IGCSE Chapter 14 Ecosystems

Define the term ecosystem.

All of the living (biotic) and non-living (abiotic) components in a place.

Give three advantages of using biological control rather than chemical pesticides.

No resistance (not immunity).

No damage to other species.

Specific to pest.

Long lasting.

Less harm to environment.

Give three reasons why 90% of the energy in herbivores is not transferred to carnivores.

Heat lost from respiration.

Some not eaten.

Some not digested (egested).

Some excreted.

How do you calculate the dry mass of an organism?

Heat until constant mass to evaporate the water.

Name one type of organism that is a decomposer.

Bacteria or fungi.

Name the bacteria that convert nitrite into nitrate.

Nitrifying bacteria.

Name the type of bacteria that break down dead organic tissue into ammonium compounds.

Decomposing bacteria.

Name the type of bacteria that convert nitrate into nitrogen gas.

Denitrifying bacteria.

Name the type of bacteria that convert nitrogen gas into ammonium compounds.

Nitrogen fixing bacteria.

Suggest three advantages of farming fish rather than catching fish from the wild.

Can control diet / water quality / oxygen / temperature / waste / predation / disease.

Less variation (among individual fish).

Less depletion of wild fish.

No risk of catching other species.

What do the arrows in a food web represent?

Flow of energy.

Is eaten by.

What is meant by the term 'community'?

The populations of all the species in a habitat.

What is meant by the term 'population'?

Number of organisms of a species.

Which biological molecules contain nitrogen?

Amino acids / proteins.

DNA.