• Created by: chantelle
  • Created on: 10-05-11 21:50


  • Ecology - the study of the inter-relationships between organisms and their environment.
  • Ecosystem - all of the interacting biotic and abiotic features in a specific area.
  • Population - a group of interbreeding organisms of one species in a habitat. 
  • Community - all the populations of different organisms living and interacting in a particular place at a particular time. 
  • Habitat - the place where a community of organisms lives. 
  • Niche - describes how an organism fits into the environment.
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Abundance is the number of individuals of a species within a given space.

  • frequency, which is the likelihood of a species occurring in a quadrat. This is useful where a species is hard to count e.g. grass. It gives a quick idea of the species present and their general distribution
  • percentage cover, which is an estimate of the area within a quadrat that a particular plant covers. It is useful where a species is particularly abundant or difficult to count. Data can be collected rapidly as individual plants do not need to be counted. It is less useful where organisms occur in several overlapping layers
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total number of individuals in the first sample x number of individuals in the second sample/
number of marked individuals recaptured 

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***INTERSPECIFIC COMPETITION - different species***

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population growth =
(births + immigration) - (deaths + emigration)

population percentage growth rate (in a given period) =
population change during the period/
total population in the same year
x 100

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Birth rates are affected by:

  • economical conditions
  • cultural and religious backgrounds
  • social pressures and conditions
  • birth control
  • political factors

    number of births per year/
    total population in the same year
    x 1000

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Death rates are affected by:

  • age profile
  • life expectancy at birth
  • food supply
  • safe drinking water and effective sanitation
  • medical care
  • natural disasters
  • war

number of deaths per year/
total population in the same year

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  • Stable population - where the birth and death rate are in balance and there is no increase or decrease in the population
  • Increasing population - where there is a high birth rate, giving a wider base to the population pyramid and fewer old people, giving a narrower apex to the pyramid - economically less developed countries.
  • Decreasing population - where there is a lower birth rate and a lower mortality rate leading to more elderly people - economically more developed.(http://upload.wikimedia.org/wikipedia/commons/thumb/0/0a/Dtm_pyramids.png/450px-Dtm_pyramids.png)
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Energy and ATP

ATP + (H2O) ---> ADP + Pi + energy

  • photophosphorylation takes place in chlorophyll-containing cells during photosynthesis
  • oxidative phosphorylation occurs in the mitochondria during electron transport
  • substrate-level phosphorylation occurs when phosphate groups are transferred from donor molecules to ADP to make ATP.

ATP is a better immediate energy source than glucose:

  • Each ATP molecule releases less energy than each glucose molecule so it is released in smaller, more managable quantities.
  • The hydrolysis of ATP to ADP is a single reaction that releases immediate energy whereas the breakdown of glucose is a long series of reactions so energy realease takes longer. 
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Energy and ATP

  • metabolic processes. ATP provides the energy to build up macromolecules from basic units. e.g. polypeptide synthesis from amino acids
  • movement. ATP provides the energy for muscle contraction. In muscle contraction, ATP provides the energy for the filaments of muscle to slide past one another and shorten the overall length of a muscle fibre.
  • active transport. ATP provides the energy to change the shape of the carrier proteins in plasma membranes. This allows molecules or ions to be moved against a concentration gradient.
  • secretion. ATP is needed to form the lysosomes necessary for the secretion of cell products.
  • activation of molecules. When a phosphate molecule is transferred from ATP to another molecule it makes it more reactive and so lowers the activation energy of that molecule. ATP therefore allows enzyme-catalysed reactions to occur more rapidly.
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  • When a chlorophyll absorbs light energy, it boosts the energy of electrons, raising them to a higher energy level so they are in an excited state.
  • The electrons leave the chlorophyll molecule and are taken up by an electron carrier. Having lost a pair of electrons, the chrorophyll molecule has been oxidised. The electron carrier has been reduced.
  • The electrons are now passed along a number of electron carriers in a series of oxidation-reduction reactions - the electron carriers form a transfer chain.
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Very good =]

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