What is Reproduction in Organisms? Types of Reproduction and Essential Roles of Reproduction in Nature

Overview

What is reproduction? Reproduction is a biological process in which an organism gives rise to new ones (offspring) similar to itself. In other words, we can simply say that reproduction is the ability to procreate. The offspring formed will further grow, mature and in turn produce new offspring. So, we can see a kind of life cycle consisting of birth, growth and death present in every organism.

The ability of feeding and breeding successfully allows organisms to pass their genes to the next generation. Of course, the organisms will die in every generation, but reproduction allows organisms to continue its species generation after generation. This is the life-cycle of every organism present on earth.

Is Reproduction Essential for Survival?

Reproduction is a fundamental role of all living organisms, but it is not a defining feature why? A feature is said to be defining if it fulfills two criteria:

• The feature is present in all living organisms
• The feature is absent in all non-living organisms

As far as reproduction is concerned, it is definitely a fundamental feature of all living organisms to reproduce, but is reproduction essential for survival? The answer is a big NO because there are many organisms surviving on earth, but not reproducing. The most common examples include mule (a cross between male donkey and female horse), worker bees, etc. Both mule and worker bees are sterile in nature and cannot reproduce, but surviving on earth successfully.

How Organisms Decide What Reproduction Type to Choose?

Reproduction is basically of two types – asexual reproduction and sexual reproduction. Well, the million dollar question is how organisms decide what type of reproduction to choose from? The answer to this question lies in organism’s habitat, and internal physiology, etc. Organism’s habitat means the address of the organism where it is residing. Whether organisms are terrestrial or aquatic? If organisms are aquatic then whether they are living in fresh water or marine environment?Internal physiology includes organisms working mechanism.

Asexual and Sexual Reproduction

Asexual reproduction involves the participation of only one organism (single parent) i.e., uni-parental in nature – with or without the involvement of gamete formation. On the other hand, when two parents (opposite sex) i.e., bi-parental participate in the reproductive process and also involve fusion of male and female gametes, it is referred to as sexual reproduction. Well, single organisms can also reproduce sexually. For example, animals that are hermaphrodite or bisexual in nature do not involve two parents because a single organism possesses both male and female sex organs. Hermaphrodite organisms include hydra, sponges, earthworms, etc.

When will an Organism Perform Asexual reproduction?

When an organism reproduces without the involvement of another parent then such kind of reproduction is called asexual mode of reproduction. However, it is not limited to single-celled organisms. Multicellular organisms such as sponges and cnidarians perform asexual reproduction. And, we all know that sessile or sedentary organisms such as sponges that cannot move from one place to another prefer to perform asexual mode of reproduction because they do not need to search for a partner to perform sexual reproduction. So, we can say that asexual reproduction is actually an advantage for sessile organisms.

Cloning is a form of asexual reproduction. Cloning means the formation of morphologically and genetically similar offspring.An individual of a clone is called RAMET. Why cloning is a form of asexual reproduction? It is because in asexual reproduction, there is participation of only one parent and thus no variation is involved. It means, there is no exchange of genetic material. And, therefore, the offspring formed would be genetically and morphologically similar to their parent.

Advantages of Asexual Reproduction

There are many advantages of asexual reproduction. When environmental factors are favorable, meaning when there is abundance of nutrients, adequate shelter, favorable climate, and optimum pH – organisms prefer asexual mode of reproduction. Organisms take full advantage of the rich supply of resources by increasing population exponentially.

Evolution of Sexual Reproduction

It is interesting and intriguing to think why nature evolved sexual mode of reproduction. Well, this has always been a puzzle for biologists. Organisms have to pay two-fold cost of sexual reproduction because only 50 percent of organisms reproduce and only 50 percent of their genes pass on to the next generation. Why only 50% of organisms reproduce and only 50% of their genes pass on to the next generation. The answer to the first question is that in sexual reproduction two parents are involved, but the major contribution is played by females only. For example, in case of humans, the major role of sexual reproduction is played by females. The answer to the second question is that since male and female gametes are formed from two parents – each parent contribute only 50 percent of their genes.

Some Organisms Reproduce Sexually and Asexually

Many organisms reproduce sexually as well as asexually. For example, aphids, sea anemones, slime molds, and some species of starfish reproduce sexually as well as asexually. These organisms change their mode of reproduction based on the changing scenarios. For instance, when food resources have been depleted, climate becomes hostile or individual survival is in danger – these organisms switch to sexual mode of reproduction.

Advantages of Sexual Reproduction

One major reason for sexual reproduction is to bringabout variation because this allows organisms to survive better and variation also provides raw materials for evolution. In case of asexual reproduction – there is no variation because of the involvement of only one parent. However, in sexual reproduction, genes from two different parents mix together and form variation. This variation brings about the ability to sustain unfavorable environmental conditions and provide a mechanism for selective adaptation to occur. The meiosis stage of the sexual cycle also allows effective repair of DNA damages. And sexual reproduction usually results in the formation of a life stage (such as seeds, spores in plants;eggs, pupa, cysts in animals) that is able to endure the conditions that threaten the offspring of an asexual parent.