7.4 How did Life Develop?

• Biologie
• 9th Grade

7.4 How did Life Develop?

A fossil is...

1. A very old bone or other body part
2. A decayed old bone or other body part
3. A petrified (stone) shape of a bone or other body part
4. An imprint in rock of an ancient animal or plant

Which is not a fossil?

1. Pollen grains inside an ancient clay pot
2. A pawprint of a dinosaur in petrified mud
3. A shell of a mollusc in a thick layer of calcium
4. A petrified human bone

An index fossil...

1. is used as an indicator to see how old a layer is
2. is used as an indicator to see which layer has the most life forms
3. shows what a certain species looked like
4. Is the best-preserved fossil in a layer of rock

Explain why we do not
find fossils of bacteria.

7.4 How life began

01:19

How did the universe change, moments after the Big Bang?

1. It expanded and became hotter
2. It expanded and became cooler
3. It exploded and became hotter
4. It exploded and became cooler

02:03

Describe ancient Earth:

1. It had water and an atmosphere, but no oxygen
2. It had water and oxygen, but no atmosphere
3. It had water but no atmosphere, no oxygen
4. It had oxygen but no water and no atmosphere

03:02

Explain why the formation of the ozone layer was required for life to begin.

1. Ozone keeps the Earth at an optimal temperature
2. Ozone protects the Earth against harmful UV-radiation

Pangea: you are here

Pangea: the ancient continent

Cambrium Explosion

4 billion years: mostly bacteria, plankton and algae

From 600 million years ago: a burst of diversification of life

Workbook

Page 229

Question 32

Homework

Questions 32, 33, 34