Episode Guide

1. What Is Life?—What distinguishes living things from dead and nonliving things? No single characteristic is enough to define what is meant by “life.” In this session, five characteristics are introduced as unifying themes in the living world.

2. Classifying Living Things—How can we make sense of the living world? During this session, a systematic approach to biological classification is introduced as a starting point for understanding the nature of the remarkable diversity of life on Earth.

3. Animal Life Cycles—One characteristic of all life forms is a life cycle—from reproduction in one generation to reproduction in the next. This session introduces life cycles by focusing on continuity of life in the Animal Kingdom. In addition to considering what aspects of life cycles can be observed directly, the underlying role of DNA as the hereditary material is explored.

4. Plant Life Cycles—What is a plant? One distinguishing feature of members of the Plant Kingdom is their life cycle. In this session, flowering plants serve as examples for studying the plant life cycle by considering the roles of seeds, flowers, and fruits.

5. Variation, Adaptation, and Natural Selection—What causes variation among a population of living things? How can variation in one generation influence the next generation? In this session, variation in a population will be examined as the “raw material” upon which natural selection acts.

6. Evolution and the Tree of Life—Why are there so many different kinds of living things? Comparing species that exist today reveals a lot about their relationships to one another and provides evidence of common origins. This session explores the theory of evolution: change in species over time.

7. Energy Flow in Communities—Communities are populations of organisms that live and interact together. The structure of a community is defined by food web interactions. The process of energy flow is the focus of this session as the interactions between producers, consumers, and decomposers are examined.

8. Material Cycles in Ecosystems—Studying an ecosystem involves looking at interactions between living things as well as the nonliving environment that surrounds them. Life depends upon the nonliving world for habitat, as well as energy and materials.