When similar environmental pressures, such as permafrost in low-altitude tundra and permafrost in high-altitude alpine tundra, cause genetically distantly related organisms to evolve similar structures for survival and reproduction under similar conditions, has occurred.

Morei would really appreciate it. his eyes snapped open. a musty smell flooded his senses. the room was lowly lit, curved with smooth light gray walls. the floor was clear black tiled. he stood up, surprised to see no door, but only a trap door on the ceiling that blended in with the walls. the room was unfurnished, which struck him as strange. as you write and revise, ask yourself these questions: 1. do all of the sentences in this paragraph belong here? (unity) 2. are all of the sentences in this paragraph in the right place? (coherence-- a method of development) 3. are all of the sentences in this paragraph smoothly connected together into a whole paragraph? (coherence--use of transitional devices) once you've made certain that your paragraphs are both unified and coherent, edit your work for problems in grammar and mechanics before submitting it to your teacher.