Speciation

Question 1

What are fossils?

Answer 1

the remains of organisms found many years ago, found in rocks

this provides evidence for early forms of life

shows how organisms have developed

Question 2

How are fossils formed?

Answer 2

from hard parts of the animals that don’t decay easily

parts of organisms that have not decayed, because the conditions needed for decay were absent

when the organisms decay they are replaced by other materials

preserved traces, e.g. footprints, burrows and rootlet traces

Question 3

Why are there few fossils of the earliest forms of life?

Answer 3

they were soft bodied and may have been destroyed by geological activity

Question 4

What causes extinction?

Answer 4

changes to the environment over geological time

new predators

new diseases

more successful competitors

catastrophic events, e.g. asteroids

through the cyclical nature of speciation

Question 5

How are new species formed?

Answer 5

isolation - species is geographically separated

variation - wide range of alleles

natural selection - alleles that control the characteristics may help the organism to survive and reproduce

speciation - populations become so different that interbreeding is no longer possible