KA3.6 - Evolution

Question 1

A mutation is a … & … change in the structure or amount of an organism’s DNA.

Answer 1

sudden & random. A mutation is a sudden & random change in the structure or amount of an organism’s DNA.

Question 2

What is the only source of new alleles?

Answer 2

Mutations

Question 3

How might a mutation affect the DNA?

Answer 3

• Change the number of chromosomes
• Order/number of genes
• Order/number of bases.

Question 4

What can cause an increase in the rate of mutations?

Answer 4

Radiation and some chemicals

Question 5

Are all mutations harmful?

Answer 5

No. They can be neutral (having no positive or negative affect), advantageous or disadvantageous.

Question 6

What are the three types of mutation?

Answer 6

1. Neutral (having no positive or negative affect)
2. Advantageous
3. Disadvantageous

Question 7

Variation in a population can be due to … creating new alleles, the combination of genes inherited from parents or … (diet, exercise etc.)

Answer 7

Variation in a population can be due to mutations creating new alleles, the combination of genes inherited from parents or environmental influences (diet, exercise etc.)

Question 8

What type of variation is controlled by genes and the environment?

Answer 8

Continuous variation. As this has any value from a minimum to a maximum (e.g. height) it can impacted by the environment (e.g. if you got enough food when you were growing).

Question 9

An adaptation is an … characteristic that makes an organism … in its environment.

Answer 9

inherited … well suited to survival. An adaptation as an inherited characteristic that makes an organism well suited to survival in its environment/niche.

Question 10

When does natural selection occur?

Answer 10

When species produce more offspring than the environment can sustain which produces selection pressures as organisms compete for limited resources, e.g. food, light, water, mates

Question 11

In the context of natural selection a selective advantage is when those … to the environment survive and …

Answer 11

best suited … reproduce. Those best suited to the environment survive and reproduce

Question 12

What are the steps of natural selection?

Answer 12

1. Species produce more offspring than the environment can sustain which produces selection pressures as organisms compete for limited resources.
2. There is wide range of variation between individuals so those best suited to the environment survive and reproduce (selective advantage).
3. ‘Successful’ characteristics are passed to offspring.
4. Those that are less well adapted and compete less successfully will die out, leaving only the ‘fittest’ to survive and reproduce.

Question 13

A species is a group of …

Answer 13

A species as being a group of organisms that are able to breed and produce fertile offspring.

Question 14

What process produces new species?

Answer 14

Speciation.

Question 15

A barrier must be present for speciation to occur, why?

Answer 15

Stops gene flow. For two groups to become different species they must not be allowed to reproduce with one another or they will not become sufficiently different to be considered different species.

Question 16

The three types of speciation barriers are: geographical, … and …

Answer 16

Behavioural and ecological.

Question 17

Describe the steps of speciation?

Answer 17

1 - Species with common gene pool separated by barrier.
2 - Mutations occur in each subpopulation.
3 - Natural selection selects for different mutations in each group due to different selection pressures.
4 - Each sub-population evolves until they become two new species as they are unable to produce fertile offspring.