Excretion

1. Excretion

2. Homeostasis • To understand excretion, we need to understand homeostasis –

3. Homeostasis • To understand excretion, we need to understand homeostasis – the ability to maintain a constant system in the face of fluctuations in the environment.

4. Homeostasis • To understand excretion, we need to understand homeostasis – the ability to maintain a constant system in the face of fluctuations in the environment. • If I ate a whole block of chocolate – instead of giving me a diabetic coma, my body balances out my blood sugar level.

5. Excretion • The removal of waste and excess products of the metabolism of the cells.

6. Excretion • The removal of waste and excess products of the metabolism of the cells. • Excretory products are water, carbon dioxide, and excess minerals.

7. Excretion • The removal of waste and excess products of the metabolism of the cells. • Excretory products are water, carbon dioxide, and excess minerals. • Kidneys are a very important organ for excretion, along with the lungs, skin and hormones.

8. Nitrogenous wastes • Amino acids are the end products of the digestion of proteins – can be made into new proteins, converted to fatty acids, carbohydrates, or used in respiration.

9. Nitrogenous wastes • Amino acids are the end products of the digestion of proteins – can be made into new proteins, converted to fatty acids, carbohydrates, or used in respiration. • These produce leftover fragments of nitrogen compounds which can be extremely poisonous.

10. Nitrogenous wastes • Amino acids are the end products of the digestion of proteins – can be made into new proteins, converted to fatty acids, carbohydrates, or used in respiration. • These produce leftover fragments of nitrogen compounds which can be extremely poisonous. Amino acid  ammonia + acid urea carbohydrates etc

11. Nitrogenous wastes • Ammonia – poisonous. Can only be used as a waste product by animals that can dissolve it in large amounts of water. EG. Fish, freshwater animals.

12. Nitrogenous wastes • Ammonia – poisonous. Can only be used as a waste product by animals that can dissolve it in large amounts of water. EG. Fish, freshwater animals. • Urea – toxic but not as bad as ammonia. Can be stored in body temporarily. Must be flushed out with lots of water. Animals that use this method must drink lots.

13. Nitrogenous wastes • Ammonia – poisonous. Can only be used as a waste product by animals that can dissolve it in large amounts of water. EG. Fish, freshwater animals. • Urea – toxic but not as bad as ammonia. Can be stored in body temporarily. Must be flushed out with lots of water. Animals that use this method must drink lots. • Uric Acid – non-toxic, excreted as a pasty substance or as crystals. Important with eggs of birds/reptiles as the wastes don’t poison growing embryo.

14. Excretion in Invertebrates • Amoeba - Excrete ammonia directly into the surrounding water by simple diffusion.

15. Excretion in Invertebrates • Amoeba • Excrete ammonia directly into the surrounding water by simple diffusion. • Also have a contractile vacuole to pump out excess water.

16. Excretion in invertebrates • Earthworms - Use nephrida tubules – cleans the fluids in the segment previous.

17. Excretion in invertebrates • Earthworms • Use nephrida tubules – cleans the fluids in the segment previous. • Any fluid passing through the tubules has close contact with a network of blood capillaries.

18. Excretion in invertebrates • Earthworms • Use nephrida tubules – cleans the fluids in the segment previous. • Any fluid passing through the tubules has close contact with a network of blood capillaries. • Water and minerals are absorbed into the blood and wastes are passed to the outside through a nephridiopore.

19. Excretion in invertebrates • Insects • Malphigian tubules connected to the area where the mid-gut and the hind-gut join.

20. Excretion in invertebrates • Insects • Malphigian tubules connected to the area where the mid-gut and the hind-gut join. • These float in body fluid where they absorb nitrogenous waste – converting them to uric acid

21. Excretion in invertebrates • Insects • Malphigian tubules connected to the area where the mid-gut and the hind-gut join. • These float in body fluid where they absorb nitrogenous waste – converting them to uric acid • As digestive wastes pass down the gut, these tubules pass the crystals into the gut and they are excreted as faeces.

22. Osmoregulation • Freshwater fish • Constant danger of drowning

23. Osmoregulation • Freshwater fish • Constant danger of drowning • Also lose a lot of salt

24. Osmoregulation • Freshwater fish • Constant danger of drowning • Also lose a lot of salt • Kidneys of these fish actively reabsorb salt and let through all the water, so they have a large, watery urine.

25. Osmoregulation • Freshwater fish • Constant danger of drowning • Also lose a lot of salt • Kidneys of these fish actively reabsorb salt and let through all the water, so they have a large, watery urine.

26. Osmoregulation • Marine fish - Problems losing water as their blood is less salty than the sea water (hypotonic)

27. Osmoregulation • Marine fish • Problems losing water as their blood is less salty than the sea water (hypotonic) • Many drink sea water

28. Osmoregulation • Marine fish • Problems losing water as their blood is less salty than the sea water (hypotonic) • Many drink sea water • These fish get rid of excess salt through special glands in the gills and give out small amounts of urine.

29. Osmoregulation • Sharks and rays • Keep urea in their blood so that it is stronger than the sea water.

30. Osmoregulation • Sharks and rays • Keep urea in their blood so that it is stronger than the sea water. • They get rid of excess salt through special glands in the intestine and excreting it through the kidneys.