Characteristics of living things
There are many kinds of plants and animals around us. They show some similarities and some differences. Yet, with the help of certain features, we can tell that they are all living things. These features are not seen in non-living things. Such features are said to be the characteristics of living things. Let us study these characteristics.
Growth
A baby grows up to become an adult person – woman or man. During the period of its growth, the baby gains in height, weight and strength. In the same manner, all animals grow into adults in a certain period. Generally, humans require 18 to 21 years for this growth. Find out how long it takes for the young ones of hens, cows and dogs to grow into adults.
Tie a thread to the tip of a potted sapling. Keep the thread stretched and tie it to a peg or nail above the plant. What do you observe after ten to fifteen days ?
What tells us that the plant has grown taller ? In all plants, it is mainly the width and height of the stem that grows. As they grow, some plants develop branches while others do not.
Though all living things grow, animals grow only for a certain period. Plants, on the other hand, grow as long as they live. The growth of living things occurs from within the body, which means that growth occurs in all parts of the body.
Food is necessary for growth
Plants make their own food in sunlight. Plants produce food from water, nutrients in the soil and the carbon dioxide present in the air. This process takes place in the leaves of plants. It is brought about in the presence of sunlight, with the help of the chlorophyll in the leaves. This process of food production is called photosynthesis. During this process, plants give out oxygen. Plants appear mainly green in colour due to the chlorophyll in them.
Animals, however, do not have chlorophyll. They do not produce their own food. They search for food. Animals such as goats, sheep, horses eat grass while wild animals such as tigers and lions meet their need for food by hunting other animals which live on plants.
Respiration
- Hold your hand in front of your nose or keep your hand on your chest. What do you feel ?
2. If we observe a sleeping dog, what movement of its belly do we see ? Living things need oxygen in order to live. Inhaling oxygen and exhaling the carbon dioxide formed in the body due to the use of oxygen is called respiration. Animals such as fish, snake, mouse, etc. have specific organs for respiration. On the other hand, plants respire by means of microscopic pores on their stems and leaves.
Excretion
Waste substances are formed during the many processes that take place in the bodies of animals. These are called excreta and the process of eliminating them from the body is called excretion.
Animals have specific organs for excretion. Plants, too, excrete. For example, some plants shed 
leaves in a specific season. Waste substances stored in the leaves of plants are shed along with the leaves.
Take a transparent plastic bag. Tie it over a leaf of a plant as shown in the picture. Observe it after six to seven hours. What do you see ? Droplets of water collect on the inside of the bag. It means that, plants excrete water in the form of vapour.
Responsiveness to stimuli and movement
Living things act in various ways when responding to a stimulus. If you suddenly enter a cowshed, the cows and buffalos stand up, begin to move, one or two may even start mooing. These are all movements.
A creeper planted in the courtyard leans towards a support. A potted plant placed in a window grows towards sunlight. It means that plants, too, show movement. Living things move of their own accord.
The movement or the change taking place in a living thing at such a time is their response to a stimulus. An event that occurs in our surroundings is a stimulus. The ability of living things to respond to a stimulus is called their responsiveness to stimuli.
Reproduction
Living things produce other living things like themselves. Some animals give birth to their young ones. Some lay eggs. Their young ones hatch out of the eggs. New plants are produced from the seeds, stems or leaves of plants. The process by which a living thing generates a new living thing like itself is called reproduction or procreation.
Reproduction is a characteristic of living things.
A definite lifespan
‘At a certain stage of life, living things become capable of reproduction. Later on in life reproduction stage, their organs become weak and still later, their life comes to an end. In other words, living things die. The lifespans of different animals and plants are different. For example, the lifespan of the dog is about 12 to 18 years, while the ostrich lives for 50 years.
You may have wondered what exactly the living things are, how they came into being, and so on.
You may have seen the small compartments of a honeycomb. These compartments are joined together to form a honeycomb. A wall has bricks. To construct a wall, we firmly join the bricks together.
A cellular structure
Living things are made of small units called cells. All the actions and processes in the bodies of living things are brought about with the help of these microscopic cells.
Some living things are made of a single cell. These are called unicellular organisms. On the other hand, the living things that are made of many cells are called multicellular organisms. The amoeba and some other microorganisms are unicellular while man, cow, mouse, cockroach, elephants, banyan tree, the onion plant, etc. are all multicellular organisms. All the characteristics of living things are seen in every cell of a living thing, whether it is unicellular or multicellular.
Institutes at work
The institutes that work for the survey and conservation of the various plants and animals in different parts of India are the Botanical Survey of India (1890) and the Zoological Survey of India (1916) respectively. In case you find an unfamiliar plant or animal in your surroundings, you can communicate with these institutes to obtain more information about it.
Useful living things
Plants are used for household as well as industrial purposes. For example, fenugreek (methi), potato, okra (bhendi), apple, banana are used as food while vasaka (adulsa), hirada, behada, asparagus are used as medicines.
Animals are also useful to us. Dogs, cats, cows, buffalos are kept for domestic uses. Fish, sheep, fowl are used as food, while animals like horses, oxen, camel prove useful in various occupations. The earthworm is very useful in agriculture.
Harmful living things
Some animals and plants around us are harmful to man. For example, mosquitoes and flies spread diseases. Cockroaches, mice, rats destroy our food. Lice, ticks also spread diseases. The bites of some poisonous lizards, spiders, snakes and scorpions can even cause death. If wild elephants enter human settlements, they cause a lot of destruction.
Some plants, too, can be harmful, as for example, the dodder, parthenium and other weeds. Pods of the nettle, colocasia leaves cause itching. Plants like oleander, lantana have strong odours. The datura plant is poisonous. Uncontrolled growth of fungi and algae in water pollutes drinking water and may cause the spread of diseases.
Wild animals
Wild animals that hunt other animals for food are called predators, for example, tigers, lions, wolves, leopards. Sometimes, due to deforestation, such animals enter human settlements in search of food and may kill domestic animals or people.