[Biology Class Notes] on Asexual Reproduction in Animals Pdf

Basically, asexual reproduction is a type of reproduction which involves simple division of the organism with the help of a single parent with or without the involvement of gamete formation. This type of reproduction is generally found in single-celled organisms. As a result, a single parent split into two daughter cells that have their own identity. The offspring organisms are physically and genetically identical to their parent cell or we can say a carbon copy. Asexual reproduction is the main type of reproduction found in single-celled organisms. However, asexual reproduction is less commonly found in the animal kingdoms. Also, asexual reproduction is commonly seen in living things and takes a variety of forms. There are rapid multiplications and growth seen in a small period of time but sometimes some of the asexual cells die when they are very young. It has been seen that the asexual reproduction animals are generally found in freshwater than in the oceans. Such type of reproduction is more prominent in small species and is not so popular in large species. It has been seen that asexually reproducing species are more commonly present in polar areas and temperate regions as compared to the tropical regions.

 

The different modes of asexual reproduction in animals are Binary Fusion, Fragmentation, Budding, Parthenogenesis, Gemmules, and Regeneration. Some examples are explained below that help in understanding the concept in a better way. 

 

Features of Asexual Reproduction

• In asexual reproduction, only one parent is involved.

• The process of this reproduction is instant as compared to sexual reproduction.

• There is no involvement of gamete formation and fertilization.

• Offspring growth is rapid in asexual reproduction.

• There is no variation in this reproduction, as offspring organisms are carbon copies of their parents.

 

Some of the Examples of Asexual Reproduction in Animals 

There are various examples of asexual reproduction in animals that provide a better understanding of the topic. 

1. Bacteria – In bacteria, asexual reproduction happens by splitting into two ‘daughter’ cells that are genetically identical to their parents. In this, the genetic material is passed ‘horizontally’ from one organism to another instead of ‘vertically’ from parent to the child. This involves very fast reproduction and that is the only reason why the bacteria are so quick to develop antibiotic resistance.

2. New Mexico Whiptail Lizards – All New Mexico whiptail lizards are females and are capable of reproducing an independent population. This species of lizard was created by the hybridization of two neighboring species.

 

Types of Asexual Reproduction 

Here, we are going to discuss some types of asexual reproduction seen in animals. 

• Binary Fusion – Bacteria and amoeba are the main organisms in which this method of reproduction is seen. In this, the DNA of the parent bacteria replicates itself and gets divided into two parts where each part has its own DNA. Hence, the parent cell divides into two identical daughter cells and these cells are identical to the parent cell.

i) Simple Binary Fission – It can occur at any place. For instance- Amoeba

ii) Longitude Binary Fission – It occurs in Flagellates such as Euglena.

iii) Transverse Binary Fission – The main example of this binary fission is Paramecium, Planaria, Diatoms, and bacteria.

iv) Oblique Binary Fission – It occurs in Cerium.

• Fragmentation – In this type of method of asexual reproduction, the parent organism is divided into multiple segments and each of the fragments develops into a new organism. One of the most common examples of this mode of asexual reproduction is Starfish. Any part of its body such as the arm can give rise to an entirely new organism.

• Budding – In this mode of reproduction, the offspring develops on the body of the parent just like a bud. Echinodermata and hydra are common examples of this type of asexual reproduction. Here, the bud falls of the parent body and starts its own independent existence.

i) Exogenous/ External Budding – In this kind of budding, a bud grows on the surface of the body. This growing bud splits away from the parent and takes an independent existence. The newly grown bud may remain attached to the parent or would become a parent itself and create independent members.

ii) Endogenous/ Internal Budding – A few marine sponges buds are formed within the parent’s body in freshwater sponges (e.g. Spongilla).

iii) Strobilation –The repeated formation of similar segments with the help of the budding process is called strobilation. Partitioned part of the body is called a strobila (i.e. scyphistoma) larva and each segment is called an ephyra larva as found in Aurelia (a coelenterate).

• Parthenogenesis – In this type of asexual reproduction, the female organism produces eggs without fertilization, and offspring are created. Lizards, some fishes, and insects are the common examples of Parthenogenesis asexual reproduction.

• Gemmules – In this type, the parents release a specialized mass of cells that develop into offspring. These gemmules can be formed at a time when parents feel harsh environmental conditions around them.

• Regeneration – It is the formation of the whole body of an organism from the small segment (morphallaxis) or the replacement of the lost part (epimorphosis). It is mainly found in amoeba, hydra, sponge, planaria, and many more organisms.

i) Reparative Regeneration – In this, only certain damaged tissues can be regenerated.

ii) Restorative Regeneration – In this, severed body parts can be redeveloped or developed into a complete body.

 

Advantages of Asexual reproduction

1. With the help of asexual reproduction, population increases rapidly. It is e
   specially useful for species whose survival strategy is to reproduce at a fast pace. One of the common examples is bacteria.

2. In asexual reproduction, species find their members themselves like fungi that grow from wind-blown spores.

3. Asexual reproduction is often accomplished by just having a part of the parent organism.

4. This reproduction is friendly to the environment. It has no concerns with regard to environmental impact. Moreover, there are no risks which can cause any type of problem to the other partner.

5. There is no need of energy and time to produce offspring. Also, it does not require any true investment.

6. Asexual animals have the ability to keep themselves alive and continue to produce offspring even during emergencies. They do not require any reproductive sources to produce cells.

7. In asexual reproduction, the organism does not require different places to produce its offspring. It just requires a single place and does not involve moving around to see the process taking place.

 

Disadvantages of Asexual Reproduction

1. In this form of reproduction, there is no control over the rapid increase of the population. It doubles its population in each of the reproductive cycles. However, scientists have found that the process would stop only where the total number of organisms becomes excessive at a certain point.

2. This kind of reproduction can create competition because some of the organisms are in close relation with each other.

3. Asexual reproduction can result in overcrowding which may be an issue. One parent can produce a high number of offspring in a very less period. Overcrowding causes a lack of resources that could stop the organism from future growth.

4. It is always not possible to adapt to a new environment for asexual reproduction. The inhabitant could destroy the entire species in a very short duration of time.

5. It may sometimes lead to unfavorable conditions like extreme temperatures that can eliminate the entire community.

With the help of the advantages and disadvantages of asexual reproduction, it will be much easier for us to take care of the organisms around us.