Fossils

Question 1

How are fossils made

Answer 1

1 gradual replacement by minerals
2 casts and impressions
3 preservation

Question 2

What is gradual replacement

Answer 2

Teeth, shells and bones don’t decay and last a long time when buried
Eventually they are replaced by minerals forming rocklike substance shaped as the original
Surroundings also turn to rock but fossils remain distinct

Question 3

What happens with casts and impressions

Answer 3

Organism buried in soft materials like clay
Clay hardens forming a cast
Footprints and animal burrows or roots also preserved as casts

Question 4

What happens with preservation

Answer 4

If the organism dies in certain places it cannot decay eg
Glaciers too cold to decay
Peat bogs too acidic
Amber and Tar pits have no oxygen and moisture

Question 5

What do fossils show us

Answer 5

How much or little organisms have evolved

Question 6

What are 2 hypotheses for how life started

Answer 6

there is no record so there are only hypotheses
1 Comets brought organic molecules which developed on earth
2 swamps or under the sea on earth - primordial soup

Question 7

What are the problems with fossils evidence

Answer 7

1 soft bodied organisms decay completely
2 geological activity may have destroyed fossils
3. Not all organisms formed fossils so picture is incomplete

Question 8

What is the largest herbivore

Answer 8

Argentinosaurus huinculensis
40 m long
80-100 Tonnes

Question 9

What is the largest carnivore

Answer 9

Giganotosaurus
14 m long
Brian size - banana
20cm serrated teeth

Question 10

Features of Komodo dragon

Answer 10

3m long

140 kg

Question 11

Explain the evolutionary history of the horse from fossils

Answer 11

1 hyracotherium 55 m years ago - small, swamp dwelling,4 toes to walk on soft ground - 0.4m
2 mesohippus -37m years ago - bigger,3 toes for faster moving on drier ground - 0.6 m
3 merychippus - 25my - 1.0m - 3 toes, 1 enlarged for speed
4 pliohippus- 5my - 1.0m - single toe as hoof - like modern horse
5 Equus - modern horse- 2my -1.6m- fast runner on one toe as hoof

Question 12

Why did Irish elk die out

Answer 12

Antlers became too large
Either caught in trees or too heavy to carry
Also probably too slow to escape predators

Question 13

Why did sabre tooth tiger die?

Answer 13

Hunted ground sloths, deer, bison - these were nearly extinct at end of last ice age
Humans arrived in North America at end of last ice age and hunted bison
Created food competition

Question 14

Why did dodo die out

Answer 14

Founded 1598 by Dutch sailors
Not the sailors who killed them all - very few settlers
Ship rats and other animals came with the ships and spread over island
Ate dodo eggs and competed for food

Question 15

Give an example of a catastrophic event causing mass extinction?

Answer 15

Meteorite
In Mexico
189km in diameter
Iridium from space found

Question 16

When were the 5 main extinction events

Answer 16

1. 3500 million years = origins of life
2. 60% lost 440 m years ago
3. 70% species lost 360-75m years ago
4. 80-95% marine species lost 251m years ago
5. 80% land quadrupeds and 50% marine invertebrates lost 205 myago
6. 50-75% species lost, dinosaurs died out - 65m years ago

Question 17

What causes extinction events

Answer 17

Catastrophic events eg volcanic activity or comet landing
Causes immediate impact and shock waves
Also causes dust to rise and block sunlight
Plants cannot photosynthesise and plants die so animals die