Evolution May Lead To Speciation

Question 1

Genetic factors that cause phenotypic variation

Answer 1

• mutation of alleles
• random fertilisation by gametes
• crossing over and independent assortment during meiosis

Question 2

2 factors that cause variation

Answer 2

Genetic and environmental

Question 3

What is a biotic factor

Answer 3

Any living component that affects the population of another organism or the environment

Question 4

Why does natural selection occur

Answer 4

• predation
• disease
• competition

All resulting in differential aural and reproduction

Question 5

What is interspecific competition

Answer 5

Competition between organisms of different species

Question 6

What is infraspecific competition

Answer 6

Competition between organisms of the same species

Question 7

What is a abiotic factor

Answer 7

Environmental factor that limits the population of a species

Question 8

How does natural selection cause a change in a population gene pool

Answer 8

Organisms with advantageous alleles are more likely to survive and pass their favourable alleles to offspring, frequency of unfavourable alleles decreases

Question 9

What is evolution

Answer 9

Change in allele frequency in a population

Question 10

Main stages of evolution

Answer 10

• Mutation causes
• variation: different phenotype/genotype in a population
• struggle for existence: section pressures eg shortage of food
• survival of the fittest: organisms with advantageous alleles survive and reproduce
• reproduction: organisms produce more offspring that can e supported by the available resources
• natural selection: frequency of advantageous allele increases

Question 11

What is stabilising selection

Answer 11

• Occurs when environmental conditions stay the same
• individuals closest to the mean are favoured
• new phenotypes selected against
• results in low diversity

Question 12

What is directional selection

Answer 12

• when environmental conditions change
• selects phenotype for one extreme
• those with suited phenotype will survive and pass on their population
• mean of population will move towards these characteristics

Question 13

What is disruptive selection

Answer 13

• both extremes of the normal distribution are favoured over he mean
• selects for booth extremes of the phenotype

Question 14

What causes selection pressures

Answer 14

Environmental factors

Question 15

Define speciation

Answer 15

• Where a population is split and isolate, there are different selective pressures on the 2 groups
• if the genetic makeup changes to the extent the 2 groups can no longer breed and produce fertile offspring

Question 16

What is meant by allopathic speciation

Answer 16

• Speciation resolution from a physical barrier eg river
• the environments occupied by the 2 groups are different and therefor different alleles are favoured

Question 17

What is sympathise speciation

Answer 17

• speciation resolution from. Non physical barrier eg. Mutation no longer allows 2 organisms to produce fertile offspring
• changes in anatomy or behaviour may also prevent breeding

Question 18

Define genetic drift

Answer 18

• A change in a populations allele frequency occurs due to chance rather than selective pressures

Question 19

Why does genetic drift affect small populations more tan large ones

Answer 19

The gene pool is smaller so there are less alleles available and any change in frequency becomes pronounced ver quickly