This is an encyclopedia entry for the term "herbivore." An herbivore is an organism that mostly feeds on plants. Text for this entry is appropriate for the upper elementary, middle, and high school grade levels.

This is an encyclopedia entry for "keystone species," a plant or animal that plays a unique and crucial role in the way an ecosystem functions. Text for this entry is appropriate for the middle and high school grade levels.

This is an encyclopedia entry for the term "omnivore." An omnivore is an organism that regularly consumes a variety of material, including plants, animals, algae, and fungi. Text for this entry is appropriate for upper elementary, middle, and high school grade levels.

This encyclopedia entry is for the term "tide." The regular rise and fall of the ocean?s waters are known as tides. Along coasts, the water slowly rises up over the shore and then slowly falls back again. Text for this entry is appropriate for the middle and high school grade levels.