B2.8 Speciation

Question 1

How do fossils form?

Answer 1

• When a plant or animal dies, it lies on the floor (sea bed usually)
• Soft tissues decompose quickly but bones and hard tissue are left behind
• Over time sediment builds up over the top
• The encased bones decay beneath the layers of rock
• Minerals replace the organic material in ‘petrification’
  or
• Body completely decays and minerals fill the cast left behind

Question 2

What evidence for evolution can be found through fossils?

Answer 2

Fossils of simpler organisms are found lower down in the ground whereas more complex animals are found higher up - suggesting that organisms have grown more complex over time

Question 3

Why are there few traces of really old organisms?

Answer 3

They were soft bodied and completely decomposed

Question 4

How has a horse changed since its predecessor 60 million years ago?

Answer 4

• Forest dwelling, 0.6 m tall, wide spread feet

- Land / meadow dwelling, 1.6 m tall, compact hooves

Question 5

What factors can cause an organism to become extinct?

Answer 5

• New disease
• New predators
• Single catastrophic event (eg eruption)
• Changes to environment

Question 6

How did the Dodo become extinct?

Answer 6

Dodos lived on Maurititus (island in Indian ocean) with no predators
Colonisation of Dutch in 1683 brought new predators (people / pigs / rats) who killed them and their young
Dodos became extinct within 80 years

Question 7

How can geographical isolation cause the formation of new species?

Answer 7

Species in the new environment need different characteristics to stay alive
For example
-Longer beaks
-More vibrant colours

The organisms in new environment evolve to cater for this and eventually create a new species

Question 8

What factors can cause speciation?

Answer 8

• Geographical isolation
• Natural selection
• Genetic Variation
• Speciation (variations of a species become so different they cannot interbreed anymore)

Question 9

What conditions are needed for decay?

Answer 9

• Warmth
• Moisture
• Oxygen

Question 10

What causes an organism to be preserved (eg in sap or bogs?)?

Answer 10

Lack of the conditions needed for decay
eg
not enough oxygen

Question 11

What conditions are optimum for decay

Answer 11

Low levels of oxygen and cold to prolong decay

Question 12

What is the name for when variations of a species become so different they can no longer interbreed anymore?

Answer 12

Speciation