APES Miller 17th ed. Chapter 3 Questions
5. Describe the 2 chemical equations used by autotrophs and heterotrophs to gain energy for
chemical functions. Compare/contrast respiration to fossil fuel combustion in both process and
efficiency.
6. Some scientists think chemosynthesis started life on earth. How does chemosynthesis work?
What is the chemical energy source? How important do you think chemosynthesis is in our
world systems today?
7. Use the dead tree in Fig 3-10 to describe the processes of detritus feeders and decomposers.
8. What are the chemical outputs of anaerobic respiration and fermentation?
9. Use the laws of thermodynamics to describe the flow arrows in Fig 3-11 and explain why these
flows are one way. Describe where you think the heat goes? Add to your Venn Diagram (+VD).
10. Compare and contrast the diagrams of food chain, food web, and pyramid of energy flow and
include the roles of producers, primary consumers, secondary consumers, and decomposers.
12. Explain the measure unit kcal./m2/yr for GPP and NPP. Why is NPP a more important measure
than GPP? What percentage of total NPP do humans use? How could we change this estimate?
14. What are the 7 unique properties of water? Describe a situation where each property is needed.
15. Which processes in the water cycle (Fig 3-16) are affected by gravity? by sun energy? Rank the 4
human impacts on the water cycle. Explain why your top pick needs to be addressed first. +VD
16. Which processes in the carbon cycle (Fig 3-19) are affected by gravity? by sun energy? Rank the
5 human impacts on the carbon cycle. Explain why your top pick needs to be addressed first.
17. Describe how bacteria change the chemical form of N in each step of the nitrogen cycle:
nitrogen fixation, nitrification, ammonification, and denitrification. How does N move through
the spheres? What are the 5 ways we interfere with the nitrogen cycle?
19. Why do living organisms need P? Why is P limiting to growth? How do we affect the P cycle?
20. Describe ways S enters the atmosphere? In what forms? Describe 3 ways we affect the S cycle?
5. Autotrophs use the photosynthesis equation. Heterotrophs reverse it.
a. C6H12O6 + 6O2 → 6CO2 + 6H2O + energy (Heterotrophs)
b. 6CO2 + 6H2O + solar energy → C6H12O6 + 6O2 (Autotrophs)
c. CH4 + 2O2 → CO2 + 2H2O + energy
i. One molecule of methane, combined with two oxygen molecules, react to form
a carbon dioxide molecule, and two water molecules usually given off as steam
or water vapor during the reaction and energy. Natural gas is the cleanest
burning fossil fuel. Coal and oil, the other fossil fuels, are more chemically
complicated than natural gas, and when combusted, release a variety of
potentially harmful air pollutants. Burning methane releases only carbon dioxide
and water. Since natural gas is mostly methane, the combustion of natural gas
releases fewer byproducts than other fossil fuels.
6. Process where specialized bacteria can convert simple inorganic compounds from their
environment into more complex nutrient compounds without using sunlight. Bacteria living near
hydrothermal vents draw energy from hydrogen sulfide gas (H2S) escaping through the vent.
7. Detritus feeders and decomposers “feed on” parts of the log and convert its complex organic
chemicals into simpler inorganic nutrients that can be taken up by autotrophic producers.
Detritus feeders and decomposers are a vital part of the nutrient cycling process.
8. The chemical outputs of anaerobic respiration and fermentation, instead of carbon dioxide and
water, are methane gas (CH4), ethyl alcohol (C2H6O), acetic acid (C2H4O2), and hydrogen sulfide
(H2S).
9. Nutrient cycling (conservation of matter) and the one-way flow of energy—first from the sun,
then through organisms, and finally into the environment as low-quality heat—link all of these
components.
10. (Show 3-12 and 3-13)
a. A food chain is a sequence of organisms, each of which serves as a source of food or
energy for the next. It shows how chemical energy and nutrients move along the same
pathways from one organism to another through the trophic levels in an ecosystem.
