The foundation for life itself begins with the cell. The cell is the fundamental unit of structure and function in every living thing; however, there are two different types of cells. There are prokaryotic and eukaryotic cells. Prokaryotic cells are smaller and less complex than eukaryotic cells. Prokaryotic cells lack a nucleus, meaning that DNA is not enclosed within the membrane of the nucleus as in Eukaryotic cells. Eukaryotic cells are much more complex than Prokaryotic cells. Eukaryotic cells are characterized by the separation of various organelles into different compartments bound by membranes. Eukaryotic cells do contain a nucleus, and the nucleus is not only the largest part of the cell, but it also encloses the DNA. Whether a cell is prokaryotic or eukaryotic has a great deal of impact on the functioning of the organism. The processes of DNA replication, protein synthesis, and many others are affected by the either eukaryotic or prokaryotic nature of the cells that make up the organism itself, ultimately affecting the way that every intracellular process occurs, including those that pertain to the processing and distribution of genetic information which is coded to design the phenotype and genotype of every living organism.
Just as prokaryotic cells are less complex than eukaryotic cells, prokaryotic organisms are similarly less complex than eukaryotic organisms. There are three domains of life in which each organism is categorized Bacteria, Archaea, and Eukarya. Prokaryotic organisms belong to the domains Bacteria and Archea. Bacteria are the most widespread and diverse prokaryotic organisms, the domain Archaea includes prokaryotic organisms that tend to reside amidst Earths most extreme environments, such as lakes and springs with very high temperatures. The domain Eukarya includes four different kingdoms, each distinguishable by different characteristics such as unicellular, multi-cellular, and method of nutrition. The kingdoms of Eukarya are Protista, Fungi, Plantae, and Animalia. The kingdom Protista consists of unicellular organisms, such as seaweeds. The kingdom fungi, plantae, and anamilia may be characterized by their modes of nutrition. Fungi are organisms that absorb nutrients from their surroundings, such as mushrooms. Plants are organisms that carry out processes such as photosynthesis, providing energy and the cycling of nutrients from light energy to the chemical energy found in food. Animals obtain nutrients by being consumers in the environment, this kingdom is defined by multi-cellular organisms which ingest other organisms.
The distinct features of each cell, whether prokaryotic or eukaryotic, prove to be defining factors in the diversity of life.