B2.6 - Old & New Species Flashcards
What are fossils?
The remains of organisms from millions of years ago preserved in rocks or ice.
What are the four ways in which a fossil can be formed?
- 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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Why aren’t there any fossils of the earliest creatures?
They were soft bodied.
Explain how a common fossil is formed.
- 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.
Give three reasons why there might not be fossils of organisms.
- 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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How are fossils used?
To determine how animals have changed.
What is extinction?
The permanent loss of all of the members of a species.
Explain how a new predator can cause extinction.
- 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.
Give four possible causes of extinction.
- A change in environment.
- A new predator.
- A new disease.
- More successful competitors.
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Explain how a new competitor can cause extinction.
- A new mutation can allow an organism to have an advantage.
- Accidental introduction can mean a new competitor that is better than the previous.
Give two examples of events that could cause mass extinction.
- Massive volcanic eruption.
- Collision of asteroids.
How does long term environmental change cause extinction?
Organisms that have been dominant in the previous climate can’t adapt fast enough so die out.
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What would an asteroid impact cause that caused extinction?
- Huge fires
- Earthquakes
- Landslides
- Tsunamis.
How do new species arise?
When two populations become isolated.
How do populations become isolated?
When they are separated geographically by a new feature.
Why do the species evolve when they become isolated?
Their habitats become different meaning natural selection takes different paths.
What new features could cause geographical isolation?
- New mountain range
- New river
- Part of the land becoming an island.
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What is speciation?
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.
What is an endemic species?
When a species evolves in isolation and is only found in one place in the world.
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Why might an organism not decay?
- There is too little oxygen.
- There are poisonous gases that kill bacteria.
- The temperature is too low.
Why does speciation occur?
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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