Life cannot exist without reproduction. This biological process is the fundamental one because every organism exists due to it. Every plant, bacteria, insect, animal and human being is the result of reproduction. Without this process, our planet would be empty. It would contain minerals, rocks and atmosphere but it would not differ from any other lifeless planet. Earth is unique and engrossing whereas it contains life. Why is the issue on reproduction so weighty for biologists? Actually, it is impossible to understand the evolution of this process. How did organisms ‘learn’ to reproduce? Why do some organisms reproduce faster and others slower? What is the primary role of reproduction for human beings? The problem of reproduction is very deep and enlightening inasmuch as there are many kinds of reproduction. Different organisms reproduce in the different way. Thus, this subject is still absorbing and thought provoking for every scientist. They conduct numerous experiments to understand this fundamental feature of the living organisms.
When we speak about reproduction, we should mention that there are two primary types of this biological process. One can define asexual and sexual reproduction. Asexual reproduction is characterized with the reproduction of an organism without the interaction or involvement of another one. Bacteria, viruses, Hydras and yeasts are able to make copies of themselves without the involvement of another organism. They do not need genetic material of the representative of the opposite gender. They just make their identical copies by budding. Next, the majority of plants reproduce asexually too. However, the mentioned organisms (Hydras, yeasts and plants) are able to reproduce in both ways – sexually and asexually. This feature makes them strong and probably ‘immortal’ forasmuch they can reproduce themselves if they cannot find the representative of the opposite sex. Animals and humans do not possess this ability. It makes their survival more complicated.
There are several other forms of asexual reproduction. Parthenogenesis is the kind of reproduction characterized with the development of embryos without the act of fertilization. An embryo develops from the unfertilized egg cell. Some plants, scorpions, bees, wasps, reptiles, fish and amphibians reproduce in this way. Another kind of asexual reproduction is fragmentation. An organism is split into several fragments that develop into the independent identical organisms. Sea stars, sponges and other organisms are known to reproduce in this way. The final type of asexual reproduction is sporogenesis or reproduction with the help of spores. Fungi, algae and some plants use this method of reproduction.
It is possible to differentiate another type of asexual reproduction related to the artificial reproduction conducted by scientists in a laboratory. Cloning is a very disputable and controversial issue whereas genetic engineers and other experts in this field grow plants and animals artificially.
There have been many attempts to clone a human being. However, the public does not approve such experiments considering them unnatural.
The second major type of reproduction is sexual reproduction, which is associated with the creation of the new organism during the combination of the genetic material of the two organisms of different sexes.
This method of reproduction is characterized with the special way of cell division. This way is called meiosis. It is easy to understand that sexual reproduction involves two organisms to create another one.
Both organisms (male and female) possess gametes or cells that interact and fuse with other cells during the act of fertilization. Gametes possess the set of the chromosomes whose number is reduced by half.
When a male gamete interacts with the female one, they form a fertilized zygote. As a result, the offspring is not the identical clone of its parent but a combination of the genetic characteristics inherited from both parents. Some plants, insects, birds, fish, mammals, reptiles, amphibians, mollusks reproduce with the help of sexual reproduction.
Reproduction is a very engrossing and notable issue for research. This subject is paramount for evolution, biology, physics, chemistry and other disciplines. It is possible to claim that reproduction is the major function of every living organism. Life would never exist without reproduction; thus, experts wonder about the evolution and development of this ability. It is natural that some organisms (insects, small mammals, fish, etc.) reproduce faster inasmuch as they are weaker and smaller. Their life is very short and time is their enemy. Big animals (elephants, rhinos, whales, etc.) are very huge and there are very few threats to their life. Consequently, the period of their reproduction is longer.
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