Category Zoology

What are the characteristics of class insect? How butterfly differ from moth? Why animals (insects) are brightly colored?

          Insects are invertebrates, animals that do not have backbones. Insects belong to a large group of invertebrates known as arthropods. Other members of this group include centipedes, spiders and scorpions, woodlice, crabs and shrimps. Instead of having an internal skeleton, arthropods have a hard outer skeleton. This is made of a light, strong material called chitin that supports and protects their soft inner parts.

          All insects have six legs and a body divided into three sections: the head, thorax and abdomen. The chitin covering the legs is jointed to allow the insect to move easily. Insects have a pair of antennae on their heads which they use to smell, touch and pick up sound vibrations. Most insects also have one or two pairs of wings.

          Insects have two kinds of eyes: simple eyes that detect changes in light, and compound eyes. The compound eyes are made up of thousands of tiny units, each of which sends an image to the insect’s brain.

          This means that insects have good, all-round vision, and are able to sense movements and judge distances very accurately.

          After mating, a female insect lays her eggs. The young are usually left to hatch and fend for themselves. Some insects, such as bugs or grasshoppers, look like tiny adults when they hatch. As they grow, they shed their hard outer skeleton several times, after a new one has grown underneath.

          Other insects, such as butterflies or bees, hatch out as larvae (caterpillars or grubs). They shed their skin several times as they grow. Then they develop a protective coating inside which they pupate (change into their adult form).

 

 

 

 

 

BUTTERFLIES AND MOTHS

          Butterflies and moths are a group of flying insects, with wings that are covered with tiny, overlapping scales. These scales give butterflies and moths their bright colours and striking markings. Most butterflies and moths have coloured scales. Others have scales that reflect the light to give an impression of colour.

          The colours and patterns of butterflies and moths are used to attract mates, for camouflage, and also to deter predators. Large spots that look like the eyes of a large animal, or bright colours to warn that the butterfly or moth is poisonous, help these insects to avoid being eaten.

 

 

 

 

 

 

         Butterflies generally fly during the daytime. They are usually more brightly-coloured than moths and have club-like antennae. Most moths are night-flyers, and have feathery antennae. Adult butterflies and moths have a long, hollow tongue called a proboscis. They use it to probe inside flowers and suck up nectar.

          Butterfly and moth larvae are called caterpillars. They feed on leaves until they have grown large enough to pupate. Then they spin a protective cocoon of silk around their bodies, inside which they completely change their structure, and finally emerge as adults. Some may migrate to warmer climates when winter comes, returning to breed and lay eggs.

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What does heart do in human body?

          All the muscles and tissues that make up the body must be continually supplied with food and oxygen. This job is carried out by the blood circulatory system.

          The heart lies at the centre of the circulatory system and pumps the blood around the body. About the size of your fist, it is an incredibly strong organ, made entirely of muscle. It beats more than two billion times during the average life span of a person and pumps about 340 litres of blood every hour—enough to fill a car’s petrol tank every seven minutes.

          Blood containing fresh oxygen travels from the lungs to the heart through the pulmonary veins. At the same time, blood with very little oxygen left in it returns to the heart along veins from the muscles and tissues. The heart pumps the fresh blood to the rest of the body and the exhausted blood to the lungs. It pumps the blood at high pressure so that it can travel upwards to the head—against gravity—as well as downwards. You can feel this pumping action by placing your fingers on the inside of your wrist or the side of your neck, both points where a main artery lies close to the surface of your skin.

 

 

BLOOD

          Pumped by the heart, blood collects oxygen from the lungs and dissolved food from the liver and delivers it to all parts of the body. It also clears away waste, helps cool the body when it overheats, clots when the skin is damaged and protects against invading bacteria and viruses.

          The veins and arteries in your body look like a page in a road atlas. There are motorways, the main blood-carrying tubes or vessels, which lead out from the heart to the limbs and the head. There are also lanes and tracks, tiny vessels called capillaries that reach all the cells in the body.

 

 

          Blood is made up of millions of tiny cells floating in a yellowish, watery fluid called plasma. There are red cells, used for carrying oxygen, white cells, which fight any infection by invading bacteria or viruses, and platelets, which make the blood clot when a vessel is damaged, so sealing the wound. Different kinds of white cell work together to protect you from disease: T-cells, which identify invaders; B-cells, which make deadly proteins called antibodies that surround the invaders; and macrophages, which swallow them up and destroy them.

