Guard cells are specialized cells in the epidermis of leaves, stems and other organs that are used to control gas exchange,
including water vapor via transpiration. Guard cells perceive and process environmental stimuli to trigger cellular responses
resulting in stomatal opening or closure. All but one environmental stimuli might trigger stomatal opening. That would be

science-ocean floors and habitats study guide by volleyballqueen3817 a major advance in ocean-floor mapping. list four sections of the ocean floor. algae that use sunlight to produce their own food through photosynthesis. all of the feeding relationships that exist in a habitat. drying out, predators, find food.

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.