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Alec Humphries
Ch5 Guided Reading
1: Define: Community Effect
One species indirectly affects another species by its own interactions within the
community
2: Explain WHY the Sea Otter is considered the Keystone Species in this
ecosystem. (Hint: Explain the food chain)
The sea otters feed on the poisonous sea urchins, keeping them from growing too
quickly, and eating the kelp forests, causing fish to lose their habitats.
3: Why were Sea Otters endangered and how did their numbers rebound?
They were being hunted for their fur, and rebounded by having a ban on hunting,
conservation efforts, and reintroduction.
5.1- The Ecosystem: Sustaining Life on Earth
1: Define Ecosystem Structure
Pattern of the interrelations of organisms in time and in spatial arrangements.
2: What two main processes must occur to maintain an ecosystem?
A cycling of chemical elements and a flow of energy.
5.2- Ecological Communities and Food Chains
1: What is the difference between a food chain and a food web?
A food chain is linear, showing one organism eating another, while a food web shows
all relationships in an ecosystem.
2: Define: Trophic Level
A position in a food chain or Ecological Pyramid occupied by a group
of organisms with similar feeding mode.
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Alec Humphries
Ch5 Guided Reading
3: Define: Autotrophs, Heterotrophs, Carnivores, Herbivores, Decomposers
Autotrophs: an organism that is able to form nutritional organic substances from
simple inorganic substances such as carbon dioxide.
Heterotrophs: an organism deriving its nutritional requirements from complex organic
substances
Carnivores: an animal that feeds on flesh.
Herbivores: an animal that feeds on plants
Decomposers: an organism that decomposes organic material.
4: Explain the food web of Yellowstone Hot Springs. Explain each trophic level
(include a photo).
First trophic level: photosynthetic bacteria and algae, only autotrophs able to survive
in the extreme conditions
Second trophic level: Ephydrid flies, only genus in the hotspring, feed on bacteria and
algae
Third trophic level: Dolichopodid fly, dragonflies, wasps, spiders, tiger beetles, and the
killdeer, all feed on algae, bacteria, and flies in the ecosystem. (photo on bottom)
5: Explain a pelagic ecosystem. Explain each trophic level (include photos).
First trophic level: Planktonic algae and bacteria
Second trophic level: zooplankton and some fish
Third trophic level: other fish, invertebrates, some whales
Fourth trophic level: Some fish and marine mammals (like killer whales) (photos on
bottom)
A Closer Look- Land and Marine Food Webs
1: Look at the terrestrial food web. Should we include people within this
ecosystem’s food web? That would place us within nature. OR should we place
people outside of the ecosystem, thus separate from nature?
People should be placed outside because our presence can alter nature
5.3- Ecosystems as Systems
1: Why are ecosystems considered to be OPEN systems?
They require a constant flow of energy and nutrients into the system, while waste
leaves the system, allowing for particles to pass in and out of the system.
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Alec Humphries
Ch5 Guided Reading
2: Define: Watershed
An area or ridge of land that separates waters flowing to different rivers, basins, or
seas
5.4- Biological Production and Ecosystem Energy Flow
1: Define: Energy
Power derived from the utilization of physical or chemical resources.
2: Explain: Ecosystem Energy Flow- What two ways does energy enter an
ecosystem?
The movement of energy through an ecosystem from the external environment through
a series of organisms and back to the external environment.
The Laws of Thermodynamics and the Ultimate Limit on the Abundance of Life
1: The First Law of Thermodynamics is also known as what? Define it.
Law of conservation of energy, and means: the fundamental principle of physics that
the total energy of an isolated system is constant despite internal changes
2: What is the Second Law of Thermodynamics say?
Whenever work is done, energy is inevitably converted to heat, recovering this energy
would require more energy than what would be recovered.
3: Define Entropy (give an example).
The measure of the decrease in order, for example, placing a marble in a large box and
shaking the box will cause the marble to have high entropy because it could be in
many places inside the box, because it is large.
4: What is an intermediate system?
An ecosystem between an energy source and an energy sink.
5.5- Biological Production and Biomass
1: What is biomass?
The total mass of organisms in a given area or volume.
2: Define the following:
*Biological Production
The capture of usable energy from the environment to produce organic matter.
* Gross Production
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The increase in stored energy before energy is used.
* Net Production
The amount on newly acquired energy stored after some energy has been used.
3: What are the 3 measures that are used for biomass and biological production?
Quantity of organic material, energy stored, and carbon stored.
4: What is primary production- who carries this out?
The production carried out by autotrophs.
5: What is secondary production- who is involved?
The production carried out by heterotrophs.
6: Who are chemoautotrophs? Explain- where are they usually found?
Autotrophs that can derive energy from inorganic sulfur compounds, and are usually
found in deep-ocean vents
5.6- Energy Efficiency and Transfer Efficiency
1: What is energy efficiency?
