Answer & Explanation:
a) a) Mutualistic relationship differs from parasitism because the first one benefits both of the involved organisms. Otherwise, parasitism benefits only one of the organisms and it can harm the host. Therefore, the parasite would have to be smaller than the host and it would be somehow extracting energy from the host.
b) The direction of evolutionary changes would follow some kind of pattern, like coevolution. Therefore, analyzing the phylogenies individually and then contrasting them, would help to understand how the host, as well as the parasite, have been evolving.
c) The phylogeny would also help to understand what changed first, or if they changed together as a result of coevolution.
An area with unifying characteristic is called as a region. The region is a broad geographic area, which is differentiated from other because of the similar features. In a region one or more than one types vegetational climax might be present. It is the continuous and extensive part of the surface. The area in a region is indefinite.
Hence, the given blank can be filled with region.
3 . Summer - Due to an increase in evaporation since it is hot .