B10 GENETIC DIVERSITY AND ADAPTATIONS

What is variation?

the difference that exits between individuals

What is interspecific variation?

variation between species

What is intraspecific variation?

variation within species

What is variation between different species due to?

genetic factors

What is variation within the same species due to?

genetic factors (different alleles) or environmental factors

What is a gene pool?

the sum of all the alleles of the genes in a population at a particular time

What is genetic diversity?

the number of different alleles of genes in a gene pool of a population

What is allele frequency?

how often different alleles occur in the gene pool of a population

What is genetic diversity acted upon by?

natural selection, resulting in a species becoming better adapted to their environment

What does being more genetically diverse mean if there is an environmental change?

the more likely some individuals will possess characteristics that better suit the new environment

What is genetic diversity within a population increased by?

• mutation which produces new alleles

• meiosis due to independent segregation and crossing over

• fertilisation due to the random fusion of gametes

What can genetic diversity be decreased by?

• certain events like genetic bottlenecks

• inbreeding

• genetic drift

What’s a genetic bottleneck?

an event which causes a large reduction in the number of individuals within a population which does not select between individuals, which reduces the number of different alleles in the gene pool

What is the founder effect?

when a small group splits off from the main population to found a colony, which has a small number of different alleles compared to the main population

What does inbreeding cause?

reduced genetic diversity

What is natural selection?

process by which organisms that are better adapted to their environment survive and reproduce in greater numbers, resulting in the increase of the frequency of the advantageous allele within the population

What are the principles of natural selection?

1. theres variation within a population due to a random mutation

2. the environment applies a selection pressure

3. better adapted organisms with the advantageous allele survive and reproduce

4. these pass on their advantageous allele to their offspring increasing the reproductive success

5. over many generations the frequency of the advantageous allele increases within the population

What’re selection pressures?

organisms are subject to selection pressures due to the environment they live in

What’re examples of selection pressures?

• competition

• disease

• predation

How can organisms be better adapted?

• anatomical adaptions (large ears)

• physiological adaptions (venom)

• behavioural adaptions (bird migration)

What does differential reproductive success mean?

not all individuals are as likely to reproduce as each other

What does increased reproductive success mean?

when the environment changes, some organisms will reproduce more successfully than others and will leave more offspring

When do organisms have increased reproductive success?

• more likely to survive and reach reproductive age

• more likely to grow sufficiently well to reproduce successfully

• more likely to attract a mate

What is evolution?

the change in frequency of an allele in a population over time

What’re different types of natural selection?

• stabilising selection

• directional selection

• disruptive selection

What is stabilising selection?

• occurs in populations where the environment is stable

• selective pressure at both ends of distribution

• selects for the average

• selects against the extremes

• reduces variability and the size of the range within the population

• reduces opportunity for evolutionary change

What is directional selection?

• environmental change may produce a new selection pressure that favours an extreme characteristic

• when conditions change optimum necessary for survival also changes

• some organisms possess the new optimum

• over time selection means these are more likely to survive and reproduce and the mean will shift

What is antibiotic resistance an example of?

directional selection

How do antibiotics work?

• prevent the formation of bacterial wall

• bacteria take in water, swell and lyse (osmotic lysis)

• may also interfere with bacterial reproduction

How can bacteria become resistant?

• some bacteria have alleles for resistance due to random mutation

• exposure to antibiotics is the selection pressure

• non-resistant bacteria will die

• resistant bacteria survive and reproduce

• frequency of resistance allele increases in population of bacteria