Unit 2 - Evolution

Question 1

What is evolution?

Answer 1

The change over time in the proportion of individuals in a population differing in 1 or more inherited traits.

Question 2

What are the non-random processes that changes in allele frequency occur through?

Answer 2

Natural and sexual selection.

Question 3

What is a random process that changes in allele frequency occurs through?

Answer 3

Genetic drift.

Question 4

What does natural selection act on?

Answer 4

Genetic variation in populations.

Question 5

What does variation in traits arise as a result of?

Answer 5

Mutations.

Question 6

What is sexual selection?

Answer 6

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

Question 7

What might sexual selection lead to?

Answer 7

Sexual dimorphism.

Question 8

What is sexual dimorphism?

Answer 8

The difference in appearance between males and females of the same species.

Question 9

What can sexual selection be due to?

Answer 9

Male-male rivalry and female choice.

Question 10

How is reproductive success increased in male-male rivalry?

Answer 10

Large size or weaponry increases access to females through conflict.

Question 11

What does female choice involve?

Answer 11

Females assessing the fitness of males.

Question 12

What are 4 signals that indicate fitness and are therefore beneficial in sexual selection?

Answer 12

Physical appearance or display
Chemical signs
Presence or absence of parasites
Earlier life history events

Question 13

When does genetic drift occur?

Answer 13

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

Question 14

Is genetic drift more important in small or large populations and why?

Answer 14

Small as more alleles are likely to be lost from the gene pool.

Question 15

What are the two major types of genetic drift?

Answer 15

Population bottlenecks and founder effects.

Question 16

When do population bottlenecks occur?

Answer 16

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

Question 17

How do founder effects occur?

Answer 17

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

Question 18

Why is a gene pool altered by genetic drift?

Answer 18

Certain alleles may be under-represented or over-represented and allele frequencies change.

Question 19

What happens to the rate of evolution when selection pressures are strong?

Answer 19

Rate of evolution is rapid.

Question 20

What are selection pressures?

Answer 20

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

Question 21

What are the two types of selection pressure?

Answer 21

Biotic and abiotic.

Question 22

Give 4 examples of biotic selection pressures.

Answer 22

Competition, predation, disease, parasitism.

Question 23

Give 5 examples of abiotic selection pressures.

Answer 23

Changes in temperature, light, pH, humidity, salinity.

Question 24

What does the Hardy-Weinberg principle state?

Answer 24

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 mutation, no mating, large population size and no gene flow.

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

What is fitness?

Answer 27

Fitness is an indication of an individual’s ability to be successful at surviving and reproducing.

Question 28

What is fitness a measure of?

Answer 28

The tendency of some organisms to produce more surviving offspring than competing members of the same species.

Question 29

What two terms can fitness be measured in?

Answer 29

Absolute and relative fitness.

Question 30

What is the calculation formula for absolute fitness?

Answer 30

Frequency of a particular genotype after selection
——————————————————
Frequency of a particular genotype before selection

Question 31

What does an absolute frequency of 1 indicate about the frequency of that genotype?

Answer 31

Frequency of the genotype is stable.

Question 32

What is the formula for relative fitness?

Answer 32

Number of surviving offspring per individual of a particular genotype
———————————————————
Number of surviving offspring per individual of the most successful genotype

Question 33

What is co-evolution?

Answer 33

The process by which two or more species evolve in response to selection pressures imposed by each other.

Question 34

What is the impact of a change in the traits of one species in a co-evolutionary relationship?

Answer 34

Acts as a selection pressure on the other species.

Question 35

When is co-evolution frequently seen?

Answer 35

Co-evolution is frequently seen in pairs of species that have symbiotic interactions.

Question 36

What is symbiosis?

Answer 36

Co-evolved intimate relationships between members of two different species.

Question 37

What is the impact of symbiotic relationships?

Answer 37

Positive, negative or neutral for all individuals involved.

Question 38

What are the 3 types of symbiotic interactions?

Answer 38

Mutualism, commensalism and parasitism.

Question 39

What is mutualism?

Answer 39

Both organisms in the interaction are interdependent on each other for resources or other services. As both organisms gain from the relationship, the interaction is (+/+).

Question 40

What is commensalism?

Answer 40

One species benefits from the relationship while the other species is unharmed and does not gain any benefit. The interaction is (+/0).

Question 41

What is parasitism?

Answer 41

The parasite benefits in terms of energy or nutrients and the host is harmed as a result of the loss of those resources (+/-).

Question 42

What does the Red Queen hypothesis state?

Answer 42

In a co-evolutionary relationship, changes in the traits of one species can act as a selection pressure on the other species so both species must adapt to avoid extinction.