My Science School

                  Have you seen some mothers keep their children in cloth pouches fastened on to their back or stomach? Such cradle-pouches are handy when the mother has work to do with her hands. Some mammals have natural pouches attached to their bodies.

                  These mammals have pouches on their stomachs. Such animals are known as marsupials. These pouches are used for carrying marsupial babies. When a marsupial baby is born, it is not fully developed. It is blind, hairless, and very tiny. The baby crawls up the mother’s tummy to the pouch, where it immediately attaches itself to a nipple. Inside the pouch, the baby is safe and gets enough milk to drink. Marsupial babies stay in the pouch fora considerable amount of time, usually until they are capable of taking care of themselves.

                  Marsupials include such animals as kangaroos and opossums. A kangaroo baby, known as a joey, sometimes stays in its mother’s pouch until it is eight months old!

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                  Have you noticed the long thin teeth of squirrels and mice? In their representations in comics and cartoons, their incisors are portrayed as their distinctive feature. Remember the squirrel of the movie, Ice World!

                  Squirrels and mice belong to the family of rodents. Rodents are the largest family of mammals. They are also known as ‘gnawing animals’ because of their large incisor teeth and the way they eat. The two long pairs of incisors are used like chisels to gnaw on hard food items like nuts and wood. These incisors grow continuously since they are worn down by gnawing.

                  There are three major types of rodents. They are squirrels, mice and porcupines. Squirrel-like rodents such as the squirrel and gopher have bushy long tails and large eyes. They live in trees or underground in tunnels. Mouse-like rodents include the mouse, the rat and the hamster. Rats and mice often live near humans, sometimes in their buildings, so they can live off human food and garbage. Porcupines differ from other mammals because they have long, sharp quills on their backs for protection. The smallest rodent is the northern pygmy mouse, which is only 2.5 centimetres long, while the biggest is the capybara of South and Central America, which measures up to 1.2 metres in length.

                  The animals that we know have certain distinct features that help us identify them. The erect ears of a rabbit, the trunk of an elephant, the tail of a monkey or the shining eyes of a cat are such features that separate them from other animals. What would we call it if an odd animal gets some of the distinctive features of other animals?

                  The aardvark is a mammal found on the African continent. The name ‘aardvark’ means “earth pig” in Afrikaans as it refers to its resemblance to a pig and to its habit of digging the earth. The aardvark is very strange looking animal indeed. Though it has the body of a pig, it has the ears of a rabbit and a tail of a kangaroo! The animal hunts at night for termites and ants. It uses its long, sticky tongue to gather the insects from their nests, as anteaters do. Therefore, the mammal is really like a jigsaw of different animal parts put together!

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                  We know that teeth are essential to eat food. Not all the teeth in our mouth have the same function, though. We use the teeth in front of our mouth for shredding and cutting hard substances such as meat. Those at the back are generally used for chewing food.

                  Some mammals, however, have no teeth at all. Some, on the other hand, have very weak teeth. These are called ‘toothless mammals’. Sloths, anteaters and armadillos belong to this group. Some toothless mammals have small ‘pegs’ at the back of their mouths, which they use for chewing. They do not have frontal teeth to bite into things.

                  In fact, these mammals do not need frontal teeth, since they either lap up their food or slowly chew leaves. Anteaters lap up and chew soft-bodied insects like ants and termites, while sloths eat leaves and fruits, which require only gentle chewing. Though armadillos are ‘toothless’ they manage to eat earthworms, insects, small reptiles as well as the flesh of dead animals.

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                  Human beings generally stay in a place for a long time. However, many animals live in the same place for a short period of time and move on to another place.

                  Some animals, including mammals, migrate or travel long distances in search of warmer climates and food or for reproduction. Some travel from one part of the world to another, past oceans, over plains or through the sky on a definite route. There are species that travel thousands of miles every year, while others make the trip just once in their lifetime.

                  Many mammals spend spring and summer in the cool northern hemisphere. During autumn and winter, when food becomes scarce, they move south in search of a warmer climate and more abundant supply of food.

                  Mammals also move from one place to another for the purposes of mating, gestation, birth and raising their young. Many ocean mammals travel thousands of miles to reach their traditional breeding grounds. For example, grey whales spend their winter in sheltered lagoons off the coast of California, where their young are born. One of the largest caribou herds in North America, on the other hand, travels up to 5,000 kilometres each year in a journey to reach its ancient calving grounds and then it goes back south to its winter range.

                  Marine biologists have now found that the mammal that has the longest migration is the humpback whale. The humpback whale is known to travel from Central America to its feeding grounds in Antarctica - a whooping distance of over 8000 kilometres!

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                  We all know that the primary purpose of our clothes is to protect our bodies from cold or warm climates. However, what do animals do, since they do not wear clothes? The thick fur coat on their body helps them keep their body warm.

                  Mammals are the only animals with hair. A mammal’s hair, also called fur, protects it from wind, rain, sun, cold, insects, and other dangers. Most mammals have a fur coat with two distinct layers-an undercoat of shorter dense hair and an outer coat of longer stiffer hairs.

