Category Science

What are flowering and non-flowering plants?

          The second largest kingdom of living things after animals is the plants. The key feature of a plant which sets it apart from other living things is that it obtains energy from light by the process of photosynthesis. Most plants have broad, flat surfaces, such as leaves or fronds, where this happens. Just as there are many groups of animals, from simple worms to complicated mammals, so there are many groups of plants. However they are divided into two main kinds—the simpler types without flowers, and those with flowers.   

 

NON-FLOWERING PLANTS

        The simplest non-flowering plants are algae. They nearly all live in water, although a few kinds can survive in damp places, like Pleurococcus alga which grows as a green powder on shady tree trunks. Nearly all seaweeds and some types of pondweeds, such as the green, hair-like spirogyra, are algae. An alga has no proper roots, stem or leaves, although it may have a stem-like part and leaf-like blade. It absorbs water and nutrients through its body surface.

        Mosses and liverworts are known as bryophytes. A moss has small green leaflets but no proper stem or roots. It absorbs water and nutrients through its leaflets so it can only live in damp places. Liverworts grow in similar places. Each has a low, flattened body known as a thallus.

        Ferns, or pteridophytes, are also non-flowering. A fern has roots which absorb water and minerals from the soil, and a stiff stern to hold up its much-branched fronds. The stem, like the stem of a flowering plant, contains tiny pipes or tube-like vessels to carry the water and other substances from the roots to the fronds. Plants with these vessels are known as vascular plants.

        All of these non-flowering plants reproduce by making tiny, dust-like spores which grow into new plants. Conifers, also called gymnosperms, reproduce by seeds. The seeds form in hard, scaly structures known as cones. Pines, firs, spruces, larches, redwoods and cypresses are all conifers.

 

 

FLOWERING PLANTS

        The flowers of flowering plants, also known as angiosperms, are body parts specialized for breeding. The flowers produce seeds which in suitable conditions grow into new plants. Flowering plants are by far the main or dominant group of plants around the world, except for seaweeds in the oceans and the conifer forests in colder regions. Flowering plants include familiar herbs, grasses, reeds, rushes, wild and garden flowers, and most trees and bushes (except for the conifers). There are some 260,000 different kinds or species of flowering plants compared to about 550 species of conifers, 11,000 ferns, 23,000 mosses and liverworts, and around 12,000 species of algae.

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What are Bacteria, Virus and Protists?

BACTERIA

          The commonest living things are bacteria. They are too small to see without a microscope. Most are about one to five microns (0.001 to 0.005 millimetres) across. A quarter of a million would fit on the head of a pin. Bacteria are all around us in their billions. They float in air and live on icy mountain-tops, in the scalding water of hot springs, in dark caves and on the bottom of the sea. There are more than 4000 known kinds, and probably many more yet to be identified. They vary in form but there are three main shapes. These are: spheres or balls known as cocci, cylinders or rods, called bacilli, and corkscrew-like spirilli. Most bacteria reproduce simply by splitting in two.

 

          Bacteria belong to the main kingdom of living things known as monerans. A typical bacterium has a tough outer skin, or cell membrane, which contains jelly-like cytoplasm. Tiny blobs, known as ribosomes, float in the jelly and make various substances for the bacterium’s life processes. Also floating in the cytoplasm is a long, coiled-up chemical called DNA, which unravelled would be more than 1000 times longer than the bacterium itself. This is the bacterium’s genes, a “manual” containing every structural detail of the organism. Some bacteria get their energy from light, like plants. Others absorb nutrients through their cell membranes.

            Some bacteria are harmful. They get into other living things, including humans, and cause diseases such as anthrax and typhoid. But most bacteria are harmless. Many kinds live in the soil and play a vital role in nature because they cause the decay or rotting of dead plants and animals.

 

 

 

VIRUSES

          The smallest living things are viruses. They are “alive” only because they can produce more of their kind if they invade another living thing. Viruses cannot reproduce on their own. They get into another living cell, the host cell, and take over its life processes to make more copies of themselves. In the process they destroy the host cell.

 

          A typical virus has an outer shell or coat made of proteins. Inside is a length of genetic material, usually DNA. Different viruses are shaped like bricks, rods, golf balls and even space rockets. Many can exist in their non-living form for years and be frozen solid, boiled or made into crystals – yet still come alive when host cells are available. Viruses cause diseases in plants, animals and people. These include the common cold, measles and AIDS (caused by the Human Immunodeficiency Virus, HIV).

 

 

 

 

 

 

PROTISTS

           Like Bacteria and other monerans, protists are microscopic single cells. But unlike monerans, each protist has its genetic material (DNA) wrapped inside a bag-like membrane to form the nucleus or control centre of the cell. Protists live mainly in water and damp places. Some are like tiny plants, absorbing their energy from sunlight and their raw materials for growth from the water around them. Others move around and consume food particles such as bacteria.

 

           Some protists have a rigid, case-like cell wall around them. The types known as foraminiferans and radiolarians make shells with beautiful shapes and patterns. Others have no rigid case and can take up any shape. A few protists cause diseases, such as plasmodia, which produce malaria.

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What is elaborative meaning of the term ‘Evolution’?

          A Fossil comes from an organism (living thing) that survived long ago. After the organism died, parts of it were buried in sand or mud, preserved in the rocks and turned to solid stone. Hard, tough body parts form the best fossils because they do not rot away quickly after death and so have more chance of being preserved. They include animal bones, teeth, horns, claws and shells, and plant wood, bark and cones.

