7th Class Science Respiration In Plants And Animals Respiration in Plants and animals

Respiration in Plants and animals

Category : 7th Class

Learning Objectives

  1. What is respiration
  2. Respiration in different organisms
  3. Cellular respiration
  4. Respiration in plants
  5. Types of respiration- aerobic and anaerobic respirations
  6. Cellular respiration


Do you know?

The right lung is slightly larger than the left. The highest recorded sneeze speed is 165 km/hour.




The biological process in which food is utilized to produce energy is called respiration. Respiration is necessary for survival of the living beings. A living being cannot survive even for a few seconds, without respiration. During respiration, it is mainly the carbohydrate which is oxidized to produce energy. This can be shown by following equation:

Carbohydrate + Oxygen\[\to \]Carbon dioxide + Water + Energy


Site of Respiration

Respiration happens inside the cells. As respiration happens inside the cell, it is also called cellular respiration. A cell organelle; called mitochondria; is the site of cellular respiration.



Aerobic Respiration

Aerobic respiration takes place in the presence of oxygen. Carbon dioxide and water are the end products of aerobic respiration. Aerobic respiration happens in most of the organisms.

Glucose   \[\xrightarrow{\text{Abresence of oxygen }}\] Carbon dioxide + Water + Energy


Anaerobic Respiration

Anaerobic respiration takes place in the absence of oxygen. Anaerobic respiration usually happens in most of the microbes. Alcohol and carbon dioxide are formed at the end of anaerobic respiration. In some cases, lactic acid is formed at the end of anaerobic respiration.

Glucose   \[\xrightarrow{\text{Abresence of oxygen }}\] Alcohol + Carbon dioxide + Energy

Glucose \[\xrightarrow{\text{Abresence of oxygen }}\]Lactic acid + Energy

  • Anaerobic respiration also happens in our muscle cells. When someone runs or walks too fast, one may feel a throbbing pain in calf muscles. This happens because of deposition of lactic acid; produced by anaerobic respiration. Once the person takes rest for some time, the pain goes away.
  • Yeast respires in the absence of oxygen.


Do you know?

  • The surface area of lungs is roughly the same size as a tennis court.
  • The capillaries in the lungs would extend 1600 km if placed end to end.
  • The breathing rate is faster in children and women than man.
  • A person at rest usually breathes between 12 and 15 times a minute.


Glucose is converted into alcohol and carbon dioxide by yeast in the absence of oxygen. Yeast is used in beverage industries to produce beer and wine. During day time, plants utilize oxygen to perform photosynthesis. During the night, plants release carbon dioxide and take in oxygen for respiration. In plants, the exchange of gases takes place through a special structure, called the stomata. The process of respiration in plants breaks down glucose and releases energy.



Respiration in plants is aerobic and is represented as

Starch (sugar) + oxygen\[\to \]energy + carbon dioxide + water



The process of taking in and giving out air; for respiration; is called breathing. Breathing involves two main steps, viz. inhalation and exhalation. During inhalation, we breathe in air which is rich in oxygen. During exhalation, we breathe out air which is rich in carbon dioxide.


Rate of Breathing

When we are doing normal activities, the rate of breathing is normal. The breath rate of human beings is 15 - 18 breaths a minute. The rate of breathing increases when we do strenuous physical works; such as running, swimming, jogging, etc. the rate of breathing decreases when we take rest or when we are sleeping.


Process of Breathing

Air passes through the tiny hair in the nasal cavity, and then through the pharynx, larynx and windpipe before reaching the lungs. The hairs in the nasal cavity prevent the entry of dust particles and pollen. The mucous lining is present from the nasal cavity to the lungs. Lungs are situated inside the chest cavity, and they rest on a large muscular sheet called the diaphragm, which forms the floor of the chest cavity Diaphragm is a membrane which is between the chest and abdomen. When you breathe in, your diaphragm and rib cage get into action. The diaphragm is protected by the rib cage. The diaphragm plays an important role in inhalation and exhalation.


The breathing is controlled by the movement of diaphragm. The movement of diaphragm is controlled by a group of muscles; called inter costal muscles.

When the diaphragm moves down, the ribcage expands. This leads to the expansion inside the lungs. As a result, the air moves into the lungs. This process is called inspiration or inhalation. When the diaphragm moves up, the ribcage contracts. This leads to contraction of the lungs. As a result, the air moves out of the lungs. This process is called expiration or exhalation.

