Asexual reproduction

Asexual reproduction is reproduction without sex.

In this form of reproduction, a single organism or cell makes a copy of itself. The genes of the original and its copy are the same except for rare mutations. They are clones.

The main process of asexual reproduction is mitosis. This type of reproduction is common among some single-cell organisms such as Amoeba. Many plants also reproduce asexually such as by means of runners. The individual zooids in a particular coral  or bryozoan are usually genetically identical. They are formed by asexual reproduction of the first individual to arrive in a place. One whole order of the rotifers, the bdelloid rotifers, has no sexual reproduction.

Many types of living things have a double cycle. At one stage, they have sexual reproduction, and at another they simply multiply by splitting or producing eggs that develop without being fertilized (aphids). All daughters of the honey bee develop from unfertilized eggs. Asexual reproduction is therefore common in many forms of life.

 Types 
 Binary fission 
Some organisms like bacteria reproduce using binary fission. They split into two, and one bacterium becomes two bacteria. That always leads to daughter cells, and the offspring is identical to the parent.

 Budding 
Budding is similar to binary fission but is used by plants and some animals, which cannot simply split into two the way that bacteria can. In budding, a small part of a plant or animal breaks off, and while they are separated from their "mother", they start to grow until both the "parent" and the "offspring" are the same size and are capable of budding again. That may happen many more times.

 Parthenogenesis 
Parthenogenesis is found in both plants and animals. Eggs develop without fertilisation. Examples occur in water fleas, rotifers, aphids, stick insects, some ants, bees and parasitic wasps. Parthenogenesis is very rare for vertebrates.

 Vegetative propagation 
Vegitative popogation is very common in some types of plants using rhizomes or stolons (such as strawberries). Other plants form bulbs or tubers (for example tulip bulbs and dahlia tubers). Some plants may form a clonal colony, where all the individuals are clones, which may cover a large area.

 Spores 
Fungi (such as mushrooms) produce spores, which may be asexual or sexual. The asexual spores have the genetic material inside, which allows them to make a whole new organism identical to its parent. The spores are produced by mitosis. Different fungi make different kinds of asexual spores, conidia, oidia, and pycniospores. The shape and the colour of the spores can be helpful to identify the species.

 Sexual vs asexual reproduction 
 Type  Advantages  Disadvantages  Asexual reproduction  No mate needed. Many offspring produced quickly  No variation in the offspring.  Sexual reproduction  Genetic variation in the offspring.   Requires both sexes to participate. 

References

 Other websites 
 Asexual reproduction in animals and plants 
 Advantages and disadvantages of asexual reproduction
 Revision site directed towards IGSCE students 

Category:Methods of reproduction