We separate living beings from non-living things on the basis of certain characters or processes. These processes are called life processes. Some of the processes are quite obvious to the naked eyes, while some others are not visible to the naked eyes. It is very easy to tell that a dog or a cat is alive because they show various kinds of motion; like jumping, running and wagging the tail. But plants do not show any movement yet we say that plants are living beings. In this lesson, you will understand the meaning of life process. Different life processes are explained in detail; like nutrition, respiration, transportation and excretion.
Meaning of Life Processes
An animal moves from one place to another and based on this fact we can easily say that an animal is a living being. In most of the big animals, the process of breathing can be clearly seen; which is another indicator of life in that animal. But plants neither show locomotion nor breathing yet we say that plants are living beings. Growth is a very good indicator of life in most of the plants. But certain organisms do not show locomotion, breathing or growth? In these organisms, movements happen at the molecular level. Movements at the molecular level are not visible to the naked eyes. Even in bigger organisms; such movements take place continuously.
We know that a big organism is made up of many organs, organs are made up of tissues and tissues are made of cells. Furthermore, a cell is made up of cell organelles which are made up of molecules. During various biological processes, these molecules undergo breakdown and need to be replaced with new molecules. Replacement of broken molecules is necessary to maintain the life in an organism. If replacement of broken molecules with new molecules stops then life ceases to exist in an organism. All the processes which are necessary to maintain life in an organism are called life processes. Nutrition, respiration, transportation and excretion are the different life processes. Reproduction is not considered a life process because it is not necessary to maintain life. Reproduction is required to continue the lineage of an organism but an individual organism can continue to live even without reproduction.
Nutrition: The maintenance processes are required to prevent damage and breakdown of molecules. Hence, energy is required for these maintenance processes. For an individual organism, the source of energy comes from outside the body. This source of energy is called food and the process of taking in the food is called nutrition. Moreover, every organism needs additional raw materials for growth and repair. These raw materials are taken from outside. We know that life depends on carbon-based molecules. Hence, most of the sources of food are carbon-based. Different organisms follow different modes of nutrition. A particular mode of nutrition is based on the complexity of the organism and on particular nutrition need of the organism.
Respiration: An organism cannot control its external environment. So, it has to depend on different kinds of molecules for its nutrition needs. These sources of energy need to be broken down into a uniform source of energy which can be broken down to produce energy. Finally, this energy would be utilised for various kinds of molecular movements to maintain the life. For this, a series of chemical reactions take place in the body. Oxidation-reduction reactions are the most common means to break down complex molecules to produce energy in the living beings. For carrying out such reactions, most of the organisms take oxygen from outside. The process of taking in and utilising oxygen to produce energy from carbon-based molecules is called respiration. Since this process takes place at cellular level hence respiration is also called cellular respiration.
Transportation: In a unicellular organism, the entire surface of the organism is in direct contact with the external environment. Hence, intake of food and oxygen and removal of waste substances take place through diffusion. Due to this, these organisms do not require specialised tissues or organs to carry on a particular function. But in the case of complex organisms, diffusion cannot be sufficient to ensure availability of food and oxygen to all parts of the body. Similarly, diffusion cannot be enough to remove waste materials from every part of the body. Hence, these organisms need specialised tissues and organs to take up nutrition and another set of specialised tissues and organs to take up oxygen. This presents a new challenge to the body. In a complex organism, food uptake would happen at one place of the body but food needs to be supplied to every part of the body. Similarly, oxygen uptake would happen at one place of the body but oxygen needs to be supplied to every part of the body. To ensure the availability of food and oxygen to every part of the body, these organisms need an elaborate system of transportation of substances.
Fig: Transportation in Unicellular and Multicellular organism
Excretion: Many chemical reactions happen in the body. Many by-products are created during these reactions. Some of the byproducts are harmful substances. If they are not removed from the body they can prove harmful and even lethal for the organisms. Removal of waste substances from the body is called excretion. Complex organisms have a specialised set of organs and tissues to remove waste products from the body.
Example: What are the raw materials used by an organism?
Solution: The various raw materials used by an organism are mainly carbon-based molecules.
Example: What processes would you consider essential for maintaining life?
Solution: Nutrition, respiration, transportation and excretion