Think about your categorization exercise from the first laboratory period. How could you tell whether something you found was an animal or a plant or something else? For the most part, you relied on common-sense distinctions - animals move, plants have roots and leaves. We would like to continue thinking about the differences between plants and animals, focusing on the five main topic areas for Biology 100. Remember that all of the things that we talk about over the next few days were discovered by application of the scientific method to questions very similar to those that you asked in lab.

1. Cells - All organisms are composed of cells, but plant and animal cells have important differences in structure. These structural differences (presence or absence of a cell wall, chloroplasts, etc) are based of the differing metabolism of plants and animals. We will cover this in detail during the unit on cells.

2. Metabolism - This is really the basic difference between plant and animal cells. Functional difference in metabolism drives all of the differences in cell structure, physiology, and ecology. Plants are prototrophs, deriving their energy from sunlight, while animals are consumers, deriving their energy from eating other living things.

3. Inheritance - Represents a commonality between plants and animals. Both use the same biological information storage and retrieval mechanisms (DNA and proteins).

4. Ecology - The difference in the metabolic roles of plants and animals defines their roles in the ecosystem.

5. Evolution - Plants and animals are grouped according to evolutionary patterns of adaptation, mirroring the process of divergence and speciation.

Evolution of land plants is characterized by a trend from simple avascular plants that have important haploid gametophyte stages toward vascular plants where the diploid stage of the life cycle predominates.

A. Bryophytes (think mosses; figure 19.4.) Note the dominance of the haploid stage. These plants must be constantly moist, and cannot grow more than a few centimeters tall because they lack a transport system for water.

B. Ferns (seedless vascular plants) These are still dependent on water, but less so than bryophytes. See Figure 19.8. Ferns can tolerate periods without water, but rely on the presence of water for reproduction.

C. Seed-bearing plants (those plants we are most familiar with) do not rely on water for fertilization. Many desert plants can survive for extended periods (years) without water.

Evolution of animals is typified by cephalization, bilateral symmetry, and increasingly sophisticated internal organization.

A. Sponges (Figure 20.6) No real tissue, just different cell types. Sometimes radially symmetrical.

B. Cnidarians (Figure 20.7) Tissues (like nervous cell, epithelial cells). Almost always radially symmetrical.

The remainder of the unit on animal taxonomy was presented by doctor Mark Davis on Friday January 15. Although there are no web notes available for this lecture, you are responsible for material from both the lecture ad the reading.