Question

Define unicellular and multicellular organisms. Give an example?

Answer 1

Hint: Every organism is made of cells. Unicellular consists of only a single cell and multicellular consists of more than one cell.

Complete Answer:
- They are also known as single-celled organisms as they contain a single cell and they carry out their life processes as one single cell.
(I) Unicellular organisms include Bacteria, Protozoa, Fungi, Algae, Archaea. For example: paramecium is a unicellular and slipper-shaped organism which takes in food from water as they are found in pond water and digest it in organelles which is called Food vacuoles.
Some of the examples of unicellular organisms are: Escherichia oil, Diatoms, Streptococcus, Pneumococci, Protista.

Characteristics of Unicellular Organisms:
- Usually reproduce by asexual means.
- They can be eukaryotes or prokaryotes.
- Possess whip-like structures for movement.
- Nutrients enter the diffusion process.

(II) Multicellular organisms- These are the organisms that contain more than one cell. Animals, plants, and most of the fungi are multicellular. These organisms arise by cell division or aggregation of many single cells.
Examples of some Multicellular Organisms: Humans, Horse, Trees, Dogs, Cows, Chicken, Cats.

Characteristics of Multicellular Organisms:
- They are complex organisms.
- They are easily visible to the naked eyes.
- Possess distinct organs and organs systems.
- They contain membrane-bound structure.
- The size increases with the number of cells in an organism.

Note: Multicellular organisms face the challenge of cancer (due to the failure of cells to regulate growth as the normal program of development).