CHAPTER 55: Ecosystems
Overview: Observing Ecosystems
A. Definition of an Ecosystem
B. Two Basic Processes of Any Ecosystem
1. Energy Flow
2. Chemical Cycling
I. Physical laws govern energy flow and chemical cycling
A. Conservation of Energy
1. First Law of Thermodynamics (as it relates to ecosystems)
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2. Second Law of Thermo as it relates to ecosystems
B. Conservation of Mass
1. Describe how it relates to biological systems
C. Energy, Mass, and Trophic Levels
1. Definition of a trophic level
2. Primary Producers
3. Heterotrophs
a) Primary, Secondary and Tertiary Consumers
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b) Decomposers: Prokaryotes and fungi
II.
Energy and other limiting factors control primary production in ecosystems
A. Introduction
1. Primary Production (know its definition)
B. Ecosystem Energy Budgets
1. Global Energy Budget
2. Gross and Net Primary Production (we either will do, have done or are in the process of
doing a lab related to these terms so you best know this concept)
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C. Primary Production in Aquatic Ecosystems
1. Light Limitation
2. Nutrient Limitation.
a) The concept of the limiting nutrient
b) Algal Blooms and nutrients
c) Eutrophication (its definition)
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D. Primary Production in Terrestrial Ecosystems
III.
Energy transfer between trophic levels is typically only 10% efficient
A. Introduction
1. Secondary Production
B. Production Efficiency
1. Introduction
2. Tropic Efficiency and Ecological Pyramids (know this well)
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Tropic Efficiency and Ecological Pyramids (cont’d)
C. The Green World Hypothesis
IV.
Biological and geochemical processes cycle nutrients between organic and
inorganic parts of an ecosystem.
A. Biogeochemical Cycles
1. Definition (from the preceding paragraph)
2. General categories (just so you have the basic concept)
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3. Figure 55.13 is good for knowing the general concept.
4. The Water Cycle (Figure 55.14)
Have a general idea of the 4 parameters of the water cycle, especially the Key Processes.
This synthesis many of the topics we cover in individual chapters with Ecology.
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5. The Carbon Cycle
6. The Terrestrial Nitrogen Cycle
7. The Phosphorus Cycle
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B. Decomposition and Nutrient Cycling Rates
1. Factors controlling decomposition
2. Decomposition in a tropical rain forest, temperate forest, cold/wet environs and aquatic
ecosystems.
C. Case Study: Nutrient Cycling in the Hubbard Brook Experimental Forest
1. This is a nice quick read but no one will ask you specifically about the Hubbard Brook
Experimental Forest study.
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V.
Human activities now dominate most chemical cycles on Earth
A. Nutrient Enrichment
1.
Introduction
a) Human activity often removes nutrients from one part of the biosphere and adds
them to another.
b)
Farms and nutrients
2.
Agriculture and Nitrogen Cycling (as an example of how human activities affect
chemical cycles)
a) Loss of nutrients
b)
Nitrogen is the main nutrient lost through agriculture
(i) How is it lost and regained?
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3.
Contamination of Aquatic Ecosystems
a) The concept of Critical Load: the amount of an ADDED nutrient (like by humans)
that can be taken in or absorbed by plants without damaging the ecosystem. By
damage we mean “taking over” or overgrowth such as an algal bloom.
B. Acid Precipitation (another way humans interfere with chemical cycles)
1.
Sulfur and nitrogen oxides (SO2, SO3, NO2) are all gases and they will dissolve in water
to form sulfuric acid, sulfurous acid, nitrous acid and nitric acid and these are the
components of acid rain (deposition)
2.
Sources of the oxides
3.
Examples of pH changes
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C. Toxins in the Environment
1.
The concept of Biological Magnification( very important and very easy to remember)
2.
Examples
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D. Greenhouse Gases and Global Warming
1.
Rising Atmospheric CO2 levels
a) Source of CO2
b)
2.
Consequences of rising CO2
(i) Increased productivity of plants: C3 vs. C4 plants (this is good way of
integrating info from 2 different chapters and the AP Committee loves to do
this)
How Elevated CO2 Levels Affect Forest Ecology: The FACTS-I Experiment
a) No one will ask you about this specific experiment but you can gain some info from
this to apply to essay questions.
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3.
The Greenhouse Effect and Climate
a) Solar radiation is reflected from the Earth’s surface back to space. On its way back
to space it is trapped by CO2, CH4 (methane), water vapor.
E. Depletion of Atmospheric Ozone
1.
Ozone protects us from incoming UV radiation.
2.
UV radiation damages DNA leading to skin cancer and cataracts.
3.
What causes the breakdown of ozone into oxygen and oxygen atoms?
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