My Science School

            Vertebrates are called so by virtue of their vertebrae, backbone. Therefore, the most special characteristic of vertebrate animal is this spectacular bone system. Vertebrae are the small bones forming the backbone. The vertebrae connect together by joints to form the backbone.

             The backbone not only supports the body, it also protects the spinal cord. All vertebrates have a skeleton, usually made of bones, inside their bodies. The skeleton of a vertebrate grows as the animal grows. The skeleton has three main parts- the skull, backbone and limbs.

                 Another characteristic of vertebrates is their hard skulls. These skulls protect the organs in their head. This may be the reason for the high intelligence of vertebrates. The protection of the skull helps brain development, and a result allows the enhancement of intelligence as a result.

               Most vertebrates have two pairs of limbs. In fish, the limbs take the form of fins, while others they have become legs and arms, or wings or flippers. Vertebrates like snake have no external limbs.

              Most vertebrates have stronger muscles and skeletons. These features help them to perform complex movements. All vertebrates have a fixed body structure.

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               Man’s existence depends on not only the other members of his society, but also on various animals around him. Most big animals that we associate within our daily life are vertebrates. Some common vertebrate animals are cows, dogs, cats, bears, giraffes, rabbits, ducks, alligators, frogs, and turtles. Vertebrates are animals with backbones.

               There are five main groups of vertebrates: mammals, birds, fish, reptiles and amphibians. Mammals are animals that have a covering of hair on the skin. They generally give birth to their young, which are breastfed by their mothers.

               Fish are vertebrates that live in water, breathe through gills, and have fins. They have an elongated body covered with scales. Birds, on the other hand, are egg-laying, feathered vertebrates. Their forelimbs have been modified to form wings in the process of evolution. Reptiles are vertebrates that lay eggs. Some of them are snakes, lizards, crocodiles, turtles and dinosaurs. They have an external covering of scales or horny plates.

               Amphibians, such as frogs or salamanders, are smooth skinned vertebrates, capable of living both on land and in water. They have gills when they are born. However, when they become adults, they develop lungs too.

               Vertebrates can be split further, into warm-blooded and cold-blooded animals. A warm-blooded animal, such as a dog or a man, keeps its body temperature the same, except when it is sick. Cold-blooded animals have fluctuating body temperature. It changes according to the surroundings. So if the weather is hot, the animal is warm, and if the weather is wintery, it turns cold!

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               Life underwater is so diverse and numerous. For Man living on the dry land, animals in the sea with strange forms and colours instill wonder and curiosity. For a long time, all living marine animals were fishes for him. The starfish, although not a fish, is such an animal. Today, scientists are in the process of renaming the animal as the sea star.

               The sea star is an echinoderm. Echinoderms are free swimming marine organisms that are found at all depths of the sea. Starfish, sea urchins, and sea daisies are some common echinoderms.

               Most starfish have five-arms. But some have as many as 45! There are more than 2000 different species of starfish. Their sizes range from less than 25 millimetres to almost 90 centimetres across. They come in a variety of colours ranging from bright red to yellow and orange. Grey and green are also found.

               The most remarkable thing about starfish is their power of regeneration. If you cut a starfish into three pieces, it will grow back as three starfish! Regeneration usually requires that the piece of starfish includes at least one arm and part of the central disc. But in some kinds of starfish, a whole animal can be regenerated from the piece of a single arm.

               There is an eye at the end of each arm, usually marked by a red spot. Star fish have feet that look like tubes. These tube feet help them move. A starfish has hundreds of feet. The mouth of a starfish is at the centre of its underside.

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               One of the ways nature contributes to Man’s well-being is by providing him with its manifold produce. Honey is an invaluable substance that Man receives from nature. It is used not only as a sweetening agent, but also for its medicinal properties.

               Honey, as we all know, is produced by the honeybee, a widely distributed flying insect known for its ability to collect nectar from flowers. Bees have stocky bodies that are covered with hair to which pollen adheres. The honeybee is considered as an important pollinator of crops.

