Q. Define the Organization Levels of Life?

Ans. The cell is the basic unit of life - the smallest unit that can carry on all the processes of life. Organisms that consist of a single cell are unicellular. These are the most numerous of all life forms. Multicellular organisms can be made up of billions of cells, or only a few. These organisms are produced by divisions of existing cells.

Some cells are organized to perform particular functions in plants and animals. An aggregation of cells that carries out a certain function is called a tissue. Muscle tissue is an example.

Several types of tissue can function together as an organ. For instance, the human stomach and intestines are organs made up of epithelial tissues (sheets of tightly connected cells like those in skin) along with nerve tissues, vascular tissues, and muscle tissues.

These organs are themselves parts of an organ system, which we call the digestive system. Plant organ systems, such as a root system and a stem system, function to absorb and transport water, minerals and nutrients, as well as provide surface protection, support, and internal storage.

An organism is composed of many organ systems that together carry out all the functions that sustain life. In unicells, a single cell assumes these functions.

In some species, individual cells are capable of sustaining life, but multicellular aggregationsare formed for reproduction, locomotion, or other purposes. An example is the cellular slime mold,Dictyostelium, in which single cells aggregate to form a stalked reproductive structure.

A group of organisms that can interbreed with each other to form viable, fertile offspring is referred to as a species. A population refers to a group of organisms of the same species within a given physical area.

Populations of different organisms within a given physical area are said to form a community.

The community, taken together with its physical environment, is called an ecosystem, and ecosystems join to compose our living world, the biosphere.