Lecture, three hours; discussion, two hours. Course 70A is enforced requisite to 70B, which is enforced requisite to 70CW or 70DW. Limited to first-year freshmen. Use of concept of evolution, as it applies to biological organisms, Earth, solar system, and universe itself, to introduce students to both life and physical sciences. Examination of evolution of universe, galaxy, solar system, and Earth. P/NP or letter grading.