My Science School

               You will be surprised to know that there are some plants which catch and eat insects. Such plants are called insectivorous plants. Since they cannot prepare their own protein, they get it by eating insects and worms. Every plant of this kind uses it own technique for capturing insects. The leaves of these specialized plants are adapted to trap and digest insects - which supplement their food supply.

               One of the famous insectivorous plants is ‘pitcher plant’. The upper part of its leaf resembles a small pitcher. Its colour is very attractive. It contains a sticky liquid. The opening of the pitcher has small fibres which allow the insects to go inside but obstruct their coming out. On being attracted by the beautiful colour, when some insect enters this pitcher, it is unable to come out. It gets entangled in the juice of the pitcher and the plant produces certain enzymes and digests it. The ‘cobra plant’ of America which appears like a snake, also eats insects. It also has pitcher-shaped mouth.

               The ‘sundew plants’ have hair on their leaves. The tips of these hairs have droplets of a liquid which appear very attractive. As soon as some insect is attracted towards a leaf, these hairs bend forward, capture the insect and digest it with the help of their own juice. The digested flesh is absorbed through their leaves. After that the hairs again become normal.

               There is a plant called ‘venus-fly trap’ which is found in America. Its leaves have beautiful red coloured elevations on both sides. Whenever an insect sits on a leaf it closes like a fork and the plant digests the trapped insect by digestive juices. The ‘uticularia’ is a water plant. It is found all over the world. The roots of this plant which are submerged in water have bulbous bladders. When some aquatic insects enter the bladder, the hairs on its opening do not allow it to come out. The walls of these bladders give out digestive juices which suck the proteins out of the bodies of these small insects.

Similarly, a plant called ‘Indian pipe’ is found in the hills of Shimla. It also eats insects. In addition to these, there are many other insectivorous plants all over the world.

 

              Bark is the protective outer covering of tree branches, trunks and roots. Bark has three layers. The outer layer called periderm is made of dead cells, such as cork. Periderm is usually thick. It protects the tree against weather, insects and diseases. The middle cortex layer is made of living, non growing cells. The innermost phloem brings food made in the leaves, down to the roots. The periderm of some trees has small openings called lenticels. Lenticels allow gases such as oxygen and carbon dioxide to enter and leave the plant.

             As wood is laid down inside a shoot, a layer of cells near the outer side begins to divide and produce cork cells. The walls of these cells soon get heavily thickened with a waterproof substance. The cells die and form bark.

           Over the years the bark is constantly added to form the inside of the tree. So as the diameter of the twig, branch or trunk increases, the waterproof barrier is maintained. But the outer bark often splits and cracks or becomes flaky.

           As already mentioned, the bark protects a tree from the weather and sudden temperature changes. It contains substances that repel insects and resist fire. Bark often has commercial uses. The actual cork comes from the bark of the Mediterranean cork oak. The drug Quinine is obtained from the bark of Cinchona trees and Cinnamon comes from the bark of the Cinnamon tree. Cough medicines and many other useful substances are also obtained from the bark.  

 

            Due to the scarcity of water and particular climatic conditions (hot, dry, windy) prevailing in the desert, it is very difficult for animals as well as plants to survive. Nonetheless, we do find some of these. These are adapted to the desert conditions. Let us see what types of vegetation and animals are found there and how do they survive.

           The vegetation of a desert is mainly thorny shrubs, cacti and palm (especially date) trees. Cacti and other desert plants have adapted themselves to live in desert conditions. They have evolved ways to store water in their fleshy stems. The leaves have squeezed themselves into tiny thorns to reduce the loss of water. The roots go deep into the ground and are wide spread to collect every drop of water available. The stem stores the water and slowly gets thinner as the water gets used up. In some cacti the thorns are pointed towards the earth. The dew drops deposited on the ends fall on the earth hence moisture is maintained below the cacti. There are quite a few animals found in deserts such as snails, pack rat, jerboa, etc. Most desert animals sleep during the day to escape the day temperature and they come out in night in search of food. Some animals sleep during the hottest part of the year. Animals such as kangaroo, rat and gerbil can survive with little or no water. Reptiles adjust their body temperatures to cope with heat and cold. The Australian desert toad stores water in its body. Some lizards, ants, owls and snakes also live in deserts. 

