The Survival Kingdom

Many types of plants are widely distributed on the earth's surface, while other species tend to be restricted in their distribution. The fact that different species of plants are often found growing under similar climatic conditions in widely separated parts of the world, shows that climatic differences alone cannot explain such distribution.

The desert regions of the south-western United States of America and of West Africa are similar climatically, but the species of plants growing in these regions are very different. For instance, numerous species of cactic are common in American deserts but are lacking in the African deserts, while spurges Euphorbia are abundant in the African deserts but are very rare in the United States deserts.

Ordinarily, similar plant species occupy the various areas of a particular region. If these areas are separated by barriers sich as high mountains or large bodies of water, over which plants cannot pass, the plants in these isolated areas tend to develop along divergent lines to become quite distinct. Hence, regions that have been separated for a very long period usually have plants that are peculiar to them. These are mainly plants found in no other parts of the world. Example of long-isolated lands with very typical and limited plants are the Hawaiian, the Fiji and other oceanic islands. The animals found in such areas too will be peculiar to the areas.

In general, as one moves from the equator to the poles, thick evergreen forests of the tropical rain forest give way to the tropical savannas, temperate deciduous forests of the cold regions and cold deserts such as the tundra which is said to be treeless. Here, the soil is frozen all the year round so that very little water is available for plants and animals most of the year. Plant life in the tundra is characterized by litchens, grasses and sedges. Very few animals are permanent residents such as the polar beer, caribou (or reindeer in the old world) and lemmings.

The nature of the soil, the quantity and distribution of rainfall determine the types of vegetation and hence, animals found in various biomes, worlwide. The tropical rain forest, with the highest annual rainfall (250-2,500mm), has the largest number of plants species and the highest primary productivity. This is about 24 per cent of the total world productivity. The temperate forest's primary productivity is about 14 per cent of the total world productivity.

Many animals that are highly adapted to high temperature and high relative humidity are numerous in the tropical rainforest. Among the numerous wild animals are large mammals like the elephant (the largest land mammal), hippopotamus, panther, hog, leopard, chimpanzee, baboon, gorilla, monkey and the tiger. The tiger the terror of the jungle fears no man nor beast. An elephant feeds on about 200kg of leaves daily, drinks a lot of water and cannot do without salt which it obtains from termites nests. There are other varieties of animals including birds and reptiles and flying mammals like bats.

In the tropical savannas are many rodents which nocturnal. Other animals include the jackals, hyenas, vultures, lions, lionesses, giraff, rhinoceros and insects. The giraffe the tallest living animal is about 5 and half meters (18 feet) tall with a long neck which enables it to reach up to the leaves of trees and look out for danger. The lion is said to be neither brave nor kind and only roars when he is not hungry. The lion is found in Africa and part of Pakistan. Many herbivores abound in the tropical savannas with very tall grasses on which many feed.

In the tropical savannas and deserts are animals like the buffalo, zebras (the lion's favourite prey), antelopes, gazelles (eaten by cheetah), sand-fox, reptiles and many insects. The cape buffalo is the most dangerous of all game, while the cheetah is the fastest mammal, speeding up to 112km per hour.