Topic 7 - Divergent and Convergent Evolution

Similar selection pressures on unrelated species may lead to convergent evolution. ● Recognise and give examples of convergent evolution. Succession is the gradual change in the mix of species in an area over time, following a disturbance Describe the processes of primary and secondary succession Species or populations that have a reduced genetic diversity have a higher risk of extinction Give examples of species with low genetic diversity

what is convergent evolution

refers to two species that resemble each other but are unrelated

why does convergent evolution occur

generally because they are able to survive similar selection pressures

what are some examples of convergent evolution

• echidna + hedgehog

• Shark + Dolphin

what is divergent evolution

slow and gradual accumlation of new characteristics to accomodate for differing selection pressures

when does divergent evolution occur

two different species share a common ancestor but have different characterisitics (speciation)

what is sucession

the change in evironmental conditions over time

what are some physical factors that can cause sucession

• flood

• fire

• glacier movement

• asteriods

what are some bioticl factors that can cause sucession

• human actitivites

• disease

• predation

• change in migration patterns

what are the two types of sucession

• primary

• secondary

what is primary sucession

occurs when communities develop on entirely new land without any established soil

where does prinary sucession occur

river deltas, glaciers, sand dunes, exposed rocks

what is the common process of primary sucession

pioneering species first colonise the region. As the lichen and moss (pioneering species) die, they decompoose which creates the first organic soil capable of sustaining plant growth

what causes does primary sucession cause

• soil depth will increase and soil pH qill alter

• soil minerls contact will increase

• soil will become aeroated and water retention will increase

what is secondary sucession

change in one established community which occurs after a major environemntal event (bush fire, flood, landslide)

what is the process of secondary sucession

• event destroys climax community but leaves behind soil rather then rock

• this creates an oppotunity for new species to get established

• occurs over a much shorter time period