(a) Write two differences between Homo erectus and Homo habilis.
(b) Rearrange the following from early to late geologic periods :
Carboniferous, Silurian, Jurassic.

Explanation

### Step-by-Step Solution

#### Part (a): Differences between Homo erectus and Homo habilis

1. **Brain Capacity**:
- **Homo erectus** had a larger brain capacity, approximately 900 cc.
- **Homo habilis** had a smaller brain capacity, ranging from 650 to 800 cc.

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