Evidence for evolution and classification — Edexcel GCSE Biology

Revision notes

4 short notes, in the order of the specification. Each one in short:

1. Fossil evidence for human evolution

   Fossils of early human ancestors show how they changed over time. Ardi, from 4.4 million years ago, could walk upright but could still climb trees. Lucy, from 3.2 million years ago, walked upright on two legs but had a small brain. Fossils from 1.6 million years ago show a larger brain and longer legs.

2. Stone tools

   Stone tools give evidence of how early humans lived, because stone survives for a very long time. The oldest tools are simple stones with a few chips knocked off, while later tools are more complex and specialised, suggesting greater skill and intelligence. Tools are dated from the age of the rock or sediment layer they are found in.

3. The pentadactyl limb

   Triple only

   The pentadactyl limb is a limb with five digits. Humans, bats, whales and frogs all have the same basic arrangement of bones: one upper bone, two lower bones, then wrist, hand and finger bones. This similarity is evidence that they share a common ancestor, with natural selection adapting the limb for different functions.

4. Five kingdoms and three domains

   Organisms were traditionally classified into five kingdoms: animals, plants, fungi, protists and prokaryotes. Improved genetic analysis showed that the prokaryotes are not all closely related, so a system of three domains was introduced above the kingdoms. The three domains are Archaea, Bacteria and Eukarya, which includes all organisms with a nucleus.