Download - Excreting wastes
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.