The study of world of life is as old as man itself. All living organisms are made up of a few elements which are repeated in each of them. The basic unit of life - cell, is a structural and functional entity of life.
The plants upon which we depend for the food we eat, and for the oxygen we breathe, depend in turn upon the soil. A good soil supplies the plants with the mineral elements they use. Vigorous, highly productive plants can be grown in solutions of fertilizer minerals in the absence of soil.
The first photosynthetic organism probably appeared almost three billion years ago. With the evolution of photosynthesis, however, organisms began to change the face of our planet and, as a consequence, to exert strong influences on each other. Organisms have continued to change the environment, at an ever increasing rate, up to the present day.
All living organisms require a continuous supply of energy for carrying out various functions. The main source of energy for all the functions, in all living organisms is cellular respiration.
Nutrition can be defined as the process by which an organism obtains food which is used to provide energy and materials for its life sustaining activities.
All living creatures need food. The food is consumed so that energy is obtained. The energy is utilised by the body for various purposes like locomotion, conduction of impulses, repair of damaged tissues, building of cell materials, etc.
Materials formed in one part of the body have to be taken up to other parts where they are needed or to be got rid of. This is an essential requirement of most animals. This function is performed by the body fluids.
The nitrogenous waste materials produced in the animal body due to metabolic reactions are of no use to the cell. These waste materials if allowed to accumulate in the body, may become toxic. Therefore, they must be removed from the body. The process of elimination of metabolic waster products from the animal body to regulate the composition of the body fluids and tissues is called excretion.
The act of changing place or position by the entire body or by one or more of its parts is called movement. Movement is one of the characteristic features of living organisms. Study of movements is called kinesiology.
Animals are different from plants because of their ability of locomotion. This ability probably developed as they have to search for food, unlike the plants that are autotrophic. Since they move from place to place, the animals have to continuously encounter changes in their environment. All animals, in order to maintain a steady state within the body (homeostasis), should be able to perceive these changes and adapt to them.
A cell, a tissue or an organ, which secretes certain useful chemical compounds required for a particular function, is called a Gland.
The creation of a life form, by a similar life is called reproduction. Reproduction is the extension of life of a species at a given time. It is a means of perpetuation of the species and also multiplies their number. By this process, the individuals transmit life to the next generation and thereby ensure the continued existence of living organisms on earth. If there was no reproduction, life on this earth would sooner or later come to an end.
The term growth is applied to several things and situations. It is quite common to hear people referring to growth of cities, the weeds, of tradition or even of indiscipline. You would have observed the growth of crystals or salt in the laboratory, but it is of non-living things.
An animal performs all its life functions with an aim to be alive till it matures and reproduces. Reproduction is the ability of living organisms to produce new individuals similar to themselves. Reproduction ensures perpetuation and survival of their species. It leads to an increase in the number of individuals of a species when conditions are favourable.
Growth is defined as an increase in the size and weight of an organism due to synthesis of new protoplasm.
he term ecology is derived from two Greek words (oikos - means 'house' or place to live and logos means 'a discussion or study'). Literally, ecology is the study of organism 'at home' in their native environment. The term was first introduced by Reiter in 1868, but was fully defined by Ernest Haeckel in 1869.
Biotic community is an association of a number of interrelated and independent populations belonging to different species, in a common environment which can survive in nature.
Biogeography reveals that living organisms (plants and animals) are found practically everywhere on this earth. The living components interact among themselves as well as with their physical environment like soil, air and water.
The term 'natural resources' refers to all the natural things on our earth. It includes everything, that is naturally available and that is not creatable by any human activity. It specifically excludes the materials created by man.
The word 'resource' means supplying a material generally held in reserve. The common natural resources include energy, air, water, land, minerals, microorganisms plants and animals.
It is aptly said that pollution is the price paid by us towards social development through scientific advancement. Pollution is a peril of our society. It is a peril out of scientific achievements applied to improvement of human facilities.
The atmosphere resource of our world is unique and available to our planet only. No other planet is found to have similar atmosphere. Earth's atmosphere is a legacy from history of this planet. It was formed billions of years back. In the formative years, as the earth started cooling, it did not have free oxygen (theory of chemical evolution by Oparin and Haldane). The atmosphere, lithosphere and hydrosphere were not clearly distinguishable. As micromolecules and macromolecules of C, H, N and O compounds like, glycerol, fat, pyrimidines, polysaccharide, lipid, proteins, nucleic acids were formed, the life forms originated.
Although population of some animals is also studied, the population of human beings is most extensively studied. Whenever the word population is used, it connotes the human population. Population is one of the most important subjects known for having large scale ramifications on economic, social, environmental and developmental scenario of a country.
One of the primary objectives of agriculture is to produce food. In the entire history of agriculture, food production has remained a prime objective.
Living organisms are exposed to various external or foreign substances and disease causing organisms like bacteria, viruses and fungi. Such organisms which can cause a disease are known as Pathogens. It is observed that some human beings are more prone to a certain disease and some others are immune to it.
Doctors use a number of simple instruments like thermometer to monitor body temperature of patients, stethoscope to listen to heart sounds, BP instrument to check the blood pressure, BP instrument to check the blood pressure and so on. But today technology has revolutionised the world of medicine and the tools used for diagnosis of diseases.