Tutor profile: Hannah J.Subject: Environmental ScienceDefine and give an example of a keystone species. A keystones species is a species within a community that is essential to its workings. An example of a keystone species is the sea otter, because through its consumption of sea urchins it is indirectly controlling the growth of kelp. If the otters were not present then sea urchins would rapidly increase in number, and the kelp would in turn diminish, affecting many other species who rely on kelp beds for protection and food. Subject: Music TheoryWhat mode begins on the 5th scale degree? The Mixolydian mode begins on the 5th scale degree. Re-write the following sentence so that it follows a parallel structure: "Stephanie enjoys swimming, to eat, and to go running. ""Stephanie enjoys swimming, eating, and running. "needs and Hannah will reply soon.