Evidence for Evolution and Fossils
Build confidence in Evidence for Evolution and Fossils for GCSE Biology with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. Fossils and antibiotic-resistant bacteria both provide evidence for evolution; learn the three main ways that fossils form.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
Evidence for evolution comes from several sources, and fossils are the most direct.
Fossils are the remains of organisms from millions of years ago, found in rocks. They form in three ways: from parts of organisms that have not decayed because conditions such as oxygen or moisture were absent; when parts of the organism are replaced by minerals as they decay; and as preserved traces such as footprints, burrows and rootlet traces.
Many early forms of life were soft-bodied, so they left few traces behind, and much of the fossil record has been destroyed by geological activity. This is why scientists cannot be certain about how life began on Earth.
Revision notes
How fossils form
From parts of organisms that have not decayed, because one or more of the conditions needed for decay — such as oxygen or moisture — was absent.
When parts of the organism are replaced by minerals as they decay. As preserved traces of organisms, such as footprints, burrows and rootlet traces.
What fossils tell us
Fossils in rocks of different ages show how organisms have changed over time.
They allow scientists to trace the development of species and to see that organisms alive today are different from those that lived in the past.
Gaps in the record
Many early forms of life were soft-bodied, so they left few traces behind.
What traces there were have been mainly destroyed by geological activity. This is why scientists cannot be certain about how life began on Earth.
Key points
- Fossils are remains of organisms from millions of years ago.
- Some form when decay does not occur due to absent conditions.
- Some form when parts are replaced by minerals.
- Traces such as footprints and burrows are also fossils.
- Early soft-bodied organisms left few fossils.
- Geological activity has destroyed much of the record.
Worked examples
Example 1
Describe two ways in which fossils can form. [2 marks]
Model answer
From parts of organisms that have not decayed because a condition needed for decay, such as oxygen or moisture, was absent (1 mark). When parts of the organism are gradually replaced by minerals as they decay (1 mark).
Example 2
Explain why scientists cannot be certain how life on Earth began. [2 marks]
Model answer
Many early forms of life were soft-bodied, so they left few traces behind (1 mark), and the traces that did form have been mainly destroyed by geological activity (1 mark).
Example 3
Explain how fossils provide evidence for evolution. [2 marks]
Model answer
Fossils found in rocks of different ages show that organisms have changed over long periods of time (1 mark), allowing scientists to trace how modern species developed from earlier forms (1 mark).
Common mistakes
Saying all organisms leave fossils.
Soft-bodied organisms rarely do, and decay usually destroys remains.
Forgetting trace fossils.
Footprints, burrows and rootlet traces are all fossils.
Saying the fossil record is complete.
It has large gaps, particularly for early life.
Not linking fossils to change over time.
That link is what makes them evidence for evolution.
Exam tips
- Learn the three ways fossils form.
- Explain gaps by referring to soft bodies and geological activity.
- Link fossils explicitly to change over time.
- Remember trace fossils count too.
Key terms
- Fossil
- The remains or traces of an organism from millions of years ago.
- Trace fossil
- A preserved footprint, burrow or similar mark.
- Decay
- The breakdown of dead material, which prevents fossil formation.
- Geological activity
- Earth processes that can destroy fossils.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.