To Show that Carbon dioxide is Released during Exhalation

Carbon dioxide reacts with limewater to make calcium carbonate. This property is utilized to show the evolution of carbon dioxide during respiration. For this, take a test tube and pour some limewater in it. Dip a drinking straw in the test tube. Blow air in the limewater through the drinking straw. It is observed that the limewater turns milky this shows that carbon dioxide is released during exhalation.



Animals, which belong to amphibian, reptilian, avis and mammalian, use the lungs for breathing. Amphibians breathe through their skin, when they are in water. Smaller animals have different organs for breathing.


Breathing in Fish

The respiratory organs in fish are the gills. Fishes take in oxygen in dissolved form. During respiration, water enters the body through the mouth, and then passes through the gills and comes out of the operculum. The gills take in the oxygen dissolved in the water and give out carbon dioxide.


Breathing in Cockroach

Cockroach and other insects breathe through spiracles and tracheae. There is a network of hollow tubes running through the body of an insect. These hollow tubes are called trachea. Each trachea opens on the body surface in the form of very small pore. These pores are called spiracles. Oxygen reaches to the cells directly through the spiracles by means of diffusion.

Breathing in Earthworm and Frogs

The skin is the respiratory organ in animals like frogs and earthworms. The skin in these animals is moist and slimy, which makes it easier for oxygen to diffuse in and carbon dioxide to diffuse out of the body. However, frogs are special animals. They can breathe through their skin in water, while on land they can breathe through their skin as well as their lungs.


Breathing in Unicellular Animals

Unicellular animals breathe through the cell membrane.


Breathing in Plants

Plants can be of various sizes. Developing respiratory organs could not be a fruitful solution for plants; because of their unlimited growth. Each plant part breathes through its external layer of cells. Roots breathe through root hairs. Stems breathe through epidermis. Leaves have numerous small pores; called stomata; for breathing. Stomata traps in air and exchange of gases take place inside the plant cells. Oxygen is absorbed and carbon dioxide is given out.

Do you know?

Respiration can be measured using a device called a Respirometer.

We exhale about half a liter of water vapor in a day.

Human breathing mechanism is called tidal breathing as air comes in and out using the same path


Structure of stomata

Surrounding the stomata are kidney shaped cells called guard cells, which control the opening and closing of the stomata. When the plant needs to close the stomata, the guard cells are filled with water, which swells them until the stomata are sealed shut. When the plant is ready to open the stomata, the guard cells are drained, which creates an opening. These cells have chloroplasts and so they can perform photosynthesis. Guard cells are further surrounded by subsidiary cells. The whole structure of stomata along with guard cells and subsidiary cells is called stomata apparatus.


Some important differences:-





It involves intake of oxygen and release of Carbon dioxide.

Respiration is more complex and it includes breathing as well as oxidation of food in cells to release


It is a physical process i.e. exchange of gases.

It is a bio-chemical process in which food is broken along with release of energy.


It involves breathing organs e.g. lungs in

It occurs at cellular level


No enzymes and catalysts are in volved.

Many enzymes and catalysts are in volved in the whole process.






It uses oxygen in the process

Anaerobic respiration takes place in the absence of oxygen.


In this process, glucose is completely broken down into\[\text{C}{{\text{O}}_{\text{2}}}\], Water along with release of energy.

In this process, glucose is broken into ethyl alcohol, \[\text{C}{{\text{O}}_{\text{2}}}\]and energy.


It occurs in all organisms like mammals.

It usually occurs in lower organisms like yeast (fungi) and bacteria. It can occur muscles of higher organisms during heavy activities.


Glucose + Oxygen\[\to \] Carbon dioxide + Water + Energy

Glucose \[\to \]Ethyl alcohol + Carbon dioxide + Energy



  1. Aerobic respiration-Oxidation of food during respiration in the presence of oxygen.
  2. Anaerobic respiration-Oxidation of food during respiration in the absence of oxygen.
  3. Spiracles——Openings of the tracheae on the sides of the body of an insect.
  4. Tracheae-Five tubes through which air circulates within the body of an insect.
  5. Respiration-Process by which a living organism oxidizes food to release energy.
  6. Cellular respiration-Respiration that occurs inside a cell.
  7. Enzymes-Protein bodies which do not take part in a chemical reaction but speeds up a reaction.
  8. Fermentation-Incomplete oxidation of food resulting in the formation of alcohol, vinegar or a dough.



Notes - Respiration In Plants and Animals

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