Download Which statement best describes the relationship between free

PROCTOR VERSION
2.3 D: Free Energy of Ecosystems Quiz
1.
Which statement best describes the relationship between free energy and the trophic levels of an
ecosystem?
(A) Since approximately 10% of the free energy available at one trophic level is available to the
organisms at the next trophic level, the number of organisms at each trophic level is
approximately 10% of the number at the previous level.
Distractor Rationale:
This answer suggests the student may understand that, as a general rule, approximately
10% of the free energy available at one trophic level is available at the next trophic level, but
does not understand that the number of organisms is different than the amount of free
energy and that the amount of free energy needed by each organism combined with the
total amount of available free energy determines the number of organisms that can be
supported at each trophic level.
(B) Since all ecosystems receive the same amount of free energy from the sun, all the
organisms at the same trophic level receive about the same amount of free energy, which is
approximately 10% of the free energy available to the organisms at the previous trophic
level.
Distractor Rationale:
This answer suggests the student may understand the 10% rule at a general level, but does
not understand that it is a broad rule and not true for all organisms/trophic levels, that each
ecosystem receives a different amount of free energy, that not all free energy comes from
the sun, and that the amount of energy transferred between trophic levels depends on many
different factors, including energy requirements, reproductive rates, and environmental
conditions, and is usually more or less than 10%.
(C) The amount of free energy that is transferred to the environment as thermal energy at each
trophic level is approximately 10%, which means that the total number of organisms that are
supported at each successive trophic level is less because of several factors, including a
reduced biomass and a decreased reproductive rate.
Page 1 of 6
PROCTOR VERSION
2.3 D: Free Energy of Ecosystems Quiz
Distractor Rationale:
This answer suggests the student may understand that less free energy is available to
organisms at the higher trophic levels than to organisms at the lower trophic levels and that
the biomass of each successive trophic level is less, but does not understand that the
majority of the energy available at each trophic level is converted to thermal energy and only
a small portion is actually transferred to the next trophic level or that the number of
organisms a trophic level can support depends on the size and energy demands of the
organisms.
(D) The amount of free energy available to the organisms at a trophic level is approximately
10% of the free energy available at the previous trophic level, but the actual amount of free
energy transferred between trophic levels depends on many factors, including the
organisms’ energy requirements and environmental conditions.
Rationale:
This answer suggests the student understands that the 10% rule is an oversimplification,
that it does not apply to all energy transfers between trophic levels, and that the actual
amount of free energy that is transferred depends on many different factors.
Aligned to: LO 2.3 CA 2.3: Predict Free Energy
2.
A small island is hit by a massive hurricane. The only two species that survive the hurricane are
frogs and mosquitoes. Frogs feed on mosquitoes and mosquitoes feed on frogs. Which
statement describes what will most likely happen to the frog and mosquito populations over
time?
(A) The frog and mosquito populations will remain in equilibrium because the individual
organisms in each population have a steady supply of free energy.
Distractor Rationale:
This answer suggests the student may understand that some energy is transferred between
the frogs and mosquitoes, but does not understand that there is less available free energy
with each transfer because some energy is converted to thermal energy (heat) by each
organism and is no longer available for use, and that no free energy is entering the system
to replace that converted into heat.
(B) The mosquito population will start to decline first, followed by the frog population, because
free energy is only transferred in one direction, from smaller organisms to larger organisms.
Page 2 of 6
PROCTOR VERSION
2.3 D: Free Energy of Ecosystems Quiz
Distractor Rationale:
This answer suggests the student may understand that energy is transferred in one direction
in an ecosystem and that both populations will decline without free energy entering this
system, but does not understand that energy may be transferred between organisms of
any size, or that the populations of mosquitoes and frogs will decline together as the
available free energy is converted to thermal energy (heat) and is no longer available for
use.
(C) The frog population will decrease in response to a decrease in the mosquito population
because frogs and mosquitoes have a predator-prey relationship and depend upon one
another for food.
Distractor Rationale:
This answer suggests the student may understand that the frog population will decrease in
response to a decrease in the mosquito population, but does not understand that frogs and
mosquitoes do not have a predator-prey relationship, that no free energy is entering this
system, and that some energy is converted into thermal energy (heat) with each transfer
between the organisms and is no longer available for use.
