Speciation

Question 1

What does evidence of early forms of life come from

Answer 1

Fossils

Question 2

What are fossils

Answer 2

Fossils are the ‘remains’ of organisms from hundreds of thousands of years ago, which are found in rocks.

Question 3

How may fossils be made

Answer 3

-from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent -when parts of the organism are replaced by other materials as they decay as preserved traces of organisms, eg footprints, burrows and rootlet traces

Question 4

Why have many early forms of life left few traces behind

Answer 4

Because many were soft bodied. What traces there were have been mainly destroyed by geological activity. This is why scientists cannot be certain about how life began on earth

Question 5

What can we learn from fossils

Answer 5

How much or how little different organisms have changed as life developed on earth

Question 6

What can extinction be caused by

Answer 6

-changes to the environment over geological time -new predators -new diseases -new, more successful, competitors -a single catastrophic event, eg massive volcanic eruptions or collisions with asteroids

Question 7

New species arise as a result of:

Answer 7

Isolation Genetic variation Natural selection Speciation

Question 8

Isolation

Answer 8

Two populations of a species become separated, eg geographically

Question 9

Genetic variation

Answer 9

Each population has a wide range of alleles that control their characteristics

Question 10

Natural selection

Answer 10

In each population, the alleles that control the characteristics which help the organism to survive are selected

Question 11

Speciation

Answer 11

The populations become so different that successful interbreeding is no longer possible