Theory question 101
Viruses, Monera, Protista and Fungi(a) Explain briefly sexual reproduction in Rhizopus. (b) A student suddenly stepped on a big snake, he cried for help and ran away. (i) Name the hormone produced in the body for the reaction. (ii) In which part of the human body is the hormone named in 1(a)(i) produced? (iii) State five changes that must have taken place as a result of the hormone named in 1(a)(i). (c)(i) In a tabular form, state three differences between excretion in flowering plants and excretion in humans. (ii) List two organelles found in a plant cell that are responsible for the excretion of metabolic wastes.
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(a) Sexual reproduction is by conjugation between hyphae of two different mating strains (+ and −).
The two hyphae touch and each grows a short side branch (progametangium) towards the other.
A cross wall cuts off a gametangium at each tip, leaving a suspensor behind.
The walls between the gametangia dissolve and their nuclei fuse to form a zygote.
The zygote forms a thick, dark, resistant wall: the zygospore, which can survive bad conditions.
In favourable (damp) conditions the zygospore germinates into a hypha bearing a sporangium.
(b)(i) Adrenaline.
(ii) Adrenal glands (adrenal medulla), above the kidneys.
(iii) Any five: faster heartbeat; faster, deeper breathing; rise in blood pressure; liver changes glycogen to glucose, so blood sugar rises; more blood sent to skeletal muscles and less to skin and gut; pupils dilate; hair stands on end; muscles become tense; faster release of energy in respiration.
(c)(i) Any three, in a table: plants have no special excretory organs / humans have kidneys, skin, lungs and liver; plants make small amounts of waste / humans make large amounts; plants excrete slowly / humans excrete fast; plants store many wastes (tannins, resins, gums, alkaloids) in their tissues / humans remove wastes from the body; plants reuse some products (CO2, O2, water) / humans cannot reuse urea; plant wastes include resins, gums, latex, tannins / human wastes include urea, sweat, salts.
(ii) Any two: vacuole; mitochondrion; chloroplast.
For (c)(i) set out a two-column table and keep each row on the same point of comparison.