Old And New Species 1

Question 1

What do the fossil records show?

Answer 1

New organisms arise, Flourish And after time become extinct

Changes that lead to the formation of new species

Question 2

Why are scientists uncertain about how life began?

Answer 2

Lack of enough valid and reliable evidence

Question 3

What are fossils?

Answer 3

Forms of life preserved in rock from many years ago

Question 4

How are fossils formed?

Answer 4

• When the hard parts do not decay easily so will stay as original material for some time and eventually be replaced by minerals
• from parts of an organism that has not decayed due to the conditions for decay being absent
• when parts of an organism gradually become replaced by other materials as they decay
• as preserved traces by impressions I sedimentary rock layers

Question 5

Why are there few traces of early life forms?

Answer 5

Soft bodies so have long since decayed

Question 6

Why are the fossil records incomplete?

Answer 6

Only a small proportion of organisms become fossilised

There are still lots of fossils to be discovered

Question 7

What might have happened to the few traces of early life forms?

Answer 7

Destroyed by geological activity

Question 8

What can we learn from fossils?

Answer 8

• get an idea of what animals and plants looked like; general shape, skeleton and deathlike of internal organs
• the deeper the layer of rock containing fossils the older it is so we can follow the development and evolution of a species of the origin by comparing the gradual changes in the evolutionary path over millions of years

Question 9

What 6 things could cause extinction?

Answer 9

Changes over geological time, techtonic movement
New predators- one species will consume another
New disease- animals immune system unable to cope
New more successful competitor- invades a habitat
A single catastrophic event (mass extinction)- volcanoe, asteroids
Speciation- new more successfully evolved species arises

Question 10

What is a species?

Answer 10

Group of similar organisms that can interbreed to give fertile offspring

Question 11

What is speciation?

Answer 11

The development of a new species which can happen when populations of the same original species become so genetically different they can no longer interbreed

Question 12

What may cause animals to die out?

Answer 12

Changes in the environment

Question 13

Speciation with 5 key terms

Answer 13

Isolation -> 
Variation -> 
Alleles selected -> 
Interbreeding no longer possible -> 
New species

Question 14

What is genetic variation?

Answer 14

A population has a wide range of alleles that controls their characteristics?

Question 15

Speciation

Answer 15

Isolated by geographical mean
2 populations have genetic variation due to mutations
Natural selection occurs differently on 2 populations
Different characteristics are favoured in each population
So different alleles are passed on in each population
Over time genetic differences result in the 2 not being able to sucesfully interbreed to produce fertile offspring