Animals, as individual organisms, appear and disappear, but the species to which we belong remains, all thanks to reproduction, one of the vital functions of living beings. Within the animal kingdom we can find two reproductive strategies, asexual reproduction and sexual reproduction, which is more widespread among animals.
sexual reproduction is the typical reproductive strategy of animals, although some of them can exceptionally reproduce through an asexual strategy. Therefore, in this article on our site we are going to explain what is the sexual reproduction of animals
Characteristics of sexual reproduction in animals
Sexual reproduction is the reproductive strategy carried out by many animals and plants to give rise to new individuals that perpetuate the species.
The characteristics that define this type of playback are various. First of all, in sexual reproduction there are two individuals involved, unlike in asexual reproduction where there is only one, a female and a male. Both of them have organs known as gonads that produce gametes. These gametes are the sexual cells, ovules in females, generated by the ovaries and sperm produced by the testicles in males.
When an egg and a sperm fuse they give rise to a zygote. This union is called fertilization Fertilization can occur inside or outside the animal, depending on the species, so there is external fertilizationwhere females and males expel their gametes into the aquatic environment to be fertilized and the internal fertilization , where the spermatozoa find the ovule inside of the female.
After fertilization, the formed zygote will have 50% maternal DNA and 50% paternal DNA, that is, the offspring produced through sexual reproduction will possess genetic material of both parents.
Stages of sexual reproduction in animals
Sexual reproduction in animals consists of several stages, beginning with gametogenesis. This phenomenon consists of the formation and development of female and male gametes within the female and male gonads, respectively.
From germ cells and through a type of cell division known as meiosis, both females and males create their gametes. The rhythm of creation and maturation of the gametes will depend on various factors, but mainly on the species and the sex of the individual.
After gametogenesis, the mechanism by which fertilization occurs is mating Mediated by hormones, individuals of childbearing age will seek the company of the opposite sex to mate and, after courtship, copulation will occur in those animals that have internal fertilization. Species with external fertilization will release the gametes into the environment to be fertilized.
After fertilization occurs the last phase of sexual reproduction, fertilization, which consists of a series of molecular changes that allow the fusion of the ovum nucleus with the sperm nucleus.
Types of sexual reproduction in animals
The types of sexual reproduction existing in animals are related to the size of the gametes that are going to unite in fertilization, thus we find isogamy, anisogamy and oogamy.
- isogamy is the fusion of two gametes of similar size, it cannot be visually differentiated which is the male or female gamete. Both one and the other can be mobile or immobile. It is the first type of sexual reproduction that appeared in evolutionary history and is typical of chlamydomonas (unicellular algae) and monocystis, a protist. It does not occur in animals.
- anisogamy is the fusion of gametes of different sizes. There are differences between male and female gametes, and both can be motile or immotile. It appears later in evolution than isogamy. It occurs in fungi, higher invertebrates and other animals.
- oogamy is the fusion of a very large, immobile female gamete with small, mobile male gametes. It is the last type of reproduction that appears in evolution. It is typical of higher algae, ferns, gymnosperms and animals such as vertebrates.
Examples of sexual reproduction in animals
There are as many examples of sexual reproduction as there are animal species.
- The mammals such as dogs, chimpanzees, whales or the human being have sexual reproduction with internal fertilization and oogamy, they are, in addition, viviparous animals, so embryonic development will take place in the womb.
- Las aves, although they lay eggs as they are oviparous animals, they also follow this sexual reproductive strategy with oogamy.
- Reptiles, amphibians, and fish also reproduce sexually, although certain species follow an asexual strategy at certain times in their lives. Some are oviparous and others ovoviviparous, many of them have external fertilization and many others internal.
- The arthropods are a large and diverse group of animals, so in this group we will find both internal and external fertilization and cases of oogamy and anisogamy. Some will be able to reproduce asexually.
Do not forget that there are hermaphrodite animals, with female and male reproductive organs at the same time, but they can only act as male or female when mating. Self-fertilization does not occur.
