TOPIC 4 - genetic diversity and adaptation

Question 1

define population?

Answer 1

all of the organisms of a particular species that live in the same place

Question 2

what is an allele?

Answer 2

different forms of a particular gene, found at the same locus (position) on a chromosome. A single gene could have many alleles.

Question 3

define genetic diversity?

Answer 3

the total number of different alleles in a population

Question 4

what advantage does high genetic diversity provide?

Answer 4

ability to adapt to a change in the environment, allows natural selection to occur.

Question 5

explain how natural selection results in development of new charactersitics?

Answer 5

• random mutations result in new alleles
  -some alleles provide an advantage, making an individual more likely to survive and reproduce
• their offspring receive the new allele, and frequency continues to increase over many generations.

Question 6

what is directional selection?

Answer 6

-occurs when environmental conditions change
-individuals with phenotypes suited to the new conditions will survive and pass on their genes
-over time the mean of the population will move towards these characteristics.

Question 7

give an example of directional selection?

Answer 7

antibiotic resistance
- bacteria with a mutation which allows them to survive in the presence of antibiotics will reproduce
- therefore frequency of this allele will increase and the population will shift to have a greater antibiotic resistance.

Question 8

what is stabilising selection?

Answer 8

• occurs when environmental conditions stays the same
  -individuals closest to the mean are favoured
• results in low diversity

Question 9

give an example of stabilising selection?

Answer 9

• birth weight
  -babies that weight around 3kg are more likely to survive than those at lower or higher weights.

Question 10

what are the three types of adaptations?

Answer 10

• anatomical (changes to the body structure) eg oily fur
• physiological (changes to bodily processes) eg venom production
  -behavioural (changes to actions) eg. hibernation

Question 11

define a niche?

Answer 11

the role of a species within an environment. species sharing the same niche will compete each other.

Question 12

what are the other factors that can affect the frequencies of allele in a population?

Answer 12

• the founder effect
• genetic drift
• the bottleneck effect

Question 13

what is the founder effect?

Answer 13

-a small number of individuals from a large parent population start a new population
-only some of the total alleles from the parent population will be present
- not all of the gene pool is present in the smaller population

Question 14

what is genetic drift?

Answer 14

• in a small population, chance can effect which alleles are passed onto the next generation
• alleles can be lost or favoured by CHANCE
• When there is a gradual change in allele frequencies in a small population due to chance and not natural selection then genetic drift is occurring

Question 15

what is the bottle neck effect?

Answer 15

• large population suffers dramatic fall in numbers
  -reduces the genetic diversity in the population as alleles are lost
  -The surviving individuals end up breeding and reproducing with close relatives (inbreeding)
  = serious lack in genetic variation