3.4.4 - genetic diversity and adaptation

Question 1

what is genetic diversity?

Answer 1

the number of different alleles of genes in a species or population

a large number of different alleles in a population means a large variety of different characteristics and a high genetic diversity

Question 2

describe the principles of natural selection.

Answer 2

-random mutations can result in new alleles of a gene
-many are harmful but in some environments they can be advantageous
-individuals with advantageous alleles have an increased chance of survival
-this makes them more likely to reproduce and pass on these alleles
-this means a greater proportion of the next generation will have these alleles
-these are more likely to survive and reproduce
-over generations, this leads to evolution as the advantageous alleles become more common.

Question 3

what are the three types of adaptation after natural selection?

Answer 3

1. behavioural adaptations
2. physiological adaptations
3. anatomical adaptations

Question 4

what are behavioural adaptations and an example?

Answer 4

the way an organism acts that increases its chance of survival

e.g. possums sometimes ‘play dead’ if they are being threatened by a predator to escape attack, increasing chance of survival

Question 5

what are physiological adaptations and an example?

Answer 5

the processes inside an organisms body that increase its chance of survival

e.g. some bacteria produce antibiotics which kill other species of bacteria in the area. this means there is less competition so they are more likely to survive

Question 6

what are anatomical adaptations and an example?

Answer 6

the structural features of an organisms body that increase its chance of survival

e.g. whales have a thick layer of fat which helps keep them warm in the cold sea, increasing chances of survival

Question 7

what is directional selection?

Answer 7

where individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce

Question 8

what is stabilising selection?

Answer 8

where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce

Question 9

what are the two types of selection?

Answer 9

1. directional
2. stabilising

Question 10

what is a factor that enable natural selection to occur?

Answer 10

genetic diversity

Question 11

when does directional selection occur?

Answer 11

in response to an environmental change

Question 12

what is an example of directional selection?

Answer 12

bacteria evolving antibiotic resistance:
-some individuals in a bacterial population have alleles which give them resistance to an antibiotic
-the bacterial population is exposed to the antibiotic, which kills the bacteria which is non resistant
-resistant bacteria survives and reproduces without competition, passing on the allele giving resistance
-after some time, all bacteria in the population will have the resistant allele

Question 13

when does stabilising selection occur?

Answer 13

when the environment isn’t changing, and it reduces the range of possible characteristics

Question 14

what is an example of stabilising selection?

Answer 14

human birth weight:
-very small babies are less likely to survive as they have a high surface area to volume ration so find it harder to maintain their body temperature which puts pressure on their respiratory and cardiac system
-very large babies are less likely to survive as giving birth to them makes it harder for them to fit through the pelvis which can lead to complications for the mother and child
-conditions are most favourable towards medium sized babies so the weight of human babies tends to shift towards the middle of the range