Maintaining a water balance Animals

Adaptations Adaptation Evolutionary adaptations Adaptations can be characteristic which makes an organism well suited to its environment. Evolutionary adaptations changes that have occurred in the genotype of an organism over a long period of time. Adaptations can be structural physiological behavioural

Water Balance in Animals  osmoregulation. Maintaining a constant fluid concentration within an animal Definitions Isotonic equal in water concentration Hypertonic lower in water concentration hypotonic higher in water concentration

Osmoregulation in freshwater bony fish  Problem: the tissues of the fish are hypertonic to the river or loch where it lives. Water enters through the gills and intestines by osmosis. Solutions: The kidney contains many large glomeruli, which filter a lot of water out of the blood. Large volumes of urine are produced in which waste (ammonia)is well diluted Loss of mineral salts in the urine is made up by the chloride secretory cells, which actively absorb salts from the water as it passes through the gills.

Osmoregulation in saltwater bony fish Problem: sea water is hypertonic to the tissues of the fish fish continuously loses water by osmosis. Solutions: Fish drinks sea water Kidney contains few, small glomeruli with a low filtration rate Little urine produced, so poisonous wastes have to be converted to non-toxic form Excess mineral salts are actively excreted by chloride secretory cells in gill membranes

Adaptations of Migratory Fish (e.g. Atlantic salmon, Eel) spends part of life in freshwater and part in salt water they are able to osmoregulate successfully in both environments

Water Conservation in a Desert Mammal Problem Limited supply of water available Obtaining Water From it’s food entirely

Water Balance in a Kangaroo rat (fed 100g seeds over one month) Water gain Water loss 6g in food 44g expired air 13.5g urine 54g in metabolic water 2.5g faeces 0g sweat Total gain: 60g Total loss: 60g Water balanced

Conserving Water Behavioural adaptations Remain in underground burrow in inactive state during extreme heat of day Inside of burrow is cooler and more humid than above ground Animal is active at night and forages for food in cooler conditions Animal has no need to sweat to give cooling effect, as is only active in cool conditions.

Conserving water Physiological Adaptations Mouth and nasal passages are dry, to reduce water loss to expiration Bloodstream contains a high level of ADH, which promotes water reabsorption Kidney tubules possess long loops of Henle, which promotes water reabsorption Large intestine reabsorbs water from waste material, produces faeces with low water content Does not sweat