Answer:
a. The original spraying has caused a permanent mutation, giving the insects genetic resistance to the spray.
Explanation:
This is a practical evidences of mutation and variation, as mechanisms of evolution.
The insecticide is the selective pressure. As a results of continuous spray, the parents of the present mosquitoes must have acquired certain characteristics or traits by gene mutation which makes them resistant to the selective pressure (insecticides), and therefore survive the spray in the past.
Therefore when these resistant parents mated, with high reproductive success (leading to large gene pool of these traits,); variation in the genetic composition increases as the resistant gene is passed from generations to generations in the population. Therefore, the population of present day mosquito with genetic resistance to insecticides increases.They are therefore naturally selected, and able to survive as the present day mosquitoes with high resistance to insecticides.
Algae, the probably compete for the
Food source.
Answer:
The main reason is growth factor ligands do not bind as efficiently to receptors.
Initially, normal cells work efficiently on binding of enzymes, growth factors or ligands and cellular growth cycle runs effectively but with the passage of time, cellular aging or organismal aging can lead to decrease efficiency of cellular recepotors binding with the growth factor ligands gradually.
