Godwit wrote: "Newts, salamanders and snakes all lack ears, yet can hear. But they are not animals."
Newts, salamanders and snakes are definitely animals!
This site gives a reasonably accessible (although somewhat simplified) explanation of the current five-kingdom classification scheme:
1. Monera - single-celled organisms with no cell nucleus
2. Protista - single-celled organism with a cell nucleus
3. Fungi - multi-cellular organisms with no chloroplasts and no mechanism for movement; acquire nutrients by absorption
4. Plantae - multi-cellular organisms with chloroplasts which make nutrients through photosynthesis
5. Animalia - multi-cellular organisms with no chloroplasts which acquire nutrients by ingestion