B4 Key Information
Sampling
Estimating population size
Quadrats
This method is only good for plants or really slow moving animals like snails.
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You are stood in a field that is 100m2, and you place 5 quadrats randomly.
You estimate the total number of buttercups in the whole field by averaging your quadrat data
(average number of flowers in one quadrat).
You then multiply your average by the area of the field. (x 100m2 in this field).
The more quadrats you throw, the more reliable your estimate.
Capture-Recapture
This method should be used for faster moving animals, like woodlice.
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Catch as many animals as you can, and mark them with a non-toxic paint, which predators won’t
see.
Wait a few days until they have spread back into the population.
Capture as many as you can all over again.
Separate them into 2 groups: marked and unmarked. Count both groups.
Use the formula:
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It is assumed that no animals die, are born, join or leave the population during the experiment.
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Photosynthesis
Glucose
You can make photosynthesis go faster by increasing light intensity, CO2 or temperature (a higher
temperature means enzymes are working faster up till the point they denature). The one in least
supply will be the limiting factor.
Leaves are adapted to help a plant to carry out photosynthesis
Feature
Large surface area and many
chloroplasts
Thin
Thin waxy cuticle
Thin transparent epidermis
Many stomata
Xylem and Phloem (vascular
bundles)
Diffusion
Function
Maximise light absorption
Short distance for carbon dioxide to diffuse into leaf
cells
Allows light to reach the palisade cells and prevents
water loss
Allows light to reach the palisade cells
Large surface area for gas exchange (carbon dioxide in,
oxygen out)
Xylem delivers water to the leaf, phloem carries sugars
away.
Diffusion happens faster if
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It happens over a short distance
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Over a large surface area
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If there is a big concentration gradient
Osmosis
Osmosis is a special type of diffusion, ONLY water moves from an area of a higher water
concentration (pure water) to an area of lower water concentration (sugar or salt dissolved in
the water) across a semi-permeable membrane.
Active Transport
Particles are moved from a lower concentration to a higher concentration (agianst a
concentration gradient using energy (from respiration), this requires proteins to help move
the particles.
Plant Transport
Plants and Minerals
Mineral
Nitrates (N)
Potassium (K)
Phosphates (P)
Magnesium (Mg)
What it is needed for
To make proteins for cell growth
Needed by enzymes involved in respiration and
photosynthesis
Needed for respiration and to make DNA
Needed to make chlorophyll for photosynthesis
Decay
The faster microbes can respire,
the more energy they have to
reproduce so the faster decay
happens. To prevent decay we
need to prevent microbes from
respiring and reproducing.
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Sealing in bottles or cans
without oxygen
Keeping the temperature low
e.g. in fridge or freezer
Pickling in vinegar – low pH
effects enzymes
Adding sugar or salt or
drying – removes water
Detritivores (earthworms) eat dead material and break it down into small pieces with a
larger surface area. Decomposers (fungi) release enzymes onto this material to digest it,
decomposers who release enzymes are called saprophytes.
Farming
Biological control is
when a natural
predator of a pest is
added to eat the best,
pesticides are not
needed.
In hydroponics, plants
are grown without
soil, in water with
added minerals and
nutrients.