[Biology Class Notes] on Reproduction Pdf for Exam

The human life cycle majorly depends on the reproductive system. Reproduction meaning in biology is to reproduce. It is a biological process in which an organism reproduces an offspring and is biologically similar to the organism. The same reproduction biology is followed in humans. Reproduction enables and ensures the continuity of species, generation after generation. Reproduction is certainly the most important feature of life on earth.

There are two types of reproduction-

1. Sexual Reproduction

2. Asexual Reproduction

Let us dive deeper into these two types of reproduction systems:

Sexual Reproduction

It is the human reproductive process under which new organisms are created through the combination of genetic information from two opposite sexes. This genetic information is carried on chromosomes within the nucleus of specialized sex cells called gametes. In males, these gametes are in the form of sperm, and in females in the form of eggs.

During the sexual production process, these two gametes come together for the further process of fertilization creating a zygote by taking half of its DNA from each of the two sexes. We, humans, carry 46 chromosomes; 23 in females and 23 in males.

Biology human reproduction or sexual reproduction is quite different from asexual reproduction. In asexual reproduction, there are no gametes, so the offspring are genetically identical to their parents. Asexual reproduction happens in bacteria, fungi, and hydras.

Types of Sexual Reproduction:

1. Allogamy:

Allogamy takes place when gametes join together during the fertilization process come from two opposite sexes. Female gametes are egg or ovum, male in the form of sperm. When these two meet, they perform the task of reproduction.

2. Internal Fertilization

Internal fertilization is the fertilization of eggs by the sperm, which is usually called sexual intercourse. Internal fertilization takes place in the female body. The further step in internal fertilization completely depends on different species. In birds and inspects, they lay eggs containing cells. After a brief period, these fully formed eggs hatch which is known as Oviparity.

3. External Fertilization

This process happens when sperm cells and eggs join outside the body. Amphibians and fish use external fertilization to produce billions of gametes at a time. Sex cells of certain creatures reproduced through external fertilization need special adaption for movement.

Asexual Reproduction

Asexual reproduction is one of the two types of reproduction where only a single organism reproduces another organism. Here, there is no involvement of gametes. So the offspring produced are genetically identical to the parent. Asexual reproduction is widely practiced by unicellular organisms.

Asexual reproduction is further divided into different parts:

• Binary Fission: Here, cells split into two cells carrying the identical copy of DNA from the parent cell.

• Budding: Here, a small bud-like outgrowth gives rise to a new individual. The outgrowth remains attached to the organism until fully grown.

• Fragmentation: Here, the parent organism divides into different parts, each growing individually.

Reproduction in Plants

The reproduction biology in plants is quite different compared to humans and other living organisms. The plant reproduces by sexual and asexual means. One such is vegetative reproduction. Roots like corm, stem tuber, stolon undergo vegetative propagation.  In plants, sexual reproduction happens through pollination in which pollen grains from the anther of a male flower transfer to the stigma of female flowers.

Reproduction in Animals

Unlike plants, reproduction in animals happens through both types of reproduction- Asexual and sexual. Under sexual reproduction, males and females gamete are involved. Under asexual reproduction, processes like binary fission, budding, and fragmentation take place.

Brief about Molecular Reproduction

Molecular reproduction involves DNA molecules serving as a code by which genetic information is stored. Under this code, DNA synthesizes one strand of ribonucleic acid (RNA). This RNA serves as a messenger to carry the genetic code to places in cells where proteins are produced.

Levels of Reproduction

Levels of reproduction also called as stages of reproduction differ according to organisms. Some of the level of reproduction:

1. Molecular Replication:

Characteristics that an organism inherits largely stored in cells in the form of genetic information. In studies, it was found that DNA molecules consist of two complementary strands. Moreover, there are four bases in DNA- Guanine, adenine, cytosine and thymine.

2. Cell Reproduction:

Chemical constituents of cells are usually not resynthesized from DNA when the cell divides. This is because each of the two daughter cells formed during the cell division inherits half of the cellular material from the mother cell. Cells of higher organisms contain complex structures. Each time these cells divide the structure gets duplicated.

3. Binary Fission

Binary fission is one of the common levels of reproduction. In bacteria, the chromosome replicates and divides into two, after which a cell wall gets formed across the parent cell.

4. Multiple Fission

Algae, protozoans, and slime molds get divided by multiple fissions. In this case, the nucleus undergoes multiple mitotic divisions.