Asexual reproduction definition in biology

Contrary to sexual production where a male and a female are involved in reproduction, asexual reproduction happens with one single parent. There is no fertilization requirement and no fusion of gametes (cells i.e. egg in female and sperm in the male). The offspring in this case are essentially clones that are genetically identical with their parents and siblings.

Examples of asexual reproduction

Asexual reproduction happens both in plants and animals. Potatoes and daffodils from plants and hydra and starfish from animals are some of the organisms that undergo asexual reproduction (De Meeûs, Prugnolle, & Agnew, 2007).

An interesting example of asexual reproduction in animals is starfish. In some cases, starfish splits into two halves and each half develops as a complete starfish gradually. Sometimes, an arm of the starfish is broken. In this case, not only does the parent starfish develop a new arm for its completion, but the disengaged arm also develops by asexual reproduction to form a complete starfish by and large.

Figure 1: Starfish

Other examples include sharks, komodo dragons, whiptail lizards, and almost all of the planarians. Planarians are asexually reproducing organisms belonging to evolutionary early groups. If they are cut into pieces, each piece will regenerate into a complete organism.
Asexual reproduction in plants takes place by mitosis (a process of cell division to produce two identical cells). For example, in the case of potatoes, the developed underground food storage organs detach and develop new plants (Neiman, Sharbel, & Schwander, 2014).
There are several advantages and disadvantages of asexual reproduction in animals and plants described below:

Advantages of asexual reproduction

There are several benefits of asexual reproduction as listed below:

1. Simplicity: Unlike the sexual reproduction system that is characterized as a complex and extensive time- and energy-consuming process, asexual reproduction is quite simple and requires less amount of time and energy (Engelstädter, 2008).
2. More Flexibility: The species that exhibit asexual reproduction have genetic flexibility to embody themselves in different forms. It is, therefore, easy for them to produce offspring in a variety of environments (De Meeûs et al., 2007).
3. Better Survival: As a result of asexual reproduction, most of the organisms reproduce exponentially, some of them reproducing billions of offspring in one single season. A huge number of such species enables them to survive even if the ecological conditions vary or the number of predators change (Schmidt, Schmid, & Grossniklaus, 2015).
4. No Need to Find Mating Partner: As aforementioned, since asexual reproduction results in huge colonies of the organisms, it is very easy for such species to find a mating partner(s). On the contrary, it is very difficult, sometimes next to impossible, to find a mating partner in case of sexual reproduction. It becomes harder especially when the species have to colonize new areas (Schmidt et al., 2015).
5. Able to Do Emergency Reproduction: Climatic severities or ecological disturbances, at times, can lead to catastrophic situations posing serious threats to the survival of the organisms, plants for example. In such cases, the plants capable of asexual reproduction can stay alive and undergo the reproductive process to produce a large number of their replicates even without a mate. Such plants have the ability to clone themselves even without a pollinator (Purcell, 2007).
6. No Need for Mobility for Reproduction: A large number of plants and animals have a natural inability for their self-locomotion, that is, the natural motility of such organisms is absent due to a biological property called sessility. Asexual reproduction enables such creatures to make offspring while staying at the same location throughout life. Most of the immotile organisms are found to have excellent ability to reproduce via asexual reproduction (Engelstädter, 2008).
7. Less Time and Energy Requirements: Due to the simplicity of its process, the asexual reproduction phenomenon requires only a little time and (hardly any) energy to produce offspring  (Engelstädter, 2008).
8. Better Sustainability: During sexual reproduction, many living beings die during the reproduction stages or at the time of delivery due to either a harsh environment, delicate organs, or biological complications. However, no such complexities or calamities are encountered in the case of asexual reproduction, hence eco-friendliness prevails (Silvertown, 2008).
9. Augmented Reproduction: Asexual organisms can reproduce themselves exponentially as soon as they settle themselves in suitable habitat (Yang & Kim, 2016).
10. Little Investment: Unlike sexual reproduction, where the living beings generally give birth to a single offspring (exceptions exist) and have to take care of it for quite some time, asexual reproduction has the advantage of the production of multiple offsprings that are not necessarily required to keep along with the parent organism. Therefore, asexual reproduction is characterized by little investment of time and money (Yang & Kim, 2016).

Apart from these, can anyone find advantages of asexual reproduction in plants?

Disadvantages of Asexual Reproduction

1. Extinction Vulnerability
Parasites and predators are very much a part of the ecological system. Organisms born as a result of asexual reproduction inherit the characteristics and weaknesses same as the parent species. If the predators are strong enough to kill one or few of the organisms, they can definitely kill the entire colony because all of the organisms have the same level of immunity (Schmidt et al., 2015).

2. Impact of Extreme Conditions
Asexual reproduction can result in extreme temperatures leading to highly unfavorable conditions to sustain. At times, the entire colony of the asexually reproduced organisms is wiped out due to extreme conditions (Engelstädter, 2008).

3. Lack of Population Control
In one reproduction cycle, each organism reproduces at least one duplicate self. This means that the population is doubled in just one reproduction cycle. There is hardly any self-regulated control mechanism to control the population. However, scientists are of the view that the increase in population would decrease after an excessive population is already reproduced (Neiman et al., 2014).

4. Crowding Issues
Due to overcrowding, the asexually reproduced organisms have to fight for their existence within their community (Yang & Kim, 2016).

5. Space and Food Shortage
At times, multiple parent organisms undergo asexual reproduction and produce offsprings that are close to each other locality-wise. It potentially originates a competition between them to acquire food and space (Yang & Kim, 2016).

6. Genetic Similarity
Asexual reproduction results in the birth of organisms that are genetically similar to a great extent. In case of any severe environmental changes, they are less immune to adaptability and are vulnerable to die (Purcell, 2007).

7. Genetic Defects
Since only a single parent takes part in asexual reproduction, any genetic defects and/or mutations are inherited into the offspring and this goes on and on from one generation to all forthcoming generations (Purcell, 2007).

8. Negative Mutations and Diseases
The asexually reproduced organisms can potentially encounter negative mutations that make them vulnerable to many diseases and consequent destruction on a massive level (Purcell, 2007).

9. Adaptability
Since the asexually reproduced organisms are less motile or immobile altogether, such animals and plants both are more susceptible to environmental severities, and attacks by predators and diseases (Yang & Kim, 2016).

10. Diversity
Sometimes genetic diversity is undesired. So, the lack of genetic diversity in asexually reproduced organisms is both a merit and a demerit simultaneously (Yang & Kim, 2016)

Want to read more about complete mechanisms and types of asexual reproduction. Don’t forget to check https://www.biologyonline.com/dictionary/asexual-reproduction

Do you think of some other disadvantages of asexual reproduction?
Alright, so I hope this article has clarified a lot of things related to asexual reproduction. Here is a little question you can answer in the comments below. Rapid reproduction is an advantage of which process? Asexual or sexual?

Thought question: Can humans produce asexually? Using one of his or her cells to produce a replica or original? What technologies are involved? Will be happy to read your answers about this.