1) How do animals keep from digesting themselves? 2) What are the biological adv
ID: 90275 • Letter: 1
Question
1) How do animals keep from digesting themselves?2) What are the biological advantages of internal versus external fertilization and internal versus external development of the embryo?(internal/extrnal fertilization) and (internal/external develpment of embryo)
3) Why are eggs and sperm so different in size. What functions can you infer from their structure?
4) Why do humans crave fatty foods? 1) How do animals keep from digesting themselves?
2) What are the biological advantages of internal versus external fertilization and internal versus external development of the embryo?(internal/extrnal fertilization) and (internal/external develpment of embryo)
3) Why are eggs and sperm so different in size. What functions can you infer from their structure?
4) Why do humans crave fatty foods? 1) How do animals keep from digesting themselves?
2) What are the biological advantages of internal versus external fertilization and internal versus external development of the embryo?(internal/extrnal fertilization) and (internal/external develpment of embryo)
3) Why are eggs and sperm so different in size. What functions can you infer from their structure?
4) Why do humans crave fatty foods?
Explanation / Answer
(1) The stomach is made up of: (a) the outer layer serosa that acts as a covering for the other layers; (b) muscle two layers - that propel food from the stomach into the small intestine; and (c) the mucosa which is the inner layer made up of specialized cells such as parietal cells, g-cells and epithelial cells. The parietal cells secrete hydrochloric acid which is useful for breaking down the food substances. In animals, the stomach is protected by a lining of epithelial cells. These cells secrete a bicarbonate-rich (alkaline/basic) soultion that neutralizes the acid secreted by the parietal cells. This continuous supply of bicarbonate helps protecting the stomach from auto-digestion and the from overall acidic environment.
(2) Internal fertilization has the advantage of protecting the fertilized egg from dehydration on land. In internal fertilization, the embryo is isolated within the female, which limits predation on the young. It also enhances the fertilization of eggs by a specific male.
Advantages: Interal development of embryo has the advantages of independency of external water medium, it prevents dessication of gametes and embryo; leads to less wastage of gametes and has a chance of successful fertilization.
In the external fertilization, the male deposits sperm into a body of water. This sperm travels until they reach an egg deposited into the water by a female. The external fertilization does not rely on hormones, mating rituals and behavioral factors or sexual intercourse. It is a very simple process.
Advantages: There is little or no parental care but high mortality of gametes and offspring. If the parents get eaten, the offspring are already available to replace the adults. Since multiple pairs are involved in external fertilization, more genetic diversity is likely to occur.
(3) The oogonium makes one oocyte and three small polar bodies, but spermatogonium will produce four spermatozoa with equivalent size. That is the major reason why egg is so much larger. The egg contains almost all organelles, materials, and nutrients required for the for growth of the zygote. A sperm only contains a haploid set of chromosome and mitochondria for movement and this is the ]reason why egg is larger than sperm.
(4) The crave for fatty foods indicate that there is a fluctuation in the essential fatty acids (EFA's) in foods.
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