biotic factors affecting pop size

give 2 biotic factors which may affect pop size:

• competition

• predation

give and define the 2 types of competition:

• interspecific competition - competition for resources between different species

• intraspecific competition - competition for resources within the same species

give a key difference between interspecific and intraspecific competition:

intraspecific competition also involves competition for a mate

what effect does increasing population density have on competition?

• increase in pop density → increase in competition intensity

• so lower birth rate

what is outcompetition?

when one species/organism is more well-adapted to the environment than another

what is predation?

when an organism (predator) kills and eats another (prey)

describe a typical predator-prey graph:

• size of predator and prey pop both fluctuate

• there will always be more prey than predators

• the size of the prey population will always change before the predator population - lag time 

explain the shape of the predator-prey graph:

• increase in prey pop → more food for predators → increase in predator pop

• → more predation on prey → decrease in prey pop

• → increases competition among predators for food → decrease in predator pop

• → increase in prey pop as more successful reproduction