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Control group in scientific experiments Essay

A control group in an experiment is a variable wherein it is not subjected on the items being tested that is hypothesized to cause effect on the subject. The idea of the control group is to represent the appearance and attributes of the subject in the absence of the other variables (McEwan, 2003). The control group also eliminates all other factors that may affect the one being tested. Also, the nature of experiments is to prove a cause and effect phenomenon. The absence of a control group will not prove that the outcome is caused by the tested variable.

2. Briefly discuss the differences between prokaryotic and eukaryotic cells. The main distinction between the two types of cell is the presence of nucleus. Eukaryotic cells have a true and distinguishable nucleus, while prokaryotic cells do not have a nucleus though they have a long strand of DNA embedded in the middle of the cell. Eukaryotic cells are larger than the prokaryotic cells. Eukaryotic cells are equipped with membrane-bound organelles located in their cytoplasm, while prokaryotic cells lack such organelles (Roberts, Reiss & Monger, 2000).

Also, the DNA of a eukaryotic cell is linear; the DNA of a prokaryotic cell is circular and has no ends. The DNA of a eukaryotic cell is composed of proteins called “histones” and it is organized inside the chromosomes of the cell. The DNA of a prokaryotic cell, on the other hand, is naked and has no histones (College of DuPage, 2000). 3. What role do enzymes play in living organisms? Enzymes are proteins that are present in all living organisms. Enzymes perform important functions in controlling various metabolic processes wherein nutrients are transformed into energy and fresh cell material.

Enzymes also help in breaking down food into simpler compounds. Enzymes also act as catalysts that hasten up various chemical processes that otherwise would run very slowly (Safe2Use, 2005). 4. What is the ultimate (originating) source of the energy contained in food? Adenosine Triphosphate or ATP is considered as the main source of energy. It is a molecule that stores high level of energy that living organism needed to perform various functions and activities (“Adenosine Triphosphate”, n. d. ). 5. Discuss how researchers decide that populations of organisms belong to the same biological species.

Researchers identify species as populations of organisms that have a high level of genetic similarity. This may be reflected on the adaptation of the species to the same niche or habitat and the transfer of genetic material from one individual to another through a wide array of ways. 6. Briefly discuss some of the problems that occurred with the cloning of animals. Reproductive cloning is very expensive and renders a low success rate. More than 90 percent of the cloning procedure failed to produce a viable offspring. Cloned animals also have a higher risk for infection and other disorders.

There are also problems that may result from programming errors from a donor cell (“Cloning Fact Sheet”, 2009). 7. The origin of life on Earth would not have been possible if the primitive atmosphere contained __________. Carbon dioxide 8. How does energy flow differ from chemical cycling? Energy flow is one-way or the energy is transferred from one location to another. Chemical cycling is circular. Chemical materials and elements are recycled. 9. Briefly define and discuss homeostasis. Homeostasis is the maintenance of a constant internal environment within the body.

It includes the maintenance of various body functions such as water balance of the blood, blood sugar level, and body temperature and blood urea level. Each of the body functions are monitored by a separate mechanism. All mechanisms pertaining to homeostasis share some common features like having a specific sensor that is able to detect the value of the factor being monitored (Givens & Reiss, 2002). 10. Briefly describe the difference in the outcomes of mitosis and meiosis. (There is no need to discuss the processes themselves – only the differences in the end product.

) Mitosis yield to two daughter cells that is genetically identical to the original. Meiosis, on the other hand, yield to four daughter cells that is none of which is identical to the original (“Mitosis & Meiosis: How Cells Divide”, n. d. ). 11. In what part of the digestive system does most nutrient absorption occur? Most absorption occurs in the duodenum and jejeunum that are parts of the small intestine. The inner surface of the intestine is composed of circular folds that more than triple surface area for absorption (Farabee, 2007).

12. In humans, oxygen is delivered to the cells of the body by the _______ system. Circulatory 13. Why do animals need oxygen; i. e. , what role does oxygen play in animals’ bodies? Respiration is the process of turning food into energy. The process uses oxygen and yield to water and carbon dioxide. Oxygen is also one of the main components of the vital molecules in the body (Teal, 2009). 14. Why do diseases involving widespread infection usually result in a fever? Fever is a natural response of the body’s immune system.

