Are Single Cell Organisms Simple - Essay Example

Single cell organisms are simple". Discuss. Single-celled organisms usually lead an autonomous way of life. Most of them are normally microscopic andpossess a cell wall or a cell membrane rather than an exoskeleton, thus, they do not have a fossil record. Single celled organisms belong to either prokaryotes including bacteria and mycoplasma or they are eukaryotes encompassing amoeba, paramecium, euglena etc. The simple nature of the single-celled organisms is attributed to their diverse characteristics which distinguish them from their eukaryotic counterparts. For instance, prokaryotes (pro= primitive; karyon= nucleus) cells lack a true nucleolus, cellular organelles such as mitochondria, chloroplast, endoplasmic reticulum (ER), Golgi bodies etc. The DNA found in prokaryotes is circular, devoid of basic histones; they do not undergo normal cell division of mitosis and meiosis, they multiply by simple replication of DNA, followed by binary fission, thereby the two daughter cells are clones (exactly similar). Single celled organisms do not possess defined nutrition and excretory mechanisms. Some single-celled organisms such as amoeba have simple cell structures known as vesicles that are responsible for excretion and osmoregulation. Moreover, they ventilate through simple diffusion process across the cell membrane. Single cellular organisms can be deemed as simple, as unlike eukaryotic cells where progeny is formed after the fusion of male and the female gametes, and the progeny possesses the characteristics of both the parents, while most single celled organism do not. As a matter of fact, they can divide a number of times within one hour. Additionally, unlike most multicellular organisms, single-celled organisms can readily synthesize most of the essential substances that they need from simple nutrients. These processes are very simple and straight forward. Also, single-celled organisms can be considered as simple due to their limited capacity to occupy a wide range of habitats. This is attributed to the fact that they do not have division of labour necessary for the exploitation and subsequent utilization of a wide range of resources. On the contrary, they achieve division of labour by formation of colonies, which they achieve by having their daughter cells remaining attached after subsequent cell divisions. Variation has been estimated as a vital component in the sustenance of species. Most single-celled organisms tend to lack variation owing to their ability to reproduce asexually, implying that organisms retain the exact genetic composition as that of their parent cells. Single celled organisms like numerous eubacteria and archaea, display numerous forms of life. Archaea are capable of proliferating in extreme environments, while other bacteria show different life forms which form some similarity with the higher life forms such as motility by means of flagella which is similar to the epithelial lining of nasal mucosa of animals. Genetic alterations in bacteria brings genotypic as well as phenotypic alterations which could be correlated with the genetic alterations that occur in most evolved species, human beings such as Albinism. Thus, single celled organisms such as bacteria display diversity in life forms which could be correlated with the higher organisms, indicating that single celled organisms are simple yet potentially capable of proliferating in diverse conditions displaying diverse functions. "The history of life is that of co-operation". Using appropriate biological examples support this statement. The history of life is solely based on co-operation, without mutual help life would have been impossible on the planet. A prokaryotic organism is also not dependent on one molecule but on plethora of chemicals that act in a co-ordinate manner to form enzymes and proteins for structural and functional aspects thereby playing vital role in cellular metabolism, cell division, replication and proliferation. Prokaryotes aggregate to form cluster of cells by means of chemical messaging which is performed in a co-ordination. Eukaryotes possess various organelles such as mitochondria, chloroplast, Golgi apparatus, endoplasmic reticulum also function in co-ordination to make the cell function appropriately. Various small eukaryotes such as slime moulds, Volvox, sponges exist in co-ordination and form colonies. Gradually with evolution such aggregation of cell turned to distribute the functions required for survival. For instance the cells on the periphery of the colony only develop flagella to move the entire colony. As organisms evolved to higher life form, co-ordination between cells became all the more sturdy and division of labor could be observed in the organisms. For instance, ants and bees distribute their work for survival. In a similar manner co-ordination is also observed in various species of animal kingdom, plant and animal kingdom, plant-animal- microbial world. In most instances, organisms may live together for a longer time with one or more benefiting from the co-operation, referred as symbolic associations. The organisms can team with other species that can serve to provide them with shelter, food as well as protection and transportation. In mutualism, where partners derive benefit from the association, as exhibited by Rhizobium, a bacterial strain harbored in the root nodule of leguminous plants. Sharks and remora fish, occur in commensalism, the fish usually attaches itself on the sharks where it enjoys transportation from one place to another in search for food. In plant world, tropical rain forests, climbing plants usually depend in the tall trees to reach to sunlight zone for photosynthesis. Disease producing organisms or parasites harm the host. Parasitic co-operations are exhibited when one organism gets benefit while causing harm to the other. Such organisms that cause harm while benefiting from the other are known as parasites while the one being harmed is known as the host. Human beings are host to parasites such as tapeworms that gets benefit in terms of shelter and nutrition while depriving the host from its nutrients. In animal body various organs and organ systems work in co-ordination to make the body function in the desired manner. Any alteration or inability of a particular organ or organ system results in disease condition or some kind or predicament. Every cell in multicellular organisms lives in association with numerous other cells for nutrition, excretion and to perform metabolic function. Thus distribution of work enhances the ability of the organism to work without much efforts. It is similar to the human societies where distribution of work makes the working effortless and people are able to enjoy their work and implement skills for further improvement and progression. "The gradual evolution of mankind is the obvious destined end-point of evolution". What flaws can you see in this statement? In the theory of evolution, the terms gradual and gradualism have both been used to refer to the rate of evolution, which means that evolution tend to occur at a fairly constant rate. The concept of gradualism in evolution has been enormously disproved owing to the fact that fossil records do not give a reflection of this. Instead, fossil records provide a rather intermittent evolution pattern. Flaw in the statement arises from the perception of humans as the destined end-point if evolution. This idea distorts the interpretation of the life’s pathway. This distortion tends to occur fallaciously, placing in the canter of things a relatively minor phenomenon that arises as a surface consequence of a physically constrained starting point. Most salient feature of the evolution of life has been the stability of bacterial mode from the beginning of fossil record up to the present day. Bacteria continues to evolve, as can be seen in terms of resistance to various drugs, implying that evolution is still continuing and man is ultimately not the end-point of the evolution process. Consequently, the fact that evolution has also reached an end-point may be disputed, especially bearing in mind, various man-made improvements on other species due to human activities have continued to occur over time, species modify themselves so as to cope with the modifications and hence a step towards evolution of the species to adjust in an otherwise less congenial conditions. Improvements in biomedical engineering have observed the evolution of new and well adapted agricultural plant and animal species, thereby defying the fact that evolution has received its ultimate end-point. According to Darwin, evolution occur as a result of natural selection. Organisms descent with modification, these modifications are coined as evolution. In the process, there is a change in the gene frequency enabling the organism to adapt to the environment. Evolution is thus a constant process and every species has been adapting to the modifying environment displaying a genetic drift and hence the progression. Thus, evolution cannot meet its endpoint as it is a continuous process. A sudden change could not be witnessed as it is a slow and advancing process and takes years to be delineated. Molecular biology techniques to study genomes and similarities between the genes in various organisms also highlight the fact that evolution is a constant process and still going on. Considering the frequency and complexity of the organisms, life began at left wall of the graph with minimum complexity and increases to more complex life forms as we move towards right. Over the period of time the organisms display alterations in complexity, tapering (as tail) indicating the insignificant alterations. These alterations are not attributed to one feature but it is an amalgamation of varied features, which are not directed to meet the end-point but occur for the betterment of organism to suite the requirements of environmental modifications. Read More