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Variation
What you should know.
- There variation between
different species.
- There is variation
between individuals of the same species.
- Some features are
inherited from parents.
- Other features are caused
by the environment.
- Some variation is gradual
such as height, other variation is clear cut, such as eye colour.
- Chromosomes are
thread-like structures found in the cell nucleus.
- The instructions for
inheritance are carried on chromosomes.
- Sex cells have half the
number of chromosomes found in other cells.
- Genes contain the
instructions that are inherited.
- Genes for a particular
feature such as eye colour are found at the same position on a pair of
chromosomes.
- For each feature there is
a pair of genes.
- Some genes are dominant
and some are recessive.
- Useful features can be
bred into some animals and plants such as the bacon pig.
- Less useful features can
bred out.
- Artificial insemination
can be used to improve some breeds of cattle.
- Embryo transplants can be
used to increase the numbers of an improved breed of cattle.
What you should be able to do.
- In a list of features
decide which are inherited and which are environmental.
- Collect information about
differences between individuals in a group.
- Look for patterns and
differences in graphs and charts.
- Know that most human
cells have 46 chromosomes that can be put into 23 pairs.
- Complete diagrams to show
how genes are passed on.
- carry out an exercise
that models the way genes are passed on.
- Decide which features are
useful and which are not useful for selective breeding.
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