Natural Selection

natural selection

process by which a species becomes better adapted to its envrionment; individuals wiht favourable characteristics have a survival advantage and so pass those characteristics to offsprings

what was natural selection based on?

• variation

• birth rate

• nature’s balance

variation

differences between individuals of a species

birth rate

all living organisms reproduce at a rate far greater that that at which food supply and resources can provide

nature’s balance

altho birth rate is hihg, each species’ numbers tended to remain at a constant level

struggle for existence

principle where the number of organisms is greater that the resources in the environment can support; therefore competition

survival of fittest

principle whereby organisms with favourable characteristics survive and weak die

selective agent

any factor that causes death of organisms with certain characteristics

heterozygote advantage

situation where a heterozygous genotype has a higher chance of survival than either homozygous genotype