Habitat definition:
The place where an organism lives
Population definition:
All of the organisms of one species, who live in the same place at the same time and who can breed together
Community definition:
All of the populations of different species, who live in the same place at the same time and who can interact with each other
Niche definition:
The role of an organism
Biotic factors in an ecosystem:
- Producers
- Consumers
- Decomposers
Abiotic factors lethal at both extremes:
- PH
- Temperature
Abiotic factors lethal at one extreme:
-Level of pollutants
Cyclic changes definition (ecosystem):
These changes repeat themselves in a rhythm. e.g. tides
Directional changes definition (ecosystem):
Changes that go in one direction. They tend to last longer than the lifetime of organisms within the ecosystem e.g. erosion
Unpredictable/ erratic changes definition (ecosystem):
Changes that have no rhythm or constant direction. e.g. the effects of lighting or hurricanes
What is the equation for ecological efficiency?
(Biomass at higher trophic level / biomass at lower trophic level) x 100
How can net primary productivity be increased?
- Drought resistant crops
- Greenhouses
- Crop rotation
- Pesticides (insects)
- Fungicides (fungal infections)
- Herbicides (weeds)
How can secondary productivity be improved?
- Harvesting animals just before adulthood, when the largest proportion of their energy is used for growth
- Selective breeding
- Antibiotics
- Supply animals with food so they don’t waste energy getting it themselves
Climax community definition:
The final stable community that exists after the process of succession has occurred
Deflected succession definition:
When succession is stopped or interfered with, e.g. grazing or when a lawn is mowed
Pioneer species definition:
The species that begun the process of succession, often colonising an area as the first livings things there
Succession definition:
Progressive change in a community of organisms over time
In the nitrogen cycle, what are the nitrogen fixing processes?
- N2 in air fixed by RHIZOBIUM bacteria in leguminous plants
- N2 in air fixed by free living bacteria in the soil e.g. AZOBACTER
- N2 in air fixed by Haber process. Turned into ammonium and nitrate ions in fertiliser
- N2 in air fixed by lighting. Turns into nitrogen oxide and then nitrates in the soil
In the nitrogen cycle, what are the nitrification processes?
In soil:
- Ammonium oxidated by bacteria e.g. NITROSOMONAS into nitrites
- Nitrites oxidised by bacteria e.g. NITROBACTER into nitrates
In the nitrogen cycle, what are the decomposition and ammonification processes?
- Organic nitrogen in soil into ammonium
- Urea into ammonium
In the nitrogen cycle, what are the denitrifyign processes?
-Nitrates in soil denitrified by bacteria into N2 in air
