Structure. A hypha consists of one or more cells surrounded by a tubular cell wall. In most fungi, hyphae are divided into cells by internal cross-walls called "septa" (singular septum). Septa are usually perforated by pores large enough for ribosomes, mitochondria and sometimes nuclei to flow between cells.
The first stage of cellular respiration is glycolysis. It does not require oxygen. During glycolysis, one glucose molecule is split into two pyruvate molecules, using 2 ATP while producing 4 ATP and 2 NADH molecules.
Beause we cut down a lot of trees. Often, so many, that the health of a forest is irreparably damaged. A forest is not just a bunch of trees. It is a whole ecosystem, in which the trees anchor the growth of many other plant and animal species, hold the ground together to prevent erosion, and produce a lot of oxygen to support animal life. If you harvest too many of the trees, the local ecosystem stops being a forest and starts turning into something else