The correct answer choice is biodiversity. Biodiversity is the area within biology focused on understanding biological diversity. The terms "disturbance" and "fragmentation" are natural processes that can have impacts on species, but they do not describe species. The terms "biomagnification" and "bioaccumulation" describe how nutrients and contaminants accumulate over time. 

The correct response is indicator species. If the indicator species is healthy, then it tells or indicates that the ecosystem as a whole is healthy. Indigenous species are native to a certain location, while invasive species are those that are not native to a location and their introduction usually causes harm to the existing ecosystem. A keystone species is one that plays a critical role in the overall health of an ecosystem.

Olfaction in fish and other marine life is very important. Smells are carried on currents and can be used to identify and find prey, recognize familiar territory, attract mates, and warn predators and/or competitors of defense mechanisms.

Somewhere between 40% and 75% of all species are indigenous to rainforests, meaning that they are found nowhere else on earth. They contain half of the extant animal and plant species currently on earth, with a large majority of all flowering plants found there. Many of the world's natural medicines have been found in tropical rainforests, and with thousands of undiscovered species still lurking within them, it is likely that there are many more medicines waiting to be discovered.

In relationships based upon commensalism, one of the species benefits greatly, while the other is neither harmed nor helped. This is different from mutualism, where both species are benefited, and parasitism, where one species is benefited and the other is hindered. "Endosymbiosis" is the theory used to describe how mitochondria developed, and "predation" describes a situation where one organism feeds on another.

Top predators will generally never "grow unchecked". By the very nature of their diet (dependent on other populations), predator population growth is limited by the availability of their food. The famous study of lynx-hare population fluctuations demonstrates how a predator population will adjust to lower prey populations.

Heavy decomposition of plant and animal matter contribute to highly acidic soil in tropical rainforests. Additionally, abundance of plant life in tropical rainforests results in "soil leaching," which means that the nutrients in the soil are drained and taken up by the plants themselves.

Boreal forests have extremely low temperatures and are characterized by pines and other evergreens. "Temperate forests" are characterized by moderate and more fluctuating temperatures, whereas the taiga stays cold year round. Taiga is found in parts of the world such as Northern Alaska, Canada, and Siberia.

Latitude is not considered in climate evaluations; for instance, the poles are considered deserts based on their precipitation levels per year, meaning deserts can occur along the equator or the poles. Temperate and tropical forests also exhibit similar precipitation levels, but due to their temperature differences, they are considered separate biomes.

Though grasslands and deserts share some of these characteristics, the tundra is the only biome listed that is characterized by a short growing season, harsh winters, no trees, mostly migratory animal species, and less than 10in of rain per year.