Ecosystems and Population Size

Question 1

Define community

Answer 1

A community is all of the populations of different species living and interacting in a place at the same time.

Question 2

Define ecosystem

Answer 2

An ecosystem is the dynamic interaction between all the living
(biotic) and non-living (abiotic) factors in a given area.

Question 3

Explain - specific ecological niche

Answer 3

Within an ecosystem, every organism occupies a specific ecological niche
A niche includes all the abiotic and biotic conditions of the environment which organisms are adapted to.

Question 4

Define carrying capacity

Answer 4

The carrying capacity is the maximum population size that can be maintained over a period in a particular habitat

Question 5

Abiotic limiting factors of the carrying capacity

Answer 5

Temperature & pH — each species has its optimum levels, and deviations from this optimum reduce population growth
Light — low light levels reduce the carrying capacity of producers, reducing the population size of consumers
Water — low water availability reduces the population size

Question 6

Biotic limiting factors of the carrying capacity

Answer 6

Interspecific competition (between different species)
Intraspecific competition (within the same species)
Predation

Question 7

How can the population be estimated, for slow-moving or non-motile organisms?

Answer 7

Randomly placing quadrats, or quadrats along a belt transect. Can count the number of individuals of each species in the quadrat or percentage cover.

Question 8

How can the population be estimated, for motile organisms?

Answer 8

mark-release-recapture

population = {sample 1 size X sample 2 size} / no. marked in sample 2

Question 9

What does mark-release-recapture assume?

Answer 9

It assumes there is no deaths, births, migration, marking has no effect and enough time for the animals to mix.