My Science School

 

                 Plants were the first to colonize the land, starting with very simple plants such as algae. Then mosses and liverworts developed, followed by ferns and other larger plants. Animals did not leave the sea until plants had become established —otherwise there would have been no food for them. Relatives of the spiders and scorpions were probably among the first animals to leave the sea and colonize the land. At first these animals would have been quite small, and probably returned to the sea to breed, like modern land crabs. Later they evolved into larger and more complex forms of life like modern insects.

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                     Gregor Mendel (1822 - 1884) was a botanist and monk who lived in what is now called the Czech Republic. He was interested in finding out how changes took place in an organism as it reproduced. He studied the garden pea plant, breeding plants with different coloured flowers, different shapes of seed pod, and other characteristics. Recording the effects, Mendel formulated simple rules that allowed him to predict how many plants would resemble one or both parents, and how many would combine characteristics of each parent.

                    Mendel’s studies formed the basis of modern genetics. Although he altered some findings to fit with his ideas, his theories are still important to the study of biology.

                    Rubber is produced from white milky liquid called latex, which oozes from cuts made in the trunk of the rubber tree. This tree originally grew in the jungles of Central and South America but although rubber was in great demand, it was in short supply because the trees grew wild. Eventually some rubber tree seeds were brought back and grown at the Botanical Gardens in Kew, England.

                   The young trees were distributed around the British Empire, and large plantations were established in countries such as India, Malaya and Sri Lanka. A huge international rubber trade quickly developed, and there is still a great demand for natural rubber even though synthetic substitutes are now widely used almost everywhere.

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                          These familiar plants were cultivated in America for centuries before being found by the early European explorers. Potatoes were brought to Europe in the 16th century, and were a great curiosity. They originated in the Andes, in South America, where they had been cultivated for 1,800 years.

                          Tomatoes were brought to Europe at about the same time, and were quickly adopted as a basic food by the Spanish and Italians. In northern Europe, it was a long time before tomatoes were accepted as a safe food because they are close relatives of the poisonous nightshade plants. Maize was also introduced by the early explorers, and is now grown widely.

 

 

 

 

 

 

 

 

 

 

            Tea is made from the leaves of a species of camellia plant. It is widely grown in cool regions of China and India. Coffee was originally grown in Ethiopia, but it is now grown throughout the world. The coffee plant is a small evergreen shrub, and the coffee bean is the seed at the heart of a fleshy red berry.

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                      Most of the farmed animals and crops that we use today are extremely different from their wild ancestors. Wild wheat is only a large form of grass, while maize produced small, hard kernels instead of the juicy  cobs we like to eat today.

                    The wild boar is also very different from the friendly pigs we see on modern day farms. Cattle were once long-legged, lean and dangerous to approach — unlike today’s slow, placid animals.

                     All dogs, however, are still exactly the same species despite the many differences in their shape and size, In 12,000 years of constant breeding, humans have still not succeeded in producing a new species of dog, in other words, one that cannot breed with its ancient ancestors. Modern dogs are still able to breed successfully with wild wolves and dingoes.

                    The world’s tropical rainforests are being lost at an alarming rate, and already the effects of this loss can be seen. Rainforest trees are cut down to provide timber as well as land for grazing and raising crops, The remaining scrub and branches are usually burned, providing a rich source of fertilizer for one or two years, Then the land becomes barren. Rainfall washes away the topsoil, leaving bare rock in which very little grows.

                    The results of deforestation are seen in countries such as Bangladesh, where heavy rains are no longer soaked up by the forests in the foothills of the Himalayas. Instead the rainwater sweeps down the valleys, causing enormous flooding and loss of life.

                     The prairies in Canada and the USA are enormous grassy plains, which were once the home of huge herds of buffalo.

                    Today the prairies are covered with enormous fields of maize, supplying most of the world’s needs for this important food crop. The agriculture here is true factory farming, where the crops are planted, treated and harvested with vast machines and using very little manual labour.

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                        About 150 types of plant are regularly cultivated as food crops, although thousands more are eaten in local areas. The Most important crops are cereals (grass- like plants), especially maize, rice and wheat. Root crops such as potatoes are commonly grown in temperate climates, and sweet potatoes, yams and cassava are grown in tropical parts. The seeds of the pea family, known as pulses, include beans, soy beans, chickpeas and lentils. They are a particularly valuable source of protein, especially in some parts of the world where meat is in short supply and malnutrition may be commonly encountered.

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                   Coral reefs are the marine equivalent of rainforests. They are home to huge numbers of a great variety of animals. Unlike some other habitats, few plants grow on coral reefs because fish and sea snails graze them. Ocean currents carry most of the food to the reef. Plankton is the basic food that powers the whole reef system. The small animals that feed on plankton are eaten by large crustaceans and fish, and so on up the food chain to predators such as sharks.

                 If a coral reef continues to grow it may begin to rise out of the water, becoming a coral island. The sea helps to break up the coral growths and pile them up. Creatures such as calcifying algae cement the pieces together to form a solid structure. If soil lodges in the coral vegetation often begins to grow on the surface. Many of the Pacific islands were formed in this way.

 

                         Temperate forests contain far more varieties of trees and shrubs than are found in conifer forests. Because the shade in these forests is not so great, there is far more undergrowth and larger clearings between the trees. During the lifetime of a tree such as the oak, large branches fall off and rot on the forest floor, providing a rich habitat for fungi and small animals. Other fungi live naturally in association with tree roots, and their mushrooms are eaten by mice and squirrels. Foxes are common predators in temperate forests. Deer graze in the clearings and feed on young trees. Many types of small seed-eating bird live in temperate forests, hunted by predators such as hawks.

 

                    Tropical rainforests contain the most varied mixtures of animals and plants of any habitat on the Earth. They contain large and small predators and a bewildering variety of birds. All these animals are supported by huge numbers of trees that produce fruit to feed them and their prey all year round. Because there is no true winter in tropical rainforests, there is no need for the cycle of eating and storing food that takes place in cooler climates.

 

  

 

                         Conifer forests cover huge areas of cool parts of the world. They are not rich in plant life apart from the trees, because the deep shade of the forested areas prevents most other plants from growing.

                         Various kinds of squirrel, burrowing rodents that feed on fallen cones, and many types of bird inhabit conifer forests. Eagles, hawks and owls prey on the small rodents. Deer graze on the bark of young trees, and the huge moose lives in wet areas, paddling around the edges of lakes and streams and feeding on water plants.

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                  Tundra is the cold, partly frozen region near the North Pole. It is covered with grasses and other low-growing plants, including the lichen known as reindeer moss. Many familiar trees such as willows and birches live in the tundra too, but they are stunted and low growing. Despite the cold, the tundra is covered with flowers in the spring, and huge numbers of flies pollinate them. Mosquitoes are present in vast numbers, biting the mammals that live in this region.

                   The plants and animals living in hot deserts have all developed ways of conserving or storing water cactuses and other succulent plants store water in swollen stems and leaves. Some cacti grow to a huge size and can live for 100 years or more. Other desert plants have tiny leaves that reduce water loss, and spines that protect the plant from grazing animals. Their roots may go down as far as 10 m to reach water.

                  Reptiles are common inhabitants of deserts because they are cold-blooded and need heat if they are to remain active. Most other desert animals are either small burrowing rodents, or birds and animals that hide from the Sun among bushes or rocks at the hottest times of the day.

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