Earthlife states that an organism that is composed of groups of cells that work together is called multicellular. All living things consist of one or more cells, and almost any living thing visible without a microscope is a multicellular being. There are three kingdoms of multicellular organisms: plants, animals and fungi.
The Encyclopedia Britannica states that multicellular organisms have many cells that are integrated and independent to varying degrees. Cellular specialization and division of labor accompany the development of multicellular organisms. This means that cells become efficient in a certain process and depend on other cells for the necessities of life.
According to the BBC, the advantages of multicellular organisms over unicellular organisms include larger size, higher complexity and cell differentiation, which means they consist of different types of cells that have varying functions. Multicellular organisms have specialized organ systems that perform various functions. The respiratory and excretory systems control exchanges with the environment. The digestive system supplies cells with nutrients, and the nervous and circulatory systems allow communication between cells.
The BBC explains that there are two types of cell division among unicellular and multicellular organisms. Through mitosis, organisms grow, repair and produce diploid cells that are identical to one another and to the parent cell. The other type of cell division is meiosis, which is used for sexual reproduction.