Eukaryotes

A eukaryote is an organism with cells that have a nucleus and other organelles enclosed within membranes. They are distinct from other prokaryotes, for example, bacteria that do not contain organelles or a membrane-bound nucleus. All multi-celled organisms as well as many of the single-celled organisms are eukaryotic organisms. Eukaryotic cells are plants, animals, fungi, and protozoa cells or have a eukaryotic cell structure.

About 2 billion years ago, eukaryotic organisms arose from their prokaryotic progenitors. This phenomenon resulted in the creation of some of today’s major organisms, such as plants, animals, and fungi. With the use of oxygen in respiration came other characteristics and functions, such as the acquisition of eukaryotes becoming more complex. Others began to work in concert with each other to build multicellular entities of greater size and complexity.

Early eukaryotes developed such a product, allowing for greater variation. Thus, eukaryotes are currently the more complex and obviously living forms, and prokaryotes constitute the bulk of the population, consisting of bacteria and archaea. This is why they are still present and alive and this is why we can see their traces in various places on earth the evidence of their ability to adapt and evolve.

Sexual Reproduction in Eukaryotes

In mammals, sexual reproduction means the joining of two forms of reproductive cells referred to as gametes. Two types of gametes are the male gamete sperm and the female gamete egg. These gametes are formed in meiosis in special tissues called gonads. In the male, this is the testis, which is responsible for producing sperm. The female gametes are known as the eggs, which are responsible for making the eggs.

If mating happens, then the male sperm joins the female ovum in a process known as fertilization. Nuclei of both gametes combine, and sperm supplies a new set of chromosomes and hence forms a diploid cell consisting of chromosomes of both parents. This cell will then go through mitosis to achieve the multicellular eukaryotic organism in question. In effect, it will lower their entropy.

The resulting organism displays DNA from the sperm and egg and consists of the genetic information from two different individuals. This mixing enables a greater quantity of genetic diversity, which is optimum for species’ existence and evolutional flexibility. Because of this segregation and variation during sexual reproductive processes, eukaryotes have sophisticated mate selection processes and sexual characteristics such as behaviors, chemicals, and appearances. In a general sense, the process of sexual reproduction, besides giving rise to gametes through meiosis, is beneficial for eukaryotic life due to elements of expanded genetic variation.

Types of Sexual Reproduction in Eukaryotes

There are two main types of sexual reproduction in eukaryotes:

Isogamy

When two sexual forms (usually + and -) unite, the gametes are referred to as equal or equal-superior. Some fungi, algae, and some of the protist forms of life show this.

Heterogamy

Heterogamy is a condition where the two mated types produce dissimilar gametes. In general, there is a bigger, more stationary female gamete (ovum/egg) and a smaller, more active male gamete (sperm). This takes place in essentially all animals and land plants.

Anisogamy can further be classified as:

Oogamy

The female gamete (egg or ovum) is large and does not possess the ability to move from place to place. The male sex cell (sperm) is tiny and aceous. Usually seen in animals as well as land plants.

Anisogamy

Male and female gametophytes are different in size, and both the male and female gametophytes are flagellated. For this reason, the female gamete is larger, although the male is smaller. This occurs in some algae species.

The process of fertilization is possible in both anisogamy as well as isogamy, when two haploid gametes fuse, forming a zygote diploid that can grow and differentiate to become another organism. The only variation pertains to the gametes’ structure, to the extent that they are of equal sizes (isogamy) or of different sizes (anisogamy). Thus, the size, the motility, and the behavior of gametes described the kinds of sexual reproduction.