Evolution is the theory that every
species has developed over billions
of years from single celled organisms
to far more complex beings
This is referred to by Darwin as Natural Selection
Individual organisms within a
particular species may show
a wide range of variation
because of differences in
their genes
Individuals with
characteristics most suited
to the environment are more
likely to the environment are
more likely to survive to
breed successfully
The genes that have enabled these
individuals to survive are then passed on to
the next generation
Where new forms of a gene result
from mutation there may be rapid
change in a species if the
environment
Darwin's "The Origin of Species"
At the time of conception, the theory
was very controversial and caused
much scepticism because:
Darwin's theory challenged the dominant
theory that God made all living things as
they are now
There was insufficient evidence at the
time to convince the leading scientists
The mechanism of
inheritance and variation was
not known until 50 years later
Darwin's theory is generally preferred to Lamarck's
as it accounts for the continued presence of simple
organisms
Lamarck's Theory
Lamarck suggested that changes in an animal's life
are made to suit their habitat and that these changes
can be passed on to their offspring
For example, a giraffe might need a
longer neck to reach higher branches and
will therefore grow its neck; a change that
is then passed onto their offspring
This theory is now deemed
impossible in most cases as this type
of inheritance cannot occur
Studying the similarities and differences between
organisms allows us to classify living organisms into
animals, plants and micro-organisms and helps us
to understand evolutionary and ecological
relationships
Genes can be transferred to the cells of living
things at an early stage so that they develop with
desired characteristics
New genes can be transferred to crop plants
These are called genetically modified crops (GM crops)
For example, crops have been developed
that resistant to insect attack or to herbicides
Concerns about GM crops include the effect on populations
of wild flowers and insects as well as the uncertainty around
the health effects of eating GM crops