Chapter 16 - Temperature regulation and water balance

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Chapter 16 - Temperature regulation and water balance
1 16.1 Temperature and water balance
1.1 Animal water levels and temperature are regulated to a further degree then plants.
1.2 In terrestrial vascular pants, water and nutrients are transpired through the xylem on a daily basis, rate of transpiration is regulated by the degree of opening of stomata
1.3 Plants in hot dry environments have adaptation which get their nutritional requirement but with lower levels of transpiration for conserving water.
1.4 Plants in saline soils have high salt levels which are regulated by secretion.
2 16. 2 Body temp in animals
2.1 Animals other then birds and mammals are ECTOTHERMS, who get their heat from their environment. Body temperature is mostly at mercy of the environment, they produce less heat then endotherms, and loose heat quicker aaswwell, they use less energy though. And in harsh environments they can become inactive.
2.2 HETEROTHERMS are some ectotherms (fish and insects) which stay warmer thenthe temperature of which they live in, they also function as endotherm, generating heat to increase their body temperature. Other ectotherms to stay warmer produce additional heat from intense muscluar activity.
2.3 BIrds and mammals are ENDOTHERMS, their body temperature is constant and is usualy higher then that of their environment. they generate heat by internal metabolic heat production and have insulating features (feathers and fur etc). They use physiological mechanisms and behaviour to regulate loss of metabolic heat.
2.4 In endothermic animals that hibernate although their body temperature drops dramatically temperature regulation is stil present. Aquatic animals loose heat more quickly.
2.5 Core temperature of most mammals is 36-38 degrees. 6 more degrees above can be lethal, 15 degrees below is now far temperature drops can be tolarated.
3 16.3 Temp regulating pathways
3.1 Regulation of body temperature involves a complex negitive feedback pathway. In endotherms the control centre for measuring the body temperature is the Hypothalamus in the brain, it initiates regulatory responses that can involve heat heat gain or loss.
3.2 Arterial blood has the most constant temperature in the body. In endotherms a group of temperature sensitive cells in the Hypothalamus act as detectors, triggering homeostatis responses. Temperature receptors also found in skin, which detect changes in the external environment and trigger responses before there is a change in core body temperature.
3.3 Animals control heat exchange by insulation, and by physiological and behavioural means. Regulatoing he rate of heat between an animal and its environment, the factors involves in this are: an effective temperature difference between the two, the area of exposed surface, effiicenecy of insulation againest heat exchange and physiological processes involving evaporation and circulatory changes
3.4 Animals loose heat by radiation, evaporation, conduction, and direct loss in body fluids. Terrestrial mammals, when surrounding temperatures are higher then their body temperature, heat can only be lost by evaporation (sweating, panting or licking fur). If the temperature is hot and humid evaporation is not effective and instead convection becomes important.
3.5 When surrounding temperatures are cold many animals increase body temperature by adopting patterns of behaviour which enable them to absorb heat from the environment through radiation and conduction often displayed by ectotherms.
3.6 Insulation reduces heat exchange with their environment, feathers and fur trap a layer of warm air next to skin.
3.7 Vertebrates do many physiological mechanisms that regulate heat and exchange with environment such as circulatory changes (constriction or dilution of openings of blood vessels in the skin) and counter current arrangements of blood vessels that cause heat to be retained within tissues.
3.8 Evaporation such as sweat contains salts and other substances, so increased sweating can cause a significant loss of salts from the body, with low sweating important substances can be reabsorbed before passing off the body. Advantages of panting over sweating are no loss of salts from the body.
3.9 For behavioural regulation of temperature, most animals to reduce heat loss reduce their exposed surface area to volume ratio. They can move in or out of the sun or go underground, or restrict activity to night where temperatures are cooler.
3.10 It is more energy effeicent to reduce heat loss then increase heat gain. Endotherms though generally increase heat gain by the production of metabolic heat by increased muscle activity by shivering, increased cellualr activity in brown fat, and to increase cellular metabolism.
4 16.4 Water balance and salt levels
4.1 Animals can regulate water balance by physiological and behavioural meas, which allows them to live in a range of environments, while some animals just restrict the environments that they can live in
4.2 Impermeable external coverings can reduce the impact of salt or osmotic gradients that are unfavouable
4.3 A water balance is necessary to control salt concentrations as in solutions salts form ions, and for biochemical processes to occur cell s require the concentrations of certain ions to be held within narrow limits
4.4 Water balance is the result of water intake and water loss. In organisms net movement of water occurs as a result of osmosis.
4.5 The concentration of marine organisms is similar to sea water. Animals moved in freshwater environments have their body fluids concentrations more dilute than sea water. Bony fish are descendants from freshwater but moved back into the sea, but there concentrations are still more dilute then sea water which makes water and salt balance an issue for them.
4.6 Most marine invertebrates have body fluids with equal osmotic concentrations to that of sea water, Some tolerate fluctuations of their body fluids concentrations (those tend to live in restricted salinity ranges), others can regulate their salt levels.
4.7 Marine and freshwater fishes have different concentrations of which that they live in which puts them under osmotic stress.
4.8 There needs to be ways of controlling salt and water concentrations, if there wasn't freshwater fishes would take in too much water and lose too much salt, and marine fishes lose too much water and gain too much salt. So their skin and scales are impermeable to water and salts, but their gills are not as they have to get oxygen which makes them highly permeable, they are continuely ventilated with water.
4.9 Freshwater fish rarely drink water, have dilute urine and actively absorb salt. Marine fish drink continuously, they have excrete samll amounts of urine and actively excrete salt.
4.10 Some marine fishes by retaining urea into their blood which makes their blood osmoconcentration is equivalent to sea water.
4.11 In freshwater, amphibians (e.g. frogs) lose salts and gain water osmotically. They remove excess water by excreting dilute water.
4.12 Availability of water in many terrestrial environments is low and varies, Animals experience thirst and seek and consume water to resume their water balance. Water can be conserved through behavioural means, water can be gained by food and is produced during cellular respiration (metabolic water).
4.13 Respiratory surfaces must be moist so air-breathers lose water by evaporation.
4.14 Kidneys lose water during excretion of nitrogenous wastes, and the gut loses water through feaces, though water can be reabsorbed in the intestines, but if the feaces passes through too quickly deheydration can occur.
4.15 Loop of Henle and vasa recta allow concentrated urine. Organisms in dry environments have a longer loop of henle and a larger medullary region then that compared of a moist environment.
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