Download Adaptation, natural selection and the evolution

Adaptation, natural selection and the evolution
of species
This next topic looks
at the way that
organisms have
changed since life
began on earth and
how this change can
be accounted for
scientifically.
Adaptation, natural selection and the evolution of species
Mutations
The first area to understand is mutations.
What are mutations?
How are mutations caused?
Do mutations happen naturally?
Success criteria
• state what mutations are
• explain how mutations occur
Adaptation, natural selection and the evolution of species
Most of the mutations that we think matter to
evolution are "naturally-occurring."
For example, when a cell divides, it makes a copy of its
DNA — and sometimes the copy is not quite perfect.
That small difference from the original DNA sequence
is a mutation.
Adaptation, natural selection and the evolution of species
How are mutations caused?
Mutations are spontaneous and are the only
source of new alleles!
What is an allele?
Alleles are the forms of genes that organisms
carry in their DNA.
Alleles are what determine your inherited
genetic characteristics.
Adaptation, natural selection and the evolution of species
Do mutations happen naturally?
Yes they do in a random and spontaneous
manner
Environmental factors like
radiation (UV, x-rays) and
some chemicals, can
increase the rates of mutation in DNA.
These would be called mutagenic agents.
http://www.twigonglow.com/films/glossary/mutation-336/
Adaptation, natural selection and the evolution of species
Mutations can occur in all dividing cells.
Cells divide throughout the body by mitosis.
Specialised cells also divide to produce gametes
(sex cells), this type of division is called meiosis.
Which type of cell division (mitosis or meiosis)
is associated with producing new individuals?
Cells undergoing meiosis may pass a mutation on to
the next generation.
Adaptation, natural selection and the evolution of species
Mutations can occur in all dividing cells.
Cells dividing by mitosis are not likely to
pass the mutation to a new generation.
These types of mutations are
commonly the cause of cancers in fully
developed organisms.
Adaptation, natural selection and the evolution of species
Cells undergoing meiosis may pass a mutation on to
the next generation.
These mutations would be carried by eggs or sperm
into the zygote.
The mutation may be neutral or might give an
advantage or disadvantage to the new organism.
It is these mutations which produce new variations
in organisms and they are the raw material for
evolution
Adaptation, natural selection and the evolution of species
Success criteria
You should be able to answer the following:
• state what mutations are
• explain how mutations occur
Adaptation, natural selection and the evolution of species
Possible mutations to discuss about their
effect on survival
Adaptation, natural selection and the evolution of species
Sickle cell anaemia
Adaptation, natural selection and the evolution of species