Gr. 8: Unicellular Organisms

Gr. 8: Unicellular Organisms

Unicellular vs. Multicellular Organism videos

Unicellular Organisms Defined:

Unicellular organisms are composed of a single cell, unlike multicellular organisms that are made of many cells. This means that they each live and carry out all of their life processes as one single cell. Most unicellular organisms are microscopic;

  • Also called microorganisms or microbes since they are only visible under a microscope.
  • The single cell is responsible for feeding, digestion, excretion and reproduction.
  • Some microorganisms make us sick, but without the others we could not survive.
  • The following are examples of unicellular organisms:
    • Bacteria
    • Protists
    • Some Fungi

Multicellular Organisms Defined: 

A tissue, organ or organism that is made up of many cells is said to be multicellular. Animals, plants, and fungi are multicellular organisms and often, there is specialization of different cells for various functions. In contrast, unicellular, or single-celled organisms are much smaller in size and less complex as they are composed of just one cell that senses its environment, gathers nutrients and reproduces asexually. The following are examples of multicellular organisms: human beings, organs and tissues,  plants, animals, birds and insects. 

~Generally speaking, we can say that unicellular and multicellular organisms are alike in that they exhibit all the functions of life, such as metabolism and reproduction, they contain DNA and RNA, they can exhibit a wide range of lifestyles, and they are essential to almost every ecosystem that we currently know of.

Amoeba, Euglena, Paramecium on the move

The paramecium are the larger protists, amoeba are the blob-like protists, and euglena are the smaller unicellular organisms.

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