Unit questions
Question 1Which of the factors (a)-(g) is/are a valid reason(s) for the fact that penguins are numerous and diverse around Antarctica but absent from the Arctic?(a) The climate in the Arctic is too...
View Article6 Conclusion
There is much more to living in polar regions than insulation against the cold. Food may be very scattered both in space and in time and breeding must be tightly synchronized to seasons and food...
View Article5.4.1 Summary of Section 5
Several anatomical and biochemical adaptations to living in very cold water have evolved in polar fish, particularly those of the southern oceans, which have evolved in isolation for many millions of...
View Article5.4 Fatty acids as indicators of diet
Although polar fish and invertebrates are difficult to study alive for the reasons just described, some information about their diet and habits can be obtained from analysis of the lipid composition of...
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5.3.1 Muscles
The rates of muscle contraction and relaxation, and the maximum force generated, are complex enzymatic processes that determine speed of swimming. Ian Johnston of St Andrews University (Johnston, 1989)...
View Article5.3 Metabolism
Molecules diffuse more slowly at low temperature: measurements of the rates of diffusion of small molecules such as lactic acid, Ca2+ and analogues of glucose and ATP through fish muscles produced Q10...
View Article5.2.1 Blood pigments
The solubility of oxygen (and of many other gases) in water increases with decreasing temperature: at 0° C, seawater holds 1.6 times as much oxygen when saturated as at 20° C. This fact, and continual...
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5.2 Passive properties
Freezing is nearly always harmful to living cells because the tertiary structure of hydrophilic molecules such as proteins is disrupted and the permeability of membranes is drastically altered. The...
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5.1 Introduction
The land and shallow water experience at least a brief summer at high latitudes, so terrestrial and freshwater ectotherms can be active during warm periods and hibernate when the temperature is below...
View Article4.3.1 Summary of Section 4
Many polar mammals and birds are obese because their food supply is highly seasonal or erratic. In large species, proportionately more adipose tissue accumulates in the superficial depots and less in...
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4.3 Humans in polar regions
Humans evolved in tropical Africa and gradually colonized colder climates during the Pleistocene ice ages. There have been permanent populations in the Arctic for several thousand years, mostly Inuit...
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4.2 Insulation in aquatic endotherms
Most seals and sealions (order Pinnipedia) are furred. The adult fur usually consists of short, dense stiff guard hairs that are oily from profuse secretions of the sebaceous glands. The hair probably...
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4.1 Insulation in terrestrial endotherms
For organisms of similar size and shape in a similar thermal gradient, the rate of heat loss from convection is up to 90 times as fast in water as in air, so in temperate climates, aquatic endotherms...
View Article3.5.1 Summary of Section 3
Penguins and many other large polar animals fast for long periods while remaining active and at near-normal body temperature. Emperor penguins fatten before the breeding season and fast for weeks...
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3.5 The structure of adipose tissue
Since food is only available seasonally or intermittently at high latitudes, many arctic birds and mammals, including polar bears, Svalbard reindeer, arctic foxes, seals and walruses, naturally...
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3.4.1 Fasting in polar bears
Polar bears (U. maritimus) are almost entirely carnivorous and are the only living species of bear to obtain almost all their food from the sea. Their main prey is ringed seals (Phoca hispida), both...
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3.3.1 Dormancy in black and brown bears
The dormant state of bears differs from true hibernation in that the body temperature does not fall below 31–35° C and a major disturbance (such as an intruding biologist) can arouse them to full...
View Article3.3 Bears
Brown or grizzly bears (Ursus arctos), and black bears (U. americanus) feed throughout the summer on grass, fruit, nuts, fish, small mammalian prey and carrion. In autumn, all brown and black bears...
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3.2 Penguins
Penguins (order Sphenisciformes) are an ancient and distinctive group of flightless, short-legged birds that evolved in the Southern Hemisphere, probably around New Zealand, about 65 Ma ago in the late...
View Article3.1 Introduction
It is clear from Sections 1 and 2 that seasonal or irregular periods of fasting are an integral part of living at high latitudes, especially for large animals. When people (and many tropical and...
View Article2.4.1 Summary of Sections 1 and 2
Large seasonal changes in temperature and sunlight dominate primary plant production and hence the food supply. Food intake is regulated by the endogenous seasonal control of appetite, fattening and...
View Article2.4 Variable fecundity
The food supply for most polar species depends on several unpredictable factors so successful breeding is far from certain, even if births are tightly synchronized with the seasons. Maintaining...
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2.3 Environmental regulation of breeding
As pointed out in Section 1.1, primary plant productivity occurs for only a few months in the summer, so the reproductive physiology of most arctic animals, particularly herbivorous species, is tightly...
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2.2 Migration for breeding
Birds do not hibernate, but like reindeer, many species undergo daily or seasonal changes in energy expenditure and appetite, and many of the endocrine changes that are an integral part of true...
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2.1 Nutrient budgeting
All plants and animals respond to environmental changes such as the light–dark cycle and temperature, but the impact of the environment on essential physiological processes such as eating, fattening...
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1.2 The polar environment
At high latitudes, the Sun's rays always strike the Earth at a large angle from the vertical so they travel through a thicker layer of atmosphere and are attenuated by the time they reach the ground....
View Article1.1 Preamble
This unit is about animals' structural and physiological adaptations to living permanently in cold climates; hibernation, a special response to transient or seasonal cold, is described in the openlearn...
View ArticleLearning outcomes
By the end of this unit you should be able to:define and use, or recognize definitions and applications of each of the bold terms;outline the special features of the polar regions as a habitat and list...
View ArticleIntroduction
This unit is the third in a series of three on Animals at the extreme. In order to get the most from it you should have previously studiedAnimals at the extreme: the desert environment...
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