On pages 85-86 of Survival
of the Sickest, Dr. Moalem discusses how the evolutionary pattern of plants
have led to the development of different chemical defense systems. This
connects to big idea 4: the process of evolution drives the diversity and unity
of life. Explain how this big idea connects to the adaptations of plants. However,
humans have not been able to take advantage of these known defenses by either
breeding plants without toxins or creating more effective pesticides. However,
scientists have not done this. Why have scientists not manipulated the
development of chemical weapons in plants? What complications arise when doing
so? Use information from the text as well as outside information when answering
the question.
The
book also then talks about the adaptations of potatoes using solanine to
prevent blighting. This also prevents other animals from eating it by causing “hallucinations,
paralysis, jaundice, and death” (86). Explain how the solanine creates these
effects. Why do humans not have adaptations like this to prevent similar
complications?
By Daniel Majeed dmajeed4@students.d125.org
The adaptation of chemical defense systems in plants is an evolutionary adaptation. This connects well to BIG idea 1 which states "The process of evolution drives the diversity and unity of life". This connects because these plants have evolved and adapted across generations to equip themselves with these special chemical defenses. They can then fight off infectious diseases and consumers who want to eat the plants.
ReplyDeleteThe reason that we have not been able to manipulate the plants for our advantage is because it is complicated. Plants weapons are aimed towards a variety of things and when we try to take away these defenses, the plants become extremely vulnerable to almost anything so they are easily finished off.
We also have issues when creating plant defenses. They can become so powerful that they become poisonous. This is the case with the potatoes and Solanine. Solanine is a fat-soluble toxin that can cause "hallucinations, paralysis, jaundice, and death". The reasons that Solanine is present in potatoes is to protect them from blight. Symptoms of potatoes that are high in Solanine includes a buildup of green underneath the skin. Eating a potato with large amounts of Solanine will be poisonous and lead to Solanine poisoning. Solanine poisoning can occur with only 2-5mg per kilogram of body weight. It can become fatal when that amount is increased. However, there has not been a case of Solanine Poisoning in the US from eating potatoes in over 50 years.
We believe we have found how Solanine creates these effects. One study suggests that the toxic mechanism of solanine is caused by the chemical's interaction with mitochondrial membranes. Experiments show that solanine exposure opens the potassium channels of mitochondria, decreasing their membrane potential. This in turn leads to Ca2+ being transported from the mitochondria into the cytoplasm, and it is this increased concentration of Ca2+ in the cytoplasm that triggers cell damage and apoptosis. (http://www.wjgnet.com/1007-9327/12/3359.asp).
The reason humans do not have these types of defenses is we do not have a large number of predators after us. We do not need to protect ourselves with a poisonous barrier on the outside of our skin. This connects to the immune system unit as we only have a barrier on the outside that protects against pathogens from entering the body.
Sources:http://www.sciencebasedmedicine.org/index.php/killer-tomatoes-and-poisonous-potatoes/
http://www.wjgnet.com/1007-9327/12/3359.asp
Patrick Austin (paustin4@students.d125.org)
Since plants are immobile, many rely on toxins to protect themselves from consumers. We can thank natural selection for this. Over time, the plants that have certain toxins were able to survive and reproduce, while those that didn’t contain toxins (or not enough of them) were eaten and therefore unable to reproduce. This toxic characteristic has been selected for in many plant species to protect them from predators. This relates to big idea 1, the process of evolution drives the diversity and unity of life, because the adaptations of these plants to survive in their predator-filled environments has led to the evolution of toxic plants.
ReplyDeleteScientists have not been able to develop chemical weapons in plants for many reasons. As we have learned, each gene can control many different traits. If scientists try to engineer the genes of a plant in order to produce more of the toxin, they run the risk of affecting other qualities of the plant that are necessary for survival. Scientists have not yet mapped out the entire genome for each plant, so there is still uncertainty in which qualities and characteristics of the plant are controlled by each gene. Scientists have also realized that when they try to raise toxin levels in the plant to create a more efficient crop yield, the plant usually becomes to poisonous to consume. Due to this, many farmers have resorted to pesticides to protect their plants. However, this also creates complications. Many pesticides are also harmful to beneficial organisms such as insect pollinators, since these beneficial organisms are generally more susceptible to chemicals than the target pest species. ¹This is harmful to the plant because without the presence of these beneficial organisms, the plants are less likely to survive and reproduce. Furthermore, using pesticides can lead to the natural selection of pests favoring the quality of pesticide-resistant pests.
Scientists also reach complications when trying to remove toxins from plants. When the toxin levels are lowered, plants become more susceptible to whatever the toxin was protecting them from. If the toxin was protecting them from a disease, then the plant is more likely to catch the disease and die. If the toxin protected the plant from predators, then there is a greater chance that the plant would then be eaten, as it would no longer be harmful to the predator.
A general complication to genetically engineering these plants is the uncertainty of the results that may be produced. Many biologists “are concerned about the unstoppable nature of the ‘experiment’. If a drug trial produces unanticipated harmful results, the trial is stopped. But we may not be able to stop the ‘trial’ of introducing novel organisms into the biosphere” (Campbell, 817).
(continued)
ReplyDeleteSolanine is a substance found in members of the nightshade family, including potatoes, tomatoes, and eggplants. Potatoes rely on solanine to protect them from blight. Solanine causes the potatoes to have a bitter taste, and appear green under the skin. This has led most consumers to refrain from eating greenish/bitter potatoes because too much solanine can be poisonous. Research by James G. Roddik, Anna L. Rijnenberg, and Stanley F. Osman has shown that solanine has a profound effect on membrane-disruptiveness of erythrocytes in rabbits.²These scientists have witnessed how increased uptake in solanine has lead to lysis of the rabbit cells.
Humans are at the top of the food chain, so there are no major predators after us. Due to this, humans do not have any main toxins for protection. Instead, there are many different mechanisms that our bodies use to protect us from potential threats. A human’s major defense mechanism is the immune system. Physical barriers, the inflammatory response, the humoral response, and the cell-mediated response do a superior job at protecting us from most pathogens. As a result, there has been no need for our body to produce toxins as a defense mechanism, so natural selection has not been in play to select for these toxins.
1. http://www.bioforce.net.nz/Sustainable+Practices++IPM/Impacts+of+Pesticides.html
2. http://link.springer.com/article/10.1007/BF01018781#page-1
(Sarah Terwilliger, sterwil3@students.d125.org)