Summary
Preserved remains or traces of ancient organisms that record the history of life.
In depth
Fossils form when organisms are buried quickly and minerals replace tissue. Rock layers (strata) are generally older at the bottom, and radiometric dating, for instance with uranium-lead or carbon-14, gives absolute ages. Transitional fossils such as Tiktaalik (fish with limb-like fins) and Archaeopteryx show intermediate traits.
The record is incomplete because fossilisation is rare.
Fossil types include body fossils (bones, shells), trace fossils (footprints, burrows, coprolites) and casts or moulds. The record is incomplete since fossilisation is rare and favours hard parts and certain habitats. Even so, it documents transitions such as Tiktaalik (fish with neck and wrist-like fins, 375 mya) and Archaeopteryx (feathered dinosaur, about 150 mya).
Relative dating uses the order of strata and index fossils, while absolute dating uses radioactive decay: carbon-14 (half-life 5730 years) for material up to about 50,000 years old, and uranium-lead or potassium-argon for rocks millions of years old.
Frequently asked questions
What is Fossils?
Preserved remains or traces of ancient organisms that record the history of life.
Which area of biology covers Fossils, and how advanced is it?
Fossils is one of the 53 topics in Evolution. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Cambrian Explosion, Ancient DNA, Human Evolution.
Why does Fossils matter?
Fossils show that life has changed through time, that most past species are extinct and that modern groups appeared in sequence.
Can you give an example of Fossils?
The series of horse fossils shows changes in size, toes and teeth.
What should I learn before Fossils?
Fossils is a Beginner topic, so no earlier topic is required. Other Beginner topics in Evolution that pair well with it include Evolution, Natural Selection, Charles Darwin.
What topics are related to Fossils?
The closest topics to Fossils are Cambrian Explosion, Ancient DNA, Human Evolution, Macroevolution. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Fossils?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Fossils. To practise the whole of Evolution, use the Evolution quiz.
How is Fossils different from Cambrian Explosion?
Fossils: Preserved remains or traces of ancient organisms that record the history of life. Cambrian Explosion: A rapid diversification of animal body plans about 540 million years ago. Read both side by side and note what each one explains.
How should I study Fossils step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Cambrian Explosion and explain the difference aloud. Finally, take the Evolution quiz and come back to this page for any question you miss.