chapter 23 - ecosystems

Ecology

the study of the interaction between organisms and their environment

Ecosystem

all the interacting living organisms and the non-living conditions in an area

Dynamic

continuously developing or changing

Biotic

the living components of an ecosystem

Abiotic

the non-living components of an ecosystem

Ectotherms

animals that use their surroundings to warm their bodies so their core temperature is heavily dependent on the environment

Endotherms

animals that rely on their metabolic processes to warm their bodies and maintain their core temperature

Edaphic

the study of the interaction between organisms and their environment

Trophic level

stage in a food chain

Biomass

mass of living material

Producer

organism that converts light energy into chemical energy

Consumer

organism that obtains its energy by feeding on another organism

Primary consumer

the first consumer in the food chain / the second trophic level / An organism that eats a primary producer (E.g. grass)

Secondary consumer

an organism that obtains its energy by feeding on primary consumers

Tertiary consumer

an organism that obtains its energy by feeding on secondary consumers

Quaternary consumer

an organism that obtains its energy by feeding on tertiary consumers

Dry mass

the mass of an organism or tissue after all water has been removed

Ecological efficiency

efficiency where energy or biomass is transferred from one trophic level to the next

Decomposition

chem reaction where a compound is broken down into simpler compounds

Decomposer

organisms that break down dead organisms, releasing nutrients back into the ecosystem

Saprotrophs

organisms that acquire nutrients by absorption - mainly of decaying material

Saprobiotic nutrition

obtaining nutrients from dead or waste organic matter via extracellular digestion

Detritovores

feeds on and breaks detritus into smaller pieces, increasing surface area and speeds up decay

Detritus

dead/decaying material

Nitrogen fixation

conversion of nitrogen gas to ammonium compounds

Nitrification

conversion of ammonium compounds into nitrites and nitrates

Nitrifying bacteria

contains the enzyme nitrogenase which combines Nitrogen with Hydrogen to form ammonia (NH₃) used in plants

Nitrobacter

oxidises nitrites → nitrates

Denitrification

in absence of oxygen (e.g. waterlogged soils), denitrifying bacteria converts nitrates back into nitrogen gas

Ammonification

process where decomposers convert nitrogen-containing molecules in dead organisms, faeces and urine into ammonium compounds

Succession

process where ecosystems change over time to reach a climax community

Primary succession

when newly exposed land with no species present is gradually colonised by an increasing number of species

Secondary succession

occurs on areas of land where soil is present, but contains no plant or animal species

Seral stage

the steps in succession

Pioneer community

the first organisms to colonise an area

Intermediate community

made up of secondary colonisers, tertiary colonisers and scrubland

Climax community

when the community is in a stable state

Humus

produced by pioneer species when they die and decompose, creating nutrient rich soil, supporting the growth of secondary colonisers

Plagioclimax

the final stage when succession stops artificially

Conservation

the maintenance of biodiversity

Line transect

a tape measure is marked along the ground and samples are taken at specified points

Belt transect

where you lay 2 tape measures, and collect samples from the areas in between

Systematic sampling

different areas of a habitat are identified and sampled separately. carried out using a line or belt transect

Abundance

the number of individuals of a species present in an area at any given time