Students know many plants depend on animals for pollination and seed dispersal, and animals depend on plants for food and shelter.

This standard addresses the much larger concept of interdependence. All organisms depend on other organisms for their existence. As we noted in Standard 2a, all animals ultimately depend on plants for matter and energy. This standard adds that plants also provide shelter for animals.

The interdependence of plants and animals with respect to pollination and seed dispersal illustrates another major concept in biology, co-evolution. Plants and animals have evolved together. This principle is beautifully illustrated in the co-evolution of flowering plants and insects. Plants develop flowers with colors, shapes, odors, and food to attract particular species of insects. The insects, in turn, develop adaptations that make them better suited to recognize and utilize particular plants. These insect adaptations then cause further specializations in plants in an unending tale of mutual adaptations.