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Chapter 4: Excretion In Living Organisms
L1: Excretion in animals
Excretion:
? A vital process by which the living organism gets rid of the waste
products are produced from the biological processes and the chemical
reactions (harmful metabolic products)
? It refers only to the materials that leave the body through the plasma
membrane.
What happens when we eat food?
1- Some food is digested, then:
? Blood carries the digested food to all body cells.
? Body cells burn the digested food to produce energy and release
some wastes to blood to expel out of the body.
? These waste materials are called excretory materials (cell wastes).
carries to by burning Energy
Blood digested food body cells
Cell wastes
2- Some food isn’t digested,
? The indigested food is useless, so it must expel outside the body in the
form of solid wastes.
Types of wastes expelled outside the body
A)Solid wastes: Indigested food stored in the large intestine; they don’t pass
out through the plasma membranes.
? N2 enters the 2 lungs & leaves them without passing the membrane.
B) Excretory materials: Waste materials produced inside the body cells,
where the body must get rid of them through the plasma membrane.
• They contain:
a) Harmless materials: the body can’t use. (H2O)
b) Poisonous materials: the body must get rid of. (Nitrogenous wastes)
2
Second Term
