BIOLOGY
Name:________________________
Chapter 36: Ecosystems and Conservation Biology
Section Goal: The student will summarize the basic pattern of chemical cycling, describe how carbon and
oxygen are cycled through an ecosystem, describe the movement of nitrogen through an ecosystem and then
describe the processes that make up the water cycle.
Vocabulary:
1. Nitrogen fixation2. Nitrification3. TranspirationConcept 36.3: Chemicals cycle in ecosystems
How is it possible that some of the carbon atoms in an apple in your lunch might once have been in a panda’s
lung?
I. The Basic Pattern of Chemical Cycling
A. Chemical cycles usually involve three general steps:
1. Producers incorporate chemicals from the nonliving environment into organic molecules.
2. Consumers feed on the producers, incorporating some of the chemicals into their own bodies
and releasing some back into the environment as waste.
3. Organisms die & decomposers break them down, supplying soil, water, & air with chemicals
in inorganic form. The producers gain a renewed supply of raw materials for building
organic matter, & the cycles continue.
B. Part of each chemical’s cycle involves nonliving processes like rain and fires.
II. The Carbon and Oxygen Cycle (see Fig. 36-10)
A. Carbon is found in inorganic form in the atmosphere as CO2 gas and dissolved in water as HCO3- .
B. Producers use the carbon and oxygen atoms to form organic compounds during photosynthesis.
C. Some organic compounds cycle to consumers as food.
D. During cellular respiration producers & consumers break down organic compounds and release CO2
gas as a waste product.
E. Decomposers break down detritus and release CO2 gas.
F. Burning fossil fuels (coal, oil, natural gas) & wood releases CO2 gas into the atmosphere.
G. Volcanic eruptions add CO2 gas to atmosphere.
III. The Nitrogen Cycle (see Fig. 36-11)
A. Nitrogen is found in all living organisms in amino acids & other essential molecules.
B. Almost 80% of Earth’s atmosphere is nitrogen gas (N2).
C. Most producers can only use nitrogen in the form of compounds like ammonium (NH4+) and nitrate
(NO3-).
D. Nitrogen-fixing bacteria convert N2 gas to ammonia (NH3) in a process called nitrogen fixation.
E. Nitrogen-fixing bacteria live in soil and in nodules on roots of plants (peas, beans, alfalfa).
F. Other bacteria in soil convert NH4+ to nitrates in a process called nitrification.
G. Producers absorb ammonium and nitrates and use them to build amino acids, proteins, and nucleic
acids.
H. Consumers that eat producers obtain nitrogen.
I. Decomposers release nitrogen (ammonium) from wastes and decaying organisms.
J. Denitrifying bacteria in soil convert some nitrates to N2 gas back into atmosphere.
IV. The Water Cycle (see Fig. 36-12)
A. Sun’s energy evaporates water putting water vapor into atmosphere.
B. Water vapor cools and condenses and falls as precipitation.
C. Plants absorb fresh water from soil.
D. Consumers obtain water from eating and drinking.
E. Water evaporates from the leaves of plants = transpiration.
F. Some water runs off land into rivers and streams and some restores groundwater.
Lesson Reflection:
Complete the three cycle diagrams. Use the Chromebooks. Go to my webpage and complete the cycle
diagrams, including the information written outside the circle.
Lesson Assessment:
1. Explain how photosynthesis and respiration are involved in cycling carbon and oxygen.
2. Describe three roles that bacteria play in the nitrogen cycle.
3. Follow a raindrop through one possible path through the water cycle, ending as water vapor in the
atmosphere.
Summary of Key concepts:
Complete the Summary of Key Concepts for 36.3 and turn into the box.
Technology/Application/Connection to real-world:
1. Study Jams: The Water Cycle, The Nitrogen Cycle and The Carbon Cycle