Theory question 104
Excretion(a) (i) List five excretory organs found in living organisms (ii) Give one example of an organism in which each type is found
(b) (i) State two ways in which the excretory organ of earthworm is similar to that of mammals (ii) Give three differences between them
(c) Describe the mechanism of opening and closing of the stomata.
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(a) Kidney – mammals (man); lungs – mammals; skin – man; contractile vacuole – Amoeba/Paramecium; nephridia – earthworm; flame cells – flatworm (Planaria); Malpighian tubules – insects; stomata/lenticels – plants
(b)(i) Similar: both are tubular; both remove nitrogenous waste and water; both are supplied with blood capillaries; both reabsorb useful materials
(ii) Differences (three): nephridia are many, in pairs in each segment – mammal has one pair of kidneys; nephridium opens by a nephrostome into the coelom – kidney tubule begins with a Bowman's capsule and glomerulus; each nephridium opens directly to the outside by a nephridiopore – kidneys drain through ureters to the bladder; nephridia not compact organs
(c) Opening: in light guard cells photosynthesise/take in K⁺ ions; sugar/solute concentration rises; water enters by osmosis; guard cells become turgid and, because the inner wall is thicker, they curve apart – pore opens
Closing: in darkness or water shortage solutes fall, water leaves, guard cells become flaccid and straighten – pore closes
Match each excretory organ with one named organism.