               Honeybees are social insects that live in large colonies. The queen bee, drones and worker bees all have specific tasks to help support the colony. The queen bee lays hundreds of eggs. It is the duty of the worker bees to bring food to the colony. When worker bees locate a new source of food, they move in circles, wagging their bodies to show other bees the location of this source. In fact, they look as though they are dancing, and this action of the bees is called the ‘bee dance’.

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               Insects are so common that we hardly spend a day without seeing them. Have you noticed the body of an insect?

               Insects have certain common features. Most insects have wings and antennae. The three parts of an insect’s body are the head, thorax and abdomen. The thorax is the middle region and the abdomen is the lower region.

               While insects have many similarities, they also come in all shapes, sizes and colours. Insects are extremely diverse in nature. In fact, there are almost one million different species of insects!

               One of the most common flying insects is the mosquito. Mosquitoes are considered to be the deadliest animal in the world as they have caused the deaths of millions of people.

               Insects are one of the largest groups of animals, with over 7,50,000 species that can be found on Earth. Insects generally have three pairs of walking legs. Some have wings, and some do not. They have a waterproof layer on the outside of their bodies, which helps them to move to environments where other organisms cannot survive.

               Some other common insects that can fly are the ladybug, bee, dragonfly and moth.

 

               The octopus does not have a backbone. In fact, the octopus has no bones at all. Its body structure allows the animal to hide in a little place and hunt under the sea.

               The octopus is a fascinating creature. It is found in shallow waters in most areas of the world. It has eight long limbs or tentacles, lined with suckers, protruding from a globe shaped head called the mantle. It uses two of its tentacles like legs to walk on the sea floor and to push off when it wants to swim. It also has the ability to grow back a tentacle if it loses one.

               The octopus has no skeleton at all, so it is able to squeeze through the smallest spaces. It has a sharp beak and toothed tongue which it uses to drill into the shells of its prey, or to force the shells open. Once it breaks open the shells, it injects a poison into its prey to paralyze it.

               The octopus is highly intelligent and also has the uncanny ability to change its colour, texture and body posture to blend in with its surroundings. This proves very useful both when it is hunting and when it wants to hide from its enemies. Another way it escapes is by releasing a cloud of purple-black ink so that the enemy can no longer see it.

               The mimic octopus can change its skin colour and texture to mimic not just one, but many other sea creatures! This fascinating creature was first discovered in 1998 off the coast of Indonesia.

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               It is unlikely that you are familiar with the name ‘mollusc’. However, you may be surprised when you learn that they are some common animals that we come across in our day-to-day life. A snail is a mollusc.

               Molluscs are a large and diverse group of invertebrates, belonging to the Gastropods species. They include a variety of familiar animals well-known for their decorative shells or as sea food. Tiny snails, clams, and squid, cuttle fish and octopuses are just some animals that belong to this group.

              Molluscs have soft bodies, and get their name from the Latin word ‘mollis’ which means ‘soft’. Some of these animals have very beautiful shells. Snails have twisted shells, while others have shells that are pearly or iridescent.

               Molluscs have a body part called a foot. Their foot is much like our foot, because it helps them move about.

               Molluscs also have a special feature called radula. The radula is a sharp tongue-like body part that is used to scrape food off hard surfaces and push it into their mouths.

              The giant calm is the largest mollusc. A giant calm can weigh upto 340 kilogrammes. They are beautifully coloured. Their mantle is usually a mixture of yellow, red, green, blue, pink and brown colour and each of them has a unique combination of colours. They have thick, bony zigzag shaped shells that cannot be closed completely.

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               Although the jellyfish has ‘fish’ in its name, it is not a fish. It is not made of jelly either.

               Unlike a fish, it is an animal without a backbone found in oceans and seas around the world. The name jellyfish derives from the jelly-like bodies of these animals.

               Jellyfish are found in oceans and seas all over the world, in the deepest as well as in shallow water. Some species thrive in salt water, others in fresh water. Jellyfish are possibly the oldest multi organ animal on this planet. Some scientists believe that they existed as far back as 700 million years ago.