The ratio of output to input.
2: How would energy efficiency look with a wolf and moose population? Explain.
Highly efficient wolves store no energy because they use it to travel and hunt, while
the most ideal moose is the one that uses little energy, because there is more energy
given to the wolf in consumption.
3: What is food-chain or trophic level efficiency?
The ratio of production of one trophic level to the next-lower trophic level.
4: Generally, how much energy is lost to heat when being transferred between
trophic levels?
90%
5.7- Ecological Stability and Succession
1: What is ecological succession?
The process by which disturbed ecosystems recover.
2: Compare and contrast primary and secondary succession- give an example of
each.
Primary: the recovery of an ecosystem that is devoid of life and soil, ex: Mt St Helens
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Secondary: the recovery of an ecosystem that still has soil present, ex: forest fire
3: Explain how succession would look in a Dune.
Invasion of dune grass, other plants have chance of germinating, new plants grow,
new species develop, slowly, larger plants appear, eventually a forest develops, and a
severe storm removes all the plants to repeat the process over.
4: Explain how succession would look in a Bog.
Open water is transformed through formation of a floating mat of sedge and deposition
of sediments into a wetland forest.
5: Explain how succession would look in an old-field.
Small plants grow that are adapted to the harsh and variable conditions of a clearing,
other large plants enter, eventually trees grow, forming a dense forest.
6: Explain how succession would look in a coral reef.
Corals settle on a solid surface and produce a hard polyp of calcium carbonate, as old
individuals die, the surfaces harbor new individuals, shelled organisms enter, and
eventually the complex structure brings in many other organisms.
5.9- How Species Change Succession
1: Explain facilitation in succession and where is it most common?
Earlier-successional species changes the local environment in ways that make it
suitable for another species that is characteristic of a later-successional stage. This is
most common in dune and bog succession.
2: Explain interference in succession and what it can lead to.
An earlier-successional species changes the local environment in ways that make it
unsuitable for another species that is characteristic of a later-successional stage. This
can lead to breaks in the covers, and can lead to more succession.
3: What is chronic patchiness? When does this occur?
When an ecosystem doesn't reach a next stage of more evolved life and just remains
until it is disturbed again. This occurs in deserts and in marine environments with
plankton.
Critical Thinking Issue: Should People Eat Lower on the Food Chain?
1:Why does the energy content decrease at each higher level of a food chain?
What happens to the energy lost at each level?
Because most of the energy is lost as the level increases, and the energy is lost as
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Ch5 Guided Reading
heat.
2: Why it is appropriate to use mass to represent energy content?
Because the energy is stored and that stored energy takes up space as fat.
3: Using the average of 21 kilojoules of energy to equal 1g of completely dried
vegetation and assuming that wheat is 80% water, what is the energy content of
the 333,000 kg of wheat shown in the pyramid? (show your work).
100% wheat is 333,000 kg, <- is 80% water. 100% - 80% = 20%, so 20% of 333,000 kg
is energy. 333,000 * .2 = 66,600 kg of dried wheat. 1 kg = 1000 g, so 66,600 kg =
66,600,000 g of dried wheat. 1 g dried wheat = 21 kJ energy, then 66,600,000 g dried
wheat = (66,600,000 * 21) = 1,398,600,000 kJ of energy
4: Make a list of environmental arguments for and against an entirely vegetarian
diet for people. What might be the consequences for the United States
agriculture if everyone in the country began to eat lower on the food chain?
For: More energy, reduces pollution, healthier, does not harm animals
Against: More expensive, forces farming jobs, doesn't taste as appealing, animals are
still present to release pollutants, food must still be stored
If the human population began to eat lower on the food chain, then there would be a
much higher demand for agricultural foods, and would force more people to become
farmers so that there is a sustainable amount of food available for the entire
population.
5: How low do you eat on the food chain? Would you be willing to eat lower?
Explain.
I eat on the third level of the food chain and below, I would be willing to eat lower
because the tastes do not bother me and I appreciate the health benefits.
Study Questions:
1: Farming has been described as managing land to keep it in an early stage of
succession. What does this mean, and how is it achieved?
This means that they keep the farm land empty so that it is easier to plant crops that
will consequently grow quicker than if other plants were present, and this is achived
by removing other plants, creating clearings, and using monocultures
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Alec Humphries
Ch5 Guided Reading
.
2: Keep track of the food you eat during one day and make a food chain linking
yourself with the sources of those foods.
Protein shake, Eggs, Granola Bar, Chicken Cesar Salad, Fresh Fish, Bratwursts.
Determine the biomass (grams) and energy (kilocalories) you have eaten.
Using an average of 5Kcal/g, then using the information on food packaging or
assuming that your net production is 10% efficient in terms of energy intake,
how much additional energy might you have stored during the day? (What is
your weight gain from the food you have eaten?)