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Ecosystems, Energy, and Trophic Pyramids
Ecosystems And Energy
Energy
Laws of Thermodynamics
Photosynthesis/Respiration
Trophic Pyramids
Energy Flow
Food Webs
Productivity
Examples of Possible Exam Questions
1. Explain what a pyramid of energy represents,
define the second law of thermodynamics, and
relate how the shape of a pyramid of energy is
due, in part, to the second law of
thermodynamics.
2. Diagram a trophic pyramid. Label each block of
the pyramid with the term describing those
organisms.
.
Examples of Possible Exam Questions
3. Explain the process of Biological Magnification.
In your explanation, provide an example of
biological magnification.
4. Explain what a food web is and discuss insights
into species importance that are gained by
understanding food webs.
5. Explain what a trophic pyramid is and discuss
insights that are gained by understanding trophic
structure..
Inductive And Deductive Reasoning
• Inductive reasoning begins with specific
observations and ends with a conclusion
that goes beyond any of the observations
that led up to the conclusion. (Based on
probabilities)
• Deductive reasoning begins with a
generalization and uses logic to create a
conclusion.
Inductive Reasoning
• A form of reasoning in which a conclusion
is reached based on a pattern present in
numerous observations.
• In inductive reasoning you draw a
conclusion based on specific evidence. The
conclusion may be more or less likely, but it
is not necessarily true.
• Most often used in science and law.
Example of Inductive Reasoning
• Between 1850 and 1930, measurements of
the population size showed that each time
the populations of Snowshoe hares
increased or decreased the populations of
lynx also increased or decreased.
• The conclusions are that the populations of
Snowshoe hares and lynx depend upon each
other.
Deductive Reasoning
• A form of reasoning in which evidence or
observations are secondary.
• In deductive reasoning the concern is to
define a commonly accepted VALUE or
BELIEF that prepares the way for the
argument you want to make.
Deductive Reasoning
• In deductive reasoning the conclusion is
that something must be true because it is a
special case of a general principle that is
known to be true.
• Based upon two premises and a conclusion
(syllogism). Logically, the conclusion is
true if the premises are true.
Example of Deductive Reasoning
• Premise one: If Sarah is ten feet tall, she can
dunk a basketball.
• Premise two: Sarah is ten feet tall.
• Conclusion: Sarah can dunk a basketball.
Valid conclusion
Example of Deductive Reasoning
• Premise one: If Sarah is ten feet tall, she can
dunk a basketball.
• Premise two: Sarah can dunk a basketball.
• Conclusion: Sarah is ten feet tall.
Invalid conclusion
Example of Deductive Reasoning
• Premise one: If there is fog the plane will be
diverted.
• Premise two: There is no fog.
• Conclusion: The plane will not be diverted.
Valid or invalid conclusion?
Ecology
The study of relationships between organisms
and their environment.
Environment = biotic and abiotic factors that
affect an organism during its lifetime.
Abiotic factors: nonliving parts of the
environment - water, minerals, sunlight,
climate.
Biotic factors: organisms that are a part
of the environment
Laws of Thermodynamics
First Law (Conservation of Energy)
Energy is neither created nor destroyed; it
is always conserved.
Second Law
Energy always tends to go from a more
usable form to a less usable form, so the
amount of energy available to do work
decreases (entropy occurs).
Consequence Of Laws Of
Thermodynamics For Living
Organisms
Organisms require a constant input of
energy to maintain a high level of
organization.
Types of Energy Systems
Photosynthesis
(Transformation of Light Energy)
6 CO2 + 12 H2O + radiant energy
C6H12O6 + 6 H2O + 6 O2
Stores energy in chemical bonds
Respiration
(Transformation of Chemical Energy)
C6H12O6 + 6 H2O + 6 O2
6 CO2 +12 H2O + energy
Provides energy for “work”
Ecological Studies Show How the Whole
System Works.
Focus:
1. The roles played by members of a
community
2. The energy/resource structure of the
system.
Ecosystem Organization
Each system can help clarify different
issues.
1. Trophic Pyramids
2. Food Webs
3. Nutrient Cycles
(Autotrophs and Heterotrophs)
Pyramids of
Energy
Suggests:
1. The number of
trophic levels are
limited. At each
trophic level, there
is a dramatic
reduction in energy.
2. Eating at lower
trophic levels means
more resources are
available.
Pyramids of Energy Suggests:
1. The number of trophic levels are limited. At
each trophic level, there is a dramatic
reduction in energy.
2. Eating at lower trophic levels means more
resources available.
3. Movement up the pyramid explains the
problems of Biological Magnification
(DDT, PCBs, etc.)
Biological Magnification
Concentration of a compound can increase at
higher trophic levels because each individual
in a higher trophic level must eat many
individuals of a lower trophic level to survive.
Although the energy acquired by eating those
organisms from a lower trophic level is used,
the toxic compounds may remain (Especially
true for compounds that are stored in fats and
are not easily broken down.).
Food webs
Are interlocking
food chains
based on which
organisms eat
which.
Arrows show the
direction of
food/energy
flow
Ecological Pyramids
• Pyramid of energy
• Pyramid of numbers
• Pyramid of biomass
Gross Primary Productivity = total
amount of energy captured by
photosynthesis for an ecosystem.
Keystone Species
Food webs suggest that keystone species may
be important. Changes in one species may
dramatically change the entire ecosystem
through links in the web.
Keystone Species = Species whose presence is
essential to community function and stability
(e.g., Krill in Antarctica).