paper 1: Genetic Diversity and Adaptations Flashcards
what is genetic diversity
number of different alleles of genes in a population
what is genetic diversity also known as
the gene pool
what is allele frequency
how often a particular allele occurs within a population
how is genetic diversity in a poluation increased
- 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
how is genetic diversity within a population decreased and why
- 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
how does geographical isolation of a small group lead to a decrease in genetic diversity
- 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
explain how an event which causes a large reduction in population size decreases the genetic diversity within a population
- 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
explain how selective breeding can decrease the genetic diversity of a population
- using individuals with desirable characteristics to parent offspring
- this redcues the variety of alleles in the population and reduces genetic diversity
where has selective breeding been used
- 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
write a model answer for a natural selection question
MASSRIFT
- a random mutation in an organism
- forms advantageous allele (name allele)
- which gives them a selective advantage in presence of a selection pressure (name it)
- organism with advantageous allele is more likely to survive and reproduce
- some offspring of organism will inherit the advantageous allele (name it)
- over many generations the allele frequency in the population increases
- is an example of directional/ stabilising selection
define evolution
the gradual chnage in species over time
what factors are key in evolution
adaptation
selection
what are adaptations
features that help organisms to survive in thier environment
what are behavioural adaptations and give an example
- organsims can chnage their behaviour in order to survive
- e.g. possums play dead to escape an attack
what are physiological adaptations and give an example
- 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
what are anatomical adaptations and give an example
- 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
describe stabilising selection
- 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
draw a graph showing stabilising selection
give an example of stabilising selection
birth mass in humans
describe diretional selection
- 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
draw graph showing dircetional selection
give an example of directional selection
antibiotic resistance in bacteria
give an example of antibiotic resistant bacteria
MRSA
how do antiobiotic resistant bacteria develop resistance to multiple antiobiotics
- 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
