Cows, buffaloes, elephants, monkeys, dogs and cats are all examples of multicellular organisms. Humans are the most complex of all multicellular organisms. All such organisms have billions of cells, tissues and different organ systems in the body.Continue Reading
All multicellular organisms may be seen with the naked eye, as they are large. Multicellular organisms have evolved from unicellular organisms. They have specialized cells for performing different functions. The cells of the heart are different from the cells of the liver and the brain.
As opposed to multicellular organisms, there are unicellular organisms, such as amoeba, paramecium, viruses of various kinds and bacteria. They do not have a well-defined organ structure or organ systems within their bodies.Learn more about Cells
In the cells of eukaryotic organisms, the subunits that will become ribosomes are produced within the subnuclear structure called the nucleolus, and the subunits then combine in the cell's cytoplasm to become functioning ribosomes. Because the ribosomes are the protein manufacturers of a cell, the size of the nucleolus can take up as much as 25 percent of the volume of the nucleus in cells that require large amounts of protein. Most eukaryotic cells contain only one nucleolus, but certain species can contain several.Full Answer >
Cells need oxygen for the efficient use of glucose in cellular respiration, the main method most organisms use to gain energy. The oxygen bonds to portions of the glucose molecule, releasing water, carbon dioxide and a large amount of energy. The cells then use that energy to generate adenosine triphosphate, commonly abbreviated as ATP, the main energy currency used by the cell.Full Answer >
Prokaryotic cells are single cells that evolved before eukaryotes, which are organisms whose cells contain nuclei and organelles. A prokaryotic cell has no true nucleus or membrane-bound structures called organelles. Prokaryotic cells are usually bacterial species.Full Answer >
Some bacteria manufacture and absorb their own food, while others must consume substances like living organisms or decaying material through their cell walls. Bacteria break down food in a process called respiration, which for some strains of bacteria requires oxygen to complete.Full Answer >