Fluid Balance - Terrestrial Organisms

Question 1

What are the three ways you gain water including their amount?

Answer 1

1. Food (700ml)
2. Drink ( 1600ml)
3. Metabolism (200ml)

Question 2

What are the 4 ways you lose water?

Answer 2

1. Lungs.
2. Skin.
3. Kidneys.
4. Faeces.

Question 3

What are two things water is important for?

Answer 3

1. Excretion.
2. Temperature regulation.

Question 4

What is excretion?

Answer 4

The removal of the waste products of metabolism (nitrogenous wastes).

Question 5

Why is water important for temperature regulation?

Answer 5

Gas exchange occurs through the moisture on membranes. Water is a component of blood that carries dissolved ions around the body and some nutrients need water to be absorbed.

Question 6

What are the 4 substances urine is composed of?

Answer 6

1. Water.
2. Urea.
3. Ions.
4. Uric acid.

Question 7

What substances are reabsorbed in the kidney at the loop of Henle?

Answer 7

• 99% of the water.
• All glucose and amino acids.
• Most salts and urea.

Question 8

What are the 3 functions of kidneys in osmoregulatory?

Answer 8

1. Removal of nitrogenous wastes.
2. Regulation of water concentration in the blood.
3. Maintiainng ion levels in blood.

Question 9

What are 4 factors that affect water loss and gain?

Answer 9

1. Environment.
2. Structure.
3. Physiology.
4. Behvourial.

Question 10

What is a structural feature that affects water loss and gain?

Answer 10

• Waterproof/impermeable outer layer.

Question 11

Describe a waterproof/impermeable outer layer as a structural feature.

Answer 11

These adaptations reduce water loss by evaporation and osmosis. Scales of reptiles are impervious to water and so decrease evaporation. Invertebrates consist of a waxy cuticle that is impervious to water. Amphibians secrete a waxy covering to decrease evaporation. The feathers of birds and the upper part of the epidermis contains keratin a protein that hardens and waterproofs the body surface.

Question 12

What are four physiological features that affect water loss and gain?

Answer 12

1. Elongated large intestine.
2. Long loop of Henle.
3. Metabolism of fats and carbohydrates.
4. Secretion of anti diuretic hormone.

Question 13

Describe an elongated large intestine as a physiological feature.

Answer 13

In kangaroos, a long large intestine means a greater volume of water can be reabsorbed and so results in dry faeces.

Question 14

Describe a long loop of Henle as a physiological feature.

Answer 14

In regard to desert hopping mice the longer loop of Henle the more concentrated the urine is and the more water saved. Therefore this maximises water conservation as they produce a low volume of concentrated urine.

Question 15

Describe the metabolism of fats and carbohydrates as a physiological feature.

Answer 15

In regard to camels, they produce water by metabolising fat in their hump, however, this source of water is not enough to compensate for the water lost by evaporation and so the camel’s body fluids become increasingly concentrated.

Question 16

Describe antidiuretic hormone as a physiological feature.

Answer 16

ADH reduces urine output. It reduces urine output by acting on the collecting ducts of the kidney. Diuretics increase urine production.

Question 17

What are two behavioural features that affect water gain and loss?

Answer 17

1. Burrowing.
2. Aestivation.

Question 18

Describe burrowing as a behavioural feature.

Answer 18

Burrows have lower temperatures and higher humidity than the open air, so water loss is reduced. Burrow will trap exhaled water vapour so there is a lower concentration gradient of water vapour between air and animal which decreases evaporation.

Question 19

Write an SRMERF for when the water balance is low.

Answer 19

S - Low water in the blood.
R - Osmoreceptors in the hypothalamus.
M - Hypothalamus.
E - Posterior lobe of the pituitary gland secretes ADH.
R - Collecting ducts are more permeable and so increase water absorption.
F - Increased water in the blood.

Question 20

Write an SRMERF for when the water balance is high.

Answer 20

S - High water in the blood.
R - Osmorecpeots in the hypothalamus.
M - hypothalamus.
E - Posterior lobe of the pituitary gland stops the release of ADH.
R - Collecting ducts are less permeable and so decrease water absorbed.
F - Decreased water in the blood.

Question 21

Describe aestivation as a behavioural feature.

Answer 21

The water-holding frog will fill its bladder and pockets under the skin with urine and tuck itself into a water-conserving cacoon. The frog’s metabolic rate slows, enabling it to enter aestivation underground. Slowing down the metabolic rate can reduce water loss as water is a product of metabolic processes.