Final answer:
Species diversity refers to the number of different species in an ecosystem or on Earth as a whole. It can be measured at different spatial scales using alpha, beta, and gamma diversity. Alpha diversity measures species richness within a specific area, beta diversity measures the difference in species composition between ecosystems, and gamma diversity measures overall diversity for different ecosystems within a region.
Step-by-step explanation:
Species diversity refers to the number of different species in an ecosystem or on Earth as a whole. This is the commonest way to measure biodiversity. Current estimates for Earth's total number of living species range from 5 to 30 million species.
When it comes to spatial differentiation, species diversity can be measured at different scales. There are three main diversity measures: alpha diversity, beta diversity, and gamma diversity. Alpha diversity quantifies species richness within a particular area or ecosystem, while beta diversity measures the difference in biodiversity between ecosystems. Gamma diversity is a measure of overall diversity for the different constituent ecosystems of a region.
For example, let's consider a hypothetical region with three different ecosystems: a forest, a grassland, and a wetland. The forest has a high alpha diversity because it contains a large number of species. The grassland has a low alpha diversity because it has fewer species compared to the forest. The beta diversity between the forest and grassland is high because they have distinct species compositions. Lastly, the gamma diversity of the region is determined by the combined biodiversity of all three ecosystems.