Living beings are self-regulated and self-organized cell-based entities that show the various characteristics of life. The major and most apparent of these characteristics are movements. Movements are of two types—visible and invisible.
Visible Movements are changes in the position of organisms or their parts—a running dog, a yelling class fellow, a flying bird. Even in sleep, one can observe breathing movements. However, plants do not show such apparent movements except in a few cases like Mimosa pudica (Sensitive Plant). Most plants show very slow movements of growth, bending, etc.
Invisible Movements occur at the level of molecules. Every cell receives nutrients and passes out wastes. It obtains energy by breaking down nutrient molecules. The energy is then used in repairing and maintaining the cellular structures.
Viruses are called semi-living because they are lifeless outside the host cell. Inside the host cell, they show movements of their molecules.
Life Process
What Is Essential For The Maintenance And Survival Of Organisms?
Life processes are those activities and functions of living beings that are essential for their maintenance and survival. They are the basic functions that are similar in all organisms.
- Energy. Maintenance processes prevent damage and breakdown of protoplasmic structures. For this, they require energy which comes from food.
- Nutrition. It is procuring food for obtaining energy, bodybuilding, and repair materials. Food for body building as well as the release of energy is a carbon-based oxidation-reduction process. Plants prepare their own food.
- Animals obtain food from outside. In the body of an animal, the ingested food is first broken into simpler forms for absorption by cells. The cells elaborate the simple nutrient molecules into cellular components as well as energy-yielding components.
- Respiration. It is the energy-yielding process of the living body. Energy is released when a carbon-based energy-storing complex (for example, glycogen, starch, glucose) is broken down in the presence of oxygen (aerobic respiration). It can also occur in some cells and organisms in the absence of oxygen (anaerobic respiration).
- Exchange Of Materials. There is a regular exchange of materials between the organisms and their environment. Most organisms obtain water, oxygen and nutrients from their environment. In return, they give out carbon dioxide, waste products and undigested matter.
- Single-celled and other simple organisms are in direct contact with the environment. Therefore, they directly obtain food and exchange materials with the same. Generally, it is through diffusion.
- In complex multicellular organisms, very little exchange occurs through the general surface. They have developed special organs for respiration (exchange of gases), ingestion, digestion and egestion.
- Transportation. Multicellular organisms require a transportation system as cell-to-cell diffusion is a very slow process with billions of cells forming the bulk of the body. The transport system can take the required material in a short span of time to all parts of the body. In animals, blood and lymph form a transport system. In plants, vascular strands (xylem and phloem) do the same job.
- Excretion. It is the expulsion of waste materials from the body. Waste materials are the by-products of metabolism which are often toxic if they accumulate in the body, for example, urea, and uric acid. They are collected from all parts of the body by the circulatory or transportation system and brought to the organs where they are separated for elimination.
- In plants, an excretory system is absent. They convert their waste products into harmless forms and store the same in the dead tissues and senescent leaves.
- Movements. Molecular movements (invisible movements) are essential for the working of the body cells. Visible movements are required to support life.
- Sensitivity. Every living organism, small or large, is sensitive to changes in the environment.
Life Processes Short Answer Type Questions
Question 1. Why is diffusion insufficient to meet the oxygen requirement of multicellular organisms like humans?
Answer:
Diffusion is a successful process of obtaining oxygen by unicellular organisms like Amoeba. However, it cannot meet the requirement of multicellular organisms because in them every cell is not exposed to oxygen oxygen-containing environment.
Oxygen is available from the lungs. In order to pass from there to other parts of the body by diffusion it has to pass through billions of cells. It is estimated that it will take three years for oxygen to reach the toes through diffusion. Multicellular organisms have a transport system that takes oxygen to the surroundings of individual cells within a span of some minutes.
Question 2. What criteria do we use to decide whether something is alive?
Answer:
- Movements. They are of two types, visible and invisible. The invisible movements are at the molecular level (and are not felt externally). The visible movements are either of locomotion (running, walking) or of parts (for example, chewing cud, breathing movements).
- Sensitivity. It responds to changes in the external environment.
- Gases. The living being picks up oxygen from the outside and releases carbon dioxide.
Question 3. What are outside raw materials used for by an organism?
Answer:
- Food, water, and oxygen by heterotrophic organisms.
- Carbon dioxide, water, minerals, and sunshine by photosynthetic organisms. When not photosynthesizing, they also require oxygen from the outside.
Question 4. What processes would you consider essential for maintaining life?
Answer:
- Obtaining or manufacturing carbon-containing food materials.
- Breakdown of carbon compounds to obtain energy (respiration).
- Assimilation of carbon compounds to build up protoplasmic constituents.
- Exchange of materials.
- Transportation.
- Excretion.
- Movements.
- Sensitivity.
Question 5. What Is oxygen required by living organisms? What is the product of its action?
Answer:
Oxygen is required by living organisms for breakdown of food sources. The reaction yields energy for various body activities. The byproduct of this activity is carbon dioxide.
Question 6. Name three life processes that are essential for maintaining life.
Answer: Nutrition, exchange of materials, irritability.