A2C2 - Chapter 10 - Variation and Evolution

Question 1

What factors produce variation between mammals?

Answer 1

Both genetic and environmental factors produce variation.

Question 2

Name the types of variation. (4)

Answer 2

Continuous
Discontinuous
Heritable
Non-Heritable

Question 3

What is discontinuous variation?

Answer 3

Type of variation that can be categorised.

Characteristic can only appear as a discrete value

Influenced by genes and not the environment.

Question 4

What is continuous variation?

Answer 4

Type of variation that cannot be categorised. Eg: Height

Characteristic produces a range of values as a continuous range.

Influenced by multiple genes and significantly by environmental factors.

Question 5

Compare Heritable and Non-Heritable variation.

Answer 5

Heritable variation is the genetic differences between individuals.

Non-heritable is aquired differences in the phenotypes of individuals that cannot be inherited.

Question 6

What is evolution?

Answer 6

The change in allele frequencies in a gene pool of a population over time.

Occurs due to natural selection.

Question 7

How does natural selection cause a change in allele frequencies over generations?

Answer 7

Organisms with advantageous genes are more likely to survive meaning their frequency increases. However the frequency of undesirable alleles decreases.

Question 8

What are selection pressures?

Answer 8

Environmental factors that drive evolution by natural selection and limit population sizes.

Can change allele frequency.

Question 9

Examples of selection pressures.

Answer 9

Predation
Disease
Competition for food
Environmental factors like temperature

Question 10

How can allele frequencies be expressed?

Answer 10

Expressed as a percentage of the total number of alleles for that gene.

Question 11

State the two types of competition.

Answer 11

Interspecific
Intraspecific

Question 12

Interspecific competition?

Answer 12

This is between members of different species.

Question 13

Intraspecific competition?

Answer 13

This is between members of the same species.

Question 14

Define gene pool.

Answer 14

All of the different versions of genes (alleles) that make up a population.

Question 15

What is genetic drift?

Answer 15

Variations in small populations due to chance (rather than due to selection pressures)

Question 16

What is meant by the founder effect?

Answer 16

When a small population of individuals become isolated, they form a population with a limited gene pool which is not representative of the entire population.

Question 17

What is Hardy-Weinberg principle?

Answer 17

A model allowing for the estimation of the frequency of alleles in a population, as well as whether allele frequency is changing over time.

Question 18

State the presumptions made by the Hardy-Weinberg principle.

Answer 18

No mutations to create new alleles
No migration
No selection (all alleles are passed down at the same frequency)
Random mating
Large population

Question 19

Explain the Hardy-Weinberg principle for calculating allele frequency.

Answer 19

p+q = 1
The total allele frequency adds up to 1.

p = dominant allele
q = recessive allele

Question 20

Explain the Hardy-Weinberg principle for calculating the genotype frequency.

Answer 20

p2 + q2 + 2pq = 1

p2 = homozygous dominant
q2 = homozygous recessive
2pq = heterozygous

Question 21

Define speciation.

Answer 21

The formation of a new species due to the evolution of two reproductively separated populations.

Question 22

Why may speciation occur?

Answer 22

Genetic Drift in isolated population
Founder Effect
Natural Selection

Question 23

What are the two types of speciation?

Answer 23

Allopatric Speciation
Sympatric Speciation

Question 24

What is the term for speciation when two populations become geographically separated?

Answer 24

Allopatric Speciation

Hallo Patrick!

Question 25

What is the name for speciation when two populations live in the same area but become reproductively isolated?

Answer 25

Sympatric Speciation Simp

Question 26

Outline geographical isolation.

Answer 26

A physical barrier (such as a river or mountain) separating two populations of the same species.

Question 27

Name the potential isolation mechanisms in Sympatric Speciation. (6) (Name like 2 tho)

Answer 27

Morphological isolation Seasonal isolation Behavioural isolation Gametic Isolation Hybrid Stability Hybrid Inviability

Question 28

What is morphological isolation?

Answer 28

The reproductive isolation of two populations due to the incompatibility of their reproductive systems.

Question 29

What is behavioural isolation?

Answer 29

The reproductive isolation of two organisms due to differences in their behaviour (eg: mating rituals)

Question 30

Describe seasonal isolation.

Answer 30

The isolation of two populations due to differences in their breeding seasons.

Question 31

Describe Hybrid Inviability.

Answer 31

Post-Zygotic barrier Successful fertilisation occurs however, it is incompatible in developing into a living organism.

Question 32

What is Hybrid Sterility?

Answer 32

The formation of sterile hybrid offspring from the reproduction of individuals of different species.

Question 33

Why may the reproduction of individuals of different species produce sterile offspring?

Answer 33

The chromosome sets from each parent differ so are unable to pair up during meiosis.

Question 34

Give an example of a sterile hybrid and a fertile hybrid.

Answer 34

Sterile Hybrid - Mule Fertile Hybrid - Wheat

Question 35

What is gametic isolation?

Answer 35

Prezygotic barrier Successful fertilisation does not occur