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4.4 genetic diversity and adaptation, mutation - Coggle Diagram
4.4 genetic diversity and adaptation
lesson 1: diversity and natural selection
definitions
genetic diversity
the number of different alleles in a population
allele
form of a gene
population
a group of individuals of the same species occupying a specific place at a particular time (can interbreed)
gene pool
the different alleles in a population
allele frequency
how common the allele is as a proportion of all the alleles of that gene
explaining evolution by natural selection (general structure - apply to given question)
mutation creates new allele and this creates variation between individuals (say what)
individuals with allele (for...) are more likely to survive and reproduce (say why)
offspring inherit the allele (for...)
over many generations the frequency of the allele (for...) increases in the population
over many generations the proportion of organisms with the characteristic (say what) increases in the population
lesson 2: evolution of antibiotic resistance in bacteria
mutation creates allele for antibiotic resistance
repeated use of antibiotic creates selection pressure
bacteria with antibiotic resistance are more likely to survive and reproduce
offspring inherit the allele for antibiotic resistance
over many generations the frequency for resistance allele increases in population
lesson 3: adaptations
the new alleles lead to adaptations, adaptations can be:
anatomical
a physical feature e.g long teeth
physiological
part of the organisms biochemistry e.g being able to oxidise fat to create water
behavioural
what an organism does e.g foraging at night
types of selection
disruptive
natural selection that maintains high frequencies of two different sets of alleles, individuals with intermediate phenotypes or alleles are selected against
e.g For example, birds that live on the Galapagos Islands use their beaks to forage for different sized seeds. The size of the bird's beaks are either small or large with the intermediate medium-sized beak selected against
stabilising
natural selection that keeps allele frequencies relatively constant over generations
things stay as they are unless there is a change in the environment
e.g human birth weight
directional
natural selection that produces a gradual change in allele frequencies over several generations
This usually happens when there is a change in environment / selection pressures or a new allele has appeared in the population that is advantageous
mutation
can be silent - not shown in phenotype
creates new alleles (these may be inherited if the mutation occurs prior to meiosis)
can be beneficial e.g bacteria - gives resistance to antibiotics
can be harmful e.g inherited disorders such as cystic fibrosis
