From the previous lesson on mutation you should be able to:

• state what mutations are• explain how mutations occur

Adaptation, natural selection and the evolution of species

In this lesson you should learn about the process of natural selection and how it explains why organisms evolve.

Success criteria:• Describe the process of natural selection• Explain how it is involved in the evolution

of organisms

Adaptation, natural selection and the evolution of species

In a previous topic you learned about variation in species.What types of variation were there?

Discrete and continuous.

How was variation produced in a species?

Through the process of sexual reproduction.

Adaptation, natural selection and the evolution of species

The variation that exists in a population allows environmental factors to have an influence on the population.

This process is called Natural selection and it determines which organisms survive to reproduce.

Adaptation, natural selection and the evolution of species

The Theory of Natural selection

Controversially proposed by Charles Darwin in hisBook ‘On the Origin of Species’ in 1859.

But other scientists had similar ideas like Alfred Russell Wallace

http://www.twigonglow.com/films/darwins-dilemma-1144/

Adaptation, natural selection and the evolution of species

http://www.twigonglow.com/films/natural-selection-1140/

Natural selection (survival of the fittest)• Organisms reproduce producing many offspring• Variation exists among the offspring• Individuals struggle to survive in their environment• Only the “fittest” survive as they are better

adapted• These survivors reproduce passing on their

successful genetic information (alleles)

Adaptation, natural selection and the evolution of species

Darwin explained that those organisms bestadapted for their environment would surviveand reproduce.

Those not well adapted would not survive and eventually would be disappear.

Darwin’s problem was he could not give a clearliving example but used his observationsparticularly of Finches in the Galapagos Islands.

Adaptation, natural selection and the evolution of species

Darwin’s finches support the idea that organismschange with selection pressure.

In the finches case it was to evolve different beak shapes and sizes as mutations allowed them tomake use of different food sources.

One original group of finches slowly spread to different islands and evolved to be bestadapted to the food on their island.

Adaptation, natural selection and the evolution of species

Darwin’s Finches

Adaptation, natural selection and the evolution of species

A modern example of Natural Selection in action is the

Peppered Moth (Biston betularia)

Adaptation, natural selection and the evolution of species

Two forms of the moth exist pale and dark.

The distribution of the different forms is determined by the environmental pressure of pollution.

Pollution levels alter the colour of the trees (soot and a change in lichen numbers).

This alters the camouflage effect of the different forms and this alters the numbers surviving.

Adaptation, natural selection and the evolution of species

In towns and cities where there is a lot of pollutionthe lichens on trees die and soot often covers thetrees making them dark.More dark coloured forms of the moth will be present. (WHY?)

In towns and cities where there is less pollutionlight coloured lichens will survive and less soot will cover the trees.More of the light coloured form will be found. (WHY?)

What do you think happens in the rural areas?

Adaptation, natural selection and the evolution of species

Bacterial resistance to antibiotics is also anexample of modern natural selection.Can you think why this is?

Adaptation, natural selection and the evolution of species

http://www.twigonglow.com/films/life-in-hot-deserts-1129/

Adaptations that have evolved through natural selectionAdaptations can either be structural, physiological or behavioural.Watch the video clips and make a note of the adaptations and whether they are structural, physiological or behavioural.You may need to watch them twice.

http://www.twigonglow.com/films/life-in-the-freezer-1128/

http://www.twigonglow.com/films/bizarre-adaptations-1132/

Adaptation, natural selection and the evolution of species

Adaptation, natural selection and the evolution of species

Other adaptations that help animals survive in their environment (for discussion).

Adaptation, natural selection and the evolution of species

Other adaptations that help animals survive in their environment (for discussion).

Adaptation, natural selection and the evolution of species

Other adaptations that help plants survive in their environment (for discussion).

In this lesson you should have learned about the process of natural selection and how it explains why organisms evolve.

• Describe the process of natural selection• Explain how it is involved in the evolution

of organisms

Adaptation, natural selection and the evolution of species