I dont understand what is being asked
Natural selection provides the outline of an explanatory theory." Biologists consider it to be a scientific fact that evolution has occurred in that modern organisms differ from past forms, and evolution is still occurring with discernible differences between organisms and their descendants.
Oxygen is a compound , phosphorus and nitrogen , and reservoirs
Carrying capacity of an ecosystem is the defined as the largest population that it can sustain indefinitely with the available resources. Biologists also refer to carrying capacity as the “maximum load”. Carrying capacity has factors it depends on. These are the many abiotic and biotic factors in the ecosystem and some are more obvious than others. The most obvious being, the availability of the basic needs of organisms which make up the different ecosystems. Some of these are food, water and shelter in which dictate how many individuals the ecosystem can sustain.
Caused by sexual contact are more difficult to treat..