B2.6- Old and new species

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Why is it difficult to be sure about the origin of life on Earth?
Not much valid evidence No one there to see it Do not know exactly when life began
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When is it thought that life did begin?
3 to 4 billion years ago
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What are fossils?
The remains of organisms from many thousands or millions of years ago that are preserved in rocks, ice and other places
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Describe the ways fossils can be formed?
1. From the hard parts of the animal such as the bones, teeth, claws etc. as these bits do not decay 2. When an animal or plant does not decay after it has died as there is low oxygen or other factor that stops the organism decaying 3. When harder
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Why are there no fossils of the very first organisms?
They were soft-bodied organisms so did not form fossils.
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Why are some fossils that are formed never found?
Many have been destroyed by geological activity, e.g. rocks have been broken down, worn away, buried or melted.
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What can the fossil record help us to understand?
How much organisms have changed since life developed on Earth
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Why is this understanding limited?
Only small bits of skeletons or bit of shells have been found in most cases.
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What animal has been shown not to have changed much in the last million years?
The shark
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Why have they not changed much?
Because they evolved early into a form that was almost perfectly adapted to their surroundings which have not changed much.
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How many species is it predicted that have existed since the beginning of life?
3 billion
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How many species are alive today?
A few million
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What is extinction?
The permanent loss of all the members of a species
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What causes the extinction of a species?
Conditions change and new species evolve to cope with the new conditions. These species out-compete the older species and so the older species slowly die out.
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Give some examples of condition changes that may begin the process of extinction.
New predators, new diseases, new or more successful competitors
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How can humans influence the predator-prey relationship and hence bring about extinction?
They can introduce a new species to an area that the current population is not adapted to flee from, this new species can quickly wipe out entire species.
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Where is a disease most likely to bring about extinction of a species?
On a island
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Describe an example in the UK of a species of animal that has hugely reduced a competitor since its introduction? (Hint: think red and grey)
The introduction of the grey squirrel has led to a huge reduction in the number of red squirrel in the UK despite the fact the red squirrel was here long before the grey squirrel.
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When we talk about climate change what timeframe are we talking about?
Millions and billions of years
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What will happen to most tropical species in the times of ice age?
They will become extinct.
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How many occasions in history have led to huge-scale extinction?
five
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What does evidence suggest is the cause for these large-scale extinctions?
Huge catastrophic events such as a massive volcanic eruption or the collision of a giant asteroid with Earth
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When did the dinosaurs become extinct?
65 million years ago
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What is thought to have been the cause?
A giant asteroid collided with Earth in Mexico.
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What would the asteroid strike have caused?
Huge fires, earthquakes, landslides and tsunamis
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Why is it likely that the world became dark?
Because lots of debris and dust got blasted into the atmosphere and blocked the sun
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What effect did this darkness have?
A drop in temperature and the extinction of many plants as they could not photosynthesise
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When do some UK scientists believe the dinosaurs began to become extinct?
137 million years ago
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What is their explanation for the extinction of dinosaurs?
The sea ice melted and flooded the seas and oceans with very cold water.
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What did they base their theory on?
The unexpected change in fossils and minerals that they found in areas of Norway
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What is thought to happen just after a mass extinction?
Many new species develop
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What stages must a population go through before a new species is evolved?
Populations with genetic variety become separated and the conditions change. Different characteristics are selected for and the two populations change. If these changes are great enough the two populations cannot breed and a new species is formed.
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What is geographical isolation?
When two populations are physically isolated by a geographical feature e.g. new mountain range or river
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Why are some animals found on Australia but not on any other continents?
Australia was separated from other continents about 5 million years ago and the different conditions caused new species to evolve.
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What does it mean when a species is endemic to that area?
It means it is only found in one place in the world.
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What is speciation?
The formation of new species
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What must no longer be possible for speciation to have occurred?
The two species must no longer be able to breed.
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Other cards in this set

Card 2

Front

When is it thought that life did begin?

Back

3 to 4 billion years ago

Card 3

Front

What are fossils?

Back

Preview of the front of card 3

Card 4

Front

Describe the ways fossils can be formed?

Back

Preview of the front of card 4

Card 5

Front

Why are there no fossils of the very first organisms?

Back

Preview of the front of card 5
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