Endotherms Ectotherms Generate heat through Absorb heat from the metabolic activity surroundings Eg. humans, birds 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.
Endotherms and Ectotherms can be further classified into two groups: Homeotherms Poikilotherms Animals that can maintain a Animals that cannot control their body relatively constant body temp temp. Body temp changes with the Eg. mammals, some insects, temp of the surroundings. Eg fish and birds reptiles Mammals can use up to 80% of the energy obtained from food simply to maintain In the image to the left, the lizard is just above room temperature, body 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.
Any organism that is hotter than its surrounding may lose heat Heat can be lost through: Radiation Conduction Convection Evaporation
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
• An example of how the human body regulates body temperature.
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 TemperatureVasoconstriction: Arterioles get smaller to reduce Vasodilation: arterioles dilate (widen) so moreblood going to skin, keeping the core warm. blood enters the skin capillaries and heat is lost.Shivering: Rapid contraction and relaxing of Sweating: Glands secrete sweat which removesskeletal muscles. Heat produced by respiration. heat when water evaporates.Piloerection: Hairs on skin stand up (trapping more Pilorelaxation: Hairs on skin flatten (trapping lessair) and decreasing heat loss. air) and increasing heat loss.Curling up: reduces heat loss, decreases surface Stretching Out: By opening up, the body has aarea. larger surface area.Huddling together: animals group together and Burrowing : To avoid heat of dayshare body heat., thus reducing heat loss.Hibernation: When an animal cannot cope withconditions animals undergoes dormancyBasking: take in heat from surroundingsFat: insulates against heat loss.Fur: Traps warm air to maintain heat Some arctic animals can also have antifreeze substances in their blood to prevent cell damage due to extreme cold!
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 in Two Different Land Mammals Water balance in Water balance in a kangaroo rat a human (2 mL/day) (2,500 mL/day) Ingested Ingested in food (0.2) in food (750) Ingested in liquidWater (1,500)gain(mL) Derived from Derived from metabolism (1.8) metabolism (250) Feces (0.09) Feces (100)Water Urine Urineloss (0.45) (1,500)(mL) Evaporation (1.46) Evaporation (900)
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. How the Kidney functions when water levels are low: 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
Osmoregulation and the kidneys (Simple) Water content of Water content of the blood LOW the blood HIGH Too much water drunk Too much salt or sweatingBrain Brainproduces Water content producesMore ADH of the blood normal Less ADHHigh volume of water Low volume of waterreabsorbed by kidney reabsorbed by kidney Urine output Urine output HIGH LOW (large volume of (small volume of dilute urine) Concentrated urine)Please Note: Urination still ends up with a net loss of water so it still needs to acquired.
Structural and Physiological Behavioural AdaptationAdaptations• Waterproof or impermeable layer can • Burrowing underground for weeks at a timereduce water loss (e.g.. Scales, hair,feathers, exoskeleton). •Earthworms curl up in a ball of mucous• Insects reabsorb water from the rectum, •Some arthropods position their bodies toexcreting a dry faeces collect condensation at night.•Birds and reptiles reabsorb water from •The desert hopping mouse wraps its fluffy tailtheir cloaca (the cavity into which their around its mouth to trap water vapour.rectum and ureter open). They excreteuric acid instead of urine. •Nocturnal life styles in dessert biomes.•Frogs swell up like a ball retains urine inits bladder for the dry season
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 Once water is available, camels rehydrate the camel’s tissues are extremely by consuming large volumes of water, up tolerant of this condition. to 40 L, in a matter of minutes.
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 spaceCyclorana platycephalus, breaking from between the body and theits cocoon after rain. cocoon becomes humid. The frog’s metabolic rate slows as it enters aestivation, the summer equivalent of winter hibernation.
Water Balance in both fresh and saltwater fish
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 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.
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