2.9 To explain how fossils were formed

Natural sciences

The earth and beyond

Fossils

Educator section

Memorandum

Assignment 7:

Ensure that a dictionary of definitions is available in class.

1. 100 years

2. About three quarters of South Africa consisted of a large marshy bowl. These unique conditions are ideal for fossilisation.

3. When something in nature dies, it is normally eaten and scattered by scavengers. These bones, that are often scattered widely, are then covered in mud and sand.

4. True. Fossils represent people, plants and animals that lived millions of years ago. We can derive a lot from them.

5. A fossil is any remains of a human being, animal or plant that remained intact in the rock formations of the earth.

6. Shells are mostly too hard to be eaten. They are part of the invertebrates that make up a large portion of the animal kingdom. A lot of fossilisation happened in water.

7. Teeth consist of bone covered by enamel. Bone is the hardest tissue in the body. Teeth are well protected against decay, because they are already mineralised.

8. A scientist manages a specific section of knowledge that consists of systematically arranged facts based on general principles.

A scientist is a person who has expert knowledge of one or more of the natural or physical sciences. (Paperback Oxford English Dictionary 2001)

9. Paleo is a prefix meaning older or ancient. (Paperback Oxford English Dictionary 2001)

Leaner section

Content

FOSSILS CAN PROVIDE IMPORTANT INFORMATION ABOUT THE HISTORY OF LIFE ON EARTH. WE FIND FOSSILS IN ROCK LAYERS. THEY ARE THE REMAINS OF PEOPLE AND PLANTS, AS WELL AS SKELETONS AND SHELLS OF ANIMALS THAT WERE ALIVE IN THE DISTANT PAST. THE ROCK LAYERS IN WHICH WE FIND FOSSILS ARE KNOWN AS SEDIMENTARY ROCKS. FOSSILS ARE VERY IMPORTANT FOR OUR ATTEMPTS TO RECONSTRUCT THE PREHISTORIC ENVIRONMENT OF OUR ANCESTORS BECAUSE PLANTS AND ANIMALS PROVIDE INFORMATION ABOUT NATURE.

• Anything that gives visual proof of past life can be called a fossil. Petrified bones and teeth provide the best fossils from prehistoric people. Bone is the hardest tissue in the body and can therefore be preserved much more easily than anything else. Footprints, tools, burnt bones from the prey that they hunted for food and remains of shells that were collected serve as fossilised proof of their way of living.

Activity: to explain how fossils were formed [lo 1.2, lo 2.3]

• It is not easy to fossilise anything. Scavengers quickly consume any creature that dies in nature and the bones become scattered. As the years pass, these remains are covered with sand and mud. This is why we hardly ever discover complete fossilised skeletons. With the passing of the centuries more and more sand and mud are deposited over the bones. The sand and mud gradually become petrified and bones of prehistoric animals and shells are conserved and even become hard and rock-like.

• Sometimes the rock crumbles or is eroded by the sea or a river, so that some of the fossils are revealed on the surface. Shells are the most common fossils, but bones from large reptiles are found quite frequently right across the world. Bones and shells are not the only things that are conserved below the ground. Even marks made by raindrops have already been discovered. The petrified faeces of some animals are among the strangest fossils that have ever been found. These are known as coprolites.