Fossils and Evidence of Past Life — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. Fossils of fish found in a desert suggest the area was once covered by water.
Grade 3 students reason the desert was once underwater because fish live in water.
2. A fern leaf preserved in rock is an example of a body fossil.
A fern leaf is a real part of the plant, so Grade 3 science calls it a body fossil.
3. Mammoth fossils in cold places suggest that region was once very cold.
Grade 3 science uses mammoth traits as evidence of cold past climates.
4. Small ancient worm tunnels in rock are examples of trace fossils.
Worm tunnels show activity, so Grade 3 science classifies them as trace fossils.
5. An organism that has died out completely is said to be extinct.
Grade 3 science uses extinct for species that no longer exist anywhere.
6. A hollow shape of a shell left in rock is a mold.
Grade 3 science names the empty shape in rock a mold fossil.
7. When minerals fill a mold, they make a cast of the original shape.
Grade 3 science defines a cast as the mineral copy that fills a mold.
8. Layers of sediment build up over time and can preserve organisms as fossils.
Grade 3 science says sediment layers protect remains and help fossils form.
9. Scientists compare fossils to living animals to tell if a species is still alive.
Grade 3 science compares fossils with modern species to see if they are still alive.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Sea fossils on a mountain
→ Area was once underwater
Evidence of past ice-age animals
Fern fossil in icy area
→ Area was once warmer
Area was once warmer
Mammoth fossils
→ Evidence of past ice-age animals
Area was once underwater
Dinosaur footprints
→ Trace fossil showing movement
Trace fossil showing movement
Grade 3 science links fossils to past environments and activity, like warm climates, oceans, ice-age life, and movement.