My Science School

 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.

The main difference between trees and shrubs is their size. Trees are much taller than shrubs and their root balls (system of roots with attached soil that supports the health of the tree) are also bigger. Unlike the thin and flexible stalks or stems of the shrubs, trees have thick stems to bear the load of the heavier and bigger leaves, branches, and fruits. Since trees are taller, they need to transport water from the soil much further up than the shrubs. This is done by several thin hair-like pipes in the stem and the branches.

The chloroplast inside the green leaves of plants is the ‘workshop’ where photosynthesis takes place. Water is supplied to the leaves by the roots, and carbon dioxide  is absorbed from the air through tiny pores on the lower side of the leaf. Both these are broken down into the elements hydrogen (H), carbon (C), and oxygen (O) with the help of chlorophyll and sunlight. Plants build ‘glucose’ (grape sugar) from these elements and oxygen is released in the atmosphere as a by-product. Photosynthesis has been the source of oxygen in the air since the origin of life on the Earth.

 

Unlike animals, plants produce their own food and except for a few carnivorous plants, do not eat other organisms. Green plants use water, nutrients, and a green matter in their leaves called ‘chlorophyll’ to produce their food. Normally water and nutrients are absorbed from the ground through their roots. Some plants, however, have developed other methods for obtaining water and nutrients. Many tree-dwelling plants make funnel-shaped ‘containers’ with their leaves to catch water. Carnivorous plants use their digestive juices to convert the insects, caught in their folding or sticky traps, into nutrients. 

Almost all plants and animals need air, water, light, and nutrition to grow. Green plants use a complicated chemical process, called photosynthesis, to create energy for survival and growth. Since plants create their own energy, they are the first link in the food chain. Animals need to drink water and eat plants or other animals to get energy. Therefore, they are present at the next step in the food chain. There are some animals, like camels, that can survive for days without drinking water. Since they live in deserts with very little water, they have adapted to the special conditions of their habitat.