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Sexual Reproduction in Animals and Plants

 
By Anaƫlle Laurent. December 9, 2020
Sexual Reproduction in Animals and Plants

There are two types of reproduction in the animal kingdom, asexual and sexual reproduction. Whereas asexual reproduction doesn't involve the fusion of gametes, sexual reproduction does, thus resulting in an offspring genetically different to its parents. This type of reproduction can also be found in plants.

In this AnimalWised article we're going to explain sexual reproduction in animals and plants. We'll go through both to see their similarities and differences, this way you'll be able to compare. We will also include examples. Keep reading to learn more!

You may also be interested in: Types of Animal Reproduction

Sexual reproduction in animals

As we have previously mentioned, sexual reproduction is a type of reproduction where there is a fusion of gametes, resulting in an offspring that is genetically different to its parents.

The characteristics that define this type of reproduction are various. In the first place, in sexual reproduction there are two individuals involved, unlike asexual reproduction, a female and a male. Both some and others have organs known as gonads that produce gametes. These gametes are the sex cells, ovules in females, generated by the ovaries and sperm produced by the testes 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, thus there is external fertilization where females and males expel their gametes to the aquatic environment to fertilize them and internal fertilization, where the sperm find the ovule inside the female.

After fertilization, the formed zygote will have 50% maternal DNA and 50% paternal DNA, that is, the offspring that are produced through sexual reproduction will have genetic material from both parents. Check out the video below to learn more about sexual reproduction!

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 the 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 rate of creation and maturation of gametes will depend on several 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 to the environment for fertilization.

After fertilization, the last phase of sexual reproduction occurs which consists of a series of molecular changes that allow the nucleus of the ovum to fuse with the nucleus of the sperm. You should also check out our article about the different modes of reproduction in animals.

Types of sexual reproduction in animals

The types of sexual reproduction 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 is not possible to visually differentiate 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 to appear in evolutionary history and is typical of chlamydomonas (single-celled 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 immobile. 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 to appear 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:

  • Mammals such as dogs, chimpanzees, whales or humans have sexual reproduction with internal fertilization and oogamy, they are also viviparous animals, so embryonic development will take place in the womb.
  • Birds, although they lay eggs as they are oviparous animals, 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.
  • 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 hermaphroditic animals, with female and male reproductive organs at the same time, but they can only act as female or male when mating. Selfing does not occur.

Sexual Reproduction in Animals and Plants - Examples of sexual reproduction in animals

Sexual reproduction in plants

Just like animals, plants also have two types of reproduction, asexual and sexual reproduction. In their sexual reproduction, plants fuse two gametes together to create an offspring. However, unlike animals, plants are immobile and therefore reproduce sexually in a different way than animals. We will take a deeper look into the different ways animals do this later on in this article.

We also encourage you to check out this video about sexual reproduction in plants!

Stages of sexual reproduction in plants

Sexual reproduction involves two fundamental processes:

  • Meiosis which rearranges the genes and reduces the number of chromosomes.
  • Fertilization which restores the chromosome to a complete diploid number.

Different types of plants and algae vary in these process, but many of them, including all land plants, undergo alternation of generations. They do this with two different multicellularis haploid containing a single set of chromosomes in each cell.

The gametophyte produces male or female gametes (or both), by a process of cell division, called mitosis. In vascular plants with separate gametophytes, female gametophytes are known as mega gametophytes and the male gametophytes are called micro gametophytes.

The fusion of male and female gametes, known as fertilization, produces a diploid zygote, which develops by mitotic cell divisions into a multicellular sporophyte. The mature sporophyte produces spores by meiosis. This is sometimes referred to as “reduction division” because the chromosome pairs are separated once again to form single sets.

Types of sexual reproduction in plants

Spores

Certain plants can reproduce sexually or asexually through spores. The spores are often located on the underside of the leaves and are carried to a new area by wind or rain. Spores, unlike seeds, are less likely to be eaten by animals, but they are at risk of being consumed by bacteria and fungi.

Flowers

Other plants will reproduce through the stamens in their flowers, this includes all flowering plants. This will be done by pollination as animals come to pollinate the stamen from other plants, allowing the ovule to be fertilized and start developing their seeds. We also encourage you to check out our article about 15 animals that pollinate.

Cones

Cones are the parts of conifers which contain reproductive structures. Female cones produce ovules and male cones, which are much smaller and not as visible, produce pollen. Once the female cone is fertilized it'll become a seed. Male and female cones are usually produced from the same plant to facilitate cross-fertilization and to avoid self-fertilization.

Fruit

Fruit is the result of of the maturation of one or many flowers, and is therefore only found in angiosperms. In botany, fruit is considered the ripened ovary of a seed-bearing plant which contains its seeds. In flowering plants, as a seed develops, its ovary begins to ripen and the ovary wall becomes fleshy (such as in berries and apples) or forms a hard outer covering (such as in nuts).

Seeds

Seeds can be dispersed by the wind, water, or animals. Seeds are a more evolutionarily advanced form of plant reproduction than spores and are present in both gymnosperms and angiosperms. However, seeds can sometimes be eaten by animals.

Sexual Reproduction in Animals and Plants - Types of sexual reproduction in plants

Examples of sexual reproduction in plants

There are thousands of examples of sexual reproduction in plants, so here are some examples of large groups of plants that reproduce sexually:

  • Ferns, such as horsetails or club-molasses, which reproduce through spores.
  • Gymnosperms, such as the Maidenhair tree or the Scots pine, which reproduce through seeds.
  • Angiosperms, also known as flowering plants, such as orchids or flower heads, which reproduce through seeds.

If you found this article interesting you can continue learning about our world with out article about the 5 different animal kingdoms.

If you want to read similar articles to Sexual Reproduction in Animals and Plants, we recommend you visit our Facts about the animal kingdom category.

Bibliography
  • Crow, JF (1994). Advantages of sexual reproduction. Developmental genetics, 15 (3), 205-213.
  • Panawala, L. (2017). Difference Between Anisogamy Isogamy and Oogamy. ResearchGate. Available at: https://www.researchgate.net/publication/316921070_Difference_Between_Anisogamy_Isogamy_and_Oogamy
  • Sawada, H., Inoue, N., & Iwano, M. (2014). Sexual reproduction in animals and plants. Springer-Verlag GmbH.

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