Evolution

Question 1

What is evolution

Answer 1

A change in inherited characteristics of a group of organisms over time

Question 2

What is evolution in alleles

Answer 2

-A change in allele frequency over time

Question 3

What is stabilising selection

Answer 3

• Occurs when environment stays unchanged
• Favours the intermediate phenotype types (increase in ‘average’ alleles than reduction in ‘extreme’ alleles
• The norms and averages are selected

Question 4

What is directional selection

Answer 4

• Associated with a change in environment
• Normal phenotype is not an advantage
• Organisms who are less common and have more extreme phenotypes will be positively selected
• Positive selection in more ‘extreme’ phenotypes

Question 5

What is disruptive selection?

Answer 5

• Opposite of stabilising disruption
• ‘Extreme’ phenotypes are selected for
• ‘Average’ phenotypes are selected against

Question 6

What is genetic Drift?

Answer 6

Variations of allele frequency in small populations due to chance

Question 7

How do genetic drift affect smaller populations?

Answer 7

• By chance, individuals have better breeding and so their alleles become more numerous
• Or due by random sampling during reproduction, some alleles are not passed on

Question 8

What is the founder effect?

Answer 8

• Extreme example of genetic drift
• Small populations arise due to establishment of new colonies by isolated individuals
• Smaller populations have smaller gene pools than original population and display less variation
• If carried to new population, the frequency of alleles in the original population will have a higher population in the new, smaller population

Question 9

Bottlenecks

Question 10

Bottlenecks

Question 11

What is a Hardy-Weinberg Principle

Answer 11

• A mathematical model to calculate allele frequency in a population

Question 12

What are the assumptions of the Hardy-Weinberg Principle

Answer 12

• Population is large
• Mating within population is random
• No selective advantage for any genotype
• No mutation, migration or genetic drift

Question 13

What is cystic Fibrosis

Answer 13

• Problems in mucus production
• Affects CTFR protein
• In Britain, 1 in 3300 babies born with cystic fibrosis

Question 14

What is a species?

Answer 14

• A group of organisms with similar morphology and physiology, which can (theoretically or actually) interbreed with one another to produce fertile offspring.
• This is the ‘Biological Species Concept’

Question 15

How to get two genetically isolated populations?

Answer 15

• A particular set of circumstances reduces gene flow between two populations of a species
• Over time, genetic differences between populations (caused by genetic drift) starts to accumulate
• Once sufficient changes occur, the populations may become reproductively isolated
• This reproductive isolation can be either pre-zygotes or post-zygotic

Question 16

What is allopatric speciation?

Answer 16

Physical barrier that leads to geographic isolation
Environments of the different groups will be different and the selection pressures result in different physical adaptation

Question 17

What is allopatric speciation?

Answer 17

Physical barrier that leads to geographic isolation
Environments of the different groups will be different and the selection pressures result in different physical adaptation

Question 18

What is Sympatric Speciation?

Answer 18

• Occurs within populations of the same habitat
• Less frequent than allopatric and occurs more in plants
• Members of two different species interbreed and form fertile offspring
• The hybrid formed will have a different no. of chromosomes and no longer interbreed with neither of the parent population
• This stops gene flow and isolates the hybrid population.

Question 19

What is artificial selection?

Answer 19

• An evoluntary process in which humans consciously select for or against particular features in organisms

Question 20

How and why do we selectively breed animals?

Answer 20

• By selecting a breeding of animals for with desirable characters by farmers
• E.g. high resistance to disease, high crop yields, producing better quality of food

Question 21

How and why do we selectively breed plants?

Answer 21

• Plants cross with plants to form hybrids more frequently than animals
• This happens by the release of the large number of pollen grains
• High growth rate, high crop yield

Question 22

What are the potential problems of selective breeding?

Answer 22

• Limiting the gene pool and decreasing genetic diversity reduces the chances of inbred organisms adapting to the changes of the environment
• Many genetic disorders can be produced e.g. cystic fibrosis (same recessive alleles)
• Pedigree dogs are used to trap animals for people to hunt, fighting or herding
• Big dogs often have heart and hip problems.

Question 23

What are gene banks?

Answer 23

• Store biological samples like seeds, sperms and eggs