34.1 The Nature of Ecosystems
An ecosystem is a community of organisms along with their physical and chemical environment.
Living components contribute to an ecosystem in their own way. Some are autotrophic and produce organic nutrients. Others are heterotrophic and consume organic nutrients.
An ecosystem is characterized by energy flow and chemical cycling.
1. What are omnivores? Answer 2. Why is it not possible for energy to cycle within an ecosystem? Answer
34.2 Energy Flow
Energy flow begins when autotrophs use solar energy to produce organic nutrients for themselves and all living things. Eventually these nutrients are broken down and solar energy returns to the atmosphere as heat.
3. What is a detrital food web? Answer4. Is there an advantage of representing trophic levels using a pyramid of biomass instead of a pyramid of numbers? Answer
34.3 Global Biogeochemical Cycles
Nutrients cycle within and between ecosystems in global biogeochemical cycles.
Biogeochemical cycles are gaseous (carbon cycle and nitrogen cycle) or sedimentary (phosphorus cycle).
The addition of carbon dioxide (and other gases) to the atmosphere is associated with global warming.
The production of fertilizers from nitrogen gas is associated with acid deposition, photochemical smog, and temperature inversions.
Fertilizer also contains mined phosphate; fertilizer runoff is associated with water pollution.
5. How have humans interfered with the global carbon cycle? Answer6. What global biogeochemical cycle is particularly dependent on the activity of various groups of bacteria? Answer