If you are adding something to the water the concentration of water would drop, as it would start off as 100% water but then with the addition of another substance it would change that from 100% free to x% free, due to the water dissolving the substance.
B
The other problems are not as easily solved; whereas, data collection over long periods of time is possible and was already done in the past, eg temperature and weather patterns. Therefore, this is the easiest limitation to overcome.
The evolution of the peppered moth is an evolutionary instance of directional colour change in the moth population as a consequence of air pollution during the Industrial Revolution. The frequency of dark-coloured moths increased at that time, an example of industrial melanism. Later, when pollution was reduced, the light-coloured form again predominated. Industrial melanism in the peppered moth was an early test of Charles Darwin's natural selection in action, and remains as a classic example in the teaching of evolution. Sewall Wright described it as "the clearest case in which a conspicuous evolutionary process has actually been observed."
Rain falling to the ground. water runs downhill and flows toward the sea.