               Jellyfish can be large or small, brightly coloured, transparent or translucent. They look like little umbrellas, with a gelatinous bell shaped body and trailing tentacles. Inside their bell-shaped body is an opening that is its mouth. They feed on fish, shrimp, crabs and tiny plants. They eat and discard waste from their mouths.

               As a jellyfish squirts water from its mouth, it is propelled forward. Jellyfish use their tentacles to sting. Most are harmless to humans but stings from some species, such as the box jellyfish, can be very painful and sometimes kill. They do not have any brains!

               The lion’s mane jellyfish, the largest jellyfish on the planet, has a mass of thin tentacles that resemble a lion’s mane. These jellyfish are found in the Arctic, North Atlantic and North Pacific Oceans.

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              Have you seen pictures of colourful coral beds under the sea? Some coral reefs are tourist attractions as visitors can go scuba diving there, and enjoy the biodiversity under water.

              Coral polyps are hard working little animals, no bigger than a match’s head, which together, build enormous coral reefs. They are invertebrates that live in colonies. Since they are small, and stay in one place, they are in danger of being attacked by larger animals.

              So, they construct hard chalky skeletons around their bodies. It is these skeletons that form the frame work of coral reefs. Corals are attached to the sea floor. Even through corals look like plants, they are animals. They stay in one place and live in groups.

              Coral reefs may look like rocks. They are made up of tiny little animals called polyps. As polyps die, they become hard and new polyps grow on top of them. This process continues until a colony is formed.

              As colonies grow over hundreds and thousands of years, they join with other colonies and become reefs. Some of the coral reefs on the planet today began growing over 50 million years ago. Corals live in tropical waters throughout the world.

              The largest coral reef is the Great Barrier Reef located off Queensland, Australia. The Great Barrier Reef stretches for 2600 kilometres.

              Coral reefs teem with life. Though they cover less than one percent of the ocean floor, they support 25 percent of all marine creatures. Coral reels are very important because they are home to some of the most strange and interesting creatures on this planet.

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               When we hear the word sponge, what comes to our mind first may be the sponge that we use to mop a wet surface or absorb water.

               The sea sponge is a type of invertebrate animal that lives in the world’s oceans. Sea sponges can be of many different colours, sizes, and shapes.

               They are the simplest multi cellular animals. They do not move around much but stay in one place. The surface of a sponge has many small pores or tiny holes.

               Water that is laden with food particles passes into its body through these pores. There are over 5,000 known species of sponges. They can be found attached to surfaces anywhere, from the shallow water near a beach to the depths of the ocean. Some types of sponges have been found to live over 300 years! Sponges can live in both warm and cold water as well as in both deep and shallow water. Sea sponges can only survive in saltwater, so if we put them in freshwater, they will quickly die. They are also very sensitive to air.

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               Invertebrates, as the name suggests have no vertebra; and therefore, most of them do not have the ability to stand erect or walk on legs. They are multi-cellular too. Their cells are working together for the survival of the organism. All of the cells have specific duties and responsibilities.

               Invertebrates do not have cell walls, whereas plants have them. One of the most important characteristics of animals is that they have no cell walls. Even though no insect looks like an animal, this quality makes it an animal.

               Most of them have tissues that are specific organizations of cells. Most invertebrates can move. Even sponges move when they are very young and very small. Once they settle down, they do not move anymore. Other invertebrates like lobsters and insects move around their whole lives. Most invertebrates are organized in a symmetrical way. Symmetrical organization means when you can draw a line down the middle of the organism and the two sides look like mirror images. If you draw a line down the middle of an octopus, you would find two sides with equal parts. However, sponges and some coral are not symmetrical.

               Invertebrates cannot make their own food; and are, therefore, heterotrophic. Heterotrophs feed off other things to get their energy. Plants are autotrophic. They make their own food. Being heterotrophic is one of the main characteristics of being an animal.

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               There is so much diversity among invertebrates. This diversity prevents classifying them under a single over-arching category. Scientists have identified more than 30 phyla of invertebrates. Since vertebrates have a single identifying factor called vertebra, it is not difficult to classify them. However, invertebrates are any other animals classified outside of that class. Let us look at some of them in detail.

