F215 OCR A2 Biology Module 3 Ecosystems and Sustainability

This is the third module in F215 for OCR Biology. As with the others I have put up it is very detailed an answers every part of the specification. 

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  • Created on: 12-06-11 13:37
Preview of F215 OCR A2 Biology Module 3 Ecosystems and Sustainability

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F215-Module 3-Ecosystems and Sustainability
5.3.1 Ecosystems
a. Define the term ecosystems
Ecosystems-All of the living organisms and no-living components in a specific
habitat and their interactions.
b. State that ecosystems are dynamic systems
They are dynamic systems because the population rises and falls due to the
interactions of living organisms between each other and with the physical
c. Define the terms biotic factor and abiotic factor using named examples
Biotic factor
o These are factors due to living organisms.
o E.g. food supply, predation, disease.
Abiotic factor
o The factors and effects of the non-living components.
o E.g. pH of the soil, temperature and soil type.
d. Define the terms producer, consumer, decomposer and tropic levels
Producer-These are the autotrophic organisms such as plants, some protoctists
and some bacteria that convert light energy to chemical energy which is then
supplied to consumers.
Consumer- Living organisms that feed on other living organisms.
Decomposer- Organisms that feed on dead organic material releasing
molecules, minerals and energy for other living organisms in that ecosystem to
Trophic levels-These are the level at which an organism feed in a food chain.
e. Describe how energy is transferred by ecosystems
Producer Primary consumer Secondary consumer Tertiary consumer
Food webs show the transfer of energy by showing which way the energy flows.
f. Outline how energy transfers between trophic levels can be measured
Pyramids of biomass
o Area of bars are proportional to the dry mass of all the organisms at
that trophic level.
Pyramids of energy
o Burning the organisms in a calorimeter and work out how much heat
energy is released per gram by calculating it from the temperature rise
of a known mass of water.

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The rate of energy flow passing through each trophic level.
o Gross primary productivity-The rate at which plants convert light energy
into chemical energy.
o Net primary productivity-The energy available to the primary consumer.
It is gross primary productivity-the energy lost when the plant respires.
g. Discuss the efficiency of energy transfer between trophic levels
At each trophic level some energy is lost from the food chain.
o Because of living organisms needing energy to carry out life processes.
o Loss via heat energy.…read more

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When the plants die and decay, nutrients accumulate in the sand making
the conditions more favourable.
o Plants like sea sandwort and sea couch grass colonise it. The sea couch
grass has long roots which help to stabilise the sand.
o More nutrients are added so plants like sea spurge and marram grass can
grow. Marram grass is a xerophyte. It also traps windblown sand in its
shoots which means sand accumulates and the dunes grow in height.…read more

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Nitrogen fixing
Can occur via lightening or the Haber process.
Mostly happens using nitrogen fixing bacteria e.g. Rhizobium.
They are in root nodules of legumes or free in the soil.
Mutualistic relationship with the plants by providing fixed
nitrogen and getting carbon compounds.
In anaerobic conditions nitrogen reductase reduces nitrogen gas
to ammonium ions.
Chemoautotrophic bacteria in the soil absorb ammonium ions.
They gain energy from oxidising ammonium ions to nitrates or by
oxidising nitrites to nitrates.
Nitrosomonas bacteria oxidise ammonium ions to nitrates.…read more

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Because of there being less predators, less prey is eaten so they prey's
population increases.
5. Because there is more prey the predator population increases.
d. Explain the terms interspecific and intraspecific competition
Interspecific competition
o Competition between individuals of different species.
o Affects both the population size of a species and the distribution within
an ecosystem.
o Could include species of the same niche but one will be outcompeted.
o E.g. Food
Intraspecific competition
o Competition between individuals of the same species.
o E.g.…read more

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o Protecting areas of land as yet unused by humans.
f. Explain how the management of an ecosystem can provide resources in a sustainable
way, with reference to timber production
Small scale production
o Coppicing-Cutting the tree close to the ground and new shoots will grow
from them.
o Pollarding-Like coppicing but cutting the tree higher so animals cannot
eat the growing shoots.
o Rotational coppicing-Dividing a wood into sections and coppicing one each
year.…read more

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Natural New drugs to cure of financial value to
environments are a diseases may be humans.
valuable source of found.
potentially Every living thing
beneficial Tourism. has a right to
resources. survive.
Wild insect species Humans have an
are needed for ethical
pollination. responsibility to
looks after species.
Reduction in
biodiversity may Genetic diversity
cause droughts or should be
flooding with maintained.
economic costs.
i.…read more

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Introduced species
o E.g. goats which out compete the giant tortoise and they trample the
o They destroy the natural environment.
o They outcompete local species.
o They can carry disease which other species may be vulnerable to.…read more


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