12. Find key sentences in each paragraph.

13. Write a title to each paragraph.

A
B
C
D
E
F
G

14. Answer the questions to Text 1.

1. Give general definition of a mammal.

2. What is the smallest and the biggest animal in the group?

3. Enumerate unique mammalian features.

4. In what habitats can mammals live?

5. What can you tell about their feeding habits?

6. Why are mammals so important to human?

15. Read the texts using your dictionary.

Retell one of the texts.

Text 2

Rodents

Rodents - any of more than 2,050 living species of mammals characterized by upper and lower pairs of ever-growing rootless incisor teeth. Rodents are the largest group of mammals, constituting almost half of the class Mammalia. They are indigenous to every land area except Antarctica, New Zealand, and a few Arctic and other oceanic islands, although some species have been introduced even to those places through their association with humans. This huge order of animals contains 27 separate families, including not only the “true” rats and mice (family Muridae) but also such diverse groups as porcupines, beavers, squirrels, marmots, pocket gophers, and chinchillas.

All rodents possess constantly growing rootless incisors that have a hard enamel layer on the front of each tooth and softer dentine behind. The differential wear from gnawing creates perpetually sharp chisel edges.

The range in body size between the mouse (18 grams, body 12 cm long) and the marmot (3,000 grams, body 50 cm long) spans the majority of living rodents.

Rodents have lived on the planet for at least 56 million years and modern humans for less than one million, but the consequences of their interactions during that short overlap of evolutionary time have been profound. For rodents, early humans were just another predator to avoid, but with Homo sapiens' transition from nomadic hunting and gathering to agricultural practices, humans became a reliable source of shelter and food for those species having the innate genetic and behavioral abilities to adapt to man-made habitats. The impact of these species upon human populations ranges from inconvenient to deadly.

Crops are damaged before harvest; stored food is contaminated by rodent waste; and objects are damaged by gnawing. Certain species are reservoirs for diseases such as plague, typhus, tularemia, etc. Only a few species are serious pests or vectors of disease, but it is these rodents that are most closely associated with people.

Various other rodents are beneficial, providing a source of food through hunting, apparel derived from their fur, test animals for biomedical and genetic research, pleasure as household pets, and insight on mammalian biology and evolutionary history.

Rodents may be diurnal, nocturnal, or sometimes active part of the day and night. Although some species are herbivorous, diets of most include vegetable and animal matter. Others are opportunistic generalists, and some are specialized predators. Food is either eaten where gathered or carried to burrows and stored. Species living in arid habitats and on oceanic islands are able to obtain their water requirements from their food. A wide variety of shelters are used or constructed; these range from tree holes, rock crevices, or simple burrows to hidden nests on the forest floor, leaf and stick structures in tree crowns, mounds of cut vegetation built in aquatic environments, or complex networks of tunnels and galleries. Rodents may be active all year or enter periods of dormancy or deep hibernation. Breeding time and frequency, length of gestation, and litter size vary widely, but two of the most prolific are both associated with humans. The brown rat (Rattus norvegicus) can give birth to litters of up to 22 offspring, and the house mouse (Mus musculus) can produce upto 14 litters annually. Population size may remain stable or fluctuate, and some species, most notably lemmings, migrate when populations become excessively large.

Text 3

Dolphins

Dolphins are warm blooded like man, and give birth to one baby called a calf at a time. At birth a bottlenose dolphin calf is about 90-130 cms long and will grow to approximately 4 metres, living up to 40 years. They are highly sociable animals, living in pods which are fairly fluid, with dolphins from other pods interacting with each other from time to time.

Dolphins use their powerful tail flukes in an up and down motion to move through the water. They also use their tails when hunting, hitting a fleeing fish up into the air with their tail, stunning it, then scooping the fish up when it falls back into the water. A dolphin slapping its tail on the water in the wild may be a sign of annoyance, or a warning to other dolphins of danger.

Their teeth are interlocking rows of conical pegs, suitable for holding slippery fish. They eat their fish whole, head first. In the wild an open mouth is a sign of aggression, as is head nodding. A sign of greater aggression is violent jaw clapping.

Dolphins breathe through their blowhole located at the top of their head. A dolphin may empty and refill its lungs in less than a fifth of a second. As the dolphin breathes the air leaves the blowhole at speeds of over 100mph. Complex nerve endings around the blowhole sense pressure changes so the dolphin knows exactly when the blowhole is in or nearing the air and can be opened. Water in a dolphin's blowhole will actually drown it so powerful muscles close the blowhole as it dives under the water again.

The dolphin's eyes produce a special slippery secretion which protects the eyes from foreign objects and water friction. To sleep, a dolphin must shut down only half of its brain, as its breathing is under voluntary control. Dolphins take short cat-naps, floating just below the surface, then slowly rising to breathe. Often dolphins are very active during night time, for some this is their main feeding time.

The dolphin's skin is completely smooth allowing the dolphin to move easily through the water, and also reduce heat loss.

Dolphins are able to dive to great depths, and also leap to great heights. They may leap to avoid predators or to show how powerful they are to females at mating time. Noisy splashing jumps may also be used to herd fish. Bottlenose dolphins can dive to depths of over 500m

Dolphins carry their young inside their womb and gestation is about 12 months for a bottlenose. The baby emerges tail first, and will suckle from its mother for up to 4 years (a calf may stop suckling sooner depending on circumstances).

The baby will however stay with its mother for between 3-6 years, during which time it learns all about feeding techniques, social interaction and group foraging.

Dolphins have defined home ranges, an area in which they will roam and feed. Though dolphins live in small groups called pods, these pods can be quite fluid and dolphins can be interacting with dolphins from other pods from time to time. If another dolphin is drowning, other dolphins will come to it's aid, supporting it with their bodies so it's blowhole is above the water allowing it to breathe.