7th Class Science Life Processes

Life Processes

Category : 7th Class

Life Processes



Food provides energy to all living organisms. Food is first broken down into simple and soluble molecules. The simple molecules are then carried to all the cells. In cells, these molecules combine with oxygen to produce energy. This process of combination of simple food molecules with oxygen to produce energy is called respiration.


Types of Respiration

There are two types of respirations: aerobic respiration and anaerobic respiration.


Aerobic respiration

Anaerobic respiration

Respiration which occurs in the presence of oxygen.

Respiration which occurs in the absence of oxygen.

Production of more energy.

Production of comparatively less energy.

End products are Carbon dioxide, Water and Energy.

End products are Lactic acid, ethanol, Carbon dioxide and energy.

Example: Plants and Animals.

Ex: Some microorganisms.


Human Respiratory System

Human respiratory system consists of nose, nasal passage, trachea, bronchi, lungs and diaphragm.

Our nose has two holes called nostrils. Nasal passage joins the nostrils to the trachea. Trachea is tube like structure called wind pipe. The trachea divided into two parts at

The lower end called bronchi. One bronchus goes to left lung and another goes to right lung. Each bronchus divides into many smaller tubes called bronchioles. The bronchioles have air sacs called alveoli at their ends through which exchange of respiratory gases takes place between air and blood vessels. The haemoglobin present in the blood carries oxygen to the cells of the body.


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Transportation is the process that involves carrying of substance into the cells and removal of the wastes from the cells. In animals, the substances move inside and out of the body with the help of respiratory, circulatory, digestive and excretory system. In plants, the substances move inside and out of the body through processes such as respiration, absorption by roots, conduction of water and the nutrients.


Transportation in Plants

The minerals and water that are absorbed through the roots of a plant reach the entire plant and leaves through vessels. The vessel which transports minerals and water is present in the every part of a plant. These vessels are formed by tissue called xylem. Food prepared by leaves of a plant is carried to the rest of the plant by separate set of vessels. These vessels are formed by tissue called phloem. Phloem is also responsible for carrying food to the plant organs that stores energy. Transportation of food to other parts of plant is called translocation.


Transportation in animals

In higher animals, digested food, waste material and gases are carried within the body with the help of circulatory system. Blood is the fluid through which all the materials are carried in the body. Blood flows in the body through tubes called blood vessels. The heart is responsible for pumping the blood. Thus the circulatory system consists of heart, blood and blood vessels.

Blood vessels are of three types namely arteries, veins and capillaries. Arteries carry blood from heart to various parts of the body. Veins carry blood from the various parts of the body to the heart. Capillaries are the thinnest blood vessels.



All living organisms reproduce in order to continue their existence on this planet. Reproduction can take place in different ways. For example, some organisms produce babies, while others lay eggs. Similarly in case of plants, new plant can grow from seed or "rom bulb. Bulbs are the underground stems that have fleshy storage leaves. For example, onion, tulip, etc. There are two ways of reproduction: asexual and sexual reproduction.


Asexual Reproduction

In asexual reproduction, an offspring is produced by an individual without the help of another individual. Two sexes are not required for reproduction.


Types of Asexual Reproduction



A Small part of the body of the parent plant grows out as a bulb-like projection called bud and eventually gets detached from the parent cell to form a new cell. For example, years reproduces by budding.



Body of parent plant breaks into fragments and each of fragment can produce an offspring. For example, spirogyra, a kind of algae reproduces by fragmentation.


Spore Formation

Many flowerless plants produce spores which are small cells protected by thick wall. These are carried by air. Under favourable conditions (like damp and warm conditions) and food, they germinate and produce new plants. For example, ferns, mosses and moulds reproduce by spore formation.


Vegetative Propagation

Many plants can reproduce through organs other than their sexual organs and are called vegetation organs which can be stem, roots and leaves. For example, in bryophyllum leaves, in potato stem tuber and in onion bulb are the vegetative organs.


Sexual Reproduction

Sexual reproduction involves the fusion of sex cells. In this type of reproduction two sexes (male and female) are involved. Flower are the reproductive parts of a plant. The function of a flower is to make male and female gametes and exhibits fertilisation to make seeds for growing new plants.



The stamen has a stalk like filament. At the head of the stamen is a pollen sac or anther the mature anther burst, produces large number of dusty pollen grains. For reproduction to occur, pollen grains must be transferred to the stigma of a carpel. This transfer of pollen grains from the anther to the stigma is called pollination.


Pollination in flowers



When the pollen grain reaches the stigma, it germinates and grows a long thin tube called pollen tube. The pollen tube carries the male gamete produced by the pollen grain.

The pollen tube pushes through the style into the ovary. The male gamete then enters the ovule, which contains the female gamete or egg. After the fusion of the two gametes. The ovary develops into the fruit and each ovule develops into a seed. Inside the seed lies the baby plant which develops from the zygote.

Fertilisation in a flowering plant


Dispersal of Seeds

New plants can grow from seeds. The seeds can be scattered or dispersed by wind, water, animals or exploding fruits. For example, the plants such as, drumstick and maple have winged seeds and are carried by the wind. The seeds of lotus and water chestnut are dispersed by water. Birds and animals such as monkeys eat fruit from plants and throw away seeds. Fruits of rubber tree, balsam and night jasmine explode on ripening. This bursting of fruit scatters seeds away from the parent plant.

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