In plants, transpiration is a process which is inevitable but potentially harmful, because it can cause loss of water. Loss of water can lead to wilting and eventual death of the plant. Even a little stress can interfere with the plant's growth process.
But, at the same time, transpiration is necessary because of a number of reasons - the transpiration stream aids the processes of mineral absorption, water absorption, energy exchange, helps provide the plant with optimum turgidity, it helps the exchange of gases and so on.
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."
<span>(According to Reference)
Whereas an onion epidermal cell has a cell wall, a human cheek cell does not. Instead, a semi-permeable membrane surrounds the cytoplasm of the cheek cell. While there are chloroplasts present in onion cells, they are absent in cheek cells. </span>
It is D. <span>chloroplast.</span>
