3. Diversity in Living Things and their Classification

The geographical conditions at different places on the earth are very different. We find that living things exist in all these diverse conditions. When we live in a certain place, we adjust to the conditions there. Various types of living things have survived because of their ability to adjust themselves to the conditions in their surroundings.

Diversity in plants

 Various types of plants are found in many places around us. Some plants like grass are short, while others are tall and have a canopy. Some plants grow underwater, while some others float on water. We find that some plants grow even in deserts. Moreover, we find that there is a lot of variety in the same type of plant. For example, there are different varieties of rice or wheat, different types of roses, and mangoes of different flavours. Some plants grow even without stems, leaves or roots. These are very different from ordinary plants. Let us study this diversity among plants.

Plants make their own food in sunlight. Such plants are called autotrophic plants. For example, the hibiscus, pomegranate, periwinkle, etc. Some plants like funguses, loranthus, dodder use other plants for food and are said to be heterotrophic. Plants like the pitcher plant even consume insects. They are insectivorous.

The root : Roots hold the soil firmly and anchor the plant. The main functions of the root are to absorb and transport water and nutrients from the soil. The roots of the carrot and radish also store food.
There are two types of roots : taproot and fibrous root

Need for classification of plants

Up to now, information about lakhs of plants has been collected. While studying the diversity in plants, they are classified for the sake of convenience on the basis of the similarities and differences in their structure, their organs and their other characteristics.

Classification of plants

We can easily notice the differences in the shape and height of the plants in our surroundings. It is easy to classify the plants on the basis of this observation.

Trees : Some plants grow tall. Their stem, or trunk, is hard and strong. They have branches at some height above the ground. They bear flowers and fruit for many years. Such plants are called trees. Trees are tall, big and perennial, i.e., they live for many years.

Shrubs : Some plants grow close to the ground. They give out branches very close to the ground. They are shorter and smaller than trees, but they have a thick and hard stem. The oleander, hibiscus, lantana, koranti and rose are shrubs that may grow up to two to three metres. 3. What are the similarities between the fenugreek and periwinkle plants ?

Herbs : Herbs grow 1 to 1.5 metres tall. The stems of herbs are green and quite flexible as compared to those of trees and bushes. Herbs may live for a few months or up to two years.

Vines : Some vines need vertical support for growing, while some others spread on the ground. Climbers like the money plant have aerial roots. Have you seen the cucumber tendrils that look like a spring? Of what use could they be ? Touch the stem of any vines. What do you feel ?

The lifecycle of plants like jowar, sunflower is completed in one year. These plants are called annuals. The lifecycle of plants like the carrot, beetroot is of two years. They are called biennials. Shrubs like the hibiscus and oleander and trees like mango and gulmohur live for several years and bear flowers and fruit. They are called perennials. According to the period of their lifecycle, plants are classified as annuals, biennials, perennials.

Plants that bear flowers are called flowering plants, while the plants that never bear flowers are called non-flowering plants. Non-flowering plants may not have organs like roots, stems, leaves

We see different plants growing in different places around us. Plants can be classified according to their habitat or the place where they grow. Land, water, marshy areas, deserts and even a big tree are the various habitats of plants.

Diversity and classification in animals

Different animals have developed different shapes to survive in the environment. There is a great variety in the body structure of animals too. The amoeba that cannot be seen with our eyes, the huge elephant, the small snail, the fish that swims in water, a kite that flies high in the sky, butterflies that flit around flowers, a house lizard that crawls on a wall are all animals. Each has different characteristics.

 Animals have body parts like a head, a neck, a torso, a tail and limbs for movement. They have various organ systems which carry on various functions inside their body. In this respect, too, there is a lot of diversity in animals.

What are the differences in the body structure of animals like a snake, a lizard, a tiger, a fish, an eagle, a hen, a crab, a housefly, an earthworm, a crocodile and a grasshopper ?

 We see a variety in animals with respect to their food as well. Since animals depend on others for their food, they are found in places where food is available. Different animals have different methods of obtaining and eating food. This, too, leads to differences in their body structure.

Take a drop of water from a puddle and place it on a glass slide. Observe it under a microscope. What do you see ? When a drop of water from a puddle is seen under a microscope, innumerable microbes can be seen moving about in it. You will see the continuously moving amoeba. The paramoecium is also a unicellular animal like the amoeba. A horse, a bear, a tortoise are multicellular animals.

  1. What is the chain of bones in the centre of our back called? Animals with a vertebral column and those without it form two groups known as the vertebrates and invertebrates, respectively. Snakes, birds, fish and kangaroos as also humans are vertebrate animals. Animals such as snails, cockroaches, earthworms do not have a vertebral column and therefore they are invertebrate animals.
  2. Name some animals which lay eggs and others which give birth to their young ones. We have learnt that producing another living thing like oneself is called reproduction. A hen lays eggs and hatches them. After a few days, the young chicks hatch out of the eggs. A cow gives birth to a calf. Before that, the calf grows within the cow’s body. According to the mode of reproduction, animals are classified into two types, namely, oviparous animals which lay eggs and viviparous animals which give birth to their young ones.
  3. Where are the animals, namely, a horse, a bear, a tortoise, an alligator, a fish, a deer and a frog to be found? According to their habitat, animals are usually classified into terrestrial and aquatic animals. However, animals like a frog, salamander, toad live in both places, namely, land and water. Therefore, they are called amphibious animals. A kite, an eagle, a crow, a butterfly, a honeybee all fly in the air, though they live in difference places. These animals are said to have an aerial mode of life.