Question

The single-celled organism are called as

Answer 1

Hint: A single-celled organism is also known as unicellular organisms. They are that category of living organisms that possess a single cell. They are mostly the bacteria, examples of such bacteria are protozoa, salmonella, E. coli bacteria, etc. single celled fungi algae are also some examples. Unicellular organisms are considered as biologically immortal.

Complete answer:
A single-celled organism or the unicellular organism consists of everything they need to live or to survive within its single cell space. These cells obtained energy from complex molecules, for locomotion, and to sense their outer environment efficiently. The ability of such single-celled organisms, to perform these functions and other functions as well, is part of their cellular organization within the cell. One of the striking features of living organisms is that living things always show an increase in size.

There are two types of the single-celled organisms. One is prokaryotes and the other is eukaryotes.

Prokaryotes-
-Are those types of organisms that lack the general occurring cell organelles in their cells like mitochondria, Golgi bodies, etc? They do not consist of a proper well-defined nucleus but, nucleoid is present, without a proper nuclear wall, containing genetic material of a cell.
-Average size of generally occurring prokaryotes ranges from 0.1 to 5.0 micrometers.
-Tail like structure is present called as flagellum which helps in locomotion.
-Examples of prokaryotic cells are blue-green algae, E. coli, and mycoplasma.

Eukaryotes-
-They are somewhat bigger in size as compared to prokaryotes. They consist of the membrane bound organelles like well-developed nucleus, mitochondria, etc. these organelles perform various functions in the cell from simple to complex.
-Capable of reproduction and reproduction takes places from mitosis or meiosis process.
-Some examples of single cell organisms are fungi like yeast, other examples are saccharomyces cerevisiae which is used in baking industries.

Note: According to the studies multicellular organisms come from the unicellular organisms in the process of gradual evolutionary development, including humans and plants also.
A unicellular organism is thought to be the first on earth and thus forms the basis of the origin of life on this planet earth, which originated about 3.5 billion years ago.