(a) Describe the water cycle using an annotated diagram (s) only.
(b) What is the importance of water tc living organisms?
Explanation
(a)
Features: Sun, cloud, plant, animal ground / earth / soil and river/ water/ body/ sea/ lake/ stream/ ocean.
Processes with corresponding arrows: Precipitation / condensation in clouds; - Evaporation of water from water body, river, sea
Evaporation of water from soil or ground; Excretion by animal; Drinking by animals; Perspiration and respiration by animals; Absorption of water by roots; Transpiration by plants; Erosion or run-off water from soil; Respiration in plants; Decay in plants.
(b) Importance of water in living organisms are:
General:
(i) Life started in water
(ii) Some organisms still live in water.
(iii) All organisms contain at least 50% of water
(iv) Biochemical reactions occur in aqueous medium organisms, e.g.; gaseous exchange, digestion and absorption.
(v) It serves as food.
(vi) It increases for the growth of organisms.
(ii) Transport Medium: (Blood plasma / tissue fluid/ lymph:
(i) for excretory products; - hormones
(ii) for end products of digestion.
(iii) dispersal of larval stages of aquatic amphibians
(iv) transfer of gauntest of mosses, ferns and some animals
(v) dispersal of some seeds.
Solvent:
(I) Removal of excretory products, ammonia and urea.
(ii) Component of secretions, digestive juices, tears and venom in snakes.
Lubricant:
(i) mucus for external at movement in snails and earthworms
(ii) for internal movement in the gut and vagina
(iii) Perivisceral fluid in the fe viscera.
Support:
(i) Amniotic fluid in mammals
(ii) vitreous/ aqueous humour of the mammalian eye, tutor pressure m in the herbaceous plants
(iii) erection of penis
(iv) hemocoel in earthworms.
Miscellaneous:
(i) temperature control through sweating, panting and transpiration
(ii) endolymph and perilymph in the mammalian ear.