Common Types of Asexual Reproduction

In asexual reproduction, one individual produces offspring that are genetically identical to itself. Reproduction is a marvelous culmination of individual transcendence in that organisms "transcend" time through the reproduction of offspring. In animal organisms, reproduction can occur by two primary processes: asexual reproduction and sexual reproduction.

Organisms produced by asexual reproduction are the product of mitosis. In this process, a single parent replicates body cells and divides into two individuals. Many invertebrates, including sea stars and sea anemones, reproduce in this manner. Common forms of asexual reproduction include: budding, gemmules, fragmentation, regeneration, binary fission, and parthenogenesis.

Budding: Hydras

Hydra with Buds — Many hydras reproduce asexually by producing buds in the body wall, which grow to be miniature adults and break away when they are mature. Ed Reschke/Photolibrary/Getty Images

Hydras exhibit a form of asexual reproduction called budding. In this form of asexual reproduction, an offspring grows out of the body of the parent, then breaks off into a new individual. In most instances, the budding is restricted to certain specialized areas. In some other limited cases, buds may come from any number of places on the body of the parent. The offspring typically remain attached to the parent until it is mature.

Gemmules (Internal Buds): Sponges

Sponge With Budding Progeny — Progeny are budding on the body of a sponge in the Red Sea. Jeff Rotman Photography/Corbis Documentary/Getty Images

Sponges exhibit a form of asexual reproduction that relies on the production of gemmules or internal buds. In this form of asexual reproduction, a parent releases a specialized mass of cells that can develop into offspring. These gemmules are hardy and can be formed when the parent experiences harsh environmental conditions. The gemmules are less likely to become dehydrated and in some cases may be able to survive with a limited oxygen supply.

Fragmentation: Planarians

Planarians exhibit a form of asexual reproduction known as fragmentation. In this type of reproduction, the body of the parent breaks into distinct pieces, each of which can produce an offspring. The detachment of the parts is intentional, and if thy are large enough, the detached parts will develop into new individuals.

Regeneration: Echinoderms

Starfish Regeneration — Starfish are able to regrow missing limbs and produce new organisms through regeneration. Paul Kay/Oxford Scientific/Getty Images

Echinoderms exhibit a form of asexual reproduction known as regeneration. In this form of asexual reproduction, a new individual develops from a part of another. This typically happens when a part, like an arm, becomes detached from the parent's body. The separated piece can grow and develop into a completely new individual. Regeneration can be thought of as a modified form of fragmentation.

Binary Fission: Paramecia

Paramecium — This paramecium is dividing by binary fission. Ed Reschke/Photolibrary/Getty Images

Paramecia and other protozoan protists, including amoebae and euglena, reproduce by binary fission. In this process, the parent cell duplicates its organelles and increases in size by mitosis. The cell then divides into two identical daughter cells. Binary fission is typically the most common form of reproduction in prokaryotic organisms such as bacteria and archaea.

Parthenogenesis

Parthenogenesis involves the development of an egg that has not been fertilized into an individual. Most organisms that reproduce through this method can also reproduce sexually. Animals like water fleas reproduce by parthenogenesis. Most kinds of wasps, bees, and ants (which have no sex chromosomes) also reproduce by parthenogenesis. Additionally, some reptiles and fish are capable of reproducing in this manner.

Advantages and Disadvantages of Asexual Reproduction

Sea Star Fragmentation — This sea star has lost an arm which can develop into a new sea star by the asexual process of fragmentation.
Karen Gowlett-Holmes/Oxford Scientific/Getty Images

Asexual reproduction can be very advantageous to certain higher animals and protists. Organisms that remain in one particular place and are unable to look for mates would need to reproduce asexually. Another advantage of asexual reproduction is that numerous offspring can be produced without "costing" the parent a great amount of energy or time. Environments that are stable and experience very little change are the best places for organisms that reproduce asexually.

One major disadvantage of this type of reproduction is the lack of genetic variation. All of the organisms are genetically identical and therefore share the same weaknesses. A gene mutation can persist in the population as it is continuously repeated in the identical offspring. Since organisms produced asexually grow best in a stable environment, negative changes in the environment can have deadly consequences for all individuals. Due to the high numbers of offspring that can be produced in a relatively short period of time, population explosions often occur in favorable environments. This extreme growth may lead to rapid depletion of resources and an exponential death rate in the population.

Asexual Reproduction in Other Organisms

Puffball Fungus Spores — This is a colored scanning electron micrograph (SEM) of puffball fungus spores. These are the reproductive cells of the fungus. Credit: Steve Gschmeissner/Science Photo Library/Getty Images

Animals and protists are not the only organisms that reproduce asexually. Yeast, fungi, plants, and bacteria are capable of asexual reproduction as well. Yeast reproduce most commonly by budding. Fungi and plants reproduce asexually through spores. Plants can also reproduce by the asexual process of vegetative propagation. Bacterial asexual reproduction most commonly occurs by binary fission. Since the bacterial cells produced through this type of reproduction are identical, they are all susceptible to the same types of antibiotics.