               A wide variety of interesting ocean animals that are invertebrates includes sponges, corals, jellyfish, anemones, and starfish.

               Molluscs, another category of invertebrates, have a soft body that is covered by an outer layer called a mantle. Many molluscs live inside a shell, but not all of them. Some examples of molluscs include squid, snails, slugs, octopuses, and oysters.

               Crustaceans are a type of arthropod. Arthropods are characterized by jointed legs. They also have an exoskeleton, meaning that their bones are on the outside like a shell. Some examples of crustaceans are crabs, lobster, shrimp, and barnacles.

              Worms are invertebrate animals that do not have legs. Worms may live in the soil, in the water, or even inside other animals as parasites. Some examples include the tapeworm, the leech, and the earthworm.

              Insects are part of the earth’s largest animal phylum, the arthropods. There are over 1 million species of insects including the grasshopper, dragonfly, yellow jacket, butterfly and praying mantis.

              Spiders, centipedes and scorpions are all part of the arthropod phylum. Spiders and scorpions are arachnids because they have eight legs. Centipedes and millipedes are myriapods and have many legs. Some myriapods have as many as 750 legs. Some example species include the tarantula and black widow, which are both spiders.

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            Most invertebrates that we are familiar with are very small. We often associate the smallness of an ant, a caterpillar, or a grass-hopper with insignificance. Therefore, we have no remorse when such small insects die. However, invertebrates play a very important role in the eco-system.

            As invertebrates are generally small, they can hide in places where larger animals cannot catch them. Therefore, their size is an advantage when it comes to protecting themselves. In spite of their small size, these animals play a key role in maintaining the balance of nature.

            Invertebrates play various roles in nature. Those that are herbivores keep plants and trees in check. Some invertebrates are carnivores, eating other invertebrates as well as larger animals, to prevent the overpopulation of some species. Others are parasites, keeping the number of a certain type of plant or animal under control. Perhaps most important of all, some invertebrates eat dead animal and plant matter. This releases important nutrients back into the environment so that other plants and animals can use them again.

            Most invertebrates also provide food for other species of animals, and even for carnivorous plants like the sundew. Therefore, though most invertebrates are small, they are far more important to the ecosystem than all the mammals, birds, reptiles, amphibians and fish put together.

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              Which is more intelligent: a dog or a mosquito? You will not think twice to answer the question. Bigger animals tend to be smarter and more intelligent. However, does their skeletal system have anything to do with their intelligence?

              It is not wise to generalize about smartness and intelligence when it comes to invertebrates. They are diverse in size and form. There are hardly any similarities among species as different as enormous moths, ethereal medusas, skittering scorpions, or stationary sponges. However, there is no need for any debate on this: the lack of a backbone may mean they are ‘spineless’, however, that does not mean that all of them are mindless!

              Cephalopods, squid and octopus in particular, are some of the most intelligent invertebrates. They are capable of learning quickly and retaining information. Spiders learn to weave better webs through trial and error. Honeybees learn to recognize their hives. At the same time, curiously enough, starfish and sponges do very well with no brains at all!

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               Can you observe some of the animals around you? It would be interesting note that most big animals such as a cow, a dog or a cat have strong internal skeletal structure. Now look at some small organisms such as a butterfly, a beetle or an earthworm. They do not possess an internal bone system. Does size have anything to do with such differences?

               Most invertebrates are small because they lack internal skeletons. An external skeleton is an inhibitor and makes it difficult for an animal to grow further. If it grows too big, it will not fit inside the skeleton. If the skeleton grew bigger to accommodate the animal’s increasing size, it would become too heavy for the animal to carry.

               However, it would be wrong to assume that all invertebrates are small. Invertebrates that live in the sea can grow quite big. There are giant clams in the South Pacific that are 1.2 metres across, and weigh a quarter of a tonne! Giant squids can reach a length of 17 metres, and weigh a tonne!

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