In Wildness is the preservation of the World.          –Henry David Thoreau, "Walking"

Over millions of years, the Earth has been transformed. Species have evolved or become extinct. Catastrophic events such as asteroid impacts have caused environmental change. And the climate has been fickle, with hot spells and ice ages. But there is no place like Earth, because all of these events have produced this planet's most valuable resource: biodiversity.

The frilled lizard is just one of Australia's many unique animals.

Biodiversity is the key to the successful proliferation of life on Earth. The world has an amazing wealth of interesting and peculiar organisms. No one knows exactly how many species exist, but biologists estimate that there are probably close to 100 million different species.

Although modern science has made major advances in physics, chemistry, technology, and genetics, there is even more to discover. The field of biology is still a relatively unexplored domain. Biologists searching the world have classified only about two million species.

No textbook could adequately explain what has been learned about and seen of Earth's organisms. Much like a sunset, biodiversity is awesome to behold but hard to describe in words.

Basking sharks, the second largest fish in the world, feed on plankton.

Life Science: Part 2 is an initial exploration of a few remarkable organisms found on this planet. There are bird-eating spiders and fish that eat their victims from the inside out. There are microbes that digest wood living in the bellies of termites and creepy critters called heartworms that may be residing in Rover or Fluffy. Other organisms include carnivorous plants, plankton-eating sharks, and egg-laying mammals. Hundreds of examples of interesting organisms populate the pages of this program. And the links offer hundreds more examples from other websites that explore why animals and plants are so remarkable.

How did each of these species come to be? To answer that question, biologists turn to the theory of evolution by natural selection, first proposed by Charles Darwin in 1859. This theory tries to explain how species adapt in response to changes in their environment. This program begins by looking at evolution to demonstrate why there are so many different and distinct types of organisms.

Life Science: Part 2 continues with a tour of the various phyla of life's kingdoms, from primitive organisms to the more advanced forms of life. Following an evolutionary timeline, the program begins with primordial microbes, then moves on to plants, invertebrates, vertebrates, and ultimately the human species.

The carnivorous venus flytrap feasts on insects such as flies.

The section "Human Biology" takes an in-depth look at a majority of the human organ systems, including the digestive, circulatory, nervous, and immune systems. The last part of this section investigates how the human species evolved over time from the early genus Australopithecus to the modern Homo sapiens.

Life Science: Part 2 concludes with an examination of ecology and the impact humans have on the environment. Here, biodiversity in action is explored in populations, communities, and ecosystems. If one species is removed from an ecosystem's food pyramid, the whole habitat can collapse. Destruction of habitats is happening at a dangerous rate across the world. In less time than it takes to snap a finger, an area of tropical rain forest the size of two football fields disappears from the planet.

The loss of biodiversity on Earth is increasingly becoming a global concern. World leaders must consider the intricate balance of life that may be upset by changes in the ecosystem. And students need to think beyond facts and figures. Science is also about observation and exploration.

To aid the learning process, Life Science: Part 2 incorporates some fun and thought-provoking interactive components. Try a picture quiz in "Adaptation" (focus 1b) and find out why cacti developed needles on their stems. Is a virus alive? Make your opinion known by voting in the poll in focus 2c.

Is that a cephalopod or a gastropod? After reading about worms, squid, spiders, and snails go to focus 5e and review for the test by identifying different types of invertebrates. Just a few sections ahead in focus 7e, play the game again — but with the vertebrate classes instead. (Here is a hint: whales are mammals!)

In the vertebrate section, click on the animal illustrations to highlight the functions of several key body parts. Discover why bony fish can remain at one depth without swimming (focus 6b) or how many teeth sharks lose in a lifetime (focus 6a).

Have trouble with the human anatomy vocabulary? Bone up on your terms with a car race activity in "Support and Movement" (focus 8a) or take a crack at digestive system hangman in focus 8b.

Along with the activities and quizzes, subtopics within all sections offer deeper investigations into such common questions as "Why did the dinosaurs become extinct?" (focus 1e) and "What is the difference between alligators and crocodiles?" (focus 6d) Other subtopics take a closer look at several unusual aspects of animals. In the section on reptiles, for example, learn about how snakes eat. (Open wide!)

Vocabulary is also reinforced with terms highlighted in yellow. Clicking on one of these terms activates a talking dictionary — handy for anyone who doesn't use such words as "Osteichthyes" on a daily basis.

Earth is full of strange and beautiful plants and animals. Knowing how individual organisms depend on each other for survival is one of the ongoing areas of research in biology. But the work to understand how these organisms adapt to and interact with other living and nonliving things is part of the fun.

Let's take a walk through the diversity of Earth's wildness.

1. Evolution: Populations in Motion
   1. Darwin's Theory of Evolution
   2. Adaptation
   3. How Populations Evolve
   4. Speciation
   5. Geologic Timetable
2. Bacteria and Viruses
   1. The Average Bacterium
   2. Bacteria: The Good, The Bad, and The Ugly
   3. Are Viruses Alive?
3. Protists, Fungi, and the Origin of Multicellularity
   1. Plantlike Protists
   2. Animallike Protists
   3. From Single Cell to Multiple Cells
   4. Fungi: Shifting Gears
4. Plants: Energy Converters
   1. The Move to Land
   2. Moss and Other Nonvascular Plants
   3. Ferns and Other Seedless Plants
   4. Gymnosperms and Angiosperms: Vascular Plants with Seeds
5. Invertebrate Animals: Rulers of the Animal Kingdom
   1. What Is Zoology?
   2. Sponges and Jellyfish
   3. Coral and Coral Reefs
   4. From Simple Worms to Complex Worms
   5. Mollusks
   6. Arthropods: Over a Million Strong
   7. Echinoderms: Phylum of Fives
6. Vertebrate Animals
   1. No Bones about Them: Jawless Fish, Sharks, and Rays
   2. Osteichthyes: Bony Fish
   3. Amphibians: From the Water to Land
   4. Reptiles
   5. Birds: Built Strong and Light
7. Mammals 'R' Us
   1. Types of Mammals
   2. Energy Requirements: Nutrition, Circulation, and Gas Exchange
   3. Regulation
   4. Development
   5. Response to the Environment
8. Human Biology
   1. Support and Movement
   2. Food for Thought: The Digestive System
   3. Nutrition
   4. Circulatory and Respiratory Systems
   5. The Nervous System
   6. The Immune System
   7. The Reproductive System
   8. Human Evolution
9. Ecology: Organisms and Their Environment
   1. Biomes
   2. Communities: Relationships Among Species
   3. Populations: Relationships within Species
   4. Ecological Succession
10. Human Impact on the Environment
    1. Pollution
    2. Destruction of Habitat
    3. Alien Invasion: Non-Native Species
    4. Extinction and Loss of Species