Mammal
mammal
a class (a large group) of animals with 5,500 species, different sizes: from 1 to 1½ inches long (bumble bee bat) to 110 feet long (blue whale); and weighs from 2 grams (bumble bee bat) to150-190 tons (blue whale); found on land, in water, and in trees, in air; must have most or some of the following characteristics:
sweat glands – all the mammals have sweat glands to keep body cool in hot weather and to send out fluid waste matter {the exception: some mammals do not have sweat glands, such as otter, weasel, mink, badgers, skunk, etc.}
mammary glands – all mammals have mammary glands – the modified sweat glands that the females have to feed (suckle) their babies {all the animals in this class are given the name ‘mammal’ for this special feature}
{the exception: some animals such as ‘platypus, echidna, etc. do not have the mammary glands in the real sense, but they do suckle (give milk to their young with thick milk-like substance that oozes from their abdomens}
three middle ear bones – these bones are used for hearing the sounds that travel in air
give birth to live young – three types in this: placental mammal; egg laying mammal and marsupials – ‘placental’ = has a connection to the mother, and the baby develops inside the mother’s womb; ‘egg-laying’ = some animals, such as platypus and echidna, lay eggs but suckle their young; ‘marsupial’ = the baby’s development is done only partly inside the mother’s womb, and then the baby is kept in a pouch (bag-like skin fold on the abdomen of the mother), and completes the growth {the exception: the ‘egg-laying’ animals (monotremes) such as platypus and echidna, etc.}
Some other non-mammals also give birth to live young, such as snakes and fish (certain species only).
four-chambered heart — the heart is divided into four parts and the blood circulatory system is controlled by the heart
warm-blooded (endothermic) – the body temperature is kept at a constant (the same) degree however hot or cold the weather may be {the exception: the ‘naked mole rat’, a mammal, is “cold-blooded” (ectothermic); and the birds which are not mammals are also “warm-blooded”}
breathe air — take in oxygen from the atmosphere (air) and the respiratory organs are: nose or mouth, lungs and the diaphragm (= a thin layer of membrane below the lungs) – the diaphragm separates the lungs from the other internal parts {the exception: though the other animals, such as ‘amphibians – frogs, salamanders, etc., reptiles – snakes, tortoises, etc. and birds take in oxygen from air, they do not have the same respiratory organs and the same position of the organs}
body hair – all the mammals have hair on their body – partly or completely or only on some parts of the body – though some water-living animals such as dolphins and whales look bare, without any hair, they do have some hair on any part of the body at one or the other stage of their life
bones – every mammals has a back-bone and some bones that form the internal skeleton {the exception: most other non-mammals also have backbones and internal skeleton}
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Mr. Kumar, an English language teacher, having taught in many countries around the world including Ethiopia and Oman shares this English Language Reference website using material that he has written and compiled during the past 20 years.
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