Fossilisation and speciation

Question 1

Describe gradual replacement by minerals as a fossilisation process.

Answer 1

> teeth shell
and bones can last a long time when buried

> as they decay they are gradually replaced with sediment that forms rock
-as does surrounding sediment

Question 2

Describe casts and impressions as a method of fossilisation

Answer 2

If the organism is buried in soft clay when it decays an impression remains

> impressions of footprints can also occur or burrows/holes of animals

Question 3

Why can a species become extinct? (6)

Answer 3

> new species develops

> change of environment

> new predator

> new disease

> competition for food

> catastrophic event

Question 4

Define a species

Answer 4

A group of similar organisms that can reproduce fertile offspring

Question 5

What is speciation?

Answer 5

The development of a new species

Question 6

What are 3 different ways an organism can become fossilised?

Answer 6

> gradual replacement with minerals

> casts and impressions

> preservation

Question 7

What two factors lead to speciation?

Answer 7

> isolation and natural selection

Question 8

Why are scientists uncertain about how life began?

Answer 8

Fossils have been destroyed by geological activity

> lack of evidence because scientists believe that first organisms were soft shelled

I.e. Lack of valid and reliable evidence

Question 9

How does speciation because of a geological barrier occur?

Answer 9

> conditions either side of the barrier will be slightly different

> the individuals with the characteristics better suited to survival are more likely to breed

> meaning that the alleles controlling the beneficial characteristics are more likely to be passed on to the next generation .

Question 10

How does preservation occur?

Answer 10

If the organism dies in a substance in which the decaying organisms cannot live

> too cold( glacier)

> lack of oxygen (Amber)

> acidic conditions (peat bogs)