ECOLOGICAL NICHE

Niche = an organism’s role or way of life in a community. Depends on the adaptive features, and the habitat of the organism. (Kind of like the organism’s ‘job’)

ECOLOGICAL NICHE

I want you to just take brief notes about all this information!

Gause – Russian biologist who studied the interactions between 2 species of protist.

Put both species in a test tube and then after a while only one species remained.

Which species survived depended on the conditions in the tube – he concluded that

“No two species can occupy the same ecological niche in the same habitat for an indefinite period”

GAUSE’S PRINCIPLE

Competition will be high if the two species’ habitats overlap.

CHARACTER DISPLACEMENT

Competition will be high if the two species’ habitats overlap.

However, is can be reduced by character displacement – a characteristic that is different on one species.

CHARACTER DISPLACEMENT

Competition will be high if the two species’ habitats overlap.

Comp. can be reduced by character displacement – a characteristic that is different on one species.

This enables the two species to co-exist.

CHARACTER DISPLACEMENT

Organisms that are evolutionarily different but share similar niches.

EG.

ECOLOGICAL EQUIVILENTS

Group of individuals of the same species living in one area at one particular time.

POPULATION

POPULATION

Difficult to count WHOLE populations, so a sample is taken.

MEASURING POPULATION

Difficult to count WHOLE populations, so a sample is taken.

Sample is usually random, so can represent the typical population.

MEASURING POPULATION

Difficult to count WHOLE populations, so a sample is taken.

Sample is usually random, so can represent the typical population.

To measure the size of a population in mobile organisms, mark-recapture techniques are used – capture, label, release.

MEASURING POPULATION

Difficult to count WHOLE populations, so a sample is taken.

Sample is usually random, so can represent the typical population.

To measure the size of a population in mobile organisms, mark-recapture techniques are used – capture, label, release.

Size of population = total number in 1 s t sample x total number in 2 n d sample

number of marked animals recaptured in second sample

MEASURING POPULATION

1. 60 stoats are caught and released. 3 months later, 25 stoats are captured, 14 of which have already been tagged.

Size of stoat population =

2. 25 blue ducks are tagged. 1 month later 20 are captured, and 12 of them already have tags. Size of blue duck population =

USING THE POPULATION EQUATION

Line placed across a habitat.

TRANSECTS

Line placed across a habitat.Transect is divided into intervals and at each interval

the population is sampled.

TRANSECTS

Line placed across a habitat.Transect is divided into intervals and at each interval

the population is sampled. Used when species are affected by environmental

factor (Eg. Trampling of plants on lawn affecting their distribution)

TRANSECTS

Square frame used to isolate area so number of organisms can be counted.

QUADRATS

Square frame used to isolate area so number of organisms can be counted.

Often used where organisms cannot move.

QUADRATS

Square frame used to isolate area so number of organisms can be counted.

Often used where organisms cannot move.

QUADRATS

INSTRUCTIONS.