Comparing Meiosis and Mitosis - Essay Example

1. Compare and contrast in detail meiosis and mitosis and indicate which is more common. All cells are formed from preexisting cells. This cell formation can only take place through cell division. Cell division happens in two different ways, mitosis and meiosis. Differences: 1. Meiosis occurs in reproductive cells, whereas mitosis takes place in somatic cells. 2. Meiosis is a 2-stage division, whereas mitosis is a single stage division. 3. Meiosis results in genetic variation. This genetic variation takes place through chiasmata formation and crossing over. In contrast in mitosis, no genetic variation is possible since there is no chiasmata formation or crossing over. 4. As a result of meiosis, 4 daughter cells are formed, and in mitosis, only two daughter cells are formed. 5. The daughter cells formed during meiosis are all haploid (consisting just half the number of chromosomes of the parent cell), such that fusion of two such cells (fertilization) restores the normal diploid chromosome number. In mitosis, all the daughter cells resemble the parent cell chromosomal number and configuration (diploid). 6. During meiosis, the daughter cells formed are genetically different; in mitosis, the daughter cells are genetically identical. 7. Meiosis causes gamete formation or reproductive cells; mitosis causes increased population of somatic cells and causes repair of worn out cells and replaces dead cells. The commoner cell division is mitosis because the number of somatic cells is far greater than the number of the reproductive cells. So, mitosis is the more frequent cell division. 2. Why is biodiversity so important Be detailed and discuss the various ramifications of losing our biodiversity. Biodiversity is the key to the survival of every species. The existence of a wide variety of species or other taxa of plants, animals, and microorganisms in a natural community is called biodiversity. The main importance of biodiversity is stability of ecosystem. It also provides huge amount of genetic material useful for humans. Biodiversity results in an interspecies relationships, such as, scavenging, commensalisms, proto-cooperation, symbiosis, etc. These interspecies relationships are caused by interaction between two species so that each can be benefited from it. Foodweb is an important part of ecosystem. More is number of species in an ecosystem, better will be the foodweb, which means scarcity of food can be prevented by biodiversity. Apart from this, it can attract tourists so that by ecotourism, the economic condition of the country can be improved. It can promote pharmaceutical research, and indirectly, it can protect our civilization. Loss of biodiversity affects the humans, animals, and nature. We know that quality of foodweb depends upon biodiversity, so biodiversity loss can decrease the food productivity causing prices of food to go up and even death in many cases. Chances of natural disasters also increase with loss in biodiversity. Biodiversity can keep a check on zoonotic diseases, so loss of it can increase health risks of humans from zoonotic diseases. Plant diversity is the source of economy for the country because it provides many products like, timber, fruits, wood fuels, etc. So damage in plant diversity can cause the downfall of economy. This might lead to labor problems too. Loss of biodiversity may lead to habitat destruction, which contributes to the extinction of the animals. Apart from these, geographically, the continuous loss of forests affects rainfall, hence can compromise the quality of water for household use. 3. Explain the following: biotic potential, carrying capacity, logistic vs. exponential growth. Biotic potential: Biotic potential is the maximum rate at which the population could increase. In ideal condition, the variables like maximum birth rate and minimum death rate are determinants of biotic potential. However, the biotic potential can be influenced by environmental resistances, such as, competition with other organisms, availability of food and space, and certain interspecies relationships like predation and parasitism. Balance between population size and the source available for population survival can be achieved by interaction between biotic potential and environmental resistances. Carrying capacity: In a population graph at a certain point, the population growth stabilizes. This is known as the carrying capacity of the ecosystem. It can be defined as the maximum size of a given population of an organism that a particular area can support indefinitely (Audesirk, G. and Audesirk, T., 1996). Carrying capacity is determined by few factors, such as, availability of renewable and non-renewable resources. Excess demand of these invariably damages the ecosystem, thereby reducing its carrying capacity. Logistic vs. Exponential Growth: It is taken for granted that a population that grows exponentially is not limited by food or disease, that is, if a population has enough supply of food and absence of disease, the population grows exponentially even if the birth rate is constant. The birth rate alone controls the rate of growth of population in exponential growth pattern, and this gives an S-shaped curve. In reality, as population grows, food and disease become important limiting factors. This is the result of stress on the environment, and there is a limit to this stress, that is, beyond a certain number, the environment prevents population growth. In these circumstances, the population shows logistic growth pattern. In an exponential growth pattern, when the carrying capacity is reached, the curve levels off to a logistic pattern. 4. Description. In your own words, write a paragraph on each of the scientists: a. Aristotle (384-322 BC): He is the father of Biology. He categorized all the living organisms that he had known, 500 organisms into 11 categories. Aristotle thought that all organisms can be arranged into an orderly scheme, called the Scala Naturae. He also was the first to formulate a logical and standardized nomenclature language for organisms. b. Louis Pasteur (1822-1895): He is the father of microbiology. Before him, organisms were considered to be generated spontaneously. He was the first to show experimentally that it was wrong. He discovered the role of microorganisms for fermentation; he observed that under aerobic condition, the alcoholic fermentation was reduced (Pasteur effect). He was the first to propose and establish the Germ theory of medicine. He discovered the antirabies vaccine, anthrax vaccine, and many other vaccines. c. Gregor Mendel (1822-1884): He is the father of modern genetics. He was an Austrian monk. He studied Botany and Mathematics. His training proved crucial to his later experiments on characters and traits and hybridization in pea (Audesirk, G. and Audesirk, T., 1996). This experiment and his postulations proved to be correct in the sense that it served as the foundation of modern genetics. d. Ernst Mayr (1904-2005): He was a German-American zoologist specializing in the area of ornithology and then biological basis of origin of species and its evolution. He was a professor in Harvard. He has notable works on the origin of species and its evolution. He modernized both the theories from the perspective of genetics. This was known as neo-Darwinism, and it proposes that genetic differences are the basic reasons for evolution (Mayr, Ernst Walter. 2007). e. E.O. Wilson (1929-) (Edward O. Wilson): He is a talented biologist, born in USA, Alabama. He was very inquisitive since his early age. At the age of 16, he made a collection of ants in Alabama. The prominent contribution he has made to biology is called by himself as sociobiology, which controversially, he is the pioneer. His proposition is that complex social behaviors are determined by genetic traits. Darwinian natural selection actually allows the organisms to survive due to useful behavior directed by trait (Wilson, Edward O., 2007). References: Audesirk, G. and Audesirk, T., (1996). Life On Earth, Prentice Hall, New Jersey. Wilson, Edward O., (2007). In Encyclopdia Britannica. Retrieved May 20, 2007, from Encyclopdia Britannica Online: http://search.eb.com/eb/article-9077123. Mayr, Ernst Walter. (2007). In Britannica Book of the Year, 2006. Retrieved May 20, 2007 from Encyclopdia Britannica Online: http://search.eb.com/eb/article-9403207 Read More