1.1 Particular genes or accidental changes in the genes of plants or
animals may give them characteristics which enable them to survive
better. Over time this may result in entirely new species. There are
different theories of evolution. Darwin's theory is the most widely
1.1.1 Darwin's theory of evolution by natural selection states that all species of living things have evolved
from simple life forms that first developed more than three billion years ago.
220.127.116.11 The theory of evolution by natural selection was only gradually accepted because the theory challenged
the idea that God made all the animals and plants that live on Earth, there was insufficient evidence at the
time the theory was published to convince many scientists and the mechanism of inheritance and variation
was not known until 50 years after the theory was published.
18.104.22.168.1 Other theories, including that of Lamarck, are based mainly on
the idea that changes that occur in an organism during its
lifetime can be inherited. We now know that in the vast majority
of cases this type of inheritance cannot occur.
22.214.171.124.1.1 Studying the similarities and differences between organisms allows us to classify
living organisms into animals, plants and microorganisms, and helps us to
understand evolutionary and ecological relationships. Models allow us to suggest
relationships between organisms.
126.96.36.199.1.1.1 Evolution occurs via natural selection. Individual organisms within a
particular species may show a wide range of variation because of
differences in their genes and individuals with characteristics most
suited 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.
188.8.131.52.184.108.40.206 Where new forms of a gene result from mutation there may be relatively rapid change
in a species if the environment changes.