Across
- 4. they respire by means of a complicated water-vascular system
- 5. They can respire by means of gills when they are in their adult stage
- 7. outer layer of skin
- 8. gas that we breathe in
- 9. the movement of air into and out of the lungs
- 11. waste product exhaled by animals
- 12. where gas exchange takes place
Down
- 1. they lack any specialized organs for respiration
- 2. commonly known as the windpipe
- 3. starfish respires by means of branchiae or
- 6. respiratory organ of fish
- 10. respiratory apparatus of mammalia includes trachea, bronchi, lungs and