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Ecosystem: All the organisms living in a particular area and all the
abiotic conditions.

Trophic levels:

Producer => primary consumer (herbivore) => secondary consumer
=> tertiary consumer

Decomposers: break down decaying material, releasing minerals that
can be absorbed by plants, e.g. fungi and bacteria and also
detritivores, earthworms.

Energy losses:…

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Pyramids of energy: Shows the amount of energy available in each trophic
level - kgm²yr¹

Always pyramid shaped ­ most accurate representation of
energy flow e.g. compared to pyramid of biomass => two
organisms of same dry biomass may store different amounts of
energy. However, collecting data can be difficult…

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Intensive farming: Involves converting the smallest possible amount of
food energy into the greatest quantity of animal mass.

The efficiency of energy conversion is increased so more
biomass is produced and productivity is increased.
Environment is kept warm to reduce heat loss from the body.
Predators are excluded so there…

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As succession continues, the ecosystem becomes more complex.
Species diversity increases and the abundance of each species
Climax community: The final seral stage, where the ecosystem is
supporting the most complex community of plants and animals it
can. ­ It won't change much more.

The Carbon Cycle: Shows how…

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provide the plant with nitrogen and the plant provides them with

Ammonification: Nitrogen Compounds (dead organisms) =>
Ammonium compounds.

Animal waste also contains nitrogen compounds which are also
converted into ammonium compounds by decomposers.

Nitrification: Ammonium compounds => Nitrogen Compounds

These nitrogen compounds can then be used by plants.…

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Phenotype: The characteristics of an organism i.e. the expression of it
genetic composition.

Dominant allele: Always expressed in the phenotype even when
there's only one copy.

Recessive allele: An allele whose characteristic is only expressed in
the phenotype if two copies are present.

Co-dominance: Where two alleles both contribute in…

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Allele Frequency is affected by differential reproductive success:

The frequency of an allele within a population can change when
the allele codes for a characteristic that affects the chances of an
organism surviving.
Therefore, not all individuals are as likely to reproduce as each
other. ­ Differential reproductive success.

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The two groups will have become two different species.

Photosynthesis converts light energy to chemical energy in the form of glucose.

Takes place in the chloroplasts.

Respiration: There are four stages in aerobic respiration: glycolysis, the
link reaction, the Krebs cycle and the electron transport chain.

Glycolysis: - the splitting…

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2 molecules of reduced NAD go into the last stage of

Krebs cycle: This is the addition of acetylcoenzyme A into a cycle of
oxidation-reduction reactions that yield some ATP and a large
number of electrons.

Takes place in the matrix of the mitochondria.
1. Acetyl CoA (2C) from…

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4. The protons accumulate in the space between the 2
mitochondrial membranes before they diffuse back into the
matrix of the mitochondria through protein channels.
5. At the end of the chain, the electrons combine with these protons
and oxygen to form H2O.
Oxygen is the final acceptor of electrons…


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