Module 2.1: Evidence of Evolution
Species change through time (microevolution), is one of the predictions Darwin’s idea of descent with modification makes that I find interesting. Darwin projected that microevolution would be a process of continuous and gradual change. Microevolution is a selection occurring on a single or few genes in a population over a short period of time. It is evolutionary change on a small scale for example, between one generation and the next generation, the frequency of a gene for pesticide resistance in a population of crop pests increases, through artificial selection. It is an alarming problem, but pests are only following the rules of evolution, the best-adapted survive. When a pesticide is first used, a small proportion of the pest population may survive exposure to the pesticide due to their distinct genetic makeup. These individuals pass along the genes of resistance to the next generation. Successive uses of the pesticide increase the proportion of less-susceptible individuals in the population. The population gradually develops resistance to the pesticide, threatening the effectiveness of the pesticide to protect crops. Taiwan, India, and Malaysia are three strains of the Drosophila melanogaster that have been found to be resistant to alpha-amanitin (α-amanitin), the most fatal of all mushroom toxins. α-amanitin is said to be 30 times more toxic than cyanide when consumed, and it is found in Death Cap and Destroying Angel mushrooms. These fruit fly species do not feed on mushroom in nature thus, they may have evolved their resistance to α-amanitin due to previous pesticide exposure.
Microevolution, and pesticide resistance is the answer
to why bed bugs have not been eradicated despite all the efforts made by
scientists. Initially, bed bugs were controlled with toxic chemicals such as
DDT. Since then, fresher classes of insecticides such as synthetic pyrethroids
have been employed to keep bed bug populations low. Currently, bed bugs have
slowly been developing resistance mechanisms and have become resistant to most
if not all, pesticides on the market. Resistance mechanisms include penetration
resistance through the thickening of the cuticle, knockdown resistance by
mutations, and metabolic resistance by increased activities of detoxification
enzymes. Mutations at the target site of the chemical make the pest unaffected
by the pesticide.
Sources
Bedbugs Evolve Rapidly to Withstand
Pesticides - WSJ
Fruit fly genetics reveal pesticide
resistance and insight into cancer | EurekAlert! Science News
I also think microevolution is very interesting. I'm a little concerned about bed bugs developing resistance, but it does make sense. It kind of makes you wonder it there will be a time when bed bugs are resistant to all types of pesticides we have, and how long that would take. Going in a different direction, imagine if we completely stopped using pesticides. Since a resistance wouldn't be necessary in the gene pool, do you think they would evolve to be less resistant? It's interesting to think about. Great post!
ReplyDeleteHi Ally,
DeleteThank you for taking time to read my post. Very interesting question. Since the use of pesticides plays a significant role in the development of pesticide resistance, I think stopping usage might minimize resistance. Once this trait is passed down to future generations, we expect evolution to occur.