Unit 1 - KA 7: Evolution And Gene Transfer

Question 1

Define the term evolution.

Answer 1

Evolution is the process of gradual change in a population of organisms over generations as a result of variations in the populations genome (genomic variations).

Question 2

Name and describe the two types of gene transfer.

Answer 2

Vertical
Genes are passed down through generations as a result of sexual or asexual reproduction.

Horizontal
Genes are transferred between organisms in the same generations.

Question 3

State the type of gene transfer which results in rapid evolutionary change.

Answer 3

Horizontal

As Organisms gain genetic material immediately

Question 4

State the type of organism that carries out horizontal transfer.

Answer 4

Prokaryotes

Question 5

Define the term natural selection.

Answer 5

Natural selection is the non-random increase in frequency of DNA sequences that increase survival and the non-random reduction in the frequency of deleterious sequences.

Question 6

In what Organisms is natural selection faster.

Answer 6

Natural selection is more rapid in prokaryotes as they can transfer genetic material horizontally.

Question 7

Name the 3 types of selection that lead to change in phenotype frequency.

Answer 7

Stabilising selection
Directional selection
Disruptive selection

Question 8

Describe stabilising selection

Answer 8

This form of selection favours the average phenotype. The extremes are selected against. This leads to a reduction in genetic diversity.

Question 9

Describe Directional selection.

Answer 9

One extreme of the phenotype is selected for.

Selection favours a version of the phenotype that was initially less common, causing a progress shift I the mean value.

Question 10

Describe disruptive selection.

Answer 10

Two or more phenotypes are selected for.

Selection pressures select extremes, at the expense of the intermediate.

Question 11

Define the term species.

Answer 11

A group of organisms capable of interbreeding to produce fertile offspring.

Question 12

Define the term speciation

Answer 12

The generation of a new biological species through evolution.

Question 13

Name 3 factors the lead to speciation

Answer 13

Isolation
Mutation
Selection

Question 14

Describe the importance of isolation barriers in speciation.

Answer 14

Isolation barriers are importing in preventing gene flow between sub populations during speciation.

Question 15

Name the three types of isolation barriers and give an example of each.

Answer 15

Geographical- mountain range, desert sea
Behavioural- differences in attraction signals
Ecological- pH, moisture, temperature

Question 16

Define allopatric speciation.

Answer 16

Sub populations of a species become isolated from each other. This occurs when gene flow between two sub populations is prevented by a geographical barrier.

Question 17

Explain allopatric speciation

Answer 17

• The members of a large population of a species occupy an environment. They share the same gene pool and interbreed freely.
• the population becomes separated by a geographical barrier.
• mutations occur at random. Resulting in variation arising within each group separately.
• natural selection affects each sub-group in a different way by favouring those alleles which make the members of that sub-population best at exploiting their environment.
• over a very long period of time, the variations cause the two gene pools to be so altered that the groups become genetically distinct and isolated.
• speciation has occurred if the the two sub populations can no longer interbreed to produce fertile offspring.

Question 18

Define sympatric speciation.

Answer 18

This occurs when two or more populations live in lose proximity but do not interbreed do to behavioural or Ecological barriers, so natural selection is able to act separately.

Question 19

Describe sympatric speciation.

Answer 19

• a large interbreeding population exists.
• some members of the population begin to exploit a new food source etc.
• the population becomes separated due to a behavioural or an Ecological barrier.
• mutations occur that produce new variation. Natural selection favours the new mutation.
• natural selection causes the mutation to increase in frequency. These two species are no longer able to interbreed to produce fertile offspring.