                  Hair helps mammals in many other ways too. The hair colour of many mammals blends with the animals’ surroundings; and therefore, helps them hide from their enemies or prey. The coat keeps out the cold and helps to keep the animal warm. It also serves to protect the skin. Hair can take on several different forms including fur, whiskers, spines, or horns. It can be kinky or straight, soft or bristly, stiff or smooth.

                  Do you know that the polar bear has fur on the pads of its feet, both to keep its feet warm and to help it get a good grip on icy surfaces? The hairs of its thick waterproof coat are hollow, which means that air is trapped inside each strand of hair. The trapped air holds in body heat and helps the bear float when it swims too.

                  While the brain coordinates and controls our body and mind, the heart plays the role being the motor that keeps the working of body steady. When the heart stops, living beings die. Therefore, the heart is one of the most vital organs of our body. A mammal’s heart is designed in a very special way.

                  All mammals have hearts with four chambers. Two of the chambers are on the right side and two are on the left. The two chambers on the right side receive blood, which carries impurities from the body. They pump it to the lungs. In the lungs, the blood passes out waste gases and receives fresh oxygen. The blood is, then, pumped to the two chambers on the left side from where it is carried to various parts of the body. This is how the heart of a mammal generally functions.

                  Since a mammal’s heart has two sides and two chambers on each side, scientists say that mammals have ‘two-in-one’ hearts.

               We know that a mammal is an animal that delivers its children and breast-feeds them. Do all mammals follow these rules? Are there mammals that lay eggs instead of delivering young ones?

                The platypus and echidna are special mammals because they lay eggs! These animals do not give birth to live babies as other mammals do. The platypus is found in burrows near streams in Australia. Its eggs are round and white with wrinkled shells. The mother platypus guards and keeps the eggs warm for 10 days, until they hatch. The babies drink the milk that oozes out of pores on her underside.

                Echidnas, on the other hand, carry their eggs in a pouch that forms on their belly. After mating, a female echidna digs a burrow, curls up her body, and lays one egg directly into her pouch. The egg hatches in about 10 days. Inside the pouch, the baby echidna drinks milk from its mother’s body. When its spines start to grow, the baby leaves the pouch. The female will feed her baby until it is about 6 months old.

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               Have you ever thought of the wonder of how a new life is brought forth in the form of a baby? We all have spent a considerable amount of time in our mother’s womb before seeing the light of this world. Most mammal babies live inside their mothers before they are born, just like us. When the baby is big enough, it comes out of its mother’s body. Baby mammals come out of their mother’s body in some odd ways too: some mammals lay eggs while others have a pouch in which they nurture the immature babies.

               Despite the diversity of the ways in which some baby mammals are born, they all drink milk that comes from their mothers’ bodies. Baby pigs, dolphins, bats and elephants all drink milk! Mother’s milk is essential for the survival of baby mammals. Due to this reason, mammal mothers have to take good care of their young. The length of time varies from a few weeks for mice to many years for humans!

              Mammal mothers nurse their babies, clean them and keep them warm. The mother is responsible for the protection of her baby, and she teaches it to look after itself. With the case of a few exceptions, male mammals do not care for their young. Some may hunt and help to guard the babies; however, the mother mostly takes on the responsibility of bringing up the babies. Therefore, it is no wonder that mammal babies are generally attached more to their mothers than to their fathers.

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               Physical prowess and the intelligence required to use it to one’s advantage for better adaptation practices are what an organism needs for dominance in nature. Mammals were able to become lords of the earth primarily because of the high level of development of their brains. This gave them the capacity to absorb information, to learn and to remember, making them superior to all other animals.

               Mammals also became dominant because of the way their body evolved and adapted. Some developed hooves and became grazers on the grasslands of the world. Others developed hunting skills and became meat eaters. Some mammals developed wings and took to the air while others adapted to life at sea. Land dwellers developed four limbs, which they used for moving about most efficiently. Many mammals developed sharp curved claws and tails that were adapted for living in trees. Others developed thin membranes of fur-covered skin that stretched between their legs, which allowed them to glide.

               Do you know the only mammals that can fly? They are bats. Most mammals can swim while some have special adaptations that make them expert swimmers. Seals, sea lions and walruses spend most of their time in water, while sea cows and whales live in the water from birth to death.

               The hair and teeth of mammals are adapted to suit a wide variety of habitats and different types of food. Mammals have also learnt to protect themselves and many have deadly weapons to attack their enemies.

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            Sometimes, myths and stories are more believable than truth, because it is difficult to digest when one says that we humans have evolved from less complex animals. In fact, science says that the present day mammals come from giant reptiles that ruled the world thousands of years ago.

             About 200,000,000 years ago, reptiles ruled the earth. The age of the reptiles is known as the Mesozoic Era, Remember, dinosaurs were present in that era. Gradually one set of reptiles began to change. They started to grow coats of hair and became warm blooded. Instead of laying eggs like other reptiles, they kept the eggs inside their body. The babies grew inside the mother’s body until they were born as live young ones. In short, these reptiles had evolved into mammals.

