pinterestImage: pinterestA 3rd grade thematic uniton the life cycle of plants will help them to observe and understand their environment in a better way. Read on to learn more. Students in elementary classes like to observe their environment. A Third Grade Thematic Unit on the Life Cycle of Plants Is this answer helpful?Thanks!Give more feedbackThanks!How can it be improved?How can the answer be improved?Tell us how 10 Ready-to-Go Resources for Teaching Life Cycles | Scholastic Life cycles are one of the great science concepts taught somewhere in every school's science curriculum. In my school, we look at the life cycles of plants and crayfish in my third grade class, while other grades study the life cycles of chickens, butterflies, and fish. Science A-Z Life Cycles Grades 3-4 Life Science Unit Life Cycles. During its life cycle, an organism goes through physical changes that allow it to reach adulthood and produce new organisms. Since these changes are common within a species, they can be grouped into stages of development. The unit Life Cycles addresses the life cycles of plants and animals, including humans.