Ecosystem and sustainability, OCR- Unit 5, module 3

Ecosystem and sustainability, OCR- Unit 5, module 3

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Sameer Jahabarali Biology
Unit 5 Module 3- Ecosystem and sustainability
An ecosystem is the interrelationship between biotic (living) and
abiotic (non-living) components. It is a dynamic system that is very
active where changes in one affect another. Factors that affect or
change the ecosystem are:
Biotic factors- factors affected by living things, such as an
increase in population of one species
Abiotic factors- factors caused by non-living thins such as
nitrogen levels in soil
Organisms within an ecosystem are categorised in relation to the food chain, which indicates the energy
transfer of one organism to another. The trophic level of an organism is the position it occupies in the food
chain, this is categorised as such:
Producer- organisms that convert light energy into chemical energy for themselves and `provide' for
others, such as plants, algae and some bacteria
Consumers- organisms who feed on other organism to obtain energy, this is subdivided in to
o Herbivores- primary consumers that feed of produces, such as snails
o Carnivores- secondary consumers and over, that feed of animals, such as lions
Decomposers- organisms that feed on waste material of dead organisms, such as fungi, bacteria
and some animals (e.g. vultures)
The rate of energy transfers between trophic levels can be measured using the measure of productivity.
This is carried out through, measuring the availability of energy to organisms in a particular trophic level, per
square meter, over a year. Efficiency of energy transfer between trophic level is decreased due to:
Respiration of the organism to carry out life processes
Respiration loses heat energy
Energy stored in the organism cannot be digested by the organism at the higher trophic level
However, humans can manipulate energy transfer to increase:
Primary productivity (rate of production of biomass (chemical energy) by improving:
Light intensity
Water levels or irrigating crops to with stand droughts
Pests and insects resistance
Fungal diseases resistance
Competition (decrease)
Secondary productivity (rate of energy transfer from producers to consumers) by controlling:
Harvesting animals just be for adulthood, as adults invest less energy for growth

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Sameer Jahabarali Biology
Unit 5 Module 3- Ecosystem and sustainability
Steroids to increase growth rate
Selective breeding, to increase growth rate, milk yield and egg production
Antibiotics, to prevent unnecessary loss of energy fighting pathogens
Prevention of grazing, to minimise energy loss of moving around and outdoors temperature loss
Successions are directional changes in community overtime. A primary
succession is the development of communities from bare.…read more

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Sameer Jahabarali Biology
Unit 5 Module 3- Ecosystem and sustainability
Microbes perform an important role carbon and nitrogen cycle
Bacteria are needed to recycle nitrogen within the ecosystem. Nitrogen is unreactive component that
makes amino acids and nucleic acid. Nitrogen cycles between biotic and abiotic components in the ecosystem
and within the nitrogen cycle, bacteria are involved in:
Nitrogen fixation- converts nitrogen into in to a more reactive form or `fixed' nitrogen, such as NH4+.…read more

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Sameer Jahabarali Biology
Unit 5 Module 3- Ecosystem and sustainability
population, unless the habitat has a higher variety of species of prey and predators. This is because:
More predators, prey eaten
Less prey available, less predators eat and survive
Less predators, more prey accumulates
More prey, more predators eat an accumulate
Cycle continues
Competition occurs when resources are not present in adequate amount to satisfy the need of all the
individuals within a habitat.…read more


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