Page 643 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 19 ecosystem essentials 607
Sun
ABIOTIC COMPONENTS
Nutrients
Cycles
— gases — water
— minerals
Heat energy released at each stage
Producers — plants
Heat
Decomposers
— Fungi — Bacteria
BIOTIC COMPONENTS
Consumers — herbivores — carnivores
Heat
Insolation
(a) Solar energy input drives biotic and abiotic ecosystem processes. Heat energy and biomass are the outputs from the biosphere.
▲Figure 19.2 Biotic and abiotic components of ecosystems. [Bobbé Christopherson.]
mites, bacteria, and fungi). The abiotic processes include gaseous, hydrologic, and mineral cycles. Figure 19.2 il- lustrates these essential elements of an ecosystem and how they operate together.
Converting Energy to Biomass
The energy that powers the biosphere comes primarily from the Sun. Solar energy enters the ecosystem energy flow by way of photosynthesis; heat energy is dissipated from the system, as an output, at many points. Of the total energy intercepted at Earth’s surface and available for work, only about 1.0% is actually fixed by photosynthesis as carbohy- drates in plants, which then become the source of energy or the construction materials for the rest of the ecosystem. “Fixed” means chemically bound into plant tissues.
Plants (in terrestrial ecosystems) and algae (in aquatic ecosystems) are the critical biotic link between solar en- ergy and the biosphere. Organisms that are capable of using the Sun’s energy directly to produce their own food (using carbon dioxide (CO2) as their sole source of carbon) are autotrophs (self-feeders), or producers. These include plants, algae, and cyanobacteria (a type of blue- green algae). Autotrophs accomplish this transformation
(c) Five or six species of lichen live in extreme Arctic climate conditions on Bear Island in the Barents Sea. Each little indentation in the rock provides some advantage to the lichen.
(b) Biotic and abiotic ingredients operate together to form this rain forest floor ecosystem in Puerto Rico.
(d) Brain coral in the Caribbean Sea, at a 3-m depth, lives in a symbiotic relationship with algae.
of light energy into chemical energy by the process of photosynthesis, as previously mentioned. Ultimately, the fate of all members of the biosphere, including humans, rests on the success of these organisms and their ability to turn sunlight into food.
The oxygen gas in Earth’s atmosphere was produced as a by-product of photosynthesis. The first photosynthe- sizing bacteria to produce oxygen appeared in oceans on Earth about 2.7 billion years ago. These cyanobacteria— microscopic, usually unicellular, blue-green algae that