Living Creatures: Exploring their Characteristics

Class 06 Science

All living beings share some common characteristics. For example, all living beings show movement, they need food, and they grow. They also respire, reproduce, excrete, respond to stimuli, and eventually, die. Absence of any of these features indicates that they are non-living things.

Movement is one of the similarities among living beings.

Even though plants do not move from one place to another, they do show certain types of movements. Opening of flowers is one of the examples of movement in plants. Another example of movement in plants is seen in insectivorous plants.

Insectivorous plants are dependent on insects for their nutrition. Drosera is one of the examples of an insectivorous plant. Drosera is featured with saucer-shaped leaves having many hair-like projections of unequal length with sticky ends. Whenever an insect enters the saucer, hairs move inward and trap the insect with their sticky ends. Whenever an insect enters the saucer, hairs move inward and trap the insect with their sticky ends.

Life Processes

Living beings need food (nutrition) for their growth and development.

In the process of breathing, when we inhale, the air moves from outside to inside our body. When we breathe out, the air moves from inside our body to outside. Breathing is part of a process called respiration.

There are tiny pores called stomata on the surface of leaves. These pores help plants in taking air in and out. All living beings respire.

The sweat consists of water and salts removed by the body as waste products. Removal of waste products from the body is called excretion. Urine is also formed as a product of excretion in animals.

Plants excrete excess water and minerals in the form of small droplets on leaves. For example, grasses and roses. All living beings excrete.

Any thing or any event that prompts living beings to respond is called a stimulus. Plants also respond to stimuli. For example, touch-me-not (mimosa, chhui-mui, lajjalu) plants fold their leaves when we touch them. The leaves of certain plants facing each other tend to come together. This can be observed in the sleeping leaves of amla (Indian gooseberry) tree. All living beings respond to stimuli.

All living beings reproduce. Reproduction is the process of producing new ones of one’s own kind. Reproduction is necessary for the continuity of life.

When a living being is not able to exhibit all of the above mentioned characteristics, despite the availability of all resources (like food, air and water) needed for being alive, it is said to be dead.

Germination of a Seed

Water: Seeds require water for germination. Water enables the seeds to carry out the processes necessary for their growth. The outer covering of the seed is called seed coat. Water softens the seed coat and helps the tiny embryo inside it to develop into a plant.

Air and Soil: Seeds need air for germination. They use the air available in the spaces between soil particles. Moreover, spaces between the soil particles allow roots to grow easily.

Light and/or dark conditions: In general, most seeds do not require light for germination. But after germination, sunlight is required for further growth of the seedling.

Growth and Movement in Plants

Shoots of plants grow upward and exhibit movement towards sunlight but roots of plants grow downwards.

Life Cycle of a Plant

A seed grows into a young plant and matures to produce flowers and fruit. The fruit contains seeds which give rise to a new generation of plants. The entire process from a seed to a plant, and then, to the next generation of seeds is called the life cycle of a plant. When a plant stops growing and all activities of life gradually come to an end, even after the availability of all the necessary conditions, the plant is considered dead.

Life Cycle of a Mosquito

Female mosquitoes are bloodsucking insects that transmit several diseases like malaria, dengue and chikungunya. Two different types of worm-like creatures are larva and pupa. Mosquito larvae and pupae observed in water bodies repeatedly come to the water surface. Mosquito larvae and pupae live in water and require air to respire. They move to the surface of the water for air.

Mosquitoes pass through four stages in their life cycle - egg, larva, pupa and adult. The adult mosquito that emerges from the pupa rests briefly on the surface of water and then flies away. The adult mosquito may survive for 10 to 15 days.

A mosquito begins its life as an egg (stage I), the egg develops into a larva (stage II), the larva grows into pupa (stage III), and the pupa transforms into an adult mosquito (stage IV). The adult female mosquito lays eggs directly on or near water, and the cycle continues.

Significant changes occur in the appearance, body shape and structure during the various stages in the life cycle of a mosquito. The shape of the egg is quite different from the larva; the larva appears very different from the pupa. The pupa appears very distinct from the adult mosquito.

Life Cycle of a Frog

There are four stages in the life cycle of a frog - the egg stage, which progresses to the embryo stage; the tadpole stage, consisting of an early stage with a tail and no legs, and a late stage with hind legs; the froglet stage, and the adult frog stage.

Tadpoles develop legs but still have tails. Tails help them swim in water. Tadpoles grow gradually and start looking like little frogs called froglets. They still live in water but begin to spend some time on land. They continue to grow and lose their tails completely. Their legs become strong to help them jump and land. They become fully developed adult frogs who live both in water and on land.