Allopatric Speciation

These images from the Smithsonian Institution depict Nancy Knowlton's work with snapping shrimp in Panama. Knowlton found that the closing of the isthmus -- dividing the Pacific Ocean from the Caribbean -- resulted in new species of shrimp.

Animal Babies

This interactive slide show illustrates the variety of animal babies that exist on earth -- some completely independent and others deeply reliant on parental care.

Animal Coverings

It takes a thick skin to withstand the hardships that life has to offer. This collection of images shows a variety of animals, each with a slightly different type of protective covering.

Animal Mouths

This collection of images of six different creatures, including insects and carnivorous vertebrates, illustrates the wide range of mouth types that exist within the animal kingdom.

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Bird Beak Gallery

This collection of images of 10 different birds illustrates the diversity of bird beaks.

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Bird Food

There are almost as many types of bird beaks as there are types of food that birds like to eat. This collection of images shows a wide range of beaks and the types of foods handled by each.

Carbon Cycle Diagram

This diagram from NASA's Earth Science Enterprise illustrates the Earth's carbon cycle .

Colorful Creatures

For animals, bright, flashy coloration can serve as a warning or as an invitation. Either way, colorful skin, feathers, and scales yell, "Notice me!" This collection of images shows examples of some of the world's most colorful creatures.

Duckweed

These images of duckweed (Lemna spp.) illustrate the basic anatomy and environment of these fast-growing plants.

Gallery of Cells

While all cells have a great deal in common, there is no end to the variation among them. These images provide a sense of the wondrous diversity found in the world of cells.

Growing Up, Growing Old

This collection of six images captures the magnificence of human development -- the transformation from baby to woman.

Laetoli Trackways Diagram

View a diagram of the hominid footprints that archaeologist Mary Leakey's team found at Laetoli in Tanzania.

Living and Nonliving

What is it that distinguishes a living organism from a nonliving object? This collection of images presents examples that aren't as clear-cut as one might think, enticing students to question the meaning of life.

Mimicry: The Orchid and the Bee

In this photograph from Oxford Scientific Films, a horned bee attempts to mate with an Ophrys orchid, which has evolved to resemble a female bee.

Seeds Away

This collection of images shows several types of plant seeds, each with a different mechanism for dispersing from the parent plant.

Shape of Trees: The Frustration Principle

This series of images shows the work of biologist Karl Niklas on the adaptations and evolution of plants. From The Evolutionary Biology of Plants.