ThermoregulationControlling the temperature of the body

Thermoregulation Endotherms

Generate heat through metabolic activity

Eg. humans, birds

Ectotherms Absorb heat from the

surroundings Use behaviours to

maintain a constant body temp

Eg fish, reptiles

Both the gecko and the scorpion are at the same temperature as the air surrounding them. Notice the

difference between these cold-blooded creatures and the warm-blooded humans holding them.

Thermoregulation Endotherms and Ectotherms can be further

classified into two groups: PoikilothermsAnimals that cannot control their body temp. Body temp changes with the temp of the surroundings. Eg fish and reptiles

HomeothermsAnimals that can maintain a relatively constant body tempEg. mammals, some insects, birds

In the image to the left, the lizard is just above room temperature, being warmed by the human hand holding it. To warm up lizards will seek a sunny area and bask in warm sunlight, as in the image to the right.

Mammals can use up to 80% of the energy obtained from food simply to maintain body temperature.

Losing body temperature

Any organism that is hotter than its surrounding may lose heat

Heat can be lost through: Radiation Conduction Convection Evaporation

Loss and maintenance in an a reptile

Ways of Losing Heat

Conduction – transfer of heat from a hotter to cooler object which is it in contact with

Convection – transfer of heat by warm air or water rising and being replaced by cool air or water

Evaporation – as water vaporises it takes heat with it form the body –cooling effect

Radiation – transfer of heat by means of infra-red waves

Heat regulation in humans

• An example of how the

human body regulates body temperature.

Remember: Adaptations

Adaptations allow an organism to survive in a range of environmental conditions that exist in their habitat.

Structural – body shape Behavioural – what the animals does Physiological – Internal metabolic functions

There are a number of adaptations animals have to be able to successfully regulate their temperature

Increase Body Temperature Decrease Body Temperature

Vasoconstriction: Arterioles get smaller to reduce blood going to skin, keeping the core warm.

Shivering: Rapid contraction and relaxing of skeletal muscles. Heat produced by respiration.

Piloerection: Hairs on skin stand up (trapping more air) and decreasing heat loss.

Curling up: reduces heat loss, decreases surface area.

Huddling together: animals group together and share body heat., thus reducing heat loss.

Hibernation: When an animal cannot cope with conditions animals undergoes dormancy

Basking: take in heat from surroundings

Fat: insulates against heat loss.

Fur: Traps warm air to maintain heat

Vasodilation: arterioles dilate (widen) so more blood enters the skin capillaries and heat is lost.

Sweating: Glands secrete sweat which removes heat when water evaporates.

Pilorelaxation: Hairs on skin flatten (trapping less air) and increasing heat loss.

Stretching Out: By opening up, the body has a larger surface area.

Burrowing : To avoid heat of day

Some arctic animals can also have antifreeze substances in their blood to prevent cell damage due to extreme cold!

Osmoregulation Maintaining a Water Balance

Water Balance: Osmoregulation

All animals have some mechanism to regulate water balance.

They balance water uptake vs. water loss and regulate solute concentration within cells and tissues

The fluid in cells, blood and tissue fluids contains a variety of solutes dissolved in water. This fluid is the medium in which everything happens – chemical reactions, transport of nutrients, gases and wastes.

Water is lost continually from the body in urine and faeces, through our sweat glands and tear ducts.

Osmoreceptors in the hypothalamus detect changes in the water concentration in the blood and body tissues

Water balance ina kangaroo rat(2 mL/day)

Water balance ina human(2,500 mL/day)

Ingestedin food (0.2)

Ingestedin food (750)

Ingestedin liquid(1,500)Water

gain(mL)

Waterloss(mL)

Derived frommetabolism (1.8)

Derived frommetabolism (250)

Feces (0.09)

Urine(0.45)

Feces (100)

Urine(1,500)

Evaporation (1.46) Evaporation (900)

Water Balance in Two Different Land Mammals

Water balance and the kidneys Living things have evolved diverse

ways of regulating their water balance.

In vertebrates including frogs, lizards and humans, the kidneys are the main organs of excretion.

If blood concentration increases:

1. Nerve impulses sent from the hypothalamus stimulates the pituitary gland

2. Pituitary gland secretes ADH (Anti-diuretic hormone)

3. ADH causes the kidneys to reabsorb more water

4. More concentrated Urine is produced

How the Kidney functions when water levels are low:

Water content of the blood normal

Water content of the blood HIGH

Water content of the blood LOW Too much water drunk

Too much salt or sweating

Brain producesMore ADH

Urine output LOW

Brain produces Less ADH

Urine output HIGH

High volume of waterreabsorbed by kidney

Low volume of waterreabsorbed by kidney

(small volume of Concentrated urine)

(large volume of dilute urine)

Osmoregulation and the kidneys (Simple)

Please Note: Urination still ends up with a net loss of water so it still needs to acquired.

Adaptations to maintain water balance

Structural and Physiological Adaptations

Behavioural Adaptation

• Waterproof or impermeable layer can reduce water loss (e.g.. Scales, hair, feathers, exoskeleton).

• Insects reabsorb water from the rectum, excreting a dry faeces

•Birds and reptiles reabsorb water from their cloaca (the cavity into which their rectum and ureter open). They excrete uric acid instead of urine.

•Frogs swell up like a ball retains urine in its bladder for the dry season

• Burrowing underground for weeks at a time •Earthworms curl up in a ball of mucous

•Some arthropods position their bodies to collect condensation at night.

•The desert hopping mouse wraps its fluffy tail around its mouth to trap water vapour.

•Nocturnal life styles in dessert biomes.

Other examples - Camels

Camels metabolise the fat in their hump, which gradually shrinks as the fat is used up.

As the fat is used up water is produced

1g of fat produces twice as much water than the equivalent mass of carbohydrates.

However the camel can’t produce enough water this way.

As water is lost, the body fluids become more concentrated but the camel’s tissues are extremely tolerant of this condition.

Once water is available, camels rehydrate by consuming large volumes of water, up to 40 L, in a matter of minutes.

Other examples - The desert frog

The Desert frog tucks itself in a water-conserving position under the ground.

It then encases itself in a cocoon of layer upon layer of shed skin.

The cocoon completely surrounds the frog except for its nostrils, and the little space between the body and the cocoon becomes humid.

The frog’s metabolic rate slows as it enters aestivation, the summer equivalent of winter hibernation.

Cyclorana platycephalus, breaking from its cocoon after rain.

Osmoregulation in aquatic animals Water Balance in both fresh and saltwater fish

Water Balance in Water Water balance is just as difficult in

aquatic organisms Some marine invertebrates have water

concentration in their cells the same as the surrounding water concentration (isotonic).

These organisms are called osmoconformers.

Jellyfish Crabs Sea Anemones

Marine Vertebrates - Salt water Fish Marine vertebrates like fish have body fluids that

tend to be hypotonic to their surroundings. This means that their body fluids are of a lower

concentration compared with the water in which they live.

In saltwater fish: water is lost to the surface by the gills to replace water they take in large amounts of surrounding water

BUT this is high in salts.

Organisms that have specialised mechanisms for dealing with water balance are called osmoregulators.

Seawater Fish

Freshwater Fish

Freshwater animals tend to have concentration of ions in their tissues higher than the surrounding water, water molecules therefore tend to enter their cells.

To Also deal with have high kidney filtration rate produce large amounts of dilute urine scales to reduce soft tissues to water

Freshwater Fish