7-18/19 Evolution + Ecosystems Flashcards
What are the five causes of evolution?
Mutation Gene flow Non-random mating Isolation Natural selection
What is evolution caused by?
A change in the allele frequencies in a population
What causes a non-evolving population?
Very large population
No migration
No mutation
Random mating
What is stabilising selection?
Where there is no environmental change
This tends to eliminate the extremes of the phenotypes
What is directional selection?
When the environmental conditions change, the optimum has changed
One extreme is favoured over the other
This causes a shift in the mean phenotype
What is disruptive selection?
Where the extreme phenotypes are favoured over the mean ones
It occurs when the environmental factor takes two forms
What is speciation?
The evolution of new species from existing ones
This involves reproductive separation
What is adaptive radiation?
The variations of alleles in the gene pools of different populations of species leads to each population becoming adapted to the local environment
What is genetic drift?
Smaller populations have a lower genetic diversity
This means that there is not an equal chance of each being passed on
Those passed on will quickly affect the whole population
This makes speciation occur faster
What is allopatric speciation?
Where two populations become geographically separated
The difference in environmental conditions between locations leads to a difference in natural selection
What is ecology?
The study of the inter-relationships between organisms and their environment, including abiotic and biotic factors
What are the two major processes within an ecosysten?
The flow of energy
The cycling of elements
What is the carrying capacity?
The size of the population that the ecosystem can support
What affects the carrying capacity?
The effect of abiotic factors
Interactions between organisms e.g. competition and predation
How is the growth of a population expressed?
Through logarithms
