1. Excretion

2. Why?

3. Nitrogen Waste Elimination Extra amino acids (protein) cannot be stored in the body. Amino acids that are not needed immediately are broken down in the liver. Ammonia is formed.

4. Amino Acid

5. Organisms either excrete ammonia directly, or convert it to urea or uric acid Compare/contrast these molecules…

6. N H H H Ammonia UreaUric Acid

7. Life in the Water

8. Most aquatic invertebrates excrete ammonia directly into the water. Flatworms Cnidaria Arthropods

9. Ammonia excretion requires a large amount of water, which is usually only available in an aquatic environment.

10. Life on Land Earthworms, Arachnids, Insects

12. What makes the challenges of life on land different from life in the water?

13. Dry Land

15. Life on Dry Land Sun and heat Dry conditions Gravity Variable weather and temperature

16. Earthworm The earthworm is very similar to a freshwater organism. It excretes ammonia directly through its skin. The earthworm excretes very dilute urine at a rate of 60% of its total body weight per day.

17. How does the earthworm’s excretion limit the habitats where it can live?

18. Insects, Reptiles (and Birds) These animals convert ammonia to uric acid. This process requires a lot of energy, but it produces nearly a solid waste that conserves water.

19. How does converting ammonia to uric acid increase the habitats where insects and reptiles can live?

20. Mammals Amphibians

21. Urea is formed in the liver. It is filtered from the blood by the kidney The kidney regulates the composition and quantity of urine that is excreted. Urine contains water, urea and hydrogen ions. The excretion of hydrogen ions helps to regulate the body’s pH.

22. Kidney Ureter Bladder Urethra

23. 4 3 2 1 1 2

24. Compare/Contrast the excretion of these animals