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Across 5. A waste product of respiration that is a gas 12. Taking excessive breaths 16. Smaller than a bronchus, larger than alveoli 17. The process of using oxygen to get energy from food 18. Weight is measured in these

Down 1. A phospholipid '..........' stops the alveoli from collapsing 2. Respiration is a '.........' process 3. The type of 'flow' that occurs in fish for successful gas exchange 4. Blood without oxygen 6. Breathing Out 7. Breathing In 8. Smallest blood vessels 9. Mammalian gas exchange organs 10. Air enters insects via these 11. They have a backbone 12. Iron-containing protein, found in blood 13. Breathing is a '..........' process 14. How gases enter, and leave, the body 15. Moves up and down when (mammals) breathe