Fossils, Extinction and Specification

Question 1

What are fossils?

Answer 1

fossils are the remains of organisms from many years ago, which are found in rock.

Question 2

Describe how fossils are found through gradual replacement by minerals.

Answer 2

Teeth, shells and bones do not decay easily and can last a long time when buried. When they eventually decay, they’re replaced by minerals forming a rock like substance shaped like the original hard part. The surrounding sediment also turns to rock but the fossils remain distinct underground until they are dug up.

Question 3

Describe how fossils are found from casts and impressions.

Answer 3

The organism is buried in a soft material like clay. The clay hardens around it and the organism decays leaving a cast of itself. Foot prints in soft materials can leave an impression when the soft surface hardens.

Question 4

Describe how fossils are found from preservations

Answer 4

Fossils can be preserved in places where no decay happens. For example in amber and tar pits there is no oxygen or moisture so decay microbes cannot survive. In glaciers, it is too cold for decay microbes to work and it Peat bogs it is too acidic for microbes.

Question 5

What is extinction?

Answer 5

Extinction is when an organism is unable to evolve quickly enough.

Question 6

For what reasons can an organism become extinct?

Answer 6

• environment changes too quickly
• new predator
• new disease
• can’t compete with others for food
• catastrophic event

Question 7

What is a species?

Answer 7

species is a group of similar organisms that can reproduce to give fertile offspring

Question 8

What is speciation?

Answer 8

the development of a new species

Question 9

When does speciation occur?

Answer 9

it occurs when populations of the same species become so different that they can no longer breed to produce fertile offspring and so a new species is formed.

Question 10

What two natural processes lead to specification?

Answer 10

isolation and natural selection

Question 11

Describe how a new species can be formed.

Answer 11

• Populations of a species can be isolated due to a physical barrier for example floods and earthquakes.
• Conditions on either side of the barrier will be different.
• Therefore different characteristics will become more common in each population due to natural selection as the alleles which control the beneficial characteristic are more likely to be passed on.
• so the two species will have adapted to their environment differently and become a new species