The basic unit of life is cell. Living organisms are divided into two groups on the basis of their cellular structure: prokaryotes and eukaryotes. The former evolved 2 billion years before the evolution of latter. Around 3.5 billion years ago, prokaryotic organisms dominated our planet. Then, about 1.5 billion years ago, a nucleated cell called eukaryote evolved. The Cambrian explosion, around 0.5 billion years ago, helped in the evolution of multicellular organisms.
Animals, plants, fungi, protozoans, and algae all come under eukaryotic cells, with bacteria being the only organisms that are prokaryotes. They are smaller and simpler in structure as compared to eukaryotes. Prokaryotic cellules have a large surface-to-volume ratio, that helps the nutrients easily and rapidly reach interior parts of the cell. Eukaryotic cellules have a limited surface area, thus, making it very difficult for the nutrients to readily diffuse in the interior parts of the cells. Thus, eukaryotes have complex organs that help them carry out metabolism and other important functions for the survival of the organisms. Although the cells are different in many ways, the main similarity is survival of the organism and carrying out the same process of life.
There are many other cell types in different forms, like neurons, epithelial, muscle cells, etc. But prokaryotes and eukaryotes are the only true cell structures and types. The following points will cover the main similarities.
- The genetic material, i.e., presence of DNA is common between the two cells.
- The presence of RNA is common.
- They both have a cell membrane covering them.
- Resemblances are seen in their basic chemical structures. Both are made up of carbohydrates, proteins, nucleic acid, minerals, fats, and vitamins.
- Both of them have ribosomes, which make proteins.
- They regulate the flow of nutrients and waste matter that enters and exits the cellules.
- Basic life processes like photosynthesis and reproduction are carried out by them.
- They need energy supply to survive.
- They both have 'chemical noses' that keep them updated and aware of all the reactions that occur within them and in the surrounding environment.
- Both these organisms have a fluid-like matrix called the cytoplasm that fills the cells.
- Both have a cytoskeleton within the cell to support them.
- They have a thin extension of the plasma membrane which is supported by the cytoskeleton.
- Flagella and cilia are found in eukaryotes; likewise endoflagella, fimbriae, pili and flagella are found in prokaryotes. They are used for motility and adhering to surfaces or moving matter outside the cells.
- Some prokaryotic and eukaryotic cellules have glycocalyces as a common material. This is a sugar-based structure that is sticky and helps the cells in anchoring to each other; thus, giving them some protection.
- They have a lipid bilayer, known as the plasma layer, that forms the boundary between the inner and outer side of the cell.
There are many differences between them, of which age and structure are the main attributes. It is believed by scientists that eukaryotic cells evolved from prokaryotic cells. In short, both are the smallest units of life.