Biology Exam Essays

Biology Exam Essays Biology Exam Paper Biology Exam Paper Describe the structure and functions of the small intestine, and explain how the liver and pancreas helps in these functions. â€Å"The small intestine is an extremely vital organ in human gastrointestinal system. Along with the stomach, it is the major organ involved in the process of digestion† (Tortora, 2004). Surely, it is not enough to say that the small intestine plays critical role in human digestion processes. The structure and functions of the small intestine tell much about the way it manages and participates in human digestion. The small intestine is approximately 6 meters in length (Tortora, 2004). In human organism, the small intestine is usually stretched between the stomach and the large intestine. Medical professionals usually divide the small intestine into the three different segments: the ililum, the jejunum, and the duodenum (Tortora, 2004). However, this division is more important in medicine than in biology. Anatomy and biology primarily pay attention to the surface structure of the small intestine, which absorbs nutrients and transfers them to other organs and systems. Functionally, the small intestine is involved into the three different types of absorption procedures (simple diffusion, active transport, and facilitated diffusion). The small intestine transports the nutrients from the stomach to the large intestine, absorbing the necessary nutrients, and transferring them to other human organs. Surprisingly or not, but the small intestine does not possess sufficient surface area to absorb all nutrients for the human organism. Moreover, the small intestine cannot support the normal functioning of human organism without the liver and the pancreas’ assistance. â€Å"The pancreas secretes digestive enzymes into the duodenum, the first segment of the small intestine† (Tortora, 2004). These enzymes break down fats, carbohydrates, and proteins. In its turn, the liver processes and filters the nutrients which the small intestine absorbs and transports to other functional human systems. The bile which is produced by the liver plays a vital role in breaking down fats in the small intestine. 2. Describe the process of development in humans from the fertilized egg to the time it becomes a fetus, during a normal pregnancy.   The development of the fertilized egg begins when it is still located in the fallopian tubes. â€Å"Repeated mitotic divisions produce a solid ball of cells called a morula† (Tortora, 2004). The newly formed morula is continuously divided, and is later turned into a kind of empty ball, which biologists call â€Å"the blastocyst†. The fertilized egg, or blastocyst, needs one week to embed itself into the female uterus. The process of â€Å"embedding the egg into the wall of uterus† actually confirms the fact of pregnancy in a woman (Tortora, 2004). The process of cells’ division proceeds after the egg has become integral with the uterus. At this stage of fertilized egg’s development, the inner cell mass of the blastocyst is being created. In about 2 months, this mass becomes a baby (a fetus). The rest of the blastocyst cells are later transformed into placenta, â€Å"which grows tightly fused to the wall of the uterus† (Tortora, 2004). Placenta becomes the major connecting channel between the unborn child and the mother. The placenta’s blood vessels connect the child’s blood system to that of the mother. Placenta significantly facilitates the transfer of nutrients from the mother’s organism into that of the fetus. The first 2 months of pregnancy usually form the basic structure of the future child: cell division and cell differentiation take place. At this pregnancy stage, the fetus is extremely vulnerable to external infections and damages. In two months, when the fetus’ organs are formed, â€Å"the fetus’ development becomes a matter of mere growth and minor structural modifications† (Tortora, 2004). 3. The evolution of species can only occur in populations. Is this an accurate statement? Explain why or why not. Evolution is noticeable, and can take place only in populations. However, it is not correct and it is not accurate to state that the mere existence of a population determines the course of evolution. We cannot limit evolution to populations, but should look deeper into what causes evolution within these or those populations. To be objective, it is not a population, but its genetic diversity that becomes the driving force of evolution. â€Å"No individual members of any population are exactly alike in their genetic makeup. This diversity, referred to as genetic diversity or variation, is essential to evolution† (Gould, 2002). This is why it will be more accurate to state that evolution takes place in genetically diverse populations. Speaking about evolution and populations, we cannot neglect the importance of genetic variation across different species and groups. Genetic variation remains a key to a stable continuous evolution and ensures the highest degree of evolutionary success.