An organelle found in most eukaryotic cells described as "cellular power plant"

Explanation:

The mitochondria is commonly called the powerhouse of the cell.

This is because it is the organelle that makes energy for the cell. The process of cellular respiration occurs in the mitochondria.

Cellular respiration turns glucose from food and oxygen into carbon dioxide, water, and ATP. ATP is useable energy for the cell, its metabolism, and its processes.

Mitochondria are found in eukaryotic cells, because it is a membrane bound organelle.

So, the organelle this question describes is the mitochondria.

on island x the species needed to adapt because they were being subject to predators which didn't inhabit island y.  

osteogenesis imperfecta (oi) refers to a congenital ailment of bones. in the condition, the bones become brittle or fragile. this ailment is a general result of the defect or mutations in the genes (colia1 or colia2). this mutation results in imperfect collagen formation either in quantity or quality wise.  

there are eight kinds of oi defects, and each kind varies with certain distinctions in symptoms. the usual symptoms include frequent bone fractures, loss of hearing in infants, protruding eyes, discoloration of the white in the eyes, respiratory issues, loosening of the joints, short stature, and other symptoms.