Cell biology, a core discipline within Biology Topics, investigates the structure and function of cells.
Importance of Respiration in Living Organisms
All the living things need energy to grow, move and stay alive. They get this energy from food through respiration. Respiration is the chemical process in which food taken by an organism combines with oxygen to release energy. This energy is used by the organism to carry out its various life processes. Carbon dioxide and water are the other products of the process of respiration. All the living things (plants and animals) undergo respiration to obtain energy from food. The process of respiration takes place inside the body of the plant or animal. For example, our body takes in oxygen from air for respiration. At the same time, it gives out carbon dioxide produced by respiration.
This exchange of gases takes place in our lungs (see Figure). The process of taking air into the lungs through nose and then expel it through nose is called breathing. When we breathe in (or inhale), the air moves from outside to the inside of our body. And when we breathe out (or exhale), then the air moves from inside our body to the outside. Air contains oxygen gas.
So, the purpose of breathing in air is to provide oxygen to our body for carrying out respiration. Thus, breathing is a part of the process of respiration. In respiration, some of the oxygen of air we breathe in is used for producing energy from food and produce carbon dioxide as the waste product. When we breathe out, carbon dioxide produced during respiration is expelled from our body.
The process of breathing can be easily observed in human beings from the movement of their ribs (chest bones). The process of breathing in animals like cows, buffaloes, horses, dogs and cats, etc., is similar to human beings. If we observe carefully any of these animals when they are taking rest, we will see a slow, up and down movement of their abdomen indicating that they are breathing (inhaling and exhaling air).
The process of breathing (or respiration) involves exchange of gases. This is because during this process, cells and carbon dioxide is removed. Some animals do not have lungs like human beings for breathing or exchange of gases, so they have different mechanisms for breathing (or exchange of gases). We will discuss the cases of earthworm and fish here.
The earthworm breathes through its skin. The skin of an earthworm is quite thin and moist, and has a good blood supply. So, the earthworm absorbs oxygen (of air) needed for respiration through its thin and moist skin (see Figure). The carbon dioxide produced during respiration is also expelled from the body of the earthworm through its skin. Thus, in earthworm, gaseous exchange takes place through its skin (which is thin and moist).
The fish has special organs of breathing called gills. The gills absorb oxygen dissolved in water. This happens as follows : The fish breathes by taking in water through its mouth and sending it over the gills (see Figure). When water passes over the gills, the gills extract dissolved oxygen from this water. This oxygen is used for respiration in the fish. The carbon dioxide produced during respiration is also expelled by the gills into the surrounding water. Thus, the fish has no lungs like us, the gaseous exchange in fish takes place in the gills.
Like animals, plants also need energy. The plants get this energy by the process of respiration. The plants use oxygen (of air) for respiration and release carbon dioxide in this process. Every leaf of a plant has a large number of tiny pores (or holes) called stomata on its surface (see Figure). The oxygen (of air) enters the plant leaves through stomata and utilised in respiration. The carbon dioxide produced during respiration inside the plant is also expelled from the leaves through stomata. Thus, the exchange of gases (oxygen and carbon dioxide) in plants during respiration takes place through the tiny pores in their leaves called “stomata”.
During day time, when sunlight is available, the plants use carbon dioxide from air to make their own food by photosynthesis and release oxygen gas into the air. So, during day time, the carbon dioxide produced in respiration is all used up by the plants in photosynthesis (The plants give out carbon dioxide produced in respiration only at night time.) The amount of oxygen produced by plants during photosynthesis in day time is, however, much more than oxygen they use in respiration (The plants take oxygen from air for respiration only at night time). Please note that photosynthesis (or food making) in plants takes place only during daytime when sunlight is available but respiration in plants takes place during daytime as well as at night time.
From the above discussion we conclude that respiration is essential for all living organisms (plants as well as animals). It is through respiration that a living organism obtains energy from food it takes. Non-living things do not respire. For example, a rock is a non-living thing which does not undergo respiration.