VERY SIMPLIFIED. A food web represents reality more, as a complex network of
interconnected food chains really develop in ecosystems. Trophic levels can be assigned.
Basically chains and webs show how producers, consumers and decomposers are
connected to one another as energy flows through the ecosystem it represents.
b. Energy flow pyramids explain the percentage of usable chemical energy that is
transferred as biomass from one trophic level to the next. The more trophic levels, the
greater the cumulative loss of usable energy. (Show 3-14)
12. GPP/NPP (Show 3-15)
a. Gross Primary Productivity is the rate at which an ecosystem’s producers convert solar
energy into chemical energy in the form of biomass found in their tissues. Measured in
terms of energy production per unit area over a given time span—kilocalories per
square meter per year.
b. Net Primary Productivity is the rate at which producers use photosynthesis to produce
and store chemical energy minus the rate at which they use some of this stored
chemical energy through aerobic respiration. NPP measures how fast producers can
make the chemical energy that is stored in their tissues and that is potentially available
to other organisms in an ecosystem.
c. THE PLANET’S NPP ULTIMATELY LIMITS THE NUMBER OF CONSUMERS THAT CAN
SURVIVE ON EARTH.
14. Unique properties of water
a. Hydrogen bonds hold water molecules together, and it therefore takes a large amount
of energy to evaporate water because of these forces of attraction between its
molecules.
b. Water exists as a liquid over a wide temperature range because of the hydrogen bonds.
c. Liquid water changes temperature slowly because it can store a large amount of heat
without a large change in its own temperature.
d. Liquid water can dissolve a variety of compounds.
e. Water filters out wavelengths of UV radiation that would harm some aquatic organisms.
f. Hydrogen bonds allow water to “cling” to solid surfaces. (Capillary action)
g. Water expands when it freezes.
15. Water cycle (show 3-16)—a cycle of natural renewal of water quality
a. Precipitation, runoff, and infiltration are influenced by gravity.
b. Sun energy influences evaporation and transpiration.
c. Human impacts on the water cycle:
i. Withdraw large quantities of water faster than nature can replace it
ii. Clear vegetation for agriculture, mining, roads, etc. and replace it with
impermeable surfaces—increases runoff, reduces infiltration, accelerates
topsoil erosion, and increases risk of flooding
iii. Increase flooding with wetland drainage/filling for farming and urban
development (Wetlands are like sponges)
iv. Introduce pollutants to the system
16. Carbon cycle (show 3-19)—exchange of carbon between various organic and inorganic elements
in the atmosphere and biosphere. Elements that release carbon are called sources, while those
that absorb carbon are called sinks.
a. Sources
i. Volcanic eruptions
ii. Respiration of animals
iii. Decay of dead matter
iv. Combustion of fossil fuels
v. Conversion of limestone to lime, metamorphism of rocks, etc.
vi. Warm water bodies
b. Sinks
i. Earth’s atmosphere
ii. Organic elements like rocks, soil, sediments, limestone, coal deposits, etc.
iii. Oceans contain a lot of dissolved carbon
c. Process
i. CO2 used by plants (with sunlight) for photosynthesis
ii. Animals consume these plants, transferring carbon
iii. Carbon sent back to atmosphere through respiration
iv. Dead organisms decay, carbon transferred to the Earth (can become fossil fuels)
v. Burning of wood, fossil fuels, combustion transfer carbon back to atmosphere
vi. Oceans and other large water bodies absorb carbon from atmosphere
1. When ocean cool, carbon is absorbed
2. When ocean warm, carbon is released
d. Human altering
i. Adding large amounts of CO2 to atmosphere through burning of fossil fuels
ii. Clearing carbon-absorbing vegetation from forests faster than it can grow back
17. Nitrogen cycle (show 3-20)—how nitrogen moves between plants, animals, bacteria, the
atmosphere, and the soil
a. For nitrogen to be used by different life forms on earth, it must change into different
states.
