1.7 Evolution

Question 1

Evolution

Answer 1

Changes in organisms over generations as a result of genomic variations

Question 2

Natural Selection

Answer 2

Non-random increase in frequency of DNA sequences that increase survival

There is a non-random reduction in frequency of deleterious sequences

Question 3

Stabilising selection

Answer 3

Average phenotype is selected for

Extremes of phenotypes are selected against

Less variation in population as average phenotype gives organism a selective advantage

Question 4

Directional selection

Answer 4

One extreme of phenotype is selected for

Advantageous trait that was initially rare is now common

Question 5

Disruptive selection

Answer 5

Two or more phenotypes are selected for

Population is split into two or more groups with different characteristics

Question 6

Gene transfer

Answer 6

Vertical gene transfer: transferred from parents to off-spring due to sexual or asexual reproduction, called inheritance

Horizontal gene transfer: transferred between individuals in same generation

Question 7

Speciation

Answer 7

Generation of new biological species by evolution

Question 8

Speciation stages

Answer 8

Isolation barrier splits population into sub-populations

Mutation takes place in both sub-populations

Natural selection acts on both sub-populations

Speciation occurred

Question 9

Isolation barriers

Answer 9

Prevent gene flow between sub-populations during speciation including: geographical, behavioural and ecological

Question 10

Allopatric speciation- Geographical

Answer 10

Gene flow prevented between populations by a physical barrier

Question 11

Sympatric speciation- Ecological and Behavioural

Answer 11

Gene flow prevented between populations without a physical barrier