Genetic diversity and adaptation

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  • Created by: Hindleyc
  • Created on: 23-06-18 16:35
What is Genetic diversity?
The number of alleles of genes in a population
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What is it a measure of
How many variations there are in the genetic code between individuals of a particular species / between different species
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What else is genetic diversity
Factor enabling natural selection to occur
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What can the gene pool do?
Change in content (new alleles arriving/ existing alleles being lost)
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What is the ratio of alleles altering due to
Mutation , natural selection, gene flow immigration emigration, mate selection
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What is the gene pool
In any population- total variety of genes and alleles present
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For evolution to occur in real populations what must happen
Some of gene freq must change with time
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What is Allele freq?
Number of times an allele for a particular trait occurs compared to the total number of alleles for that trait
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Calc
No. of a specific type of Allele/ Total number of alleles in the gene pool
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What is reproductive success?
Passing genes to a new generation so that the new generation may also produce offspring to pass those genes on
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Process of natural selection
Random mutation can result in new allele of a gene- many M harmful but in certain environments the new allele of a gene might benefit its possessor leading to inc R.S
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Then
Advantageous allele is inherited by members of next generation and as a result over many generations the new allele inc in freq in the population
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What does natural selection result in
Species that are Better adapted to their environment- adv may be anatomical, physiological or behavioural
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Although members of a species have many features in common
They aren't identical to each other
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What variation occur as a result as
Mutation that creates new forms of genes (alleles) which can be inherited by the next generation
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What do some members of a species do
Reproduce at a rate that creates more offspring that the environment can support and so some die because of factors such as predation, food shortages or disease
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What are well adapted individuals
Those which have inherited characteristic such as the ability to avoid predators, compete strongly for food or resist disease- have inc reproductive success
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So what do they do?
Survive and reproduce passing on genes that make them successful- have selective advantage
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What does the process of natural selection ensure
That most members of a species are well adapted to their environment
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What does natural selection allow
Species to respond to changes in the environment
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What happens over many generations
New alleles increases in freq in the population
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The larger the gene pool
Greater the genetic diversity of the population
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A population with large genetic diversity *(large GP) has
Survival advantage and likely to be more resilient to change in the environment beauuse some individuals will have genes that allow them to survive under new conditions
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What does a population with low genetic diversity lose
It ability to adapt to new conditions
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What is selection
Process by which organisms that are better adapted to their environment survival and breed while those that are less well adapted fail to do so
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what do populations do over time
Change as their environment changes
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What do different environmental conditions favour?
different characteristics
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Why is direction selection common
As most environments do change
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When does it occur?
When one extreme phenotype is favoured over the other extreme
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When does this happen
When the environment changes in a particular way( biotic and abiotic so organisms evolve in response to each other)
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What are these individuals more likely to do
Survive and breed therefore contribute more offspring to next generation that other individuals
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What happens to mean
Shift/moves in direction of these individuals
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what happens to phenotypes at one extreme of population
They are selected for and those at other extreme are selected against eg antibiotic resistance
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What is Disruptive/ diverging selection
Both extremes of phenotype favoured- selected over intermediate types eg bird beaks
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What is stabilising or normalising selection
Occurs when intermidate phenotype is selected over extreme phenotypes and tends to occur when the environment doesn't change much. eg birth weights
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What are individuals with phenotypes at the extremes less likely to pass on
Their alleles
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what does it do
Eliminate phenotypes at extremes and selects for phenotypes around mean
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What doesn't natural selection have to cause
Directional change- if environment doesn't change there is no pressure for well adapted species to change
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What do fossils suggest
Many species remain unchanged for long periods
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Other cards in this set

Card 2

Front

What is it a measure of

Back

How many variations there are in the genetic code between individuals of a particular species / between different species

Card 3

Front

What else is genetic diversity

Back

Preview of the front of card 3

Card 4

Front

What can the gene pool do?

Back

Preview of the front of card 4

Card 5

Front

What is the ratio of alleles altering due to

Back

Preview of the front of card 5
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