Polar bear

Formed less skin walking to give environment freezing relatively swimming spending prey blood breeds tissue remains insulation coat reaches den circulates relatives to transmit features insulating reduces supplying enable absorbing

Choose the correct word to complete the text.

Match the adjectives with the nouns to construct word combinations. Use three of these word combinations in your own sentences.

Complete the word combinations with prepositions. Use three of the received word combinations in your own sentences.

to nourish ……. milk to result ……. diseases

to distinguish ……. features to live ……. the coasts

to develop ……. the womb to contaminate ……. waste

to attach ……. the body to damage ……. gnawing

to attribute ……. the ability to associate ……. humans

to range ……. size to move ……. the water

to arrange ……. families to breathe ……. the blowhole

to depend ……. mammals to dive ……. the water

to hunt ……. sport to float ……. the surface

to expell ……. the cavity to carry ……. the womb

to compete ……. food to convert ……. signals

to prey ……. herds to refer ……. the body mass

buccal salivary radiant digestive direct rectangular flattened marine wide vertical central nervous reproductive radial

tract tip world movement system organ axis cavity contact pupil symmetry range glands energy

The polar bearlives in the Arctic, …………… much of its time on snow and ice. Several physical …………… contribute to its adaptation to this cold ……………. It is a very large bear, which means that the ratio of its surface area to its volume is …………… small. The relatively small surface area means that the polar bear loses proportionately …………… heat than its more southerly……………. Also its ears are small, another feature which …………… heat loss.

It has a thick …………… with long loosely packed сoarsehairs (guard hairs) and a denser layer of shorter wooly hairs forming an ………….. layer. The long hairs are oily and water-repellant and ………… the bear to shake off water when it emerges from a spell of …………...

The principal thermal …………… comes from a 19 cm layer of fat (blubber) beneath the ………….. The thermal conductivity of fat is little different from any other …………… but it has a limited blood supply. This means that very little warm blood …………… close to the skin surface.

The hollow hairs of the white fur are thought …………… the sun's heat to the black skin below. Black is an efficient colour for …………… heat. The white colour is also probably an effective camouflage when hunting its ……………, mainly seals.

Aspecific adaptation to …………… on snow and ice is the heat-exchange arrangement in the limbs. The arteries …………… the feet run very close to the veins returning ………… to the heart. Heat from the arteries is transferred to the veins before the blood …………… the feet. So, little heat is lost from the feet but their temperature is maintained above …………. point, preventing frost-bite.

The polar bear …………… in winter when temperatures fall well below zero. However, the pregnant female excavates a …………… in the snow in which …………… birth and rear her two cubs. In this way the cubs are protected from the extreme cold. The female …………… in the den for about 140 days, suckling her young on the rich milk which is …………… from her fat reserves.

Дата добавления: 2014-12-29