Asexual reproduction can be defined as the process by which offspring are produced from a single parent rather than through fertilization. It is most common in environments that favor rapid population growth over genetic diversity, as the offspring inherits its genetic traits completely from one parent. The methods of asexual reproduction vary greatly among different types of species.
Some protozoans and many bacteria, plants and fungi reproduce via spores. Spores are structures naturally grown as part of an organism's life cycle and designed for separation from the organism and dispersal via a medium such as air or water. When conditions are correct, the organism will release its spores, which are each then considered entirely separate and autonomous organisms. Given an environment suitable for life, the spores will then develop into fully grown organisms and eventually grow their own spores, repeating the cycle.
Prokaryotes and some protozoa reproduce via binary fission. Fission occurs at the cellular level when a cell's contents are replicated internally and then subjected to division. The cell then forms into two distinct entities and separates itself. Each partial cell then reconstitutes the missing parts of its internal structure. At the end of the process, the single cell has become two new fully developed cells, each with identical genetic properties.
Many plants have evolved specialized genetic features that allow them to reproduce without the aid of seeds or spores. Examples include the prostrate aerial stems of strawberries, the bulbs of tulips, the tubers of potatoes, the shoots of dandelions, and the keikis of orchids. This form of specialization is most common in environments with seasonally harsh conditions; it allows plants to survive and thrive in situations where the traditional seeding process is subject to frequent interruption.
Organisms like proteins, yeast, and some viruses reproduce via budding, a process by which an entirely new organism grows on an existing one. Unlike fission, this is not brought about by the separation of an existing organism into two partial entities. The developing organism begins its life as an entirely separate life form from its "parent", separating into an autonomous entity only when it has fully matured. As the "child" organism proceeds through life, it will produce its own buds.
Segmented worms and many echinoderms such as starfish reproduce asexually via fragmentation. In this process, an organism physically splits and develops new, genetically identical organisms out of each segment. The segments rapidly grow new cells to constitute their muscle fiber and internal structure through mitosis. This split can be either intentional or unintentional on the part of the organism.