| Genetic bottleneck | - Occurs when a population is greatly reduced in size, limiting the genetic diversity of the species. |
| KEY WORDS | - Gene pool
- Variety of alleles
- Mutation
- Selection pressure
- Selected for/against alleles
- Survive and reproduce
- Increase allele frequency |
| Selection pressure | - Those factors that influence the direction of natural selection
e.g. use of antibiotics or predation |
| Speciation | - The evolution of new species from existing species
- The driving force is natural selection |
| Species | - A population of organisms that reproduce to produce fertile offspring |
| What speeds up rate of speciation? | - Mutation rate
- Geographical isolation/emigration
- Selective pressures
- Genetic bottleneck
- Generation time
- Size of genome |
| Evolution of species | - Geographical isolation
- Separate gene pools
- Variation due to mutation
- Different selective environmental pressures
- Selection for different alleles
- Organisms survive and reproduce
- Leads to change in allele frequency |
| 2 types of speciation | - Allopatric speciation
- Sympatric speciation |
| Allopatric speciation | - A population is geographically isolated
- Different environmental selection pressure lead to formation of new species |
| Sympatric speciation | - A population (in the same area) is reproductively isolated
- Different environmental selection pressure lead to formation of new species |
| Carrying capacity | - The maximum population size that an ecosystem can support |
| Factors that affect carrying capacity | - Food/nutrients - nitrogen conc, glucose conc
- Predators
- Temperature
- Avaliabluty of nesting sites
- O2 conc...light intesity....
- The effect of abiotic factors
- Interactions between organisms: interspecific and intraspecific competition and predation |
| Calculation for growth rates | N = No x 2^n
N = size of pop
No = no. of generations
n = starting size |
| Genetic drift | - A change in allele frequency in small populations
- Small populations have a smaller variety of alleles
- Mutant alleles will increase in populations quicker
- Speciation is quicker |
| Founder effect (type of genetic drift) | - When the genetic variation of a population is reduced when a small group of individuals becomes separated from a larger population |
| Genetic bottleneck (type of genetic drift) | - Sharp reduction in the size of a population (decreasing genetic diversity) due to environmental events and/or human acitivity |
| Explain how evolutionary change over a long period of time has resulted in a great diversity of species | - Through speciation.... explain this |
