Population, evolution, speciation, artificial selection

Question 1

Continuous Variation

Answer 1

A characteristic that can take any value within a range e.g height

Question 2

Discontinuous Variation

Answer 2

A characteristic that can only result in a discrete value e.g blood type

Question 3

Cause of continuous variation

Answer 3

Both genetic (polygenic) and environmental factors

Question 4

Causes of discontinuous variation

Answer 4

Mostly genetic

Question 5

What are three types of selection pressures that can affect evolution

Answer 5

Stabilising, directional and disruptive

Question 6

What is stabilising selection?

Answer 6

A type of natural selection where intermediate phenotypes are favoured and extremes are selecting against, creating consistency e.g medium sized peacocks

Question 7

Directional selection?

Answer 7

A type of natural selection that occurs when an environmental change favours a new phenotype= changes population mean e.g black peppered moth

Question 8

Genetic drift

Answer 8

Change in frequency of an existing allele in the population due to random chance/event

Question 9

Genetic bottleneck

Answer 9

When a population size shrinks and increases again- caused by the events that kill almost the the whole population only leaving a few individuals— reduces gene pool

Question 10

What does the Hardy Weignberg equation assume?

Answer 10

• Large population sample
• Mating is random
• No mutation, genetic drift or founder effect

Question 11

Population

Answer 11

Members of a species living in the same place at the same time that can interbreed

Question 12

What are isolating mechanisms/speciation in organisms?

Answer 12

Mechanisms that divide populations into subgroups and could lead to evolution of new species

Question 13

Allopatric speciation

Answer 13

Formation of two different species from one due to geographical isolation

Question 14

Sympatric speciation

Answer 14

Formation of two different species from one due to reproductive isolation, while two populations inhabit the same geographical location

Question 15

Artificial breeding

Answer 15

Selective breeding of organisms where humans choose desired phenotypes and interbreeding them individually

Question 16

What can artificial breeding lead to?

Answer 16

Interbreeding depression- Inheritance of harmful recessive alleles due to homozygosity

Question 17

Hybrid vigour

Answer 17

Crossing individuals from seperate gene pools to obtain heterozygous alleles

Question 18

What are desirable characteristics in crops that a selectively bred for?

Answer 18

• Drought tolerance
• Increased yield
• Resistance to insects
• Shorter ripening time

Question 19

Desirable characteristics for livestock

Answer 19

• Higher milk yield
• Leaner meat
• Increased wool production

Question 20

Ethical considerations of selective breeding of dogs

Answer 20

• Susceptible to diseases due to inbreeding
• Body pains

Question 21

Ethical considerations of selective breeding of livestock

Answer 21

• More lean meat (die at colder temsps)

Question 22

Why can a genetic bottleneck lead to low genetic diversity?

Answer 22

Many alleles are lost when population drops and modern population descends from few survivors

Question 23

Founder effect

Answer 23

The reduction in genetic variation that occurs when a small group of individuals becomes relocate to an isolated area from a larger population— small pop breeds = small gene pool