Final answer:
The term used to describe Species Evenness is the 'biodiversity index' which includes species richness and relative abundance of species.
Step-by-step explanation:
The term used to describe Species Evenness (or relative species abundance) is biodiversity index. This index is a measure of biodiversity that considers both the number of different species within an area and their relative abundances to each other. Biologists and ecologists use biodiversity indices to quantify biodiversity for comparing between and within ecosystems. Biodiversity itself is a broad term that encompasses the variety of life at multiple levels of organization, including species diversity and genetic diversity. The concept of species richness, which refers to the number of species living in a habitat or biome, is related to the biodiversity index but focuses specifically on the count of species.