| what is evolution | the gradual change of a species over time which can lead to change within a species or production of a new species |
| what does the evolution process depend on? | variation within a species
there must be variation within a species for evolution to occur |
| what is a mutation | a random change to an organisms genetic material (DNA)
they are spontaneous and are the only source of new alleles |
| name environmental factors (mutagenic agents) that increase natural rate of mutation | radiation
chemicals |
| what is different type of effect can mutations have on an individuals ability to survive and reproduce | advantageous: increased ability to survive and reproduce
disadvantageous: decreased ability to survive and reproduce
neutral: no change on an individuals ability to survive and reproudce |
| what can new alleles produced by mutation result in? | plants and animals becoming better adapted to their environment |
| what does variation within a population make possible? | for a population to evolve over time in response to changing environmental conditions |
| describe the four stages in the evolution process | species produce more offspring than the environment can sustain
natural selection or survival of the fittest occurs when there are selection pressures
the best adapted individuals in a population survive to reproduce, passing on the favourable alleles that confer the selective advantage
these alleles increase in frequency within the population |
| what is meant by speciation? | the formation of new species |
| what are the four stages of speciation? | isolating mechanisms
mutations
natural selection
speciation |
| describe the isolating mechanisms stage of speciation | speciation starts after a part of a population becomes isolated by an isolation barrier. This may be
geographical: rivers, mountain ranges, etc
ecological: differences in the level of an abiotic factor
behavioural: birds with different mating behaviours or times when active |
| describe the mutation stage of speciation | different random mutation occur in each population |
| describe the natural selection stage of speciation | natural selection selects for different mutations in each group due to different selection pressures |
| describe the final stage of the speciation process | each sub population evolves until they become so genetically different that they are two different species |
| what is an adaptation | an inherited characteristic that makes an organism well suited to survival in its environment/niche |
