Biology 7. Ecosystems and the Distribution of Organisms

Ecosystem

An ecosystem consists of all the organisms living within a particular habitat (the community) and the non-living components with which the organisms interact

Habitat

The place where an organism lives

Community

All of the organisms living within a particular habitat

Population

A group of organisms of the same species

Biodiversity

Refers to the range of species in an ecosystem

Niche

The role an organism plays within a community

It relates to the resources it requires in its ecosystem and it’s interaction with other organisms in the community eg biotic and abiotic factors

Producer

An organism that can make its own food. Typically green plants through photosynthesis

Consumer

An organism that eats other organisms to gain energy. Can be primary, secondary, or tertiary

Herbivore

A consumer that consumes producers

Carnivore

A consumer that only consumes other consumers

Omnivore

A consumer that consumes both producers and consumers

Biotic factors and examples

Biotic factors are those which originate form the presence or activities of other living things eg competition, disease, food availability, grazing and predation

abiotic factors and examples

Abiotic factors are those which have a non living origin, they can often be measured using instruments eg light intensity, soil moisture, pH, temperature

Interspecific competition

Occurs among individuals of different species for on or a few resources they require eg food

Intraspecific competition

Occurs amongst individuals of the same species and it for all of the resources the require. Intraspecific competition is therefore more intense than interspecific competition

How do you measure soil pH/moisture

Use a pH/moisture meter

Place probe in the same depth each time

clean and dry the probe in between uses

How do you measure light

Use a light meter

Don’t cast a shadow over the meter

Take readings at the same time of day

Take reading at the same height

How to use a quadrat

Always throw the quadrat at random

Decide what to do with organisms that are in the boundary of the quadrat

Make sure everything counted is living within the area (not detached dead or with roots outside the quadrat

Problems and solutions of a pitfall trap

The result may not be representative of the ecosystem as a whole-set up multiple traps

birds may eat trapped animals-have a cover supported in sticks to camouflage the trap from predators

Trap may fill up with water-have drainage holes

Animals may eat each other whilst in the trap- check traps regularly and release animals quickly

Animals don’t fall in-ensure the cup is level with the surface if the soil

Trap too shallow so organisms can crawl out-dig trap deeper

Line transect

A series of quadrants places at regular distances along a sample line

All sample sites must be selected randomly, without bias, in order to give a representative sample

Take multiple samples to ensure the results are reliable

What do arrows represent in a food chain

The flow of energy

What causes loss of energy in a food chain

Foot raten is undigested and expelled as feaces

Some of the energy is used for moving about

Some of the energy is used for heating/keeping warm

Predator

An animal which kills and eats its prey

Prey

Pyramids of energy

A diagram showing the total energy contained within organisms at each level of the food train. The size of the bar represents the energy present at each level. They are always regular because energy is always lost at each tropic level

Pyramid of numbers

A diagram showing the relationship of numbers of organisms at each tropic level in a food chain, the size of the bar represents the size of the population. Numbers often decrease along a food chain to give a regular shape, but not always