Prehistoric life

Natural sciences

Grade 8

Biodiversity

Module 23

Prehistoric life

For millions of years, life on earth consisted of microscopic single cell organisms only. True animals, like jellyfish and sponges, appeared about 700 million years ago.

They had soft bodies, but the development of shells, teeth and claws has made it possible for us to determine their appearance. How do we do this? By studying newly discovered fossils.

Finds of fossils dating from after the Cambrian period include animals like crocodiles and sharks.

Some animals quickly became extinct when conditions changed. Others were able to adapt and survive. Massive extinctions have occurred at various times in the history of the earth.

The age of the earth is counted in billions of years.

Find out more about this: Visit www.ucamp.berkeley.edu/exhibit/geology.html

Like clock time that is divided into hours, minutes and seconds, the history of the earth can be divided into four large “blocks”. We refer to these as AEONS. The first three aeons together are known as the Precambrian period. Our information about this period is scant because few fossils have survived to be studied.

The last period is known as the Proterozoic aeon. This aeon commenced approximately 540 million years ago and is divided into four eras.

The eras are divided into periods that might have lasted for 2 to 80 million years each.

Activity: to do research and to collect data

1. Explain what you understand by geological time:

2. Use the circle to illustrate geological time as described above.

3. What would have caused the massive extinctions referred to in the above passage?

4. Explain what fossils are.

5. How do you think scientists determine the age of the earth? Find out about carbon dating.

Research: carbon dating

• www.howstuffworks.com/carbon-14
• or: www. Enchantedlearning.com/subject/dinosaurs/dinofossils/fossildating.html

6. Find out about EVOLUTION as documented.

• Bear in mind that this is a sensitive topic and that not all people hold the same opinions. The scientist, however, has a duty to examine all phenomena and theories and to share his / her deductions with other people. Each individual can then decide whether he or she agrees or not. Make an informed decision!

Research: evolution

• Search in google.com

Assessment of RESEARCH:

Could you find any information on carbon dating and evolution?

[ LO 1.2]

Assessment

Learning outcomes 1: Scientific investigations

The learner will be able to act confidently on curiosity about natural phenomena, and to investigate relationships and solve problems in scientific, technological and environmental contexts.

This is evident when the learner

1.2 is able to conduct an investigation and collect data.

Memorandum

Activity: COMPREHENSION TEST AND RESEARCH

• Preparation – read about carbon dating and find sources of information on evolution.
• As well as mass extinctions.
• Find appropriate video material.