EXCRETING WASTES

7.3

INTRODUCTION Many products from metabolism

harmful.Lungs eliminate CO2Large intestine removes toxic waste

digestive systemLiver 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.

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 0.005 mg can kill a human. Two ammonia + CO2 urea: 100 000 x less toxic

NUCLEIC ACID METABOLISM Uric acid: formed by breakdown of

nucleic acids. Kidneys help in excretion

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.

EXCRETION: SIMPLE Unicellular & simple multicellular

(sponge)Every cell in contact with external

environmentWastes released directly from cellFluid regulation?

Ameoba & paramecium: hypertonic to freshwater: contractile vacuoles.

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.

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.

GRASSHOPPER Malpighian

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

..TO MORE COMPLEX...

SUMMARY

SEATWORK/HOMEWORK Page 345 # 1-4.