Cellular Reproduction Essay -- Biology

Cellular Reproduction Cellular Reproduction is the process by which all living things produce new organisms similar or identical to themselves. This is essential in that if a species were not able to reproduce, that species would quickly become extinct. Always, reproduction consists of a basic pattern: the conversion by a parent organism of raw materials into offspring or cells that will later develop into offspring. (Encarta, 2) In almost all animal organisms, reproduction occurs during or after the period of maximum growth. (Fichter, 16). But in Plants, which continue to grow through out their lifetime, therefore making the process more complex. Plants' reproduction is usually caused by a stimulant, mostly environmental or growth factors. The reproductive process, whether asexual or sexual always involves an exchange in hereditary material from the parent(s) so that the new organism may also be able to reproduce. Reproductive processes can be categorized in many diffrent ways although the most common is to put them into either asexual reproduction or sexual reproduction. Asexual reproduction is the process by which a single organism gives rise to two or more daughter cells. Most single celled organisms reproduce by the asexual process known as fission, which is commonly called mitosis. Fission (or Mitosis) is the division of one cell into two identical daughter cells. Interphase, the first phase of the cell cycle and also the phase before mitosis, starts as soon as the cell is born. Interphase is broken up into three phases, G1, S, and G2. During the G1 phase, the cell increases in mass except for the chromosomes, which stay the same, uncoiled. Protein synthesis is also occurring rapidly in this phase. If a cell doesn't divide further, it remains permanently in the G1 phase. Next is the S phase, in which the mass of the cell continues to increase, and DNA is duplicated, and then the chromosomes divide to form identical sister chromatids attached by a centromere. (Harold, 45). During the G2 phase of Interphase, the cell becomes double its mass at birth, the chromosomes begin to shorten and coil, and the centrioles appear, the cell is now ready to enter into mitosis. In the first and longest phase of mitosis, prophase, the chromosomes become visible and the centrioles split in half and then move to opposite sides of th... ...on’t seperate correctly. This is called nondisjunction. There are three types of nondisjunction, Trisomy- when a gamete with an extra chromosome is fertiized with a normal gamete. Monosomy- when a gamete with one chromosome is missing and is then fertilized by normal gamete. And Trioloidy- where both zygotes have an extra chromosome. Reproduction is as essential to a species as food, water, or shelter. If a species cannot reproduce anymore, that species will eventually become extinct. There are many means of reproduction but primarily only two: asexual and sexual. In asexual reproduction, One organism gives a part or its whole self, in order to give rise to two or more new organisms. During sexual reproduction, two parents each form sex cells, which unite, and eventually form a new individual. Works cited Biggs, Alton & others. Biology: The Dynamics of Life. Glencoe McGraw-Hill.: New York, NY, 2000 Encarta Encyclopedia. CD-ROM. 1998 Fichter, Sheila. Reproduction. Universal Press: Columbus, OH, 1994 Harold, Christopher. Cells: A Guided Tour. Simon and Schuster: New York, NY, 1987 O’Neil, Franklin. Cells. McMeel Publishing, Inc.: Atlanta, GA, 1990