Fossils & Relative Dating — Drills · Grade 9 Science

Chapter: Earth’s History

What these drills covers

By the end of Fossils & Relative Dating you should be able to:

8 questions, multiple choice, numeric and written answer, each with a worked explanation.

Vocabulary used: fossil, relative dating, index fossil, cross-cutting relationship.

Problem 1

Fossils are most commonly found in
  1. igneous rock
  2. sedimentary rock
  3. metamorphic rock
  4. magma
Answer and explanation

sedimentary rock

Burial in sediment preserves remains; melting and intense metamorphism destroy them.

Problem 2

Which is most likely to be preserved as a fossil?
  1. A jellyfish on a beach
  2. A shelled animal buried quickly in mud
  3. A leaf left on the surface
  4. A bird in open air
Answer and explanation

A shelled animal buried quickly in mud

Hard parts and rapid burial both greatly improve the chance of preservation.

Problem 3

A trace fossil is
  1. a body part
  2. evidence of activity such as a footprint or burrow
  3. a mineral
  4. a type of rock
Answer and explanation

evidence of activity such as a footprint or burrow

Trace fossils record behaviour rather than anatomy.

Problem 4

In an undisturbed sequence, a fossil appears in layers 3, 4 and 5 counting from the bottom. In how many layers does it appear?
Answer and explanation

3

Layers 3, 4 and 5 — three layers, giving its range in that sequence.

Problem 5

Marine fossils found high in a mountain range indicate
  1. the fossils were carried there by people
  2. that rock formed under water and was later uplifted
  3. sea level once covered the mountain top as it is now
  4. the fossils are not real
Answer and explanation

that rock formed under water and was later uplifted

The rock formed on a sea floor and tectonic processes raised it.

Problem 6

The fossil record is biased toward organisms that
  1. were soft-bodied
  2. had hard parts and lived where sediment accumulated
  3. lived on mountain tops
  4. were rare
Answer and explanation

had hard parts and lived where sediment accumulated

Hard parts resist decay and sediment-rich settings bury remains quickly.

Problem 7

Explain why the absence of a species from a rock layer is weak evidence that it did not exist then.
Answer and explanation

Fossilisation is rare and selective: it needs hard parts, rapid burial and conditions that preserve the remains, and the rock must then survive and be exposed and found. A species could be present and leave nothing detectable. Absence therefore has several explanations besides non-existence, which is why conclusions rest on positive finds and on how thoroughly an interval has been sampled.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

Problem 8

How can fossils indicate the environment in which a rock formed?
Answer and explanation

Species live in particular conditions, so their remains indicate those conditions where the sediment accumulated. Coral and marine shells point to warm shallow seawater; fern and tree fossils to a humid land surface. Combining the fossils with the rock type — fine mud, coarse sand, limestone — gives a more confident reconstruction than either alone.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

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