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life processes in biosphere (part 2) (factors affecting mortality rates…
life processes in biosphere (part 2)
conservation of plagioclimax communities
plagioclimax = human activity that deflects the climax community occurs regularly, so the natural climax community does not have time to reform and a new community of species develop
if the human activity that produced plagioclimax stops, then secondary succession will eventually re-establish the climax community
species diversity and ecological succession
extreme environments with fluctuating abiotic factors = low species diversity
simpsons diversity index formula
secondary succession - ploughing, burning etc; recreate the conditions that were suitable fir the species that colonised the area earlier in the sequence of ecological succession .
population dynamics
the processes that can cause populations to change in size and structure
population regulation
number of species that live in an area is controlled by the balance of factors which tend to increase or reduce the population
birth rate
death rate
r - selected species = species that can respond rapidly to low survival rates = produce many young and disperse widely - mice
k - selected species = recover slowly from a decline in population = produce few long but live for a long time - whales, elephants
maximum sustainable yield = an estimate of the greatest exploitation that is possible without causing unsustainable long-term population decline
factors affecting mortality rates
density independent factors = factors where the population density has no effect on the chances of survival of an individual
density dependent factors = factors where the chances of an individual surviving depend on the population density of species
survival chances are usually higher when the population density is low
carrying capacity
= greatest population that an area can support indefinitely without damaging or over exploiting the environment
predator-prey population relationships
- when the prey populations rises there is a lot of food for the predators - so their population rises = decrease prey population
artificial population control
- intervention to artificially control the population though culling may be required to enable the species to or habitats to survive where natural control mechanisms no longer regulate the population