Use process of elimination. From what you gave me to read, you can cross off competition. A drought killed the plants and not competition to live. Go down the list of words and look up the definition. Look at nudation and ecesis later because they are different words that may or may not be challenging to understand. You know what reaction and migration is without looking it up. Once you cross off all words answers that don't match up, ask yourself, which remaining answer goes? Nudation is basically new plants that have successfully started growing after a huge environmental change. Ecesis is sort of similar however, the establishment in a new habitat or environment is not from a big change. Therefore, nudation is the correct answer.
All living organisms have ways of maintaining homeostasis. They have mechanisms for controlling such factors as their internal temperature, water balance, and acidity. Homeostasis is necessary for normal life processes that take place inside cells.
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."
