Have you ever been curious to know what animal reproduction is like? In that case, you have come to the right place. In dotcoms we are going to explain everything to you!
Animal reproduction as part of the maintenance of the species
All living beings, without exception, try to survive. If you look closely, all the actions that move the animals are focused on survival. From breathing, to feeding, sleeping or protecting ourselves from predators and other animals. The functions of nutrition and relationship serve precisely to ensure survival. And, along with these two important functions, there is a third one, that of reproduction.
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But reproduction as such goes beyond the survival instinct. It is directly related to the maintenance of the species. What is the difference with the other two functions? Well, reproduction in animals is much more important than the survival instinct itself. Think that among living beings there are some species that die to reproduce and ensure the maintenance of the species. Do you have any case? We give you a couple of examples: plants and certain types of insects and arachnids.
- The plants. Seasonal-type plants, which live only one year, are characterized by simply living to perpetuate their species. These plants complete their life cycle by leaving the seeds. After that they perish.
- Some insects and arachnids. Many of these animals die devoured by the female while the sexual act is taking place. This happens, for example, with the praying mantis. This insect is known to devour the head of the males after the sexual act.
Species are not interested in independent individuals, but in the creation of new generations that survive and perpetuate the species. This is precisely the reason why the individuals of the previous generation become expendable after procreation. However, although the species does not fight for individuals as such, it will fight for the new generations. This makes the instinct compels the individuals that reproduce to try that the offspring reach adulthood safe and sound. And, to guarantee survival, the animals that are going to procreate will choose the best moment to do so. This survival instinct of the species means that most hatchings and births are generated in spring. Precisely at the time when there are better weather conditions and more food.
What is animal reproduction?
Now that we have seen the relationship between animal reduction and the survival of the species, it is time to explain what animal reproduction is.
Animal reproduction is understood as that process that allows living beings to generate copies of them. These copies are the descendants with which they ensure the survival of their species. An effective way to ensure that this species will not become extinct or disappear.
As we have explained a few lines above, animal reproduction favors the survival of the species, leaving the individuals that compose it in the background. In other words, the individual who procreates remains in the background of importance and sometimes even dies.
Reproduction types
Reproduction can be divided into two main types. For both multicellular and unicellular beings. These two main types are:
- Sexual reproduction
- Asexual reproduction
Today there are some species that alternate these two types of reproduction. This type of reproduction is known as alternating reproduction, if it occurs in animals and alternation of generations if it occurs in plants.
The most normal thing is that asexual reproduction gradually disappears from animals. As organisms become more complex, asexual reproduction disappears. In the case of humans, for example, we maintain asexual reproduction in wound healing. In the case of plants, however, even if they are higher plants, they usually maintain asexual reproduction or alternation of generations.
Asexual reproduction
Asexual reproduction is the most primitive that exists. It is the simplest type of reproduction that exists since it does not require specialization in cells or structures. In this type of reproduction, any part of the living being is used to reproduce. This type of reproduction consists in the generation of two or more exact copies from a single individual without any change in the genetic information they contain.
The most common types of asexual reproduction are.
- This type of asexual reproduction occurs in isolated cells. The stem cell splits into two cells. These cells, known as daughter cells, will be identical to the parent cell.
- In this case the individual generates a group of cells. These cells, known as buds, gradually grow. Finally they separate and generate new individuals.
- In this case, the individual using this reproduction technique generates many small cells known as these cells are released naturally into the water or air. When they germinate they give rise to the appearance of a new individual.
- In these cases, reproduction by fragmentation is generated when the individual accidentally or naturally loses a part of his body. Once this fragment is detached from it, it becomes a new individual. Can you think of any animal that performs this type of reproduction? A very curious example is that of the starfish.
This type of reproduction would not be possible without mitosis. Mitosis is a process of nuclear division with which the DNA chains are distributed between the daughter and mother cells. In this way, all the daughter cells that are born have the same genetic information as the stem cells.
Sexual reproduction
Sexual reproduction is more complex than asexual reproduction because it requires many more elements: for example, two different individuals and specialized cells and organs.
Unlike what happens with asexual reproduction, sexual reproduction does include changes in genetic information. It should not be forgotten that to carry out this type of reproduction, two different individuals whose genetic information is different are needed. The combination of both creates generations of individuals with genetic information different from that of the parents. Usually with a more favorable genetic combination.
