4.4 Genetic diversity and adaptations

Question 1

What is a species

Answer 1

A group of organisms with similar characteristics that can breed together to produce fertile offspring.

Question 2

What is genetic diversity

Answer 2

The number of different alleles in a population of a species.

Question 3

What is a population

Answer 3

A group of individuals of the same species that live in the same place and can interbreed.

Question 4

Why is a high genetic diversity beneficial

Answer 4

It means there is greater variation, so more individuals are likely to survive if the environment changes.

Question 5

What is evolution

Answer 5

A change in allelic frequencies of a population over time.

Question 6

What is natural selection

Answer 6

The process through which evolution occurs which may result in the formation of a new species.

Question 7

What is a selection pressure

Answer 7

Environmental factors that affect chances of survival and successful reproduction.

Question 8

What are some examples of selection pressures

Answer 8

• Competition (for food, water, space, mates,etc)
• Presence of predators
• Disease
• Extreme temperatures
• Natural disasters

Question 9

What is an adaptive trait

Answer 9

A trait that increases the chance of survival and/or reproductive success in current environment.

Question 10

Explain the process of evolving a certain trait (e.g. explaining why giraffes have long necks)

Answer 10

• Random mutations occur which leads to new alleles and genetic variation among giraffes
• A new selection pressure is exerted by a change in the giraffes environment
• There is competition for survival due to the selection pressure
• Individuals with advantageous alleles (alleles which code for proteins that grow a longer neck) are more likely to survive
• These individuals reproduce and pass on the advantageous alleles
• Over time this increases the frequency of the allele in the population
• Therefore there is a decrease in frequency of non-advantageous alleles

Question 11

What are 3 types of adaptation

Answer 11

• Anatomical
• Behavioural
• Physiological

Question 12

What is an anatomical adaptation

Answer 12

Physical adaptations, e.g. shorter ears and thicker fur in arctic foxes compared to foxes in warmer climates.

Question 13

What are behavioural adaptations

Answer 13

Changes in behaviour which increase the organisms chance of survival, e.g. oxidising fat rather than carbohydrate in kangaroo rats to produce additional water in a dry desert environment.

Question 14

What are physiological adaptations

Answer 14

Processes inside an organisms body that increase its chance of survival, e.g. autumn migration of swallows from the UK to Africa to avoid food shortages in the UK winter.

Question 15

What do courtship behaviours do

Answer 15

They increase the rate of successful mating and eventual reproduction.

Question 16

What are 4 reasons why animals have courtship behaviours

Answer 16

• Ensure mating occurs between individuals of the same species but opposite gender
• Allow identification of mates capable of breeding (fertile, sexually mature)
• Form a pair bond (some species mate for life, this will lead to successful mating and raising of offspring)
• Synchronise mating. Displays and scents can be used to stimulate gamete release.

Question 17

What is a genotype

Answer 17

The genetic constitution of an organism.

Question 18

What is a phenotype

Answer 18

The expression of this genetic constitution and its interaction with the environment.

Question 19

What is a polygene

Answer 19

• Characteristics that are influenced by more than one gene
• The more polygenic a phenotype, the greater the effect of environmental interaction upon the phenotype

Question 20

What do polygenetic characteristics produce

Answer 20

A normal distribution curve.

Question 21

What are the 3 main categories of selection when observing phenotypes

Answer 21

• Stabilising selection
• Directional selection
• Disruptive selection

Question 22

What is stabilising selection and when does it occur

Answer 22

• Occurs when environmental conditions remain relatively constant
• The mean phenotype = modal phenotype
• Extreme phenotypes are selected against
• The mean phenotype is selected for

Question 23

What is directional selection and when does it occur

Answer 23

• Occurs when environmental conditions/selection pressures change
• Advantageous alleles change
• Modal phenotypes shift to right/left
• Individuals with these alleles are more likely to survive and reproduce

Question 24

What is disruptive selection and when does it occur

Answer 24

• When an environmental factor takes forms, causing selection pressure(s) to interact differently with different phenotypes
• Both extreme phenotypes are selected for (modal phenotypes at both extremes)
• Individuals with extreme alleles are more likely to survive and reproduce
• If consistent over generations, can lead to speciation

Question 25

Mutations example: In Africa today, most of the human population are resistant to malaria caused by P.vivax. Explain why this resistance is so common in Africa (4 marks)

Answer 25

1. Mutation produced by allele 2. Those with allele/ resistance are more likely to survive malaria/ P.vivax 3. So more likely to reproduce and pass on the allele 4. Over generations the allele frequency increases