paper 1: Genetic Diversity and Adaptations

Question 1

what is genetic diversity

Answer 1

number of different alleles of genes in a population

Question 2

what is genetic diversity also known as

Answer 2

the gene pool

Question 3

what is allele frequency

Answer 3

how often a particular allele occurs within a population

Question 4

how is genetic diversity in a poluation increased

Answer 4

• meiosis and random fertillisation of gametes
• random mutation in DNA
• gene flow (different alleles being intorduced into the population when individuals from another population migrate into it and reproduce

Question 5

how is genetic diversity within a population decreased and why

Answer 5

• when a small number of organsisms from a population start a new colony as they are geographically isolated from the rest of the population
• when an event causes a big reduction in the size of a population
• selective breeding

because
- they all lead to a decrease in the number of different alleles in a population
- the frequency of certain alleles in a population can decrease

Question 6

how does geographical isolation of a small group lead to a decrease in genetic diversity

Answer 6

• a small number of organisms from a population start a new colony as they are geographically isolated from the rest of the population
• so smaller number of alleles from original gene pool
• by chance the frequency of each allele in the new colony might be different to the frequencies in the original population - may not be representative
• e.g. a rare allele in the original population may become more common in new population
• can lead to higher incidence of genetic disorders e.g. the Amish people

Question 7

explain how an event which causes a large reduction in population size decreases the genetic diversity within a population

Answer 7

• reduces the number of different alleles in a gene pool and so reduces the genetic diversity
• the survivors reproduce ceating a larger poulation from a few individuals so there is reduced genetic diversity e.g. northern elephant seals

Question 8

explain how selective breeding can decrease the genetic diversity of a population

Answer 8

• using individuals with desirable characteristics to parent offspring
• this redcues the variety of alleles in the population and reduces genetic diversity

Question 9

where has selective breeding been used

Answer 9

• has been done extensively with farm animals and crop plants to produce high yielding strains e.g. breeding cows that produce high yields of milk

Question 10

write a model answer for a natural selection question

MASSRIFT

Answer 10

1. a random mutation in an organism
2. forms advantageous allele (name allele)
3. which gives them a selective advantage in presence of a selection pressure (name it)
4. organism with advantageous allele is more likely to survive and reproduce
5. some offspring of organism will inherit the advantageous allele (name it)
6. over many generations the allele frequency in the population increases
7. is an example of directional/ stabilising selection

Question 11

define evolution

Answer 11

the gradual chnage in species over time

Question 12

what factors are key in evolution

Answer 12

adaptation
selection

Question 13

what are adaptations

Answer 13

features that help organisms to survive in thier environment

Question 14

what are behavioural adaptations and give an example

Answer 14

• organsims can chnage their behaviour in order to survive
• e.g. possums play dead to escape an attack

Question 15

what are physiological adaptations and give an example

Answer 15

• chemical process inside an organisms body which increases chnaces of survival
• e.g. brown bears hibernate by lowering metablosim over winter, conserving energy so they dont have to hunt when food is scarce

Question 16

what are anatomical adaptations and give an example

Answer 16

• structural features of an organisms bosy which increases the chnages of survival
• e.g. whales have large layer of blubber which helps insulte them, increasing thier chnaces of survival in cold waters where food is found

Question 17

describe stabilising selection

Answer 17

• ocurs in all populations where environment is stable
• selective pressure at both ends of distribution
• decrease in frequency of the extremes
• reduces the size of range within a population
• reduces range of possible characteristics in the population

Question 18

draw a graph showing stabilising selection

Answer 18

Question 19

give an example of stabilising selection

Answer 19

birth mass in humans

Question 20

describe diretional selection

Answer 20

• mean population represents optimum for existing conditions
• environmental chnage may produce new selection pressure thay favours an extreme charcateristic
• ## when conditions change, optimum charcateristics also change

Question 21

draw graph showing dircetional selection

Answer 21

Question 22

give an example of directional selection

Answer 22

antibiotic resistance in bacteria

Question 23

give an example of antibiotic resistant bacteria

Answer 23

MRSA

Question 24

how do antiobiotic resistant bacteria develop resistance to multiple antiobiotics

Answer 24

• due to random mutation
• ana llele for resistance to penicillin may already exist in the population
• when penicillin is used this creates a selection pressure in environment
• allele for resistance gives bacteria the selective advantage in presence of penicillin
• bacteria is more likely to survive and reproduce than bacteria without allele
• some offspring inherit penicillin resistant allele
• allele frequency increases in population over time
• example of directional selection