History of life

Question 1

define geological timescale?

Answer 1

earths history divided into time intervals based on significant events

Question 2

sections of geological time scale?

Answer 2

Eons- eras- periods- epochs

Question 3

what are boundary events?

Answer 3

significant events which divide history

Question 4

When did Cambrian explosion occur and how long?

Answer 4

Paleozoic era(500-600mya) lasted 38my

Question 5

explain Cambrian explosion?

Answer 5

cyanobacteria and algae in water photosynthesize which increase oxygen in atmosphere. ozone is formed and warmer atmosphere- habitable climate and sea levels rise- evolution of complex life forms- all major kinds of animals develop

Question 6

What are trilobites?

Answer 6

hard flat segmented organisms which protect from predators and make good fossils for paleontologists to study

Question 7

Define mass extinctions?

Answer 7

period of time where large number of species die out

Question 8

Why and how do mass extinctions occur?

Answer 8

volcanic eruptions
asteroids and comets
extraterrestrial radiation
glaciation and ice age

climate change and animal not suited- death of animal

Question 9

dinosaur mass extinction?

Answer 9

cretaceous (asteroids) to tertiary period (65mya) - allowed space for mammals to develop

Question 10

Why will sixth extinction occur?

Answer 10

human impact
-overpopulation
-pollution
- global warming
-destroy habitats and kill biodiversity

Question 11

Define Fossils and 3 importance?

Answer 11

fossils are remains of organisms that are preserved
-emergence of life
-trend in biodiversity
-past environmental changes

Question 12

How does fossilization happen?

Answer 12

organisms die- trapped in mud or sand covers in flooding
more sediment is deposited and compressed and hardens to rock
hard parts of animals like bones and teeth are petrified with minerals and are then fossilized

Question 13

4 types of fossils and explain?

Answer 13

body fossils- minerals petrify hard parts
trace fossils- marks left behind by organisms
mold fossils- organisms trapped in rock and disintegrates. mould left behind to form cast fossil if minerals are deposited in mould
natural/ unaltered- trapped in resin/ tar / ice

Question 14

difference between relative and radiometric dating?

Answer 14

relative- oldest are at bottom, youngest at top
give order but not age
radiometric- some elements are radioactive and change over time- if scientists know how long certain elements decay they can determine how much an element has changed over time in fossil and therefore how old fossil is

Question 15

3 important fossil places in SA

Answer 15

Barberton- cyanobacteria
karoo- mammal like dinosaur fossils
Sterkfontein caves(cradle of mankind)- human Mrs. ples fossil

Question 16

earth dividing parts and how?

Answer 16

continental drift due to tectonic plates
pangea- laurasia and gondwana- continents