Biology 1b Evolution and Environment GCSE CORE Key words: change, disease, predator, competitor, climate change

Biology 1b Evolution and EnvironmentBiology 1b Evolution and EnvironmentGCSGCSEE

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Key words: change, disease, predator, competitor, climate change


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Objective

Why do species become extinct?Why do species become extinct?

Success Criteria

By the end of the lesson I:

• can explain that many organisms have evolved and then become extinct over the lifetime of the earth

• can explain that ‘extinction’ means that every organism of a particular species has died.

•There are a number of changes that can cause a species to become extinct


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Dead as a dodoWhy did the dodo become extinct?


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Why did the dodo become extinct?The dodo was a large flightless bird that lived on the island of Mauritius.It nested on the ground in forests, producing one egg at a time.

When human settlers arrived on the island in the mid-1600s, they brought animals such as rats and dogs to the island, which ate the dodos’ eggs.

The dodo became extinct sometime in the late 1600s.What traits might have helped the dodo to survive longer?

The settlers chopped down the forests in which the dodos lived, and may have even hunted the dodo for food.


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Dead as a dodoWhy did the dodo become extinct?

•New predatorNew predator

•DiseaseDisease

•Destruction of habitatDestruction of habitat

•Nests/eggs being predatedNests/eggs being predated


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Extinction means that a species that had once existed has now been wiped outExtinction means that a species that had once existed has now been wiped out

Extinction can be caused a number of factors but always Extinction can be caused a number of factors but always involves a change in circumstance.involves a change in circumstance.

• A new disease may kill all members of a species• Climate change may make it too cold or hot, wet or dry,

for a species and reduce it food supply• A new predator may evolve or be introduced to an area

that effectively kills and eats all of the species• A new competitor may evolve or be introduced into an

area. The original species may be left with too little to eat

• The habitat may be destroyed


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Extinction of dinosaurs

The dinosaurs ruled the earth for millions of years but when the The dinosaurs ruled the earth for millions of years but when the whole environment changed, they could not adapt & died out. By whole environment changed, they could not adapt & died out. By the time things began to warm up again, mammals, which could the time things began to warm up again, mammals, which could control their own body temperature, were becoming dominant. control their own body temperature, were becoming dominant. The age of the reptile was over!The age of the reptile was over!


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EXAM TIP

When answering a question on extinction use

the word ‘change’‘change’

If there is no change then species If there is no change then species do not become extinct!do not become extinct!


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Multiple-choice quiz


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EXAM PRACTICEThe Galapagos Islands are a group of islands in The Galapagos Islands are a group of islands in

the Pacific Ocean. The nearest country on the the Pacific Ocean. The nearest country on the mainland is Ecuador, 1000 km away. By some mainland is Ecuador, 1000 km away. By some means, a few seed-eating finches were the first means, a few seed-eating finches were the first birds to reach the islands. This single ancestral birds to reach the islands. This single ancestral species has since evolved into many different species has since evolved into many different species. Charles Darwin visited the islands and species. Charles Darwin visited the islands and noted that each species had a beak adapted to noted that each species had a beak adapted to the type of food it ate.the type of food it ate.

Using the theory of natural selection, explain how Using the theory of natural selection, explain how the ancestral species might have evolved into the ancestral species might have evolved into birds with different-shaped beaks……6 marksbirds with different-shaped beaks……6 marks


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EXAM PRACTICE• When the ancestral species arrived on the islands there would be

no competition from other birds.• There would be a variety of different types of food available,

e.g. vegetation, seeds, insects.• The ancestral species would have bred rapidly and built up a

large population and so created competition between its members for food.

• Sexual reproduction and/or mutations over many generations would have created variety amongst the individuals in the population.

• Some of this variety would have been in the types of beak, with different ones being suited to different food sources, e.g. a longer, thinner beak would allow its owner to capture insects in small holes or crevices that were inaccessible to birds with shorter and wider beaks.

• These birds with thinner beaks had an advantage over the other birds of an additional food supply and were therefore more likely to survive long enough to mate and raise offspring.

• These offspring would most probably possess the same genes for a long, thin beak that their parents had and so they too were more likely to survive.


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Some people reject evolution and natural selection in favour of alternative explanations such as intelligent design (ID).

Evolution or design?

Supporters of ID claim it is a valid theory based on scientific evidence, but critics say it is simply a disguised version of creationism.

What do you think about teaching intelligent design in a science class?

According to ID, organisms are too complex to have arisen by evolution alone, and their development must have been guided by a higher intelligence at some point.


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Science vs religion

Read page 116 and answerRead page 116 and answer

Why is it important for students to know Why is it important for students to know about evolution?about evolution?

Include – evidence of evolution- the current scientific theories- final comment stating your opinion


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Objective

Why do species become extinct?Why do species become extinct?

Success Criteria

By the end of the lesson I:

• can explain that many organisms have evolved and then become extinct over the lifetime of the earth

• can explain that ‘extinction’ means that every organism of a particular species has died.

•There are a number of changes that can cause a species to become extinct

Documents

Biology 1b Evolution and Environment GCSE CORE Key words: change, disease, predator, competitor, climate change