Pre-IB Chemistry/Biology
Activity: “An Infinite Loop”
Task: Read the information below. With a partner, discuss how to draw the CARBON CYCLE.
Create a labeled diagram of the cycle (each person needs to create their own diagram). Include
all applicable biotic and abiotic factors, & arrows to show the cycling.
CARBON CYCLE FACTS
1. Carbon, (C ) is found in all living things’ biomolecules (carbohydrates, proteins, lipids and nucleic
acids). It is also found in the atmosphere as carbon dioxide (CO2).
2. Plants take carbon dioxide from the air along with water (H2O) from the soil and build glucose
(C6H12O6). This process, called photosynthesis, is powered by the sun’s energy. (A plant makes all
its biomolecules from glucose). The byproduct or waste of photosynthesis, oxygen (O2), is released
into the air.
3. Primary consumers, as well as higher-order consumers, digest their food’s larger biomolecules into
smaller ones like glucose.
4. All living things – including plants – need to get energy to live, grow and reproduce. They do this
with a process called cellular respiration. In respiration, glucose is burned (that means combined
with oxygen) to provide energy for an organism. The byproducts of respiration, water and carbon
dioxide, are released into the atmosphere.
5. As land animals and plants die or excrete wastes, they become detritus – organic matter in the soil.
6. Decomposers in the top layers of the soil use the glucose in detritus for energy. The byproducts of
the decomposers’ respiration, carbon dioxide and water, are released into the atmosphere.
7. Over long periods of time, pressure from overlying soil or water can compress carbon from some
dead organisms into peat, and then into coal, natural gas, or oil.
8. Phytoplankton (photosynthetic plankton) in the ocean do photosynthesis just like land plants. They
use water from the ocean, and dissolved carbon dioxide. Just like land plants, the photosynthesis of
phytoplankton builds glucose (and other biomolecules). The byproduct of photosynthesis, oxygen
gas, is dissolved into the water.
9. As aquatic animals and plants die, aquatic decomposers use the dead organisms’ carbon compounds
for energy, using oxygen dissolved in the water. The byproducts, carbon dioxide and water, are
released into the water.
HUMAN ADDITIONS TO THE CARBON CYCLE
When humans burn fossil fuels such as coal, natural gas or oil – or wood – the carbon in the fuel
combines with oxygen in the air, releasing carbon dioxide and water into the atmosphere. Some of the
energy liberated from the fuel is recaptured for use, as in automobile engines or steam-driven turbines in
power plants.