Transcript tolerate adverse conditions

Density dependent factor
Only affects the population once it has grown to a certain
density (size)
Density independent
Affects the growth of a population regardless of the
population density
Give two examples of a density-independent factors
Flood,drought (forest fire)
Give 4 examples of an density-dependent factors
Availability of food, disease, predators, build up of toxic
wastes
As the density of the population increases what effect would each of
the above factors have?
As the density increases the availability of food could limit the growth
of the population ie intra-specific competition would increase
As the density increases then disease can spread quickly through the
population and this will decrease the numbers
As the density increases then predation will increase
As the density of the population increases there will be a greater build
up of toxic wastes which will decrease the population.
List 4 reasons why it would be useful to monitor the population of
animals or plants
Need the animal or plant as a food supply eg fish
Species is endangered and in need of protection and conservation
Species can be an indicator species and by its presence or absence it
indicates the level of pollution
They could be a pest like mosquitoes / locust
Succession begins with pioneer species
List two pioneers
Lichens and mosses
Why can they grow at the start of succession and not other
species?
Pioneer species have adapted to tolerate adverse conditions
eg a Hardy plant / shallow root system / use wind dispersal
The area the pioneers are growing in will have very few
nutrients
What increases as succession moves towards the climax
community?
The nutrients will increase
Organic matter will increase
Ability to retain water will increase
Succession is unidirectional – explain this term
Each group of species makes the soil suitable for the next group of
species to grow and establish itself.
Lichens/ mosses ---- small flowering plants---- bushes--- trees
Climax community
Increased stability - will not be taken over by other species
Increased biomass – a lot mote living matter
Increased species diversity