Life

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What is Life?

The biological definition of life is when a living matter, or any matter that shows certain attributes which include responsiveness, growth, metabolism, energy transformation, and also reproduction. 

Life comprises living beings, and they are segregated into groups known as taxonomy. Each individual is composed of one or more than one minimal living unit, known as cells. Some studies state that life began as early as 4.1 billion years ago. It can be traced to fossils dated billions of years ago.

Biological Definition of Life

The nonliving things might show some of these characteristic traits, but the living things show all of them mentioned below:

1. Organization

Living things are highly organized, which means they contain specialized, and co-ordinated parts. All living organisms on this planet are made up of either one or more than one cell. Cells are considered to be the most fundamental units of life.

Even unicellular organisms are peculiar and complex. Inside each cell, the atoms make up molecules, which then makeup cell organelles and also structures. In multicellular organisms, those similar cells form tissues which in turn, collaborate to create organs. Organs are body structures with distinct functions and they work together to form organ systems.

Multicellular organisms like humans are made up of many cells. The cells in multicellular organisms are specialized to do different jobs. These cells are organized into tissues, such as the connective tissue, the epithelial tissue, the muscle, and the nervous tissue. The tissues make up organs, such as the heart or the lungs that carry out specific functions when needed by the organism.

2. Metabolism

Life on earth depends on a various number of interlocking chemical reactions. These reactions make it possible for all the organisms on this planet to do work like moving around or catching prey, growing, reproducing, and also maintaining the structure of their respective bodies. Living things use energy and consume nutrients to carry out the chemical reactions that help them to sustain their life. The total of the biochemical reactions that occur in an organism is known as its metabolism.

Metabolism is further subdivided into anabolism as well as catabolism. In anabolism, the organisms make complex molecules from simpler ones. In catabolism, they are just the reverse of anabolism. Anabolic processes always consume energy, whereas the catabolic processes can make the stored energy available.

3. Homeostasis

All living organisms on this planet regulate their internal environment to maintain the relatively narrow range of conditions needed for their cellular function. This maintenance of a stable internal environment, of the living organism even in the face of a changing external environment, is called homeostasis. 

4. Growth

Every living organism on this planet undergoes regulated growth. The individual cells become larger, whereas multicellular organisms accumulate many cells through the cell division. You have started as a single cell and then the growth depends on anabolic pathways which build large, complex molecules such as the proteins and the DNA. The DNA is the genetic material.

5. Reproduction

All living organisms can reproduce themselves to create new organisms. Reproduction can be either asexual which involves a single parent organism or can be sexual, which requires two parents. Single-celled organisms, such as the dividing bacterium, can reproduce themselves simply by splitting in two.

In sexual reproduction, two-parent organisms produce sperm and egg cells that contain half of their genetic information. These cells fuse to form a new individual from them with a full genetic set. This process is called fertilization.

6. Response

Living organisms show “irritability,” which means that they respond to stimuli or change according to their environment. For example, people pull their hands away as fast as possible when coming in contact with a flame. Many plants turn towards the sun like sunflowers. There are unicellular organisms that may migrate towards a source of nutrients or even away from a noxious chemical. 

7. Evolution

Populations of living organisms can undergo evolution according to the situation. This means the genetic makeup of a population may change over time. In some cases, evolution involves natural selection

Over the generations, a heritable trait that provides a fitness advantage might become more common in the population, and making the population better suited to its environment. This process is known as adaptation.

FAQ (Frequently Asked Questions)

Q1. Write a Short Note on Introduction to Life.

Ans: Generally, biology is the study of life and living organisms. From one-celled creatures to the most complex living organism of all, human beings come under the study of biology. It includes the study of genes as well as the cells that give all the living things their special characteristics.


All living things on this planet share some basic properties. Cellular Organization, reproduction, metabolism which means to obtain and use energy,  homeostasis, heredity, responsiveness, growth, and also development is adapted through the process of evolution. The unicellular Organisms, the entire organism is made up of only one single cell. For Example, bacteria, and protists. Multicellular Organisms are made up of many cells. They have specialized functions in their cells within the organism.


Reproduction is the process of producing very new organisms of almost the same type. In  Asexual Reproduction, only a single parent organism itself is involved in the process of reproduction. In Sexual Reproduction two different parent organisms contribute genetic information which involves the combination of male as well as female sex cells.


Living organisms need the energy to grow, develop, repair damage, as well as to reproduce. Anabolism is the very process of building complex substances from simpler substances.  Catabolism is the process of breaking down complex substances into very simpler subsets.

Q2. How would You define Life?

Ans: How can one tell that either one thing is alive and another is not?! Describing life is almost difficult as people have an intuitive understanding of what it means for something to be alive. It’s very difficult to come up with a precise definition of life. Due to this, many definitions of life are operational definitions. 

They generally allow us to separate living things from nonliving ones, though they don’t pin down what is life. To make this separation, we come up with a list of properties that are, as groups, and also uniquely characteristic of living organisms.