It also makes the environment unfavorable for the pathogens that caused the infection and eventually slows the growth of the pathogens. Also, the high temperature whenever there is an infection activates the heat-sensitive proteins and hastens the production of enzymes. 15. What is biology? Biology is the field of science that pertains to life and living organisms. The scope of this study ranges molecular aspect of an organism to how it interacts in its ecosystem. 16. The appendix, bone marrow, thymus and spleen are all parts of the ______ system.

Immune 17. What process results in offspring that is adapted to their current environment? Evolution is the process of organisms to adapt on their current environment. It is a way in adjusting to the changes in biotic and abiotic conditions (Chiras, 2006). 18. What is the difference between a phenotype and a genotype. Does knowledge of an organism’s phenotype always allow you to determine the genotype? Why or Why not? The genotype of an organism groups the organism according to its actual material that made up the DNA that was passed by its parents.

Phenotype, on the other hand, groups the organism based on its physical and behavioral characteristics (Lewontin, 2004). No, though some of the characteristics of an organism are influenced by its genotype, the phenotype and genotype are not always correlated (“Genotype”, 2007). 19. Briefly compare and contrast the processes of cellular respiration and photosynthesis. Photosynthesis is the process where plants or the producers utilize sunlight, water and carbon dioxide to make food and oxygen. Cellular respiration, on the other hand, is the process wherein the cells utilize the food and release its stored energy (Willis, 2001).

20. Discuss the validity of the following statement (providing your reasoning): Cutting the tails off mice for 100 generations will result in a strain of mice for short tails. The statement is invalid. Cutting the tails of the mice does not alter the genetic make-up of the organism. It just changes the physical appearance of the mice. The genetic code embedded in the chromosomes of the mouse is still the same when its tail is still intact. References Adenosine Triphosphate. (n. d. ). Retrieved June 11, 2009, from http://hyperphysics. phy-astr. gsu. edu/hbase/Biology/atp. html. Chiras, D. D.

(2006). Environmental Science. Sudbury, MA: Jones & Bartlett Publishers. Cloning Fact Sheet. (2009, May 11). Human Genome Project Information. Retrieved June 11, 2009, from http://www. ornl. gov/sci/techresources/Human_Genome/elsi/cloning. shtml. College of DuPage. (2000). Prokaryotic and Eukaryotic Cells. Retrieved June 11, 2009, from http://www. cod. edu/PEOPLE/FACULTY/FANCHER/ProkEuk. htm. Farabee, M. J. (2007, June 6). The Digestive System. Retrieved June 11, 2009, from http://www. emc. maricopa. edu/faculty/farabee/BIOBK/BioBookDIGEST. html. Genotype. (2007, September 26). Citizendium.

Retrieved June 11, 2009, from http://en. citizendium. org/wiki/Genotype. Givens, P. & Reiss, M. (2002). Human Biology and Health Studies. United Kingdom: Nelson Thornes. Lewontin, R. (2004). The Genotype/Phenotype Distinction. Stanford Encyclopedia of Philosophy. Retrieved June 11, 2009, from http://plato. stanford. edu/entries/genotype-phenotype/. McEwan, P. J. (2003). Making Sense of Research: What’s Good, What’s Not, and How To Tell the Difference. Thousand Oaks, California: Corwin Press, Inc. Mitosis & Meiosis: How Cells Divide. (n. d. ). Retrieved June 11, 2009, from http://www. guidanceassociates.

com/mitmeioshowc. html. Roberts, M. , Reiss, M. & Monger, G. (2000). Advanced Biology. United Kingdom: Nelson Thornes. Safe2Use. (2005). What are Enzymes? Retrieved June 11, 2009, from http://www. safe2use. com/data/enzymes. htm. Teal, A. (2009, May 23). The Role of Oxygen in the Human Body. Scienceray. Retrieved June 11, 2009, from http://www. scienceray. com/Biology/Human-Biology/The-Role-of-Oxygen-in-the-Human-Body. 724015. Willis, B. (2001). Photosynthesis and Cellular Respiration. Retrieved June 11, 2009, from http://www. worsleyschool. net/science/files/photosynthesis/page. html.

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