OCR F212 Biodiversity

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Module 3: Biodiversity and Evolution
2.3.1 Biodiversity
(a) define the terms:
Species A group of individual organisms with similar morphological, physiological and behavioural
characteristics, whose members are able to interbreed freely to produce viable offspring.
Habitat The type of environment where an organism lives.
Ecosystem All the living organisms (biotic) and abiotic factors which make up an area, such as weather, soil
type, altitude, pressure, pH, etc.
Biodiversit The variety of living organisms the range of living organisms to be found.
(b) explain how biodiversity may be considered at different levels; habitat, species and genetic.
Habitat The range of habitats in which different species live. Each habitat will be occupied by a range of
Species The differences between species. This could be structural differences (between a tree and an ant) or
functional differences (between bacteria that cause decay and those that help to digest food).
Genetic Genetic variation between individuals belonging to the same species, ensures that they do not all
look alike.
(c) explain the importance of sampling in measuring the biodiversity of a habitat
In order to measure the biodiversity of a habitat, you need to observe all the species present . However, observing
the whole habitat is timeconsuming and difficult. Sampling involves taking a small portion of the habitat and
studying the area carefully. You can then multiply up the numbers of individuals of each species found, on order
to estimate the number in the whole habitat.
Sampling is a balance of ease and accuracy . To improve the accuracy of the estimation, repeated samples are
taken and also the sample size must be large .
(d) describe how random samples can be taken when measuring biodiversity
Where do you sample?:
1. Random Sampling A basic way to do this is to stand within the area, and just throw the quadrat, however, it
is not truly random. A better way is to use a calculator to generate random numbers, to get coordinates of where
you will place your quadrat. The first number is the x coordinate and the second number is the y coordinate.
2. S ystematic Sampling In some situations, you may want to sample more systematically. In this case, you could
sample along a transect. A transect is a line taken across a habitat. You stretch a tape measure across the habitat
and take samples along the line. You can use a:
Line Transect recording each organism which is touching the line at suitable, regular intervals.
Belt Transect placing a quadrat against the line, recording its contents, then placing the next quadrat
immediately touching the first one, repeating this along the transect.
Interrupted Belt Transect placing quadrats at regular intervals along the transect.
Sampling Plants:
Quadrats are square frames used to define the size of the ample area. It's important to choose the right size of the
quadrat (normally 50cm or 1m quadrats are used) depending on the size of the area. The quadrat is placed
randomly and the abundance is measures. You could:
Count the number of individuals of each species.
Abundant 80100%
Common 6080%
Frequent 4060%
Occasion 2040%

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Module 3: Biodiversity and Evolution
Rare 020%
Estimate the percentage cover of each species this is the proportion of the area within the quadrat which
it occupies.
Use an abundance scale, such as the ACFOR scale, by estimating which one of these best describes the
abundance of each species within the quadrat.
A point quadrat may be used. This is a frame holding a number of long needles or pointers. You lower the
frame into the quadrat and record any plant touching the needles.…read more

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Module 3: Biodiversity and Evolution
You can use a quantitative survey to measure this.
For plants, take a sample and then count the number of plants of each species per unit area
(larger plants), or measure the percentage cover of each species (smaller plants e.g. grass and
For animals, observe and count the number of individuals present (larger animals) or take
samples of the animals present and use the captureandrecapture method to estimate the
population size of the species (smaller animals).…read more


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