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Genetic Variation and Change (Natural Selection (Disruptive Selection…
Genetic Variation and Change
Natural Selection
Charles Darwin (creator)
Disruptive Selection
when selections pressure acts against individuals in the middle of the trait distribution.
results in the two extremes of the curve creating their own smaller curves and increasing
Stabilizing Selection
when selective pressure selects against the two extremes of trait
Survival of the fittest
increases favorable alleles
survivors of environmental change successfully reproduce
survivors pass on favorable alleles
decreases unfavourable alleles
low number of survivors during environmental change
alleles can be lost
directional selection
when selective pressure selects againts one extreme of the trait
Sexual reproduction
Requires two parent organisms
Organism with sperm and an organism with Ova
Takes time
variation
bottleneck effect
A population can sometimes be reduced to low numbers in a population due to human action or environmental effects
Founding population are smaller than the parent population and this may result into reduced frequency and range of alleles. Genetic biodiversity decreases amongst a population.
founders effect
Emigration
Founding population are smaller than the parent population and this may result into reduced frequency and range of alleles
genetic drift
refers to how the frequency of alleles can change due to small chance rather than selection pressure.
tends to decrease the variation within a population
likely to occur after the founder effect
genetic drift is chance or random changes in the frequencies of alleles
asexual reproduction
one parent required
no variation
Fast process
Plants
photosynthesis
evolution
The change of characteristics over a long period of time
The survival of the fittest
Millions of years