2126870
Description
Mind Map by Georgia Knight, updated more than 1 year ago
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Created by Georgia Knight
almost 10 years ago
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AQA AS Biology: 2.7 Variation
- Interspecific Variation: when one species
differ from another.
- Intraspecific Variation: when members of
the same species differ from each other
- Sampling
- samples should be representative of the
population as a whole
- sampling bias: selection process may be biased due to
unrepresentative choices from the samplers. for example, samples
may only be taken from dry, not muddy areas of a field.
- chance: by pure chance, chosen samples may not be representative.
- minimise the effects of chance by: 1. having a bigger sample size. 2.
analysing data collected, for example spotting anomalies
- minimise the effects of chance by: 1. having a bigger sample size. 2.
analysing data collected, for example spotting anomalies
- sampling bias: selection process may be biased due to
unrepresentative choices from the samplers. for example, samples
may only be taken from dry, not muddy areas of a field.
- Random sampling helps to eliminate bias. One method is to: 1. divide study area into grid
of numbered lines. 2. using a random number generator obtain coordinates. 3. take
samples at intersections of pairs of coordinates.
- samples should be representative of the
population as a whole
- Causes of Variation
- Genetic differences
- due to different genes that each organism posesses
- mutations - sudden changes to genes may be
passed on to the next generation
- meiosis - the type of nuclear division that forms the gametes. this mixes
up genetic material before it is passed into the gametes
- fusion of gametes - in sexual reproduction, offspring inherit
some characteristics of each parent and are therefore
different from both of them
- mutations - sudden changes to genes may be
passed on to the next generation
- due to different genes that each organism posesses
- Environmental influences
- e.g in plants: pH, food avaliability and
climatic conditions can affect plant's
growth etc.
- e.g in plants: pH, food avaliability and
climatic conditions can affect plant's
growth etc.
- Genetic differences
- Types of Variation
- due to genetic factors
- represented on bar charts or pie charts as
characteristics like eye colour are not continuous
- represented on bar charts or pie charts as
characteristics like eye colour are not continuous
- due to environmental influences
- characteristics such as height and mass - controlled by
polygenes and environmental factors.
- portrayed on normal distribution curves
- characteristics such as height and mass - controlled by
polygenes and environmental factors.
- due to genetic factors
- Mean and Standard
Deviation
- Mean - a measurement at the maximum height of the
curve, provides an average value and useful for comparison
- Standard deviation - a measure of the width of the curve. it gives an
indication of the range of values either side of the mean
- Mean - a measurement at the maximum height of the
curve, provides an average value and useful for comparison
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