The Cycling of Matter
Name _________________________
Earth is a system that relies on the constant input of energy from the sun and on the cycling of matter.
You may refer to the completed reading questions on the topics of nutrient cycles, population density,
photosynthesis and cellular respiration. Text references can be found in Chapters 3, 5, 8, and 9.
Question #1
Plants and animals impact the cycling of carbon into and out of the atmosphere.
a) Imagine that you are an atom of carbon. Describe how you might cycle through the biosphere
starting as a CO2 molecule in the atmosphere. You must go through at least 4 different transformations
before being returned to the atmosphere.
In your description, be sure to:


Describe the path of the carbon atom, being sure to include the atmosphere, plants and animals
Identify the molecule that contains the carbon in each step of the path
You may use words, chemical formulas, and/or labeled diagrams in your answer.
b) Imagine that an entire forest is wiped out by a large fire. How would this affect the cycling of
carbon?
c) How has this fire affected the population of other organisms in the forest ecosystem?
In your description be sure to:


Identify an organism in the forest ecosystem
Describe how the population of that organism could be limited by the removal of trees
Question #2
Todd and Ana own a house on 10 acres of land south of Kennewick. One of the things they enjoy
watching are the rabbits that feed on the shrubs and grasses surrounding their home.
a) Describe the cycle of carbon through this outdoor ecosystem
In your description be sure to:


Describe how carbon became a part of the shrubs and grasses
Describe how that carbon will become part of the rabbit’s tissues when it eats the plants
Carbon in plants:
Carbon in rabbits:
b) Describe two ways the carbon could be released from the rabbit back into the ecosystem.
One way:
Another way:
Question #3
All living things have a life expectancy, and Todd and Ana know that if they come across a dead plant or
animal somewhere on their property, they can just leave it alone and, in time, it will no longer be there.
a) Desribe how scavengers and decomposers help play a role in the cycling of nitrogen in this
ecosystem.
(answer box is on the top of the next page)
b) Todd and Ana have noticed that there seems to be a dramatic increase in the number of jackrabbits
on their land this year. Describe two factors that would allow the rabbit population to increase rapidly.
In your description, be sure to


Describe two conditions in this ecosystem that could allow for the rabbit population density to
increase
Describe how each condition caused the increase in rabbit population density.
One condition:
Another condition:
*Bonus*
Todd and Ana know that jackrabbits love a small native shrub called bitterbrush. They want to
determine the population density of bitterbrush on their land. Explain to them how this could be done.