Lesson 51: Respiration and Photosynthesis
Photosynthesis uses light energy to build sugars, while respiration makes energy from food available for living processes. The lesson connects plant growth and gas exchange with the cycling of matter and the flow of energy.
Key Ideas
- Plants need water, carbon dioxide, and minerals to grow. Their new material does not all come from soil.
- Plants take in carbon dioxide from the air through tiny openings, often in their leaves. They use its carbon to help build sugars and new plant parts.
- Photosynthesis uses light energy to make sugars. Cellular respiration releases energy from food. Plants do both.
- Carbon moves between living things, air, water, soil, and rocks. Eating, breathing, decay, and burning are some ways it moves.
- Matter is reused in nature. Energy passes through living things and eventually spreads into the surroundings as heat, so food webs need a continuing energy supply.
Vocabulary
- Photosynthesis: The process plants use to make sugars from water and carbon dioxide with light energy.
- Cellular Respiration: The process cells use to release energy from food.
- Stomata: Tiny openings in leaves that let gases move in and out.
- Carbon Cycle: The movement of carbon between living things, air, water, soil, and rocks.
- Biosphere: All the living things on Earth and the places where life is found.
- Atmosphere: The layer of gases surrounding Earth.
Discussion Questions
- A wooden log weighs fifty pounds. Where were those fifty pounds a hundred years ago? Trace it back as far as you can.
- You are designing a sealed spacecraft for a two-year trip. What would you have to bring, and why might plants be part of the answer?
- Van Helmont ran the right experiment and got the wrong answer, because he did not know carbon dioxide existed. Was his experiment still worth doing? Why?