1.7 Evolution

Question 1

Define ‘Evolution’

Answer 1

Evolution is the gradual changes in organisms over generations as a result of genomic variations.

Question 2

What is the difference between vertical and horizontal inheritance?

Answer 2

Vertical- passing of genetic material from parent to offspring
Horizontal- passing of genetic material across the same generation by transfer of plasmid between adjacent cells

Question 3

Give an example of an organism that can transfer genetic material through vertical or horizontal inheritance

Answer 3

Prokaryotes

Question 4

What is an advantage of horizontal gene transfer?

Answer 4

Allows for rapid evolutionary change

Question 5

Describe the process of horizontal gene transfer

Answer 5

Bacteria takes up a plasmid from another bacteria

Question 6

Define ‘Natural Selection’

Answer 6

Non random increase in the frequency of DNA sequences that increase survival chance of organism and the non-random decrease in deleterious sequences.

Question 7

What is a deleterious sequence?

Answer 7

A deleterious sequence is a gene sequence that decreases the organism’s chance of survival

Question 8

How are deleterious sequences removed by natural selection?

Answer 8

Decrease the organism’s survival rate and so are selected against, meaning their frequency will decrease

Question 9

Describe the process of natural selection

Answer 9

1 - Mutations change genotypes which changes phenotypes
2 - Selection pressures acts on phenotypes
3 - Phenotypes with selective advantage survive and reproduce which increase in frequency of advantageous mutations with successive generations
4 - Phenotypes with reduced advantage become extinct

Question 10

What are the three types of selection pressures?

Answer 10

• Stabilising
• Disruptive
• Directional

Question 11

What selection pressure is baby weight an example of?

Answer 11

Stabilising

Question 12

What type of selection pressure favours the two extremes and is the driving force between sympatric selection?

Answer 12

Disruptive

Question 13

Describe Directional selection pressure

Answer 13

• favours one extreme
• shifts graph to left or right
• example: peppered moths

Question 14

A species is a group of organisms capable of …

Answer 14

A species is a group of organisms capable of interbreeding and producing fertile offspring, and which does not normally breed with other groups

Question 15

What is ‘Speciation’

Answer 15

The formation of a new species

Question 16

Why must populations be separated for speciation to occur?

Answer 16

So interbreeding is prevented to have no gene flow.

Question 17

What are the three main steps in speciation?

Answer 17

• Isolation
• Mutation
• Natural Selection

Question 18

Describe what happens in the natural selection stage of speciation

Answer 18

Mutations may confer an advantage in habitat of population and so the the mutation will be selected for and will increase in frequency

Question 19

What are the two types of isolation barriers?

Answer 19

Geographical

Behavioural/Ecological

Question 20

What type of isolation barrier does sympatric selection need?

Answer 20

Behavioural/Ecological

Question 21

Describe Allopatric Selection

Answer 21

Formation of new species with a geographical barrier separating them

Question 22

How can scientists prove a new species have been formed?

Answer 22

If two members of the populations interbreed and produce infertile offspring