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Inheritance and Selection
Worthing High School
Variation is a name given to differences in a species, e.g. dogs:
Variation is due to each animal having different GENETIC
INFORMATION in their cells.
Where is this information stored?
Section of a chromosome:
Different species have different numbers
of chromosomes. Humans have 46 (23
pairs) in every cell.
Genetic information is stored by genes which are arranged on
Clearly, not all differences are due to just our genes…
Variation due to
Variation due to
Variation due to a
bit of both
Sexual reproduction involves two organisms of the same
species. Each organism produces a GAMETE.
For example, in animals
the gametes are the egg
and the sperm:
When the sperm penetrates the egg the egg is fertilised and
cells start to reproduce to form a new individual:
In plants, the gametes are the egg and pollen:
Any type of sexual reproduction helps a species to become
more varied because the offspring inherit characteristics
from both parents.
I raise cows. Each type of
cow is good at a certain job.
The Friesian cow produces
large quantities of milk, the
Jersey cow produces very
nice milk and the Hereford
cow produces lot of beef.
If, for example, I want lots of
milk I would only breed
Friesian cows with each other
– this is SELECTIVE
Plants can reproduce ASEXUALLY. The offspring are
genetically ________ to the parent plant and are called
_________. Two examples:
1) This spider plant has grown a rooting
side branch (“stolon”) which will
eventually become __________.
2) A gardener has taken cuttings of
this plant (which probably has good
characteristics) and is growing them
in a ____ atmosphere until the
Words – clones, damp, independent, roots, identical