- Generally microorganisms
- Secrete enzymes onto dead and waste material
- Enzymes break down material
- Molecules are absorbed into the organism
- Once absorbed, molecules are stored to be respired in order to release energy
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The Nitrogen Cycle and bacteria's role within it
- Nitrogen is highly unreactive so needs to be fixed for plants to utilise it.
- Bacteria such as Rhizobium live within root nodules of bean plants.
- The bacteria supply the plant with fixed nitrogen in exchange for carbon (mutualistic relationship)
- Occurs once chemoautotrophic bacteria absorb ammonium ions.
- These bacteria gain energy from absorbing by oxidising ammonium ions to nitrates or nitrites to nitrates.
- Some bacteria convert nitrates into nitrogen gas.
- Occurs in anaerobic conditions- bacteria use nitrates as a source of oxygen, releasing nitrogen gas nitrous oxide.
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- Only a few individuals.
- Still adjusting to a new habitat.
- Rate of reproduction is slow.
- Individuals have adapted to habitat.
- Resources are plentiful and competetion is minimal.
- Reproduction exceeds mortality.
- Population size is rapidly increaseing.
- Population has levelled out.
- This is the carrying capacity.
- The habitat can't maintain a higher population.
- Reproduction and mortality rates are equal.
- Population size remains fairly constant.
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Factors that determine carrying capacity
- Factors that are related to living things such as:
- Competition, both interdependent and intradependent
- Factors that are not related to living things:
- Availabity of water or food
- Extreme, freak weather
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Predators and Prey
Population of both predator and prey size often follows a pattern similar to:
- Predator population increases
- Demand for prey increases from the predator
- Prey population decreases as a result of predation
- Predator has less prey for food so competition increases
- With increased competition, predator populaton decreases
- As a result of decreased predator population, prey population increases
- With an increase in prey the predator population increases
- The cycle starts again
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