3.2 Natural Selection Flashcards
What is an ecological niche?
The role of an organism in its environment. How it feeds, its predators and how it interacts with the non-living environment around it
What is adaptation?
The process by which an organism becomes fitted to its environment
What are the different types of adaptation?
Anatomical
Phsiological
Behavioural
What are physiological adaptations?
Changes to the metabolism of an organism
What are anatomical adaptations?
Changes to the actual structure of an organism
What are behavioural adaptations?
Changes in the behaviour of an organis
Why does a population have natural genetic diversity?
Random mutations of genes
Genetic variation from meiosis
What selection pressures can cause natural selection?
Predators
Availability of food
Diseases
Explain the steps of natural selection
Genetic variation Selection pressure Allele gives advantage Organisms survives Reproduce Over many generations Allele frequency increases
What is evolution?
The development of new types of living organisms from pre-existing types by the accumulation of genetic differences over a period of time
What are pieces of evidence for evolution?
Fossils DNA molecule is the same DNA as a molecular clock Proteonomic and genomics Ribosomal RNA studies
How can DNA be used as a molecular clock?
Mutations happen at a constant rate so you can estimate time of divergence into two species of a species
What is a species?
A group of organisms which can interbreed to form fertile offspring
What is the gene pool?
All the possible genes and alleles present in a population
What is speciation?
The process by which a species is formed from another one
Give the stages of speciation
Reproductive isolation Separate gene pools Different selection pressures on the gene pools Natural selection occurs Change in allele frequency Different so cannot breed
In what ways can reproductive isolation be brought about?
Allopatric speciation
Sympatric speciation
What is allopatric speciation?
When two populations are physically separated from each other using a physical barrier so they cannot interbreed and gene pools cannot mix
What is sympatric speciation?
When two populations can mix freely but they cannot interbreed
Give examples of changes which can lead to sympatric speciation?
Mismatched genitalia
Behavioural changes
Formation of sterile offspring
What is stabilising selection?
Environmental conditions are stable and favourable alleles are preserved. Gets rid of abnormalities
What is directional selection?
Where conditions change so that it’s favourable to change in one direction
What is disruptive selection?
Mean trait is eliminated
Extreme traits are favoured
