Give students handout. Review the vocabulary terms habitat, niche and adaptation. Ask: what is in an aquatic environment? How might these environmental factors vary from one lake to another. Are they different in lakes and rivers? What about in the ocean?
Have students examine pictures of fish heads on handout or actual fish heads.
Ask the question, "How are these fish heads different?" What features do they have which vary and which are the same? Look at the shapes of their heads, the size and shape of their mouths and teeth, and the location of their eyes.
What might these similarities and differences tell you about where the fish lives, what kind of food it eats, and where it is in the food chain?