Reproduction: Definition and Types

Reproduction is the process of formation of new organisms from the parent organism. It occurs in both plants and animals. There are two types of reproduction: asexual and sexual.

• In asexual reproduction, new organisms are produced from a single parent. Animals that reproduce asexually are bacteria, fungi, archaea, etc.
• In sexual reproduction, new organisms are produced from a male and a female parent. Plants, mammals, and reptiles are animals that reproduce asexually.

In this article, we will dive deep into what is reproduction, types of reproduction, plant and animal reproduction.

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What is Reproduction?

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A biological process whereby an organism reproduces to give rise to an offspring is called reproduction. This process enables and ensures the continuity of species, generation after generation, and is the main feature of life on Earth. 

• Reproduction takes place in both unicellular and multicellular organisms like amoeba, bacteria, yeats, algae, paramoecium, humans, etc.
• This process occurs by the division of cells. Cell division in asexual reproduction is called mitosis whereas in sexual reproduction it is called meiosis.

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Types of Reproduction

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Reproduction is the basis of life which is usually categorised into two types:

1. Asexual Reproduction 
2. Sexual Reproduction

Asexual Reproduction

Asexual Reproduction is a type of reproduction the production of offspring by a single parent. The offspring produced are identical to the parent as no fusion of gametes takes place. 

• In this type of reproduction, multiplication, and growth occur rapidly in a short time period. 
• Cell division occurs by mitosis by which the cell divides into two daughter cells
• Asexual reproduction is commonly observed in the plant kingdom and some single-celled organisms.
• Examples of asexual reproduction include Amoeba, paramecium, fungi, plants, etc. 

Figure: Asexual Reproduction in Amoeba 

Sexual Reproduction

Sexual reproduction is a process of the development of new organisms in which both parents are involved. It involves the fusion of male and female gametes. In this process, genetic variation can be observed.

• This is a complex type of reproduction where multiplication and growth occur very slowly.
• Cell division occurs by meiosis. It is a process where four haploid cells are produced from one diploid cell (parent cell).
• Sexual reproduction is commonly observed in multicellular organisms.
• Examples of sexual reproduction is human reproduction and flowering plant reproduction.

Figure: Sexual Reproduction in Humans 

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Reproduction in Plants

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Reproduction in plants takes place asexually and sexually. In this section, we will discuss these types in detail.

Asexual Reproduction in Plants

Plant reproduce by asexual reproduction and is commonly observed in lower plants and is further divided into four types:

1. Budding
2. Vegetative Propagation
3. Sporogenesis
4. Fragmentation

Budding

Budding is a type of asexual reproduction, where a new individual grows from a small outgrowth (bud) of the parents’ body. The bud remains attached to the parent body but later detaches and develops into a mature organism.

• Examples of budding include potato, dahlia, etc. 
• When a potato is left undisturbed for a long time, the formation of bud takes place, also called the ‘eyes of the potato’.

Vegetative Propagation

It is a process of asexual reproduction, where plants reproduce via different parts of the plants like the stems, roots, or buds. These parts are called the vegetative parts of the plant. The following are the common ways of vegetative propagation.

• Sub-aerial stems called stolon and runners take part in vegetative propagation. 
• Modified roots or tubers give rise to new plants. Examples of roots include Dahlia, tapioca, sweet potato, etc.
• Buds present on the leaves of certain plants detach and form new organisms. Examples: Begonia and Bryophylum

Sporogenesis

Spore formation or sporogenesis is a process of reproduction that occurs by spores. Examples of organisms that produce spores are most fungi.

• In most flowering plants, both male and female gametes reproduce by this process. 
• Other examples include mosses and ferns which grow in favorable conditions to give rise to new individual organisms.

Fragmentation

In fragmentation, the parent organism divides itself into many fragments giving rise to new organisms. Fragments of the plant is mediated by the winds for the formation of new plants. Example- Mosses and liverworts.

Sexual Reproduction in Plants

Sexual Reproduction in plants involves the fusion of two gametes; a male gamete and a female gamete. This type of reproduction usually occurs in flowering plants where the male gamete is the anther and the female gamete is the egg cell. Sexual reproduction takes place via pollination followed by fertilization.

• Pollination: It is defined as the transfer of pollen grains from the male gamete to the female gamete of a flower. 
• Fertilization: After pollination, the process of fertilization occurs where both male and female gametes fuse to form a zygote.

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Reproduction in Animals

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Just like plants, animals also reproduce asexually as well as sexually. In this section, we will discuss these types in detail.

Asexual Reproduction in Animals

Asexual reproduction in animals does not involve the formation of gametes. It takes place by four means namely:

1. Binary fission
2. Budding
3. Fragmentation
4. Parthenogenesis

Binary Fission

Binary fission or fission is an asexual mode of reproduction where a single cell divides into two individual cells. These cells carry the same genetic information as their parent cell.

• Examples of binary fission include Amoeba, paramecium, etc. 
• The new organisms produced by binary fission are identical to their parent (or parent cell). 

Budding

The process of budding is similar to the plants where an organism develops from a bud or an outgrowth.

• Examples of budding include hydra, corals, etc.
• In hydra, a bud develops on the body of the parent organism and detaches when the organism is formed.

Fragmentation

This type of reproduction is generally seen in sponges, cnidarians, echinoderms, annelids, and planaria. Here, the body of the organism breaks into fragments from which new organisms are formed. 

Parthenogenesis

Parthenogenesis is a process in which the development of an organism takes place without the egg being fertilized.

• This mode of reproduction occurs in both vertebrates and invertebrates.
• Examples of parthenogenesis include wasps, bees, ants, reptiles, amphibians, etc.

Sexual Reproduction in Animals

Sexual reproduction in animals takes place via two processes: fertilization and embryo development. When male and female gametes fuse to form a zygote (embryo) this process is termed fertilization. Fertilization is further divided into two types: internal and external.

• In internal fertilization, gamete fusion takes place inside the organism's body. Example- Mammals.
• In external fertilization, gamete fusion takes place outside the organism's body. Example- fish.

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Things to Remember

• Reproduction is a process that introduces genetic variation in the offspring and plays an important role in the evolution of species.
• Gametes are the reproductive cells of an organism.
• Females reproduce through gametes called ova, while male gametes are called sperms.
• The fusion of sperm (male) and egg cells (female) gives rise to a fertilized egg or zygote.
• Sexual reproduction in flowering plants takes place by transfer of pollen grains called pollination.