             Majority of people believe bamboo to be a kind of shrub or plant. In fact, it is neither. It is a type of grass. It can reach a height of about 35 metres and upto a thickness of about 30 cm. It has many varieties. About 600 species of bamboo have been studied. All kinds of bamboos have smooth, hard and strong trunks. The rate of their growth is very fast. It can grow up at the rate of 40 cm a day. One bamboo reportedly grew 90 cm in 24 hours. Some bamboos blossom only once in 30 years. Others may take 100 years to blossom. A bamboo plant dies after it blooms. The seeds from these blossoms grow into new plants.

            It is only the stem of the bamboo grass that is of most use in the construction of roofs, huts, walls, houses, etc. It is used to make mats, baskets, musical pipes, paper, as a fishing rod and weapon for defence; it is cooked as vegetable and pickle is also made of them; some medicines are made from a fluid in the stem joints of bamboo branches. Its hollowed stems are used as water pipes especially in Japan.

            It is found in abundance in South-East Asia, Indian subcontinent and the islands of the Pacific Ocean.

 

               Bacteria belong to the lowest category of plants. They are unicellular micro-organisms. They are as small as 25,000th part of an inch. Some of them are even smaller and cannot be seen with the help of an ordinary microscope. They reproduce through the process of cell division (fission) i.e. one cell divides itself into two. Under favourable circumstances the rate of their reproduction increases. Within twenty minutes the cells of the new bacterium divide into two, in forty minutes one bacterium multiplies to four and to sixty four in two hours. In this way, in twenty-four hours, one bacterium multiplies into 4,000,000,000,000 bacteria. If the rate of the reproduction of bacteria remains the same, the weight of the bacteria produced within 72 hours will become 33,000 times more than the weight of the earth. But this is impossible because in the struggle for food and water only one percent of them can survive. They may live in soil, water, air or in any other organisms.

               Bacteria can be broadly classified into four types. Some bacteria are round, they are called coccus. The rod-shaped are called bacillus, spiral-shaped the spirillum and the comma-shaped vibrio.

               Bacteria are both harmful and useful. They spread many diseases in human beings, animals and plants. Typhoid, tetanus, T.B., cholera, diphtheria, dysentery, whooping cough etc. are some of the well-known diseases which are spread by bacteria. But, on the other hand, some bacteria are very useful for mankind. Conversion of milk into curd is done by bacteria. They destroy the dead plants and animals by setting decay in them. Vinegar is also prepared by them. It is the bacteria which make yeast for bread, and colours the hides (animal skin). Certain antibiotics are also prepared by using them. Thus, bacteria are both useful and harmful to us. Antibiotics and sulpha drugs are used to control bacterial diseases. 

 

 

 

 

 

 

 

              In rainy season, you must have seen the growth of soft, white, cottony and velvety patches of mould on stale bread, pickles, damp cloth, leather, food, leaves, fruits and vegetables. These are called fungi and are classified flowerless plants having no roots, no stems and no leaves and are without chlorophyll - the green colouring matter. Due to the lack of chlorophyll, fungi depend for their food either on a living organism (parasite) or on the dead organic matter (saprophyte). When we examine the fungi under a microscope, we see that they consist of a large number of black, green, yellow or blue fibres. These fibres have two parts - one part is mycelium which spreads like roots and takes food from the material on which it grows. The other part is round, ball-like lymph, which contains spores. Always present in the air, they start multiplying whenever they get bread, fruits and other eatables in hot and humid places.

