The mechanism of evolution that has been exhibited here is known as bottleneck effect. The fact that a sudden incident of the tree falling caused the death of rare alleles and this resulted in the decrease in genetic diversity of the population. I hope that this is the answer you were looking for and it has helped you.
nature and a house are two main forms of habitats
The answer is water vapor.
Water is presented in the form of tiny gas particles called water vapor in the atmosphere. The clouds are formed when this invisible water vapor in the atmosphere condenses onto microscopic particles (dust, dirt,...).
1. 50% will have the RR phenotype and 50% will have the Rr phenotype.
2. 25% will be RR, 25% will be rr and 50% will be Rr
3. 100% will be rr