1.7 Evolution

Question 1

Define ‘Evolution’

Answer 1

the changes in organisms over generations as a result of genomic variations

Question 2

Define ‘Natural Selection’

Answer 2

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

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Question 3

Describe the steps of natural selection

Answer 3

1. Mutation changes genotype
2. Changes phenotype
3. Selection pressure acts on phenotype
4. Phenotype with selective advantage survive and reproduce which increases frequency of advantageous mutations with successive generations
5. Phenotype with reduced advantage become extinct

Question 4

Describe step 1 of the natural selection

Answer 4

Mutation changes genotype

Question 5

Describe step 2 of the natural selection

Answer 5

Changes phenotype

Question 6

Describe step 3 of the natural selection

Answer 6

Selection pressure acts on phenotype

Question 7

Describe step 4 of the natural selection

Answer 7

Phenotype with selective advantage survive and reproduce which increases frequency of advantageous mutations with successive generations

Question 8

Describe step 5 of the natural selection

Answer 8

Phenotype with reduced advantage become extinct

Question 9

Define ‘genotype’

Answer 9

An individual’s alleles for a particular characteristic

Question 10

Define ‘allele’

Answer 10

Different forms of a gene that produce different phenotypes

Question 11

Define ‘phenotype’

Answer 11

The outward appearance resulting from an individual’s genotype for a particular characteristic

Question 12

Give an example of a selection pressure

Answer 12

Predation, food availability, food type etc.

Question 13

State the three types of natural selection

Answer 13

1. Stabilising selection
2. Directional selection
3. Disruptive selection

Question 14

Define ‘stabilising selection’

Answer 14

An average phenotype is selected for and extremes of the phenotype range are selected against.

Question 15

Define ‘directional selection’

Answer 15

One extreme of the phenotype range is selected for.

Question 16

Define ‘disruptive selection’

Answer 16

Two or more phenotypes are selected for.

Question 17

State the two types of gene transfer

Answer 17

1. Vertical gene transfer
2. Horizontal gene transfer

Question 18

Define ‘vertical gene transfer’

Answer 18

genes are transferred from parent to offspring as a result of sexual or asexual reproduction

Question 19

Define ‘horizontal gene transfer’

Answer 19

genes are transferred between individuals in the same generation.

Question 20

Is evolution faster in prokaryotes or eukaryotes and why?

Answer 20

Prokaryotes. They can exchange genetic material horizontally, resulting in faster evolutionary change than in organisms that only use vertical transfer.

Question 21

Define ‘species’

Answer 21

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

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Question 22

Describe what speciation means?

Answer 22

the generation of new biological species by evolution as a result of isolation, mutation and selection.

Question 23

Describe the steps of speciation

Answer 23

1. A population become separated into two populations by an isolation barrier. This prevents gene flow.
2. Geographical isolation causes allopatric speciation and behavioural/ecological isolation causes sympatric speciation.
3. Over time different mutations occur in the two populations.
4. Some mutations may be favourable.
5. Natural selection causes the non-random increase in frequency of genetic sequences that increase survival.
6. Selection may be disruptive, directional or stabilising.
7. After many generations a new species will form and the populations can no longer interbreed to produce fertile offspring.

Question 24

Describe step 1 of the process of speciation

Answer 24

A population become separated into two populations by an isolation barrier. This prevents gene flow.

Question 25

Describe **step 2** of the process of speciation

Answer 25

Geographical isolation causes allopatric speciation and behavioural/ecological isolation causes sympatric speciation.

Question 26

Describe **step 3** of the process of speciation

Answer 26

Over time different mutations occur in the two populations.

Question 27

Describe **step 4** of the process of speciation

Answer 27

Some mutations may be favourable.

Question 28

Describe **step 5** of the process of speciation

Answer 28

Natural selection causes the non-random increase in frequency of genetic sequences that increase survival.

Question 29

Describe **step 6** of the process of speciation

Answer 29

Selection may be disruptive, directional or stabilising.

Question 30

Describe **step 7** of the process of speciation

Answer 30

After many generations a new species will form and the populations can no longer interbreed to produce fertile offspring.

Question 31

State the two types of speciation

Answer 31

1. Allopatric 2. Sympatric

Question 32

Define 'allopatric speciation'

Answer 32

separation of populations by a geographical barrier

Question 33

Define 'sympatric speciation'

Answer 33

Populations become separated by either a behavioural or ecological barrier

Question 34

Describe the differences between allopatric and sympatric speciation

Answer 34

Allopatric relies on geographical barriers while symaptric relies on behaviour or ecological barriers

Question 35

Why is a barrier needed during speciation?

Answer 35

To prevent gene flow

Question 36

How do you know speciation has occured?

Answer 36

the populations can no longer interbreed to produce fertile offspring