3.4 Adaptation, natural selection and the evolution of species

• isolation barrier is introduced • organisms are now exposed to different conditions(climate, food competition…) • random mutations occur • -favourable mutations survive and are passed onto the next generation • unfavourable mutations are killed and die • this happens for many generations • eventually the two subpopulations are so different that they can no longer interbreed and produce fertile offspring

• geographical • ecological(change in abiotic factors) • behavioural(organisms may select different food sources or mating)

• ionising radiation(x-rays, nuclear fallout) • ultraviolet radiation(from the sun) • chemical mutagen(mustard gas)

• soot covered the trees and the light variety weren’t able to camouflage and were killed • the dark variant survived and passed their characteristics onto the next generation • the abundance of the dark variety increased and the species survived as a result

the process in which the weak are “weeded out”. organisms that are better adapted to their environment have a better chance of passing these favourable characteristics onto the next generation it ensures that the best adapted individuals survive

an inherited characteristic that makes an organism suited for survival in its environment

the formation of a new species due to natural selection and changing environmental conditions

• camouflage • long necks in giraffes • insulated fur

neutral-no effect on the phenotype disadvantageous-have a negative effect(cystic fibrosis) advantageous-has a positive effect(pepperd moth example)

Behavioural - hibernation, migration Physiological - temperature regulation structural - camouflage

to evolve over time in response to changing environmental conditions

a change to the structure or composition of an organisms genetic mater

a favourable characteristic which gives an organism an increased chance of survival

a factor that affects a population resulting in the death of some individuals and survival of others

a isolation barrier caused by adaptation to living conditions

an isolation barrier caused by differences in timing, location or complexity of mating rituals that prevents members of the populations from mating even if they are not geographically separated

barrier that prevents interbreeding and gene exchange between sub-populations of a species

• predation • food shortage • disease