natural selection Flashcards
(17 cards)
What are all organisms subject to in their environment?
Selected pressures
What are examples of selected pressures?
Predation, disease and competition
What is the process of evolution dependent on?
Natural selection
What is selection due to?
The environmental conditions favouring particular phenotypes
What does a change in environment result in?
A particular phenotype being better adapted to this environment to survive and reproduce
What is this called?
Differential survival and differential reproductive success
What will happen with these alleles?
They will be passed on to the next generation.
What increases in frequency?
Selected phenotype, favourable allele.
What are the different types of natural selection?
Stabilising, directional, disruptive.
When does stabilising selection occur?
When the environment isn’t changing.
What does stabilising selection favour?
Organisms with alleles with characteristics towards the middle of the range.
When does directional selection occur?
The environment is changing.
What does directional selection favour?
An extreme end of the range.
What does this result in?
More organisms with an extreme phenotype.
What is disruptive selection?
The opposite of stabilising selection.
What does disruptive selection involve?
Favour of the phenotypes at the two extremes.
What would disruptive selection result in?
Divisions in the two extremes - could cause distinct populations.