Continue reading "What is Fungus? "

 Mangroves are plants that grow in the tidal zone of tropical coastal areas and are constantly subjected to ascending and descending water levels of high and low tides. They have adapted to this environment by anchoring themselves in the soil with their stilted roots. This way, they also prevent the coast from being destroyed by storms or flood waves. After the devastating tsunami of 2004, many countries have started planting mangroves at the coasts to try and prevent similar catastrophes in future.

The term ‘tree-line’ describes the height above which trees can no longer grow in the mountains. The main reason for this is the very low temperature in these places. If we climb a mountain, we find a temperature drop of about 6°C for every kilometre. In addition, the temperature fluctuations between day and night as well as summer and winter are very high. The soil cover is thin so the roots of trees do not get a firm hold. Only small pine trees, cedars, grass, and moss grow above the tree-line before the start of the rocky and icy area. 

Steep slopes with very little soil cover; rugged rocks, snow, and ice are the habitat in high mountains. Although the plant cover above the tree-line is scanty, you can still find animals living there. In the Alps, we find the climbing chamois, ibexes, and groundhogs. 

Continue reading "Which animals and plants live in the mountains?"

In a greenhouse, the air gets heated up because the warm rays of the sun get trapped by the roof and the walls and are not reflected outwards completely. This situation is comparable to the conditions currently prevailing on the Earth. The layer of the atmosphere, which acts like the glass roof, contains greenhouse gases, such as water vapour, carbon dioxide, methane, nitrous oxide, and ozone, in appropriate amounts to keep the Earth comfortably warm. Due to irresponsible human activities, the carbon dioxide content has increased by 20% and methane content by 90%. As a result more heat is getting trapped and making the Earth warmer than usual. The increased temperature is causing the ice of the polar caps and glaciers to melt; this has led to a rise in sea levels and drastic climate changes all over the world. 

Symbiosis is a phenomenon in which two living organisms live together in such a way that they are mutually beneficial to each other. For example, the colourful clownfish live in a symbiotic relationship with the sea anemones. The clownfish enjoy the protection of the poisonous nettle fibres of the sea anemone and the sea anemone survives on the left-over food of the fish. The lichens that live in association with a fungus and an alga are also good examples of symbiotic relationships. Through the close interaction between its symbiotic partners, the lichens are able to grow in places, where they could never have existed alone.

Plants reproduce in a variety of ways. Many species build side shoots, from which new plants grow. Plants like mosses and ferns reproduce with the help of spores, which are distributed by the wind and grow to become new plants. ‘Higher plants’ or the seed plants with male and female sexual organs have stamens with pollen and the stigma. The male pollen sticks to the stigma and is passed on to the egg cell in the ovary. A fertilized egg ripens to become a fruit, which contains the seeds. The seeds can be dispersed widely through wind or through animals who eat the fruits and discard the seeds.

 

Roots absorb water and the dissolved nutrient salts from the soil. They also store the nutrients as a reserve that the plant can survive on, when the soil dries up. The roots also anchor the plant firmly in the soil to safeguard against uprooting due to wind and bad weather. Roots change shape and adapt depending on their environment. Shallow-rooted plants, such as spruces, can hold their ground even at places where the soil cover is very thin. Plants such as pine trees, whose tap root grows deep in the ground, are found at places where water is available at great depths inside the earth.

When trees grow, they accumulate wooden fibres around their heartwood. These fibres are bright and porous in spring so that a lot of water can reach the fresh leaves through them. By autumn, they become darker and thicker so the tree becomes stable and resistant to frost in the winter rest period. This process forms a bright ring and a dark ring around the heartwood every year. If you count the dark rings of a horizontal cross section of the tree trunk, you can find out the age of the tree. In the tropics, where there are no distinct seasons, the trees do not develop any rings. They grow all round the year and do not have any rest period. 

Algae are plant-like living organisms. They live in the seas, freshwater or damp land areas. They range from tiny single-celled organisms, which can be seen only under a   microscope, to larger plant-like planktons, used as food by blue whales or flamingoes. Large, leaf-like algae, known as ‘seaweed’, grow extensively in shallow waters to form dense underwater forests.