                 The first mammals were very tiny and timid creatures. These early mammals were small, nocturnal, hairy, and warm-blooded and ate mainly insects. Later as conditions on Earth changed and dinosaurs disappeared from the face of the earth, mammals began to grow bigger. They also started to spread out until they took over the world!

 

          How many kinds of mammals can you think of? Even if we start counting the mammals that we encounter every day, the number would be very high. There are about 5,000 species of living mammals.

          Mammals are divided into three sub-classes, and about 26 orders. They display a remarkable array of adaptation abilities. Their intelligence enables them to inhabit a wide range of habitats. They vary in size from the minute bumblebee bat, which measures a mere three centimetres in length, to the magnificent blue whale, which can measure 33 metres from head to tail. The main orders of living mammals are given in the box here.

MONOTREMATA: Mammals that lay eggs. Example: Platypus

MARSUPIALIA: Their young are very immature at birth; females usually have pouches. Example: Kangaroo                        

INSECTIVORA: Small insect-eating mammals. Example: Mole.                                                

DERMOPETRA: Gliding mammals. Example: Flying lemur

CHIROPETRA: Mammals with wings. Example: Bat                                                          

PRIMATES: Mammals with highly developed nervous systems; most have opposable thumbs. Example: Monkey                                                          

EDENTATA: Mammals that usually have simple, peg-like teeth. Example: Anteater                              

PHOLIDOTA: Mammals with coverings of overlapping scales. Example: Pangolin                                     

LAGOMORPHA: Small-to medium-size mammals with clawed toes; tails are either stubby or lacking. Example: Rabbit

RODENTIA: Gnawing mammals. Example: Rat

CETACEA: Water-dwelling mammals with fish like forms. Example: Whale

CARNIVORE: Flesh-eating mammals. Example: Dog

TUBULIDENTATA: Long-snouted, long-clawed, insect-eating mammals. Example: Aardvark

PROBOSCIDEA: Huge mammals with trunks. Example: Elephant

HYRACOIDEA: Small, rodent like mammals with hooves. Example: Hyrax or rock rabbit

SIRENIA: Water-dwelling mammals with flippers, paddle-shaped tails, and no hind legs. Example: Manatee

PERISSODACTYLA: Hoofed mammals with odd numbers of toes on each hind foot. Example: Horse

ARTIODACTYLA: Hoofed mammals with even numbers of toes on each foot. Example: Cow

 

               How did Man become the most prominent animal in Nature? It is partly due to Man’s intelligence and ability to adapt and adjust. Mammals, in general, are more intelligent and creative than others and have the ability to adapt to adverse environments.

               For these reasons, mammals are considered the most advanced and probably the most popular class of all the classes of animal life. They are the only animals that possess true hair and have the capacity to produce milk.

               Their superior brains, warm blood and the way they care for their young have given them a great advantage over other animals in the struggle for survival.

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               What is the difference between a cow and a caterpillar? The question seems very silly because the difference is very explicit. Mammals are special because they are the most advanced of all the different classes of animal life. They are also the animals that we know best, because most of our pets, from dogs and cats to squirrels and rabbits, are mammals.

               Mammals are one of the commonest animals as they are found almost everywhere, from the Arctic snowfields to burning deserts and from tropical jungles to lofty mountains. Mammals are the ruling animals of the world today.

               Mammals live on land, at sea, in the air, and even underground. All mammals, from bats to whales, share a number of important traits that make them different from other animals. Mammals are warm-blooded, they have fur or hair, and most mammals give birth to live babies—rather than laying eggs. Mammals are superior to all other animals in the care and protection of their young. The female nurses the babies with milk that is produced by special glands called the mammary glands. In fact, they are the only animals that produce milk. Naturally, this makes them truly special!

               Life on earth is sustained by reproduction. There is so much diversity in reproduction too. The way in which a chick comes to life is different from the way a calf is born. Mammals are those animals that deliver young ones, and breast feed them.

               Mammals are one of the six main classes of animals. These classes are categories of animals that scientists consider to be alike in some important ways.

               A mammal is placed at the highest level of vertebrates, animals that have a backbone and a spinal cord. Human beings are mammals too. All female mammals give birth to live babies, with the exception of the platypus duck and the spiny anteater, which reproduce by laying eggs. However, regardless of how their babies are born, all female mammals nurse their young with milk, which they produce from special glands called the mammary glands.

              Another important characteristic of mammals is their lungs. They breathe in air for oxygen supply in their bodies. A mammal is warm-blooded. This means that their bodies are built to maintain just about the same temperature all the time. Warm-blood allows the mammals to be very active and live in a wide variety of places.

               Most mammals are covered either partially or completely with hair or fur. There are about 5000 types of mammals, including chimpanzees, elephants, bears, horses, pigs, bats, camels, mules, dogs and cats.

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