Adaptation, natural selection and the evolution of species

Adaptation, natural selection and the evolution of speciesThis 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

MutationsThe 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.

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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 criteriaYou should be able to answer the following:

• state what mutations are• explain how mutations occur

Possible mutations to discuss about their effect on survival

Adaptation, natural selection and the evolution of species

Adaptation, natural selection and the evolution of species

Sickle cell anaemia