1. Maintaining a water balance Animals

2. 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

3. 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

4. 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.

5. 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

6. 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

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

8. 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

9. 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.

10. 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