Homework

For Thursday 19th January Read pages 66 – 69 in the purple book Complete the activities on those pages Read pages 152 – 168 in Joe Walker book Complete the questions on page 168

Lesson Aim To learn about Darwin's theory of evolution

through natural selection

What do we know about the Theory of Evolution?

4 minutes

The Theory of Evolution

Charles Darwin ‘Survival of the fittest’ Slight mutations Adaptation to environment Great length of time Extinction

Charles Darwin

HMS Beagle: 1831-1836

Evolutionary Theory

The word ‘evolution’ means ‘gradual development’

Darwin’s original theory was written in his book Origin of Species in 1859.

He later, in Descent of Man , Darwin applied this controversial theory to humans.

The Theory?

A living thing depends upon its environment to survive

It can only survive if it fits into the environment in which it lives

Fitting in to the environment depends on a living thing being able to stay alive by getting food and coping with the climate

For Example

Heat trapping fur is needed to survive in the Northern Artic

A specific beak is needed to acquire food in the Galapagos Islands

A living creature best suited (or adapted) to that environment will survive. Others not suited to the environment will die off

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An example

There are rabbits living in a cold, snowy, polar region. All of the rabbits are brown and many of them are killed and eaten by other animals each year, so not all of them survive.

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These rabbits are competing for life and struggling to survive, partly by trying to avoid predators, to "not be the one who gets eaten.“

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Each rabbit is a little bit different from other rabbits, but one time a few rabbits are born albino, white, because of a mutation in the genes.

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This variation in colour helps the albino rabbits to survive. Against the white snow, predators have a harder time seeing them, so more of the albino rabbits are able to survive and therefore to reproduce.

Can you see the hares?

Exactly!

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In the next generation there are more white rabbits, because the white hair gene is passed on. In this generation, too, more white rabbits survive and reproduce. They pass the albino trait on to their offspring, who also survive and reproduce more than the brown rabbits do. Gradually, there are more and more white rabbits in the population, until the entire population is made of white rabbits, because the brown-haired rabbits are more likely to get eaten

When Charles Darwin visited the Galapagos Islands, the vice-governor of the Islands told him that he could identify what island the tortoise was from simply by looking at him.

On dry islands, tortoises with long necks had an advantage over the tortoises with shorter necks -- long necks allow an individual to reach the foliage on the cactus plants that grow on the island

This would lead to only the long-neck gene surviving on dry islands

Just as breeders select what qualities they want in an animal....

....so nature selects species which develop the necessary features to survive in a particular environment

Competition amongst species lead to the fittest offspring surviving (there are always more babies than the environment can support – they compete for resources to survive and best adapted wins!)

If the environment changes, then only those who adapt to the change will survive, reproduce, and pass on their survival advantages to their offspring

This is called evolution through natural selection

“Describe what is meant by the theory of evolution” 8KU