Explain which biotic factors used by the beaver are related to its role as a keystone species

A keystone species refers to a species on which other organisms in an ecosystem are largely reliant on, like that if they are withdrawn, the ecosystem would change radically.  

The prime biotic factors used by a beaver are trees. The beavers utilize trees to construct a dam to obstruct the movement of water that in turn modifies the influence of the abiotic factor water on the surrounding.  

answer: "circumcision is a common procedure in which the skin covering the tip of the penis is surgically removed."

prophase: we can observe the chromosomes to coil up and condense. they become visible. nuclear membrane and envelope disintigrate.s

metaphase: chromosomes align at the center, the metaphase plate. spindle fibers attach to centromeres of the sister chromatids. they meet at kinetochores.

anaphase: sister chromatids are pulled towards each opposing centromere, set on different poles.

telophase: chromosomes are now clustered up only on either sides of the cell. nuclear membranes reform, and a new cell wall forms along the cell plate. this will lead to cytokinesis, the process that divides the cell membrane and forms the cell wall.