Evolution

Question 1

What is evolution?

Answer 1

The change in organisms over generations as a result of genomic variations.

Question 2

What is natural selection?

Answer 2

The non-random increase in frequency of DNA sequences that increases survival and the non-random reduction in frequency of deleterious (harmful) sequences.

Question 3

What are the three types of selection?

Answer 3

• stabilising
• directional
• disruptive

Question 4

What is stabilising selection?

Answer 4

The average phenotype is selected for whilst the extremes on either side are selected against.

Question 5

What is directional selection?

Answer 5

One extreme of the phenotype range is selected for as it gives a selective advantage.

Question 6

What is disruptive selection?

Answer 6

Two or more phenotypes are selected for on either side of the average.

Question 7

What is the effect of stabilising selection?

Answer 7

There is a smaller range of values so less variation as having the average phenotype gives the organism an advantage.

Question 8

What is the effect of directional selection?

Answer 8

There is still a range of values but the average has changed as the advantageous trait that was rare is now more common.

Question 9

What is the effect of disruptive selection?

Answer 9

The population is split into two or more distinct groups with different characteristics (not speciation).

Question 10

What are the two methods of gene transfer?

Answer 10

• vertical

- horizontal

Question 11

What is vertical gene transfer?

Answer 11

Genes are transferred from parent to offspring due to sexual or asexual reproduction - called inheritance.

Question 12

What is horizontal gene transfer?

Answer 12

Genes are transferred between individuals in the same generation.

Question 13

What type of cell does vertical gene transfer occur in?

Answer 13

Eukaryotes and prokaryotes.

Question 14

What type of cell does horizontal gene transfer occur in?

Answer 14

Prokaryotes.

Question 15

What impact does horizontal gene transfer have on the population?

Answer 15

Faster evolutionary change.

Question 16

What is speciation?

Answer 16

The generation of new biological species by evolution.

Question 17

What are three ways speciation can occur?

Answer 17

• isolation
• mutation
• natural selection

Question 18

What is an isolation barrier?

Answer 18

It splits a population into sub-population allowing mutations to take place in both sub-groups, then natural selection takes place, then speciation.

Question 19

What do isolation barriers prevent?

Answer 19

Gene flow between the sub-populations.

Question 20

What are the three types of isolation barriers?

Answer 20

• geographical
• behavioural
• ecological

Question 21

What is a geographical barrier?

Answer 21

Separates a population by natural features like a mountain or river - resulting in allopatric speciation.

Question 22

What do geographical barriers result in?

Answer 22

Allopatric speciation.

Question 23

What is a behavioural barrier?

Answer 23

Two populations capable of interbreeding that don’t due to differences in reproductive strategies - sympatric speciation.

Question 24

What do behavioural barriers result in?

Answer 24

Sympatric speciation.

Question 25

What is an ecological barrier?

Answer 25

Separation by an ecological niche such as pH levels, salinity, or breeding locations differing between populations - sympatric speciation.

Question 26

What do ecological barriers result in?

Answer 26

Sympatric speciation.

Question 27

What is allopatric speciation?

Answer 27

Populations become isolated due to geographical barriers physically separating them.

Question 28

What is sympatric speciation?

Answer 28

Populations live in close proximity in the same environment yet become isolated due to behavioural or ecological barriers.