The correct answer is: A. Diversity of species
The biosphere is the part of Earth where life exists. It includes the land, water, and air, as well as all of the living things that inhabit it. The biosphere is home to an incredible diversity of species, from bacteria and algae to plants and animals. This diversity is essential for the health of the biosphere, as each species plays a role in the ecosystem.
Option B, animal population, is incorrect because the biosphere encompasses all living things, not just animals. Option C, photosynthesis, is incorrect because photosynthesis is a process that plants use to create food, not a measure of the diversity of life. Option D, weight, is incorrect because the biosphere is not measured by weight.
In conclusion, the biosphere encompasses the total diversity of species in a region or the globe. This diversity is essential for the health of the biosphere, as each species plays a role in the ecosystem.