B2.6 - Old & New Species

Question 1

What are fossils?

Answer 1

The remains of organisms from millions of years ago preserved in rocks or ice.

Question 2

What are the four ways in which a fossil can be formed?

Answer 2

• The hard parts of an animal.
• The organism doesn’t decay.
• Hard parts of the animal are replaced with minerals.
• Traces of organisms left behind.

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Question 3

Why aren’t there any fossils of the earliest creatures?

Answer 3

They were soft bodied.

Question 4

Explain how a common fossil is formed.

Answer 4

• The animal dies and falls to the ground.
• The flesh rots, leaving just the skeleton to be covered in sediment.
• Over millions of years, the skeleton becomes mineralised and turns to rock.
• The fossil emerges as the rocks move.

Question 5

Give three reasons why there might not be fossils of organisms.

Answer 5

• The conditions weren’t right for fossilisation.
• The fossil was destroyed by geological activity.
• They might not have been discovered yet.

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Question 6

How are fossils used?

Answer 6

To determine how animals have changed.

Question 7

What is extinction?

Answer 7

The permanent loss of all of the members of a species.

Question 8

Explain how a new predator can cause extinction.

Answer 8

• The prey animals do not have the adaptations to avoid them.
• The predators can move in quickly.
• Human intervention may put the predator in the area.

Question 9

Give four possible causes of extinction.

Answer 9

• A change in environment.
• A new predator.
• A new disease.
• More successful competitors.

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Question 10

Explain how a new competitor can cause extinction.

Answer 10

• A new mutation can allow an organism to have an advantage.

- Accidental introduction can mean a new competitor that is better than the previous.

Question 11

Give two examples of events that could cause mass extinction.

Answer 11

• Massive volcanic eruption.

- Collision of asteroids.

Question 12

How does long term environmental change cause extinction?

Answer 12

Organisms that have been dominant in the previous climate can’t adapt fast enough so die out.

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Question 13

What would an asteroid impact cause that caused extinction?

Answer 13

• Huge fires
• Earthquakes
• Landslides
• Tsunamis.

Question 14

How do new species arise?

Answer 14

When two populations become isolated.

Question 15

How do populations become isolated?

Answer 15

When they are separated geographically by a new feature.

Question 16

Why do the species evolve when they become isolated?

Answer 16

Their habitats become different meaning natural selection takes different paths.

Question 17

What new features could cause geographical isolation?

Answer 17

• New mountain range
• New river
• Part of the land becoming an island.

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Question 18

What is speciation?

Answer 18

When the isolated population evolves by natural selection, because of the success of particular alleles in that area, they can no longer interbreed with the new original organism.

Question 19

What is an endemic species?

Answer 19

When a species evolves in isolation and is only found in one place in the world.

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Question 20

Why might an organism not decay?

Answer 20

• There is too little oxygen.
• There are poisonous gases that kill bacteria.
• The temperature is too low.

Question 21

Why does speciation occur?

Answer 21

The successful alleles of the new population are unlikely to be the same as the alleles that gave success in the original environment.

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