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How do we breathe?

          The body needs continual supplies of oxygen. This invisible gas makes up about one-fifth of the air around us. It is needed for chemical processes inside the body’s cells that release energy from food. Breathing draws air into the body so that oxygen can be absorbed.

RESPIRATORY SYSTEM

          The respiratory system draws fresh air into the body, absorbs the vital oxygen from it into the blood, and then passes the stale air out again. The main parts of the system where oxygen is absorbed are the lungs. Breathing muscles stretch the lungs to make them larger and suck in air. These muscles are the diaphragm below the lungs, and the intercostal muscles between the ribs. Fresh air passes in through the nose and mouth, down the pharynx (throat) and trachea (windpipe), into the lungs. The lung airways, called bronchi, divide many times and become thinner, ending in terminal bronchioles, narrower than human hairs.

          Each terminal bronchiole ends in a cluster of microscopic air bubbles, called alveoli. There are about 300 million alveoli in each lung, giving the whole lung a spongy texture. Besides fresh air, the lungs also receive low-oxygen blood from the heart along the pulmonary arteries. These divide and form networks of microscopic blood vessels (capillaries) around the alveoli. Oxygen from the air inside the alveoli passes easily through the thin walls of the alveoli and capillaries into the blood. This high-oxygen blood returns along pulmonary veins to the heart.

CLEANING THE LUNGS

          The lungs are delicate and easily damaged. Hairs in the nose filter bits of floating dust and other particles from air as it is breathed in. The airways are lined by sticky mucus which traps dirt and dust. Microscopic hairs, called cilia, line the smaller airways. They sweep mucus and trapped dirt into the throat, where it can be swallowed.

SPEECH

          Air emerging from the lungs not only carries waste carbon dioxide. It has another use—speech. At the top of the trachea is the larynx (voice box). This has a shelf-like fold of cartilage projecting from each side, known as the vocal cords. To speak, muscles pull the vocal cords together so that there is only a very narrow slit between them. Air rushing through the slit makes the cords shake or vibrate, which produces sounds. These sounds are shaped into clear words by movements of the mouth, cheeks, teeth, tongue and lips.

 

BREATHING RATE

          As oxygen passes from the air in the alveoli into the blood, the waste substance carbon dioxide passes the opposite way, from the blood into the air. This stale air is then pushed out of the lungs when the breathing muscles relax and the stretched lungs spring back to their smaller size. At rest, an adult person breathes in and out about 12 times each minute. Each breath is around half a litre of air. After running a race, a person may breathe 60 times each minute and take in more than two litres of air each time, to obtain extra oxygen for the active muscles.

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What is the role of various organs in digestion?

          The entire digestive system, from the mouth to the anus, is about nine metres long. Looped and coiled into the lower abdomen, the small intestine makes up two-thirds of this length. Digestive juices from the small intestine’s lining are added to the food to complete its chemical breakdown. The resulting nutrients are so small that they can pass through the lining into the blood, to be carried away to the liver. The liver acts as a kind of food processor, making new chemicals from the nutrients it receives and storing them until they are required. Those substances the body does not need, including impurities in the blood, it sends on to the kidneys.

THE KIDNEYS

          The two kidneys receive a very large flow of blood—more than one litre per minute. It passes through about one million microscopic filtering units, called nephrons, packed into the outer layer of each kidney. The nephrons remove waste substances and excess water from the blood. These flow through the kidney’s inner layer, where some water is taken back into the blood according to the body’s needs. The resulting liquid waste is called urine. It dribbles down a tube, the ureter, to a stretchy bag in the lower abdomen, the bladder. It is stored here until it can be passed to the outside.

