1.3 Homework Assignment
(IB Environmental Systems and Societies)
Directions: All answers must be in your own words. Use citations when appropriate. Copying from your classmates
results in a zero for both you and your classmate.
1. In a separate Word document, create a matching vocabulary quiz with the following terms:
First Law of Thermodynamics (Principle
of the Conservation of Energy)
Assimilation (relating to Food Chains)
Stability
Stable Equilibrium
Positive Feedback
Albedo
Keystone Species
r-Strategist
Genetic Diversity
Second Law of Thermodynamics
Heat Energy
Steady-State Equilibrium
Unstable Equilibrium
Homeostasis
High Resiliency
Eutrophication
K-Strategist
Climax Ecosystem
Lotka-Volterra Model of PredatorPrey Interactions
Efficiency
Static Equilibrium
Negative Feedback Loop
Entropy
Low Resiliency
Monoculture
Biodiversity
Tipping Point
2. We experience the second law of thermodynamics in our everyday lives. Define, in your own words, both the first
and second laws of thermodynamics and provide an everyday example of how we experience the second law of
thermodynamics.
3. Equilibrium is the tendency of the system to return to an original state after a disturbance; at equilibrium, a state of
balance exists among the components of that system. Draw a simple, labeled graph representing each of the four
equilibria. Provide a brief example of each.
4. Below you will find a number of examples of how both positive and negative feedback mechanisms might operate in
the physical environment. No can be sure which of these effects is likely the most influential, and consequently, we
cannot know whether or not the Earth will manage to regulate its temperature, as a result of human interference
with many natural processes.
Directions: Label each example as either positive or negative feedback. Draw diagrams for Example A and Example C.
Include feedback loops in your diagrams. Label your diagrams.
A. _______________________________________________
As carbon dioxide levels in the atmosphere rise, the temperature of the Earth rises. As the Earth warms, the rate of
photosynthesis in plants increases, more carbon dioxide is therefore removed from the atmosphere by plants, reducing
the greenhouse effect and reducing global temperatures.
B. _______________________________________________
As the Earth warms, ice cover melts, exposing soil or water. Albedo (the fraction of light that is reflected by a body
or surface) decreases. More energy is absorbed by Earth’s surface. Global temperatures rise and more ice melts.
C. _______________________________________________
As Earth warms, upper layers of permafrost melt, producing waterlogged soil above frozen ground. Methane gas is
released into the atmosphere. The greenhouse effect is enhanced and the Earth warms, melting more permafrost.
D. _______________________________________________
As Earth warms, increased evaporation produces more clouds. Clouds increase albedo, reflecting more light away
from Earth. Temperature falls. Rates of evaporation fall.
E. _______________________________________________
As Earth warms, organic matter in the soil is decomposed faster. More carbon dioxide is released. Enhanced
greenhouse effect occurs and the Earth warms further. Rates of organic matter decomposition increase.
F. _______________________________________________
As Earth warms, evaporation increases. Snowfall at high latitudes increases. Icecaps enlarge and more energy is
reflected by increased albedo of ice cover. Earth cools and rates of evaporation fall.
G. _______________________________________________
As Earth warms, polar ice caps melt, releasing large numbers of icebergs into the oceans. Warm ocean currents such
as the Gulf stream are disrupted by additional freshwater input into the Ocean. Reduced transfer of energy to poles
reduces temperature at high latitudes. Ice sheets reform and icebergs retreat. Warm ocean currents are
reestablished.
5. Discuss the causes and consequences of lake eutrophication. Lake eutrophication is considered a tipping point. You
may use a diagram if necessary.
6. Predator-Prey Interactions and Negative Feedback: See Figure 1.3.16 in your textbook.
A. On average, what was the cycle length of the lynx population?
B. On average, what was the cycle length of the hare population?
C. Why do lynx numbers lag behind hare numbers?
D. Why are lynx numbers smaller than hare numbers? Use what you know about the First Law of Thermodynamics.
E. In regions, where lynx died out, hare populations still continued to fluctuate. Why do you think this was?
7. Use the diagram on Page 40 of your textbook to answer the following questions:
A. How is the growth of the animal population regulated in the diagram?
B. Explain why this diagram is an example of negative feedback control.
C. Complete the diagram of a generalized ecosystem showing inputs, outputs, and stores. Remember to add in
human activities.
S
Inputs
Stores
Outputs