(D) The frog and mosquito populations will both decline because individual organisms will
convert some available free energy into thermal energy, and a constant input of free energy
is needed to maintain the system.
Rationale:
This answer suggests the student understands that energy transfer between organisms
always involves a transfer of some usable energy into thermal energy (heat) by cellular
processes and is no longer available for use, and that the two species cannot feed off each
other indefinitely because no free energy is entering this system and all the free energy will
eventually be converted into thermal energy.
Aligned to: LO 2.3 CA 2.3: Predict Free Energy
Page 3 of 6
PROCTOR VERSION
2.3 D: Free Energy of Ecosystems Quiz
3.
The diagram below shows the flow of energy through some species in an ecosystem.
Which statement best supports the information in the diagram?
(A) The individuals in species K have a high reproductive rate and a fast maturation rate
because they are a food source for all consumers in the ecosystem.
Rationale:
This answer suggests the student understands that a species that is a source of food for
many other species needs to have a relatively high growth and reproductive rate in order to
sustain its population due to the high rate of predation.
(B) Species J has the greatest total biomass of all species in the ecosystem since it obtains
energy from both primary and secondary consumers.
Distractor Rationale:
This answer suggests the student may understand that species J obtains energy from both
primary and secondary consumers, but does not understand that producers generally have
the greatest biomass in an ecosystem because the amount of free energy is greatest at the
producer trophic level and can support the most organisms.
(C) Species F has the least amount of available free energy because it obtains its energy from
decomposers rather than producers.
Distractor Rationale:
This answer suggests the student may understand that species F obtains some of its energy
from decomposers, but does not understand that species F is a primary producer and has
the greatest amount of available free energy of all species in the food web.
Page 4 of 6
PROCTOR VERSION
2.3 D: Free Energy of Ecosystems Quiz
(D) The removal of species G would be catastrophic to the other species in the ecosystem
because species G is a predator.
Distractor Rationale:
This answer suggests the student may understand that predators often play a vital role in
keeping other populations in balance within an ecosystem, but does not understand that
there is no evidence to support the claim that the removal of species G would be
catastrophic for the ecosystem (species G is not the only predator or even the top predator),
or that species H and J are also predators in the ecosystem and they also help keep other
species in balance within the ecosystem.
Aligned to: LO 2.3 CA 2.3: Predict Free Energy
4.
The diagram below represents a partial food web for an ecosystem.
Which statement describes the most likely impact if species A is removed from the ecosystem?
(A) Species C, D, and E will all be equally affected because they all receive free energy from
species A.
Distractor Rationale:
This answer suggests the student may understand the general flow of energy in a food web,
but does not understand that species with multiple sources of free energy (food) will be
less affected than species that connect within the food web and depend on only one primary
food source.
Page 5 of 6
PROCTOR VERSION
2.3 D: Free Energy of Ecosystems Quiz
(B) Species B will rapidly evolve to fill the niche left by species A and will become the only
primary producer.
Distractor Rationale:
This answer suggests the student may understand that species A and B have the same role
in the food web and that a species can adapt to expand into another species’ niche when
the competing species is removed, but does not understand that this expansion depends
on many factors, does not always happen and is not supported by the food web as being the
most likely impact.
(C) Species C and G will be most affected since the free energy for these species comes
directly or indirectly from species A.
Rationale:
This answer suggests the student understands how free energy is transferred through food
webs, that some species obtain energy from multiple sources but that other species may
rely on only one source, and that a species that relies on only one source is affected more if
its only food source is removed than a species with multiple food sources.
(D) Species F, G, H, and J will be minimally affected because they receive free energy from
other sources rather than from species A.
Distractor Rationale:
This answer suggests the student may understand that a primary consumer is directly
impacted by the removal of part or all of its food source, but does not understand that this
reduces the available free energy for the higher trophic levels in the food web and that the
reduction in free energy at a lower trophic level has a direct impact on those species in the
higher trophic levels.
Aligned to: LO 2.3 CA 2.3: Predict Free Energy
Page 6 of 6