[Biology Class Notes] on How Do Organisms Reproduce? Pdf for EXAM

Reproduction is a scientific process to produce species of its own kind to help the existence of the species, generation after generation. It is one of the most important processes to sustain life on earth of different species. It helps the species to maintain the chain of life and not get extinct. 

The process of reproduction in organisms is quite interesting. Let’s have a look to know better – how do organisms reproduce.

Types of Reproduction

The organisms reproduce in two different ways:

1. Asexual Reproduction is a process where there is an involvement of a single parent. There is no formation of gametes. One of the prominent aspects of asexual reproduction is that the offspring produced are identical and exact copy of the parent. Amoeba and the algae are the perfect examples of asexual reproduction. It is a simple and rapid process. 

2. Sexual Reproduction is a process where there is a fusion of a male and a female and successively, gametes are formed. The zygote is formed by the successful fusion of a male and the female gamete giving birth to an offspring. The offspring is not identical to the parents in sexual reproduction but they do inherit the traits of both the parents. It is an elaborate and complex process compared to asexual reproduction. Humans are a perfect example of sexual reproduction.

Asexual Reproduction

There are different types of an asexual reproduction process:

• Fission

• Budding

• Vegetative Propagation

• Spore Formation

• Regeneration

1. Fission

The process of fission takes place in unicellular organisms. There are two types of fission.

• Binary Fission – In binary fission, the parent cell divides into two equal daughter cells. The two daughter cells contain a nucleus. Binary fission takes place when there is adequate moisture and food available.

• Multiple Fission – Multiple fissions take place in unfavorable circumstances when there is a scarcity of food, temperature, and moisture. The parent nucleus divides several times into multiple daughter nuclei. A membrane surrounds the daughter nuclei, and it further multiplies into a large number of daughter nuclei by the process of amitosis. 

2. Budding

Budding is a type of asexual reproduction that gives birth to a new organism from the small part of the parent’s body. In this process, a bud outgrows from a part of the parent cell, and it remains attached to it till it matures. Once matured, it detaches itself from the parent body to form a new life. It leaves behind a scar tissue on the parent body. Yeast and hydra are few examples of budding.

3. Vegetative Propagation

In vegetative growth, new plants grow from any part of the plant, be it root, stem, leaves, or specialized reproductive structure of the parent plant. The new organism is the clone of the parent plant. From one single mother plant, you can have numerous new plants in your garden. 

4. Spore Formation

In non-flowering plants, asexual reproduction takes place by spore formation. Knob-like structure develops in the parent body in unfavorable conditions when there is a lack of nutrients and moisture. The outgrowth structures are known as sporangium. They are dormant in adverse conditions. In favorable conditions, the sporangia containing the spores burst to release the spores and give life to multiple new organisms. Protozoa and the fungi are a few examples of spore formation.

5. Regeneration

In many organisms, it is possible to regrow into a new organism by just severing the parts into multiple parts. The process of regeneration takes place due to the existence of specialized cells. The specialized cells multiply profusely, producing a large number of cells. Further, the multiplied cells undergo prominent transformation by developing different cells and tissues. Hydra and planaria are examples of regeneration.

Sexual Reproduction

The process of reproducing new organisms in multicellular organisms is by sexual reproduction. As said above, a new life comes into being by the fusion of male and female gametes. 

Flowering plants are capable of sexual reproduction because they have both male and female reproductive organs. The pollen grains produce male gametes that fuse with the egg cell of the female. The pollen grains travel from the anther to the stigma of the flower by the aid of wind, insects, water, and animals. The process of traveling of pollen grains from the anther to the stigma of the same flower or different flower is known as pollination. The male and the female gametes fuse to form a zygote. The zygote undergoes cell division changes to form an embryo which grows to become a seed, and the ovary develops into a fruit. The seed has the potential to produce a new life.

The male and female reproductive organs are responsible for producing offspring. The sperm is produced in a male’s testes, and eggs of the female are produced in her ovary. The sperms are morbid, and it interacts with the eggs, resulting in the process of fertilization. Both sperm and egg fertilize which results in the formation of a zygote. It is attached in the uterine wall. The tissues between the embryo and the female uterine walls form the placenta. The placenta is the source of the supply of nutrients to the embryo, and it starts growing. There is a gestation period of approximately nine months, and a new full-fledged life is born.