Answer:
Cancer is caused by changes to certain genes that alter the way our cells function. Some of these genetic changes occur naturally when DNA is replicated during the process of cell division. But others are the result of environmental exposures that damage DNA.
The alveoli needs of the epithelium for the gaseous exchange and stratified squamous epithelium are formed of multiple layers the difficulty in a gaseous exchange
The genetic equilibrium represents the condition of a genotype or an allele in the genetic pool of a particular population, where there are no changes in the frequency in the successive generations. This basically means that the population has managed to reach the peak of its evolution for the environment in which it leaves, so there's no evolutionary pressure for changes.
In order for the genetic equilibrium to be maintained for prolonged period of time, the population should not face any evolutionary pressure that will cause changes in it. In essence, this means that the environment in which the population lives should remain exactly the same as it is for longer period of time, so the population will have no need to change its appearance or behavior.
