Content
- What is sexual reproduction of animals?
- Stages of sexual reproduction of animals
- Types of sexual reproduction of animals
- Examples of sexual reproduction in animals
- Difference between sexual and asexual reproduction
Animals, as individual organisms, appear and disappear, but the species to which they belong continues to exist. This happens 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, more common among animals.
THE sexual reproduction it is the typical reproductive strategy of animals, although some can reproduce exceptionally through an asexual strategy. Therefore, in this PeritoAnimal article, we will explain the which is the sexual reproduction of animals.
What is sexual reproduction of animals?
Sexual reproduction is the reproductive strategy that many animals and plants adopt to give rise to new individuals and perpetuate the species.
The characteristics that define this type of reproduction are several. First, in sexual reproduction two individuals are involved, one male and one female, unlike asexual reproduction, where there is only one. Both have organs known as gonads, which produce the gametes. These gametes are the sex cells, the eggs generated by the ovaries in females and the sperm produced by the testes in males.
When an egg and sperm fuse together, they form a zygote. This union is called fertilization. Fertilization can take place inside or outside the animal, depending on the species. So there is the external fertilization, in which females and males expel their gametes into the aquatic environment to be fertilized, and there is internal fertilization, in which the sperm meets the egg inside the female.
After fertilization, the zygote formed will have 50% maternal DNA and 50% paternal DNA, that is, the offspring generated by sexual reproduction will have genetic material from both parents.
Stages of sexual reproduction of animals
Sexual reproduction in animals consists of several steps, starting with the gametogenesis. This phenomenon consists of the production and development of female and male gametes in female and male gonads, respectively.
From germ cells and through a type of cell division known as meiosis, females and males create their gametes. The rate of creation and maturation of gametes will depend on several factors, but mainly on the species and sex of the individual.
After gametogenesis, the mechanism by which fertilization occurs is the mating. Through the action of hormones, individuals of childbearing age will seek the company of the opposite sex to mate and, after courtship, copulation will occur in animals that have internal fertilization. In species with external fertilization, the gametes will be released into the environment for them to be fertilized.
After fertilization, the last stage of sexual reproduction occurs, the fertilization, which consists of a series of molecular changes that allow the fusion of the egg nucleus with the sperm nucleus.
Types of sexual reproduction of animals
The types of sexual reproduction existing in animals are related to the size of the gametes that will unite during fertilization. In this way, we have isogamy, anisogamy and oogamy.
- At isogamy it is possible to visually differentiate which gamete is male or female. Both can be either mobile or immobile. It is the first type of sexual reproduction to appear in the history of evolution, and is typical of clamydomonas (single-celled algae) and monocystis, a type of protist. It does not occur in animals.
- THE anisogamy it is the fusion of gametes of different sizes. There are differences between male and female gametes and both can be mobile or immobile. This type appeared in evolution after isogamy. Occurs in fungi, higher invertebrates and other animals.
- THE oogamy it is the fusion of a very large and immobile female gamete with small mobile male gametes. It was the last type of reproduction that appeared in the history of evolution. It is typical of higher algae, ferns, gymnosperms and higher animals such as vertebrates.
Examples of sexual reproduction in animals
There are as many examples of sexual reproduction as there are animal species.
- You mammals, like dogs, chimpanzees, whales and humans, they have sexual reproduction with internal fertilization and oogamy. They are, in addition, live-bearing animals, that's why their embryonic development takes place inside the mother's uterus.
- At birds, although they lay eggs because they are oviparous animals, they also follow the sexual reproductive strategy with oogamy.
- You reptiles, amphibians and fish they also reproduce sexually, although some species follow an asexual strategy at some points in their lives. Some are oviparous and others are ovoviviparous, many of them have external fertilization and several have internal fertilization.
- You arthropods they are a wide and diverse group of animals, so in this group it is possible to find both internal and external fertilization and cases of oogamy and anisogamy. Some can reproduce asexually.
Don't forget that there are also hermaphrodite animals, with both female and male reproductive organs, but which can only act as either female or male during mating. In this case, self-fertilization does not occur.
Difference between sexual and asexual reproduction
Now that you know what the characteristics of sexual reproduction are, it's important to know what the differences between sexual and asexual reproduction. Asexual reproduction is a reproductive strategy that differs from sexual reproduction at several points. The first one is duration, in asexual reproduction the duration is much shorter than in sexual reproduction.
The second point of difference, and the most important one, is that the result of asexual reproduction is individuals equal to the parent ie without any DNA changes, clones. Briefly, in sexual reproduction there are two individuals, that is, two different genetic materials. Together they result in a third individual with 50% of each person's genetic material. On the other hand, in asexual reproduction there is no production of gametes and the result is identical individuals, without any genetic improvement and the offspring tend to be weaker.
See 15 examples of hermaphrodite animals and how they reproduce in this PeritoAnimal article.
If you want to read more articles similar to Sexual reproduction of animals: types and examples, we recommend that you enter our Curiosities section of the animal world.