Final answer:
The description matches alpha diversity, which measures the species richness within a single habitat or ecosystem.
Step-by-step explanation:
The description "Counts the number of species in a single habitat type" refers to alpha diversity. Alpha diversity is concerned with the diversity within a particular area or ecosystem, including species richness and the relative abundance of different species. This term is often used by ecologists to describe the number of different species living in a specific habitat or biotic community.
Beta diversity, on the other hand, describes the differences in species composition among ecosystems or habitats and is a measure of species uniqueness between areas. Beta diversity can increase when locations differ more from one another.
Gamma diversity refers to the overall diversity for the different constituent ecosystems of a region and is measured at a broader geographic scale, providing insight into regional or continental species patterns.