i. Atmosphere—N2
ii. Nitrates—NO3
iii. Nitrites—NO2
iv. Ammonium—NH4
b. Most important part of the cycle is BACTERIA, as bacteria help the nitrogen change
between states so it can be used. When N is absorbed by the soil, bacteria help to
change it to states that can be used by plants. Animals then get their nitrogen from the
plants.
c. Processes
i. Fixation—first step in the process of making nitrogen usable by plants. Bacteria
change nitrogen into ammonium.
ii. Nitrification—ammonium gets changed into nitrates by bacteria. Nitrates are
what plants can then absorb.
iii. Assimilation—how plants get nitrogen. Absorb nitrates from the soil into their
roots. Nitrogen gets used in amino acids, nucleic acids, and chlorophyll.
iv. Ammonification—part of the decaying process. When a plant or animal dies,
decomposers like fungi and bacteria turn the nitrogen back into ammonium so it
can re-enter the cycle.
v. Denitrification—extra nitrogen in the soil gets put back out into the air. Bacteria
perform this task as well.
d. Human altering
i. Add large amounts of nitric oxide (NO) into atmosphere as we burn any fuel at
high temps (car, truck, jet engines). This converts to NO2 and HNO3, which
returns to surface as acid rain.
ii. Add nitrous oxide (N2O) to atmosphere through the action of anaerobic bacteria
on commercial inorganic fertilizer or organic animal manure applied to the soil.
(Greenhouse gas)
iii. Destruction of forests, grasslands, wetlands releases large amounts of gaseous
N stored in soils and plants.
iv. Upset cycle in aquatic ecosystems by adding excess nitrates through agricultural
runoff of fertilizers/animal manure and through discharge from municipal
sewage systems.
v. Remove nitrogen from topsoil when we harvest nitrogen-rich crops, irrigate
crops, and burn/clear grasslands and forests before planting crops
19. Phosphorus cycle (show 3-21)—phosphorus is an essential nutrient for plants and animals that
plays a critical role in cell development and is a key component of molecules that store energy
(ATP, DNA, lipids). Low phosphorus can lead to decreased crop yield.
a. Process
i. Rain and weathering cause rocks to release phosphate ions. Inorganic
phosphate is distributed in soils and water.
ii. Plants take up inorganic phosphate from soil. Plants then consumed by animals.
Phosphate then incorporated into organic molecules (like DNA). When plant or
animal dies, it decays, and organic phosphate is returned to the soil.
iii. Organic forms of phosphate within the soil can be made available to plants by
bacterial that break down organic matter to inorganic forms of phosphorus.
(Mineralization)
iv. Phosphorus in soil can end up in waterways and eventually oceans. It can then
be incorporated into sediments (and eventually rocks) over time.
b. Human effects
i. Removal of large amounts of phosphate to make fertilizers
ii. Reduce levels in tropical soils by clearing forests
iii. Eroded topsoil from fertilized areas (crop fields, lawns, golf courses) carries
large amounts of phosphates into streams, lakes, oceans. Stimulates the growth
of producers, like algae, which can upset chemical cycling in those water bodies.
iv. Basically, we remove scarce phosphate ions from land areas and feed them in
excess to producers in aquatic systems, causing these producer populations to
explode (algal blooms).
20. Sulfur cycle (show 3-22)—sulfur is one of the components that makes up proteins and vitamins.
It is important for the functioning of proteins/enzymes in plant and in animals that depend on
plants for sulfur. Plants absorb sulfur when it is dissolved in water. Animals consume these
plants.
a. Enters atmosphere
i. Naturally through volcanic eruptions, bacterial processes, evaporation from
water, decaying organisms
ii. Human processes—industrial processes release sulfur dioxide (SO2) and
hydrogen sulfide (H2S)
b. Human effects
i. Burn sulfur-containing coal and oil to produce electric power
ii. Refine sulfur-containing oil to make gasoline and heating oil
iii. Extract metals (copper, lead, zinc) from sulfur-containing compounds in rocks
that are mined for these metals.
iv. Once the sulfur is in the atmosphere, sulfuric acid and sulfate salts are created,
which return to earth as acid rain