Evolution of species Flashcards
What are alleles?
Different versions of the same gene.
What is a mutation?
A random change to genetic material. This means the order of the bases is different. If the order of the bases is different this may result in a change to the structure of the protein that the DNA codes for.
What is variation?
The differences within a population.
What is evolution?
The gradual change in organisms over a very long period of time.
Why do mutations happen?
Mutations are spontaneous. This means there is often no cause for a mutation happening. Some environmental factors can increase the rate of mutation. E.g. radiation and some chemicals.
What is natural selection?
A scientific theory that explains how evolution happens.
When does natural selection occur?
When there are selection pressures on organisms.
What re the steps of natural selection?
1) Species produce more offspring than the environment can sustain.
2) The best adapted individuals in a population survive.
3) The survivors reproduce and pass on favourable alleles with the selective advantage.
4) The favourable alleles increase in frequency within the population.
What is speciation?
The process of new species evolving. Speciation occurs in 3 major steps.
What are the 3 steps of speciation?
1) Isolation- Part of a population becomes isolated by an isolation barrier, which can be geographical, ecological or behavioural.
2) Mutation- Over a long period of time, different mutations will occur in each sub population.
3) Natural Selection- There will be different selection pressures acting in the 2 groups. Each sub-population evolves until they become so genetically different that they are 2 different species.
Examples of geographical barriers
Rivers, oceans, mountains
Examples of ecological barriers
pH, salinity, different habitats
Example of behavioural barriers
Differences in mating behaviour