Sexual reproduction takes place through three different processes.
- A total of four gametes are created from the stem cells. These are formed in the gonads and gametangia. Gametes are generated through meiosis, which is a process of cell division very similar to mitosis. However, although it is very similar, the biological result is different, since it consists of halving the number of chromosomes so that the number of the species does not double after fertilization.
- In this case, fertilization is obtained when two gametes from different individuals fuse. From this fusion a new cell is born known as a zygote.
- Embryonic development. The zygote is transformed to create a new organism.
Reproduction in animals
In animals, sexual reproduction slowly replaces asexual reproduction. The greater the complexity of living beings, the greater the complexity in their way of reproducing. When the animal is extremely complex, asexual reproduction disappears.
When sexual reproduction becomes the only one possible among animals, a series of changes in their behavior also appear. These changes include mating rituals. Mating rituals will allow some animals to reproduce while others will not. Can you think of any kind of mating ritual that animals do? Some of the most common are usually fights, songs or the demonstration of certain skills against the opponent for copulation.
Animals with asexual reproduction
This type of reproduction is more frequent among invertebrates, which are the most primitive animals on the face of the earth. For example, it occurs among worms, echinoderms or coelenterates. As we have explained a few lines above, in asexual reproduction only one individual is necessary. This individual generates genetically exact copies of himself. This type of reproduction aims to obtain many offspring as quickly as possible. Among its functions there is no genetic improvement since it does not combine genes from different individuals.
Sexually reproducing animals
Sexual reproduction is present in all animal groups. However, in the case of invertebrates, this type of reproduction is less important than asexual reproduction.
In sexual reproduction there are two types of individuals depending on the gametes they produce.
- Individuals with only one sex. These individuals have a single type of gonads that generate a single type of gametes.
- Male individuals. The gonads of this type of individual are known as testicles. The gametes they produce are called sperm.
- Female individuals. The gonads of these individuals are known as ovaries, and the resulting gametes as ova.
- Individuals who share both sexes. These individuals are called hermaphrodites since they have both gonads and generate two types of gametes. Despite having both gonads, they cannot self-fertilize. They always require another individual. Can you think of any hermaphroditic animal? For example land snails and earthworms.
Fertilization by sexual reproduction varies depending on where the sperm and egg are located.
- External fertilization. In this case, both the male and the female release the sperm and eggs to the external environment. It occurs among aquatic invertebrate animals. Also among certain aquatic vertebrates, such as fish and amphibians.
- Internal fertilization. In these cases, the male deposits the sperm inside the female. To do so they can:
- Use specialized organs, as in the case of spiders (which use pals), sharks (which use fins), or octopuses (with modified tentacles).
- Through ovulatory organs.
- Connecting the sewers.
Once fertilization occurs, the zygote or egg cell is generated that will give rise to the embryo. During embryonic development a new individual will be created.
Embryonic development
Embryonic development varies depending on the group of animals and the place where it occurs.
- Depending on the group of animals
- Direct development. The zygote creates an individual different from the adult only in size. This is the type of development that human beings have.
- Indirect development. In this case, the zygote creates a free intermediate form known as this larva, in turn, can have several stages before generating an adult animal. A classic example is that of the butterfly. It is born as an egg, from there a caterpillar is generated, which gives rise to a pupa that finally becomes a butterfly when it reaches its full development.
- According to the place where embryonic development occurs
- Oviparous. In this case, embryonic development takes place outside the mother’s body, in an egg. It occurs in invertebrates and in aquatic and terrestrial vertebrates. For example in fish and amphibians.
- Ovoviviparous. In this case, embryonic development occurs inside an egg but inside the mother’s body. There it hatches. It occurs in many fish and some snakes. Viviparous. Embryonic development is generated in the uterus, and the new individual is born.
- In this case, no placenta forms inside the uterus. The fetus is born prematurely and the mother finishes raising it in the pouch. In this bag are the udders that will feed the fetus until its full development.
- Placated. Placental viviparous develop the embryo and fetus in utero and within the placenta. The placenta is the means by which they receive nourishment. It occurs in most mammals.
