Surviving The Cold Flashcards
Roughly how much does the temperature drop with every 1000m rise in altitude?
6.5 degrees c.
How might enzyme structural changes influence metabolic reactions?
Any changes might slow down or speed up the reactions.
Define thermoregulation.
As the term implies, thermoregulation is a process (consisting of many related processes!) by which organisms maintain their internal temperature within their optimum range for survival. They achieve this by constantly balancing heat loss with heat gain.
Why do organisms need enzymes? What effect can temperature change have on enzymes?
Living organisms rely on enzymes to control metabolic reactions or, in the case of heterotrophs, also to digest macromolecules. Changes in temperature, either increases or decreases, can affect the structural integrity of the proteins that control biochemical reactions and/or the fluidity of biological membranes.
Define torpor.
State of controlled lowered body temperature and metabolic rate.
Define Endothermic.
Controls temperature through internal means such as muscle shivering or increased metabolism (e.g. birds, mammals, some plants, some reptiles, fish and many insects).
Which organisms are ectothermic?
Gains heat from external sources (e.g. plants, fungi, amphibians, lizards, snakes, turtles, many fish and most other invertebrates, such as crustaceans).
What is homethermic?
Maintains a stable temperature irrespective of the external environment.
Define Poikilothermic
The organism’s temperature is highly variable and tends to respond to that of its environment.
Is a hummingbird Endothermic, Ectothermic, Homeothermic or Poikilothermic (a) during the daytime and (b) at night?
(a) In the daytime a hummingbird is endothermic; (b) at night it is poikilothermic.
Is a marine invertebrate that lives in a constantly stable water temperature Endothermic, Ectothermic, Homeothermic or Poikilothermic?
The animal can be described as both ectothermic and homeothermic. However, if it lived somewhere with a variable water temperature, its body temperature would vary, therefore changing the latter description to poikilothermic.
What features do small animals have that put them at a disadvantage in relation to thermoregulation?
Small animals have large surface area to volume ratios, resulting in high rates of heat loss. They also have high basal metabolic rates (BMR) and a reduced capacity for internal energy storage and hence, additionally, minimal insulation in the form of adipose tissue (fat, i.e. lipid stores).
Define heterothermy
The regulation of body temperature within a limited range (but not as narrow a range as in homeothermy), independently of ambient temperature by switching between strategies and utilising torpor.
What is the thermoregulatory pathway for birds and marsupials throughout their life stages.
Young are Poikilothermic and progress to heterothermy in adulthood.
Define thermogenesis.
The process of producing heat in human or animal body tissues, although thermogenesis also takes place in some plants.
Define physiology.
Physiology is the study of the functions of living organisms and their systems.
What special features do you think might enable animals that live on ice floes or in cold waters to avoid experiencing physical damage to their extremities? (Frostbite)
waterproofing, insulation (fur, feathers, adipose tissue pads) or thickened skin, even the use of natural antifreeze compounds. These are all features used by various organisms. A number of mammals and birds also have more specialised circulatory features (covered in Section 3.2.2) which allow them to spend longer periods of time in closer contact with their cold environments.
Define metabolic rate.
The amount of energy used by an organism in unit time. An organism’s energy utilisation per unit time, including overall biochemical activity of the tissues, thermogenesis, movement, digestion, growth, etc. There are many ways of measuring metabolic rate, and hence many different units used to express it, of which the most basic is watts (W).
Define sympathetic nervous system
Part of the autonomic system which controls many involuntary processes (e.g. the gut and the cardiovascular and respiratory systems). Nerves carry signals from the sympathetic system using neurotransmitters such as noradrenalin.
Homeostasis describes the means by which various physiological systems restore the normal functioning of certain key variables within specific limits, after disturbance, by causing responses (signals or feedback) that return the system to its optimum state. Use the example of temperature regulation to explain a negative feedback response.
A control mechanism reacts to a change in the output of the system by initiating a restoring action. If the brain receives a message to inform it that body temperature is not optimum, it then triggers action that will result in a body that is too hot being cooled (e.g. by sweating) or a body that is too cold being warmed (e.g. by shivering) These subsequent changes are fed back to the brain, negating the effects of the original, non-optimum situation and restoring body temperature to the optimum value. Because negative feedback systems maintain a pre-set state, they are stabilising, and therefore an important feature of homeostasis.
how can a plant can regulate its water status in response to perceived drying of the soil but before any dehydration of the plant has occurred.
The roots detect the drying soil and use the chemical messenger, abscisic acid (ABA) to close the stomata in the shoot or leaf to reduce water loss even before the shoot or leaf has experienced any change in water status. This again is a feed-forward response.
Give examples of physiological adaptations and behavioural responses to the cold.
insulative, i.e. increase of subcutaneous (under the skin) fat layer
circulatory adjustments to decreased skin temperature.
metabolic, i.e. shivering or non-shivering heat production, which are both examples of thermogenesis.
Give examples of short term changes in response to the cold
Short-term changes in response to cold include homeostatic and behavioural adjustments. Torpor and hibernation can also be viewed as short-term responses/adaptations.
Explain the process of shivering.
Most terrestrial vertebrates (and certain other animals) can increase thermogenesis by shivering. Their muscles perform mechanically useless movements, but in doing so generate heat which warms the muscles and, eventually, the rest of the body. Shivering is, in a sense, ‘metabolically inefficient’ as the cellular energy stores are used for warming rather than for other processes.
What methods are employed by animals to store extra nutrients for survival in the colder weather?
External caches of food (for example squirrels burying nuts) or subcutaneous layers of blubber (for example baby seals)
Outline the difference between torpor and hibernation.
Torpor is a short-term reduction of body temperature on cool days. Hibernation is an extended form of torpor. Torpor is driven by ambient temperature and food availability; hibernation is associated with day length and hormone changes.
Outline the longer term changes employed by organisms in response to cold.
Adaptations to cold also include external and internal structural changes such as modifications of the form and density of the body hair, circulatory changes and/or metabolic generation of heat by specialised tissues.
Outline the survival strategy of the rock ptarmigan in the Arctic. What changes does the bird undergo in winter?
In preparation for winter they build up a thick layer of subcutaneous adipose tissue over the breast which acts as both insulation and an energy store. It also develops a thick white winter plumage to camouflage against the snow. It moves less in winter but burns the same calories as in the active summer months when it is lean and brown.
What major areas of a typical marine mammal are not protected by blubber?
You may have suggested that the head or flippers (limbs) or tail have minimal coverage of blubber.
Explain the countercurrent heat exchange
A countercurrent exchanger consists of a pair of channels lying in close proximity that contain fluids (or gases) flowing in opposite directions, e.g. where heat loss from the body core to the extremities is minimised by heat transfer between adjacent blood vessels before reaching the outer body surfaces.
What adaptations are found in the respiratory systems of animals which live in cold conditions?
In cold environments, species such as reindeer have elaborately folded nasal turbinals (soft, vascularised tissue supported by fine webs of bone), which warm the air as they inhale, and cool it as they exhale, thereby conserving both heat and water.
