Sexual Reproduction in Animals

Reproduction is a vast process that happens in living organisms. Reproduction is further divided into two broad classes, which are sexual reproduction and asexual reproduction. Because of sexual reproduction, organisms have a wide genetic diversity. Meiosis, a process that produces sperm and egg cells, is the first step in sexual reproduction.

In this article, we further study elaborately about sexual reproduction in animals.

Etymology of Sexual Reproduction in Animals

The word sexual derives from the Late Latin sexualis, which comes from the Latin word sexus, which means “of copulation or generation.” Reproduction is derived from the Latin words re, which means “again,” and production, which means “creation.” Syngenesis is a synonym for syngenesis.

Sexual Reproduction in Animals Definition

Sexual reproduction in animals’ definition may be defined as the process of sperm from a male parent fertilising an egg from a female parent, an offspring is born who is genetically distinct from both parents.

Sexual reproduction in animals induces a wide genetic diversity in organisms. Meiosis, a process that produces sperm and egg cells, is the first step in sexual reproduction. Because they have half the amount of chromosomes as the parent, these cells are referred to as haploids. A diploid zygote is produced when haploid sperm from the male parent fertilises a haploid egg from the female parent during sexual reproduction.

A fertilised egg is referred to as a zygote. The usual number of chromosomes found in all of an organism’s regular cells is called the diploid number of chromosomes.

The zygote evolves into a new creature as it matures. It is genetically distinct from both parents since it inherited half of its chromosomes from the male parent and half from the female parent, giving it a unique set of genes.

Different ways of Sexual Reproduction in Animals

Sexual reproduction in animals takes place in a number of ways. After the female has placed the eggs, certain species, such as fish, release sperm over them. The male discharges sperm into the female reproductive canal in other animals, such as birds and most mammals, including humans.

Earthworms, for example, are hermaphroditic, meaning they have both male and female sexual organs and can generate both sperm and eggs. They do, however, mate with other earthworms to create genetically varied worms.

Fertilisation, or the joining of the gametes, can take place either internally or externally in animals. A man discharges sperm over eggs that have been discharged by a female in external fertilisation. Many invertebrates, as well as most fish and amphibians, utilise this method of fertilisation.

Internal fertilisation occurs when sperm and egg meet inside an adult’s body. Fertilisation occurs in the female’s body in the great majority of situations.

Different forms of Sexual Reproduction in Animals

Syngamy and conjugation are the two main methods of sexual reproduction in animals.

The merging of haploid sex cells that results in the production of a diploid zygote is known as syngamy. Syngamy is, in essence, the process of fertilisation. It is the most prevalent kind of reproduction in multicellular sexual populations, including humans. 

Conjugation differs from syngamy in that it involves two organisms forming a temporary fusion (for example, via a cytoplasmic bridge) in order to exchange micro nuclear material. Single-celled creatures, such as bacteria, protozoans, and single-celled fungus, exhibit this. Conjugation is a transient fusing of two cells, whereas syngamy is a permanent union of two cells.

Steps of Sexual Reproduction in Animals

Pre-Fertilisation 

The events leading up to fertilisation are included in this stage. The two processes that occur at this stage are gamete production (gametogenesis) and gamete transfer. Gametes are sex cells that are naturally haploid (23 chromosomes) and distinct in men and females. 

The male gamete is termed sperm, whilst the female gamete is called ovum or egg. These gametes originate among different structures in all organisms. Since female gametes are immobile, male gametes need to be transported for fertilisation. In plants, this  pre-fertilisation occurs by pollination. Sexual intercourse is how unisexual animals transmit gametes. 

Fertilisation

Fertilisation, also known as syngamy, is the process by which haploid male and female gametes encounter and combine to generate a zygote. This can happen within or outside of the body, also commonly known as external fertilisation, and internal fertilisation is known as fertilisation inside the body.

Post Fertilisation 

Fertilisation results in the creation of a diploid zygote. The zygote eventually splits and develops into an embryo by mitotic division. Embryogenesis is the name given to this process. During development, cells differentiate and change in response to their environment. The organism and its life cycle have an impact on zygote development. 

Based on the development of the zygote externally or internally of the body, organisms are divided into viviparous and oviparous.

Oviparous Organisms 

An oviparous animal is one that produces eggs, which are then pushed out of the female’s body and hatch to generate offspring.The majority of fishes, amphibians, reptiles, and even birds are oviparous. Insects and other invertebrates are oviparous. 

Ovoviviparous animals are another type in which the eggs hatch inside the animal’s body, and the young emerge. Some snakes, sharks, and other creatures are prone to this.

Ovoviviparous Organisms

Ovoviviparous organisms are the organisms which produce eggs and develop within the maternal body and hatch within or immediately after release from the parent. Some example of ovoviviparous organisms include Fishes, sharks, snakes and others.

Viviparous Organisms 

A viviparous animal is one that develops an embryo inside the female’s body and gives birth to a live young one. 

The embryo grows in unique organs within the female’s body, where the mother gives the embryo critical nutrients. 

Except for birds, all vertebrate groups have viviparous creatures. Even though none of the groups is exclusively viviparous, fish, amphibians, reptiles, and mammals all have viviparous individuals. 

Viviparity is said to have evolved from oviparity, in which the egg lingered inside the female for a longer period of time, leading it to hatch into a young one.

Conclusion 

To summarise, sexual reproduction in animals has several advantages, including genetic variety, the ability to erase mutations through recombination, increased resistance to parasites, and the ability to produce creatures that are distinct from one another.