Worm Casts and Fossil Evidence

Steve Jones explains how fossils form, starting with their definition as remains or signs of animals. Fossils are often found in rock layers formed at the bottom of lakes or seas, and their position helps determine their age. Shells of sea creatures and worm casts are common examples of fossils. Worm casts, formed by burrowing worms, provide evidence of marine life. Fossils form when animal remains or signs are preserved in rock, with different materials filling the spaces left by the original organism.

What are fossils primarily composed of?

• Living animals

• Remains or signs of animals

• Plant materials

• Minerals and metals

How can the age of a fossil be determined?

• By its position in rock layers

• By its color

• By its weight

• By its size

Which of the following is a common type of fossil?

• Tree leaves

• Shells of sea creatures

• Bird feathers

• Human bones

What is a worm cast?

• A fossilized worm

• A burrow filled with different material

• A type of rock

• A shell of a snail

Why are worm casts considered evidence of marine life?

• They contain marine animals

• They show the presence of filtering worms

• They are made of seaweed

• They are found only in oceans

What happens to the hole left by a worm cast over time?

• It is filled with water

• It is filled with lighter colored material

• It disappears completely

• It remains empty

What can the presence of worm casts in rock tell us?

• The color of the rock

• The direction the rock has been bent

• The age of the rock

• The type of minerals in the rock