mutation.

Question 5

What is mutation?

Answer 5

The original source of new sequences of DNA. These new sequences can be novel alleles.

Question 6

What are most mutations?

Answer 6

Harmful or neutral, but in rare cases they may be beneficial to the fitness of an individual.

Question 7

What can populations produce?

Answer 7

More offspring than the environment can support.

Question 8

What do individuals with variations that are better suited to their environment tend to do?

Answer 8

Survive longer and produce more offspring, breeding to pass on those alleles that conferred an advantage to the next generation.

Question 9

What does selection result in?

Answer 9

The non-random increase
in the frequency of advantageous alleles and
the non-random decrease in the frequency of deleterious alleles.

Question 10

What is sexual selection?

Answer 10

The non-random process
involving the selection of alleles that increase the individual’s chances of mating and producing offspring.

Question 11

What may sexual selection lead to?

Answer 11

Sexual dimorphism.

Question 12

What can sexual selection be due to?

Answer 12

Male-male rivalry and female choice.

Question 13

What is male-male rivalry?

Answer 13

Large size or weaponry increases access to females through conflict.

Question 14

What is female choice?

Answer 14

It involves females assessing the fitness of males.

Question 15

When does genetic drift occur?

Answer 15

When chance events cause unpredictable fluctuations in allele frequencies from one generation to the next.

Question 16

Where is genetic drift more important?

Answer 16

In small populations, as alles are more likely to be lost from the gene pool.

Question 17

What is important for genetic drift?

Answer 17

Bottleneck and founder
effects.

Question 18

When do population bottlenecks occur?

Answer 18

When a population size is reduced for at least one generation.

Question 19

How do founder effects occur?

Answer 19

Through the isolation of a few members of a population from a larger population. The gene pool of the new population is not representative of that in the original gene pool.

Question 20

What is a gene pool altered by?

Answer 20

Genetic drift because certain alleles may be underrepresented or over-represented and allele frequencies change.

Question 21

When can the rate of evolution be rapid?

Answer 21

Where selection pressures are strong.

Question 22

What are selection pressures?

Answer 22

The environmental factors that influence which individuals in a
population pass on their alleles.

Question 23

What can selection pressures be?

Answer 23

Biotic: competition, predation, disease, parasitism;
Abiotic: changes in temperature, light, humidity, pH, salinity.

Question 24

What does the Hardy-Weinberg (HW) principle state?

Answer 24

That, in the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations.

Question 25

What are the conditions for maintaining the HW equilibrium?

Answer 25

No natural selection, random
mating, no mutation, large population size and no gene flow (through migration, in or
out).

Question 26

What can the HW principle be used to determine?

Answer 26

Whether a change in allele frequency is occurring in a population over time.

Question 27

How do you use the HW principle to calculate allele, genotype and phenotype frequencies in populations?

Answer 27

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

Changes suggest evolution is occurring.

Question 28

What is p?

Answer 28

Frequency of dominant allele.

Question 29

What is q?

Answer 29

Frequency of recessive allele.

Question 30

What is p^2?

Answer 30

Frequency of homozygous dominant genotype.

Question 31

What is 2pq?

Answer 31

Frequency of heterozygous genotype.

Question 32

What is q^2?

Answer 32

Frequency of homozygous recessive genotype.