List some steps of evolution by natural selection by which a population of mosquitoes becomes resistant to the insecticide DDT. Begin with a DDT-susceptible population, before DDT is introduced. Remember, microevolution is a change in allele frequency.
plz explain how do u do this? I'm confused...
2007-02-13 11:23:36 · 2 answers · asked by sdt3 1 in Science & Mathematics ➔ Biology
First, remember what the rules are for natural selection. They are easy: 1) organisms vary; 2) variations influence survival when more offspring are produced than can survive; c) the survivors reproduce.
OK, so not all mosquitos are the same. Some are more resistant and some are less resistant to the chemical. So, the resistant ones will survive while the others are killed. So, who reproduces? And in the next generation, how many of the offspring will be resistant?
2007-02-13 11:35:35 · answer #1 · answered by matt 7 · 1⤊ 0⤋
Within a large population of mosquitoes there may be some who have a gene for resistance to DDT. If you start heavily spraying DDT, you will rapidly eliminate all the mosquitoes that are susceptible to the insecticide. If you continue spraying, only mosquitoes who are resistant will be left alive to reproduce, and will have a better chance of mating with another one who is also resistant to DDT. In a short time most of the mosquitoes will be resistant to DDT. The ones who will survive to pass on their genes will not be the best fliers or the ones who sound prettier like before :) , but only the ones who can survive the new definitive threat... now the allele frequency for resistance to DDT has increased. That's why they need to use different insecticides on a rotational basis, so the pressure on the population is not always the same one..
2007-02-13 11:40:58 · answer #2 · answered by nmaria 3 · 0⤊ 0⤋