Tropical rainforests have thin, acidic soils, yet they contain dense vegetation and high biodiversity. how can these tropical forests have poor soil and support such a diverse array of life?

A large complement of decomposers rapidly turns dead plant and animal matter into nutrients that are quickly taken up by plants. Also, some animals live on eating plants, other animals eat those that live on plants, and animals that live on eating other animals die to make nutrients that are eaten by plants; this also, is called an ecological food chain.

Mitochondria produce atp, a high energy compound. atp is used for all sorts of enzyme-mediated reactions, such as making proteins/nucleotides/etc, certain compounds cross the cell membrane, muscles move, etc.  without this source of energy, a cell will die. it will not be able to repair itself, defend against pathogens, etc.