Similarities between sexual and asexual reproduction

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Similarities between sexual and asexual reproduction

Introduction

Reproduction, also known as procreation or breeding, is essential to all forms of life as without it; living organisms will most likely become extinct after a single generation. These various processes are defined as the biological methods used by living organisms to produce new individuals in order to prolong the survival and continuation of a particular lineage or species [1]. There are two main types of reproduction in living organisms, namely sexual and asexual reproduction. While asexual reproduction involves a single parent and results in the generation of offspring that are genetically identical to the parent; sexual reproduction on the other hand involves contribution of genetic information from two parents in order to produce unique offspring [2]. While both of these processes have a range of similarities and differences between them, each individual process has their own advantages and disadvantages depending on the organism and surrounding environment in which they live.

 What is sexual reproduction?

Sexual reproduction is defined as a process where two different individuals allow fusion of their reproductive cells to form a new distinct being which is commonly referred to as offspring. The formation and fusion of gametes from two different individuals are essential for the formation of their offspring which usually requires what is known as male sperm and female eggs to complete the process. These reproductive units are defined as the germ cells of the parents and involve a meiosis stage during gamete formation. Initially the cells of individual parents have two sets of chromosomes and are thus known to be diploid. However when the sexual cells form (also known as gametes) they undergo a process of cell division known as meiosis. This results in cells with one set of chromosomes thereby making them haploid.

The offspring that arises as a result of sexual reproduction occur due to gamete fusion from the male and female cells. During meiosis, a process of crossing over occurs resulting in recombination of genes which means that the offspring are genetically different from the parent cells as well as different from other offspring which may be produced by the same parent individuals. After fertilization occurs, both sexual cells fuse into one to form a zygote [2]. This fusion results in restoration of the diploid state. Sexual reproduction is a common form of reproduction in animals, plants, some protists and fungi.

What is asexual reproduction?

Asexual reproduction is commonly defined as the production of offspring without sex. This form of reproduction usually involves a single parent or sex cell that makes an identical copy of itself [3]. This means that the genes of the original parent cell as well as the offspring will be the same unless an unusual mutation has occurred. These offspring are usually referred to as clones [4]. While sexual reproduction involves the process of meiosis, the main process of asexual reproduction is known as mitosis and involves no formation and fusion of gametes. Since the reproductive process is uni-parental and involves only mitotic divisions, these processes are quite rapid and result in the production of large numbers of offspring. Asexual reproduction commonly occurs in plants and single-celled organisms like amoeba.

Types of sexual reproduction

There are two main types of sexual reproduction and these are known as conjugation and syngamy [3]. Conjugation is also known as genetic recombination that occurs between two organisms. It is a short-term pairing process of two parent organisms in an attempt to exchange male and female gametes via a temporary cytoplasmic bridge. Syngamy, on the other hand is also known as fertilization and involves the complete fusion of two haploid gametes from parent organisms. This fusion is permanent and allows for the formation of a diploid zygote. It is one of the most common forms of sexual reproduction and involves gametes known as the sperm and ovum.

Types of asexual reproduction

There are several different types of asexual reproduction but the most common ones include binary fission, budding, fragmentation and spores. Binary fission is very similar to the process of mitosis and involves a single parent cell splitting and becoming two daughter cells. Both daughter cells should be identical however since mutations can occur, some daughter cells may be slightly different [5]. Each daughter cell then develops further to form individual parent cells which undergo binary fission again to form their own daughter cells and so on. Budding, while similar to binary fission occurs when a small part of a plant or animal breaks off. Both then start to grow until the parent and offspring are the same size and capable of budding again [6]. Fragmentation occurs when a piece of an individual species breaks off and a completely new organism forms around that broken piece. This usually occurs in species that have viable parts that can survive independently from the parent organism. Spores are a commonly used measure of reproduction by many plants and fungi. During the diploid phase of their life-cycle, these asexual organisms produce diploid spores which contain the genetic material inside [5]. This genetic material then allows them to make a whole new organism that is identical to the parent and which does not need fertilization from a mate.

Advantages and disadvantages

Each form of reproduction has their own advantages and disadvantages depending on the species and surrounding conditions. Asexual reproduction is best for organisms that stay in one particular place and in stable unchanging environments [2]. These organisms are usually unable to look for a suitable mate which makes this mode advantageous. That being said, one of the biggest disadvantages associated with asexual reproduction is that it does not lead to genetic variations between organisms [6]. This in turn could mean that entire clusters of an organism could be wiped out by diseases or surrounding environmental changes as the majority of offspring are identical to the parent cells. Sexual reproduction on the other hand allows for genetic variations between parents and offspring which in turn allows for evolution and adaptations to change environmental conditions. However, a great deal of energy and effort is usually required to find a suitable mate.

Similarities between sexual and sexual reproduction

While there are a vast range of differences between sexual and asexual reproduction, there are however fewer similarities between the two [1]. Regardless of the differences, they both still form a mode of reproduction that is meant to continue the lineage of life forms. Both modes of reproduction pass on genetic material and result in the production of offspring that are then able to go on and reproduce themselves either asexually or sexually to form more offspring [4]. Both forms use DNA to create new life forms and both have a mitosis phase. The offspring also have the same number of chromosomes as the original parent cells. Both of these forms of reproduction occur in plants, fungi and animals however the specific form of reproduction will depend on the species [3].

Conclusion

Reproduction, regardless of the type is essential for sustaining and prolonging lineages of all life forms [1]. While asexual reproduction may involve one parent organism, sexual reproduction requires two, a male and female. While some plants and unicellular organisms reproduce asexually, many mammals utilise sexual reproduction. On the other hand, some organisms like corals, can reproduce using both sexual and asexual means depending on the surrounding conditions [4]. Despite their mode of reproduction, each has their own advantages and disadvantages that are aimed at ensuring survival and continuation.

Comparison of sexual and asexual reproduction

  Asexual Sexual
Parent organisms required One parent Two parents
Cell division methods Fission, budding, regeneration Meiosis
Common types of reproduction Budding, binary fission, fragmentation, spores Syngamy, conjugation
Advantages Time effective, requires less energy, does not require searching for a mate Allows for genetic variations and evolution of a species
Disadvantages No genetic variation which could lead to entire groups being destroyed by disease Requires a mate to reproduce and more energy
Chance of evolution Very little unless a mutation occurs High chance due to genetic variation in offspring
Gametes No formation and fusion of gametes Formation and fusion of gametes
Time taken Short periods Long periods of up to several months
Number of offspring produced Two or more One or more
Similarities Mode of reproduction that allows for genetic material to be passed on
Results in offspring
Allows for continuation of a species
Both have a mitosis phase
Offspring have the same number of chromosomes as the parent cells

Author: Shalinee Naidoo

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