 

NUTRIENTS

          The body needs a wide range of nutrients to stay healthy. There are six main groups of nutrients—proteins, fats, carbohydrates, vitamins, minerals and fibre. Different kinds of foods are rich in different groups. Proteins are found in meat, poultry, fish, milk, beans and green vegetables. They help to build and maintain muscles and other body parts, so they are important for growth. Fats (lipids) are found in meat, dairy products, pies, and some oily fruits and vegetables like avocado, olive and sunflower seeds. Small amounts are needed to build the walls around the body’s microscopic cells, and also for healthy nerves. Carbohydrates such as starches and sugars are found in bread, pasta, rice and other grains, and potatoes. They are the main source of energy for movement, digestion and other life processes.

 

 

 

VITAMINS AND MINERALS

          Many vitamins and minerals are needed for good health, but usually in small amounts. Vitamins have letters such as A, B and C. Lack of a vitamin may cause illness. For example, lack of vitamin A from tomatoes, carrots, cheese, fish and liver may result in poor eyesight. Minerals include calcium and iron. Iron is found in meat, green vegetables and nuts. It is needed for healthy blood. Its lack causes a type of anaemia.

 

FIBRE

          Fibre is found only in plant foods, chiefly in breads, pastas and other products made from whole meal grains or cereals, and also in many fresh fruits and vegetables. Fibre is not actually digested and absorbed by the body, but it helps the digestive system to work effectively and stay healthy. It adds bulk to the food so that the stomach and intestines can grip and squeeze the food along.

 

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How do we digest the food we take?

 

 

         

 

 

                    The body needs energy to power its chemical life processes. It also needs raw materials for maintenance, growth and repair. The energy and raw materials are in our food. Digestion is the process of taking in, or eating, food and breaking it down into tiny pieces, small enough to pass into the blood and be carried all around the body. The parts that take in and break down food are known as the digestive system.

 

 

 

 

 

 

 

 

 

INSIDE THE MOUTH

                     The teeth cut off and chew pieces of food into a soft pulp. Saliva (spit) makes the food moist and slippery, for easy swallowing. The tongue tastes the food, to make sure it is not bad or rotten, and moves it around in the mouth, for thorough chewing. The lips seal at the front of the mouth to stop food and drink dribbling out during chewing.

 

 

 

 

TEETH

                     There are four main kinds of teeth. The sharp-edged, chisel-like incisors at the front of the mouth slice and cut pieces from large food items. The taller, pointed canines tear and rip tough food. The premolars and molars at the back of the mouth squeeze and crush the food. Each tooth has a long root that fixes it firmly in the jaw bone, and a crown that sticks up above the soft, pink gum. The whitish enamel covering the crown is the hardest substance in the body.

 

 

 

 

 

 

OESOPHAGUS AND STOMACH

               Swallowed food is squeezed down the oesophagus by wave-like muscular contractions of its wall, called peristalsis. The food enters the stomach, a J-shaped muscular bag. This expands like a balloon to hold about three litres of food and drink. It churns up the food, mixing in its strong digestive juices to break it into smaller and smaller particles. An average meal takes between three and six hours to be digested in the stomach. If the food is bad or unsuitable in some way, peristalsis works in reverse and pushes it up and out of the mouth, a process called vomiting.

                  Two large organs aid the process of digestion. The pancreas gland is wedge-shaped and lies behind the stomach on the left. It makes strong digestive juices that flow along a tube, the pancreatic duct, into the small intestine. These juices dissolve the food further. The other organ is the liver, in front of the stomach on the right. It makes a yellow-green liquid, bile. This is stored in the gall bladder and then added to the food in the small intestine, to help digest fatty foods.

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What are organs and systems in brief, of Human Body?

          The Human Body is the most studied object in all of science. Yet every year we learn even more about its most detailed structures and its innermost workings. Even in ancient times people have known basic facts—for example, that there are 206 bones in its skeleton. Since the invention of the microscope nearly 400 years ago, people have studied the body’s billions of tiny building blocks, known as cells. In more recent years we have learned about the instructions or “blueprint” for making the body—its genes.

 

ORGANS AND SYSTEMS  

         The body’s main parts, like the brain, heart, lungs and stomach, are called organs. Different groups of organs work together as systems. Each system has a vital job to keep the whole body alive and healthy. For example, the heart, the body-wide network of tubes, called blood vessels, and the red liquid called blood, together form the circulatory system. This carries essential nutrients and oxygen to all body parts and collects waste materials for disposal. There are about a dozen major systems.

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