For protection from the outside elements & harmful insects I would assume. Unless that's already obvious & they wanted a more in-depth answer.
Answer:
Strictly speaking, species diversity is the number of different species in a particular area (species richness) weighted by some measure of abundance such as number of individuals or biomass. ... An ecosystem where all the species are represented by the same number of individuals has high species evenness.
If you are talking about frequency in terms of waves, it is in seconds^-1