          Fossils show that many kinds of animals, plants and other organisms have lived during the hundreds of millions of years that make up the Earth’s past. Most of these organisms, such as ammonites, trilobites, dinosaurs and mammoths, are no longer alive. Other types have survived almost unchanged for millions of years. Sharks and turtles are examples of these. Some have appeared quite recently, such as human beings. The study of fossils, known as palaeontology, is one part of the evidence for evolution—the way that living things change through time.

         Why does evolution happen? Why don’t living things simply stay the same? Life is a continual struggle to avoid predators and bad weather, to find food and shelter, and to breed. Living things that survive the struggle are those best suited or adapted to the conditions. However the conditions change naturally with time. Some kinds of food may become more scarce. The climate may become colder or warmer. New diseases may appear. Living things must evolve to suit new conditions or die out.

 

   

 

 

          Besides studying fossils, we can see evolution at work by observing living things today. Some types of animals are very similar to each other. Hawaiian finches for example, differ only in small ways. They probably all evolved from one original species. Their beaks changed, or adapted, to eat different foods.

 

 

 

 

EVIDENCE FOR EVOLUTION

          An embryo is a living thing at an early stage of its development, like a human baby during the first few weeks of life growing in its mother’s womb. At this early stage, a developing human embryo looks very similar to the embryo of any other mammal, such as a monkey or cow. It is also similar to the embryo of a bird, a reptile like a turtle, and even a fish. The simplest explanation as to why these very young organisms are so similar to each other is evolution. Over millions of years they have evolved from the same ancestors. They are now different as adults. But they have kept the similarities to their ancestors, and so to each other, during the early stages of their development.

 

 

 

 

 

 

 

 

NATURAL SELECTION

          Evolution happens by the process of natural selection. In the struggle for survival, some living things adapt better to the conditions. These individuals are more likely to survive and produce offspring. If the offspring inherit the same features, they too have more chance of survival. It is as if nature chooses who will survive and who will not.

 

          Evolution by natural selection explains the bodily features and behaviours of living things—even those that seem to be a hindrance. The long, colourful feathers of a male bird of paradise may seem a drawback. They make him more obvious to predators and less able to escape from them. But they also attract females for breeding, and so this feature is passed on to his offspring.

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What is Life?

          Look at your surroundings. There may be walls, windows, chairs, tables and similar objects around you. Perhaps there are also machines, cars and gadgets. There may be other people too, and pets and plants. Which ones are alive? You can probably tell at a single glance if an object is living or not. For example, a dog is alive but a book is not.

          But exactly how did you decide which things are alive and which are non-living? Perhaps you watch them to see if they move. A person or animal moves. Even a sleeping cat breathes softly. But a toy electric car moves and it is not alive, while a plant does not seem to move yet it is a living thing. Perhaps you look for signs of breathing. But the snails and plants in an aquarium do not seem to breathe, and they are alive. The giant panda is just a picture, but you know from looking at it that a real panda would be alive. How?

          Living things are called organisms. We know if something is a living organism, rather than non-living, from several features. First, an organism grows and develops at some stage, usually changing its shape and getting bigger. Second, life processes happen inside the organism that change chemical substances from one form to another and which use up energy. Third, an organism must take in raw materials for its growth and also take in energy to power its life processes. Fourth, an organism reproduces—it produces more of its own kind.

 

 

ORIGINS OF LIFE

          How did life begin? Scientific studies show that planet Earth formed about 4600 million years ago, from a massive ball of cloud, dust and gases whirling through space. At first, the rocks of Earth were far too hot for life. But gradually they cooled and massive rainstorms lasting many thousands of years filled the lakes, seas and oceans with water.

          These seas contained all kinds of salts, minerals and other chemical substances. By chance, some of them joined to each other—perhaps helped by the energy of lightning flashes from the storms that raged across the globe. A few simple chemicals gathered as blobs. Other chemicals joined around them. These others then broke off to form blobs of their own. The first very simple living things had reproduced. This may have happened as long as 3000 million years ago. Life stayed as simple microscopic organisms for another 2000 million years.

 

 

 

 

 

 

GROUPS OF LIVING THINGS

          To understand how living things have changed or evolved in the past, and how they work and survive today, it helps to know which ones are similar to each other. So organisms are classified or put into groups. There were once only two main groups or kingdoms, plants and animals.

 

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Are there schools that accept plastic as fees?

           Does your school accept plastic as fees? There is a unique school in the outskirts of Guwahati, Assam which does. If a student brings 25 pieces of plastic, it is accepted as fees in Akshar School. The plastic waste that they bring is recycled to make eco-friendly bricks that can be used for construction.

          When Parmita Sarma and Mazin Mukhtar started this school in June 2016, their aim was to provide free education to poor kids. Their plan took a slight twist when they saw the villagers making bonfires of plastic to beat the cold.

           They wanted to educate the villagers about the harmful effects of plastic and hence modified the fee structure from having no fees to plastic waste as fees. A practical lesson in recycling! The school provides socially and environmentally relevant education.

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Which is the first Indian state to ban disposable plastic bags?

           Sikkim, a tiny state in the foothills of the Himalayas is famous not only for its natural beauty and biodiversity, but also for its eco-friendly stands.

           In 1998, Sikkim became the first Indian state to ban disposable plastic bags. They were eliminated from both rural and urban areas and labelled as hazardous. 2016 is an environmentally important year for Sikkim as the state took two landmark decisions. The first was to ban packaged drinking water in government offices and at government events.

           The state has also banned the use of disposable styro-foam and thermocol plates and cutlery.

           It now targets single-use plastic bottles.

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