Geoscience Reference
In-Depth Information
2
Light energy
from Sun
3
Photosynthesis
CO
2
Atmosphere
5
Respiration
Water
Oxygen
CO
2
4
Sugar
Oxygen
Sugar
Water
Heat
Water
(from dead
tissue)
CO
2
(from dead
tissue)
Plants
(primary producers)
Water
(from soil)
1
Heat
8
Water (rain)
9
Glucose
(in roots, stems,
leaves, and grass)
SOIL
6
Carbon
(in dead tissue)
Dead Tissue
Microorganisms
(bacteria)
7
Decomposition
Figure 10.3 Photosynthesis, respiration, and decomposition cycles.
Water, oxygen, and carbon dioxide take various pathways within
the biosphere. Plants are part of these pathways through the processes of photosynthesis and decomposition, while animals (including
people) are part of respiration and decomposition processes.
Figure 10.3 shows the photosynthetic and respiratory
cycles, including the various pathways that oxygen, water, and
carbon dioxide take within the system. As you work through this
discussion, follow the numbered stages in the diagram. These
numbers are not meant to imply that stages occur in a specific
order, but merely to help organize the flow of the presentation.
For simplification, think of the cycle as broadly consisting of
primary producers, such as plants, and decomposers, such as
bacteria. Plant consumers are also present, but they are not
really relevant to the photosynthetic cycle.
A logical place to begin to trace the various pathways is in
the soil, which provides water to the living plant (1). At the same
