Level III units were designed for 9th grade but I used them with 7th graders too. The units are self-paced, hands-on, and inquiry based.
The Why You Are You book uses fruit flies as an option. Good hands-on basic study of Genetics.
Investigating Variation is a good hands-on introduction to Science and measurement.
Environmental Science starts with the Black Plague and covers many issues.
INVESTIGATING VARIATION (metric, statistics)