Osmoregulation - Paramecium
Osmoregulation
Many animals control the solute concentration of their cells. Paramecium is a single celled
animal which lives in fresh water. It is constantly at risk from inward osmosis of water.
1. Add annotations illustrating how this single celled Paramecium, which lives in fresh
water is coping with constant inward osmosis from the surrounding water into its
cytoplasm.
Include the following labels but also use arrows and add your own words to explain what
they do.
Plasma membrane
Cytoplasm
Contractile vacuole
Fresh water environment
Higher solute concentration
Lower solute concentration
Osmosis (water moves in this direction)
Exocytosis (water moves in this direction)
© David Faure, InThinking www.thinkib.net/biology 1
Osmoregulation - Paramecium
2. There are three systems of osmoregulation mentioned in the presentation.
These systems are compared in the table below.
Paramecium Insect Mammal
Organ (or
organelle) used
Contractile vacuole Malpighian tubule Kidney
to control water
balance
It uses active transport to Malpighian tubules Kidney nephrons collect
pump ions into the collect excess water excess water from the
contractile vacuole. Water from blood in the blood through
How does it then enters by inward insect’s abdomen and ultrafiltration. This water
function? osmosis and then is pass it into the hind gut collects in the in the
released into the of the digestive system. kidney pelvis and is
surrounding environment More water can be stored in the bladder in
(by exocytosis). absorbed here. urine.
The c.v. is constantly Water released three or
How much water Excess water leaves the
pumping water directly four times a day from the
does it release body in faeces
out of the cell bladder
Answer the following questions.
1. Name the three specialist structures which control osmoregulation?
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2. Describe one similarity between all three methods of osporegulation shown in the table.
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3. Put the three animals in order of the amount of water they release through
osmoregulation (when compared to body volume
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4. Which animal would survive longest without water?
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© David Faure, InThinking www.thinkib.net/biology 2
