KA2.2 - Evolution

Question 1

Define ‘evolution’

Answer 1

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

Question 2

Define the term ‘fitness’ in the context of evolution?

Answer 2

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

Question 3

State the two ways that changes in allele frequency occur?

Answer 3

1. Non-random Processes = Natural selection AND Sexual selection
2. Random Process = Genetic drift

Question 4

What does natural selection act on?

Answer 4

genetic variation in populations

Question 5

Explain how variation in traits arise?

Answer 5

As a result of mutation(s)

Question 6

State the original source of new sequences of DNA?

Answer 6

Mutations

Question 7

Mutations can be harmful, ________ or ________

Answer 7

Mutations can be harmful, neutral or benefical

This is in terms of fitness - how likely the organism is to survive

Question 8

Describe the first step of natural selection

Answer 8

Populations produce more offspring than the environment can support

Question 9

Describe the second step of natural selection

Answer 9

Individuals with variations that are better suited to their environment tend to survive longer and produce more offspring, breeding to pass on those alleles that conferred an advantage to the next generation.

Question 10

Describe the third step of natural selection

Answer 10

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

deleterious = harmful and will decrease fitness

Question 11

State the three types of natural selection

This is from Higher Biology

Answer 11

1. Directional selection – favours a single extreme phenotype.
2. Stabilising selection – favours the average phenotype, giving a decrease in variation as more extreme traits do not survive.
3. Disruptive selection – favours two extreme forms within a population.

Question 12

Define ‘sexual selection’

Answer 12

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

Question 13

State the two forms of sexual selection?

Answer 13

1. Male-Male rivalry
2. Female choice

Question 14

Describe male-male rivalry in sexual selection?

Answer 14

Individuals compete with each other with ritualised displays of strength and stamina to warn off competitors or defend their mate(s).

Males with larger size or weaponry have increased access to females through conflict.

Question 15

Describe female choice in sexual selection?

Answer 15

females assess the fitness of males to choose a partner that will give her offspring a better chance of survival.

Question 16

Define ‘genetic drift’

Answer 16

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

Question 17

Explain why small populations are impacted by genetic drift more than larger ones?

Answer 17

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

because losing individuals in a small population has a greater impact

Question 18

State the two causes of genetic drift

Answer 18

1. Bottleneck Effect
2. Founder Effect

Question 19

Define ‘bottleneck effect’ form of genetic drift

Answer 19

occur when a population size is reduced for at least one generation.

Question 20

Define ‘founder effect’ form of genetic drift

Answer 20

occur 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 21

How is a gene pool altered by genetic drift?

Answer 21

Because comapred to the original population certain alleles may be underrepresented or over-represented, and allele frequencies change.

Question 22

State when the rate of evolution is rapid?

Answer 22

When selection pressures are strong.

Question 23

Define ‘selection pressures’

Answer 23

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

Question 24

Describe examples of biotic selection pressures?

Answer 24

competition, predation, disease, and parasitism

Question 25

Describe examples of abiotic selection pressures?

Answer 25

changes in temperature, light, humidity, pH, and salinity

Question 26

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

Answer 26

in the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations | e.g. if no evolution was happening

Question 27

What are the conditions for maintaining the Hardy-Weinberg equilibrium?

Answer 27

* no natural selection * random mating * no mutation * large population sizes * no gene flow (through migration, in or out).

Question 28

What is one use of the Hardy-Weinberg principle regarding evolution?

Answer 28

Used to determine whether a change in allele frequency is occurring in a population over time, which would indicate evolution is occurring

Question 29

Describe what is fitness a measure of in evolution.

Answer 29

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

Question 30

State the **two** types of evolutionary fitness

Answer 30

1. Absolute fitness 2. Relative fitness

Question 31

Define '**absolute fitness**'

Answer 31

the ratio between the number of individuals of a particular genotype after selection, to those before selection

Question 32

State the **absolute fitness** formula

Answer 32

frequency of a particular genotype **after** selection **divided by** frequency of a particular genotype **before** selection

Question 33

Define '**relative fitness**'

Answer 33

the ratio of the number of surviving offspring per individual of a particular genotype to the number of surviving offspring per individual of the most successful genotype

Question 34

State the **relative fitness** formula

Answer 34

number of a surviving offspring per individual of a partiular genotype **divided** by number of a surviving offspring per individual of the most successful genotype

Question 35

Define '**co-evolution**'

Answer 35

the process by which 2 or more species evolve in response to selection pressures imposed by each other

Question 36

How does a change in one species affect another in a co-evolutionary relationship?

Answer 36

acts as a selection pressure on the other species

Question 37

What often results from co-evolution?

Answer 37

**symbiosis**, which are co-evolved intimate relationships between members of 2 different species

Question 38

State the **three** types of symbiosis

Answer 38

1. Mutualism 2. Commensalism 3. Parasitism

Question 39

Define '**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

Define '**commensalism**'

Answer 40

Only one of the organisms benefit from the interaction (+/0)

Question 41

Define '**parasitism**'

Answer 41

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

Question 42

What does the Red Queen hypothesis state?

Answer 42

that, in a co-evolutionary relationship, change in the traits of one species can act as a selection pressure on the other species

Question 43

What does the Red Queen hypothesis imply for species in co-evolutionary relationships

Answer 43

That species in these relationships must adapt to avoid extinction