Biology

Even if you can't see them, that doesn't mean they're not there! Prokaryotes are one good example of why you can't always trust the naked eye to show you everything that's going on around you. Prokaryotes are single-celled organisms that can't be seen without the use of a microscope. Prokaryotic organisms fall into one of two groups: bacteria and archaea. Despite bacteria’s bad reputation as the cause of diseases in humans, animals, or plants, most bacteria are harmless, and they function as beneficial ecological agents. Archaea, too, fulfill important ecological roles in cold and temperate ecosystems. Without archaea and bacteria, our lives would be much more difficult: soil would not be fertile, and our ability to prepare certain foods, chemicals, and antibiotics would be hindered, among other difficulties.

The field of biology is subdivided into separate branches for convenience of study, though all the subdivisions share basic principles. Biology encompasses fields such as botany, genetics, marine biology, microbiology, molecular biology, and much more.

Even if you feel you have nothing in common with a stinkbug or a ficus, you're guaranteed to share one crucial aspect of life with these beings: you are all made up of cells, the fundamental molecules of life, of which all living things are composed. As an individual unit, the cell is capable of metabolizing its own nutrients, synthesizing many types of molecules, providing its own energy, and replicating itself. In a multicellular organism, cooperative assemblies of similar cells form tissues, and a cooperation between tissues in turn forms organs, which carry out the functions necessary to sustain the life of an organism.

Earth has housed a vast variety of plants, animals, and other living things throughout the history of its existence, and many living things have changed in discernible ways over the years. The theory of evolution, one of the fundamental keystones of modern biological theory, examines the way in which such changes unfold. Heredity describes the biological processes by which certain characteristics are transmitted from parents to their offspring. Genetics studies heredity in general and genes in particular.

Fungi, protists, and viruses may not be the most cuddly of organisms, but they’re no less worth studying for it. Fungi, whose ranks include yeasts, rusts, molds, and mushrooms, are among the most widely distributed organisms on Earth. Protists such as algae and protozoans are microscopic eukaryotic organisms. Viruses are infectious agents of small size and simple composition that can multiply only in living cells of animals, plants, or bacteria.

None of us are born looking exactly the way that we do today; this is because humans, like other species, undergo a series of changes as they mature and age, in accordance with their biological life cycle. This process can look very different across different species. In many simple organisms and in higher animals, the life cycle is completed within a single generation, while in most plants, the life cycle is multigenerational.