Methanogens, thermophiles, and halophiles are some of the most primitive life firms found on earth

They are the primitive organism means they were the first to inhabit earth, they are often called LIVING FOSSILS Methanogens are found in Rumen of cattles, Halophiles are found in salt lakes, Thermoacidophiles are found in Hot Sulphur springs.

Explanation:

unicellular organisms, like bacteria, are able to perform all life functions within one single cell. multicellular organisms need many different types of cells to carry out the same life processes. each of these special types of cells has a different structure that it perform a specific function.