The dog I can hear barking is alive, and so is the tree outside my window. However, snow falling from the clouds is not alive. The computer you’re using to read this article is not alive, and neither is a chair or table.

What is living?

Anything which shows characteristics of life is called living. The fundamental characteristics of life are- growth, reproduction, metabolism, cellular organization and consciousness. Living things are highly organized, meaning they contain specialized, coordinated parts.

Growth

Living things tend to grow in size. The increase in the number and mass of individuals are two unique characteristics of growth. Multicellular organisms exhibit growth by cell division. Growth varies in plants and animals. If we consider unicellular organisms, they tend to grow in size by cell division. Moreover, this can be easily detected by counting the cells during in vitro cultures under a microscope.

Reproduction

Reproduction is the process by which organisms replicate themselves.

Reproduction can primarily be of two types- sexual reproduction and asexual reproduction.   

Reproduction generally refers to sexual reproduction. Asexual reproduction is used by the lower organisms like Bacteria that divide asexually via Binary fission, Virusestake control of host cells to produce more viruses; Hydras (invertebrates of the order Hydroidea) and Yeast are able to reproduce by Budding.

Sexual reproduction is a biological process that creates a new organism by combining the genetic material of two organisms in a process that starts with, meiosis a specialized type of Cell division

 

budding of Hydra

Metabolism

Metabolism is the sum of the chemical reaction that takes place within each cell of a living organism and that provides energy for vital processes and for synthesizing new organic material.

All living organisms are made up of chemicals. These chemicals, small and big belonging to various classes, size and function, etc are constantly being made and changed into other biomolecules.

There are thousands of metabolic reactions occurring simultaneously inside all living organisms, be they unicellular or multicellular.

Cellular organization

Cellular organization – All living organisms are made up of cells that perform all functions inside the body. The cellular organization is the components that make up the cell and how they are arranged inside it. Each component called an organelle, performs a specific function vital for the cell.

Consciousness

All living organisms have an inherent ability to sense their surroundings or environment and respond to their environmental stimuli which could be physical, chemical, or biological. Plants and animals both respond to external stimuli. Human beings are the only organisms who are aware of themselves, i.e., have self-consciousness.