2 - Niches

Predator prey cycles: what happens as prey numbers grow?

there will be more food for predators

Predator prey cycles: what happens when theres more food for predators?

predator population will increase

Predator prey cycles: what happens as predator numbers increase?

prey numbers will be driven down

Predator prey cycles: what happens as prey numbers decrease?

predators will run out of food and numbers will drop

Define a niche

what position an organism takes in an ecosystem and how it interacts with the environment

Early concepts of niches: Darwin (1859)

recognised the concept of the ecological niche

Early concepts of niches: Grinnell (1917)

defined a habitat niche - the position of an organism in the environment

Early concepts of niches: Elton (1927)

defined niches as roles of organisms in its community in the sense of jobs

What can niches be seen as a balance of?

requirements and tolerances

Interspecific competition

when under competition for a limited resource, individuals of one or both species will suffer decreased growth, fecundity, or survivorship

Give an example of indirect competition

diatoms require silicate to grow but don’t interact directly, so the use of silicate by one limits what the other can use

Give an example of direct competition

barnacles competing for space on a beach

The competitive exclusion principle

no two species can co-exist in a stable environment without niche differentition

State two outcomes of competition for niches

• one species will be competitively excluded (extinction or emigration)

• the two will be driven apart to reduce competition

Give an example of spatial partitioning

plants thriving in different light levels

Give an example of temporal partitioning

life cycles of mantids being 2-3 weeks out of phase