1. Excreting wastes
7.3

2. Introduction Many products from metabolism harmful.
Lungs eliminate CO2
Large intestine removes toxic waste digestive system
Liver transforms toxins (alcohol & heavy metals) into soluble compounds that kidneys can deal with.
Kidneys play crucial role in removing waste, balancing pH, and maintaining water balance.

3. Protein metabolism Average Canadian consumes more protein than needed.
Excess protein  carbohydrates
Nitrogen + 2H need to be removed from amino acids
Deamination: occurs in the liver.
Ammonia is a water-soluble gas: extremely toxic.
Build-up of mg can kill a human.
Two ammonia + CO2 urea: x less toxic

4. Nucleic acid metabolism
Uric acid: formed by breakdown of nucleic acids.
Kidneys help in excretion

5. Water balance Maintained by kidneys
Humans lose approx. 2L of water a day: urine, perspiration, exhaled air.
Drop in fluid intake by 1% = thirst. 5% = pain and collapse. 10% = death.

6. Excretion: simple Unicellular & simple multicellular (sponge)
Every cell in contact with external environment
Wastes released directly from cell
Fluid regulation?
Ameoba & paramecium: hypertonic to freshwater: contractile vacuoles.

7. Excretion: complex
Not every cell in contact with external environment.
Wastes need to be collected and temporarily stored.
Excretory system: cells work together to remove wastes from body or store waste until signalled to remove them.

8. earthworm
Nephrostome: funnel-like structure: draws fluids from body cavity into tiny tubules. Collecting tubule: collects fluids from nephrostome. Bladder. Nephridiopore: small pores in which wastes are released.

9. Grasshopper
Malpighian tububles: throughout body cavity: absorb wastes by diffusion. Wastes released into gut and eliminated as solid wastes from the anus.

10. ..to more complex...

11. summary

12. Seatwork/homework
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