Unit 1 Key area 7

Question 1

Define the term “evolution”?

Answer 1

Evolution can be defined as, the changes in organisms over generations as a result of genomic variations.

Question 2

Define the term “natural selection”?

Answer 2

Natural selection can be defined as, the non-random increase in the frequency of DNA sequences that increase survival, and the non-random reduction in the frequencies of deleterious sequences

Question 3

Name the three different types of selection?

Answer 3

• Stabilising selection
• directional selection
• disruptive selection

Question 4

Describe stabilising selection?

Answer 4

In stabilising selection the averages of the phenotype range are selected for, and the extremes are selected against

Question 5

Describe directional selection?

Answer 5

In directional selection one of the extremes is selected for and the average and the opposite extreme of the phenotypes are selected against.

Question 6

Describe disruptive selection?

Answer 6

In disruptive selection both of the extremes of a range of phenotypes are selected for and the average phenotype is selected against.

Question 7

What is meant by the term “horizontal gene transfer”?

Answer 7

When genes are transferred between individuals of the same generation.

Question 8

Explain if natural selection would be faster in prokaryotes or eukaryotes?

Answer 8

Natural selection would be faster in prokaryotes as a result of them being able to use horizontal gene transfer. Allowing rapid evolutionary changes faster than that seen in eukaryotes that must rely on vertical gene transfer.

Question 9

What is meant by the term “vertical gene transfer”?

Answer 9

When genes are transferred between parent and offspring as a result of sexual or asexual reproduction.

Question 10

Define the term “speciation”?

Answer 10

Speciation is defined as, generating a new biological species by evolution as a result of isolation, mutation, and selection.

Question 11

What is meant by a species?

Answer 11

A species is an group of individuals that can interbreed to produce fertile offspring and do not typically breed with other groups.

Question 12

State the role of isolation barriers in speciation?

Answer 12

Isolation barriers act to prevent gene flow between subpopulations in speciation.

Question 13

What type of speciation is caused by geographical barriers?

Answer 13

Allopatric speciation

Question 14

What type of speciation is caused by behavioral or ecological barriers?

Answer 14

Sympatric speciation