2023 STAAR Grade Bio Science Rationales
Item #
Rationale
1
Option D is correct
The axolotl salamander has gills, so it is adapted to live in water.
The tiger salamander has lungs and stout legs, so it is adapted to
live on land.
Option A is incorrect
The locations where the two species live are reversed. The axolotl
salamander lives in the water, and the tiger salamander lives on
the land.
Option B is incorrect
There is no evidence that suggests that either salamander is
adapted for living in trees or in caves.
Option C is incorrect
There is no evidence that suggests that either salamander is
adapted for living in trees or in caves.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
2
Option A is correct
Glucose is a product of photosynthesis, the cellular process shown
in the diagram.
Option B is incorrect
Phospholipids are not a product of photosynthesis.
Option C is incorrect
Insulin is not a product of photosynthesis.
Option D is incorrect
DNA is not a product of photosynthesis.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
3
2 pts.
The student describes and explains one of the following: An increase
in grasses (because mice consume grasses), a decrease in snakes
(because snakes consume mice), a decrease in rabbits (because, in
the absence of mice as a food source, hawks would prey upon more
rabbits), a decrease in lizards (because, in the absence of mice as a
food source, hawks would prey upon more lizards ), a decrease in
hawks (because hawks consume mice as a food source), or an
increase in grasshoppers (because grasshoppers compete with mice
for grasses as a food source).
1 pt.
The student describes one change but does not explain the reason
for this change.
0 pts.
The response is incorrect or irrelevant.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
4
Option B is correct
The diagram shows cell differentiation, which results from cells
expressing different sets of genes at different times.
Option A is incorrect
All these cell types replicate by mitosis.
Option C is incorrect
All these cells contain the same DNA in their nuclei.
Option D is incorrect
All cells of an organism use the same enzymes to replicate genetic
material.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
5
Option D is correct
The diagram shows a translocation mutation in which parts of the
chromosomes replace each other.
Option A is incorrect
In a deletion mutation, a portion of the chromosome would be
lost.
Option B is incorrect
In an insertion mutation, one or more nucleotides would be added
to a chromosome.
Option C is incorrect
In a duplication mutation, one or more copies of a DNA segment
would be inserted within or added to a chromosome.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
6
Part A
Option A is correct
In primary succession, first mosses will cover the rocks, creating
new soil, then small shrubs will grow, and then small trees will
begin to grow.
Option B is incorrect
Trees do not become rooted before small shrubs grow.
Option C is incorrect
Mosses cover rocks, breaking the rocks into smaller pieces, before
shrubs can grow.
Option D is incorrect
Soil must be produced by the action of mosses before small shrubs
can grow.
Part B
Option C is correct
The nunataks are bare rock, so they will undergo primary
succession.
Option A is incorrect
The slope of a location does not relate to the type of succession
that takes place.
Option B is incorrect
The slope of a location does not relate to the type of succession
that takes place.
Option D is incorrect
Secondary succession takes place in areas that have an established
plant community and existing soil.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
7
Viruses: Utilize a
capsid structure
Both: Contain
genetic material
Bacteria:
Replicate
independently,
Have active
metabolism
The phrase “Utilize a capsid structure” is placed in the “Viruses”
portion of the Venn diagram because the genetic material of viruses
is encased within a protein structure that is known as a capsid,
whereas the genetic material of bacteria is found within the
cytoplasm of these cells.
The phrase “Contain genetic material” is placed within the overlap in
the Venn diagram because viruses and bacterial cells both contain
some form of genetic material.
The phrase “Replicate independently” is placed in the “Bacteria”
portion of the Venn diagram because replication of the genetic
material of viruses is dependent upon a host cell, whereas replication
of the genetic material of bacteria takes place within the bacterial
cell’s own cytoplasm.
The phrase “Have active metabolism” is placed within the “Bacteria”
portion of the Venn diagram because bacteria are cells and therefore
are capable of metabolism, whereas viruses lack most of the
components found in cells and are therefore unable to perform the
processes of metabolism.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
8
Option C is correct
As sharks eat otters, the prey that otters eat will increase, and the
kelp forest will become less stable.
Option A is incorrect
A decrease in predation pressure is likely to cause an increase in
the prey that feed on kelp.
Option B is incorrect
The replacement of one top predator with another is likely to
cause changes to multiple trophic levels in an ecosystem.
Option D is incorrect
The kelp forests will become less stable, but since sharks are top
predators that prey on sea otters, they are unlikely to prey
significantly on organisms in lower trophic levels of the ecosystem.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
9
Option B is correct
Active transport requires ATP because this process moves
materials against the concentration gradient. Passive transport
does not require an additional energy input from ATP since
materials move along the concentration gradient.
Option A is incorrect
Active transport and passive transport occur in all cells.
Option C is incorrect
Active transport moves materials against a concentration
gradient. Passive transport moves materials along the
concentration gradient.
Option D is incorrect
Passive transport does not require any input of the energy stored
in ATP.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
10
100 or any
equivalent value is
correct.
The gene for the condition is dominant (A). One parent is
homozygous dominant (AA), while the other parent is homozygous
recessive (aa). The only possible outcome of a cross between these
parents (AA × aa) is that 100% of their offspring will have the
genotype Aa and the phenotype of achondroplasia.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
11
Slide 1 shows
prokaryotic cells.
Slides 2, 3, and 4
show eukaryotic
cells.
Although some eukaryotic cells have flagella, and some eukaryotic
cells are single-celled, the characteristic of having no nucleus allows
an observer to classify the cells on Slide 1 as prokaryotic.
The ability to go through mitosis is unique to eukaryotic cells, as is
the presence of linear DNA and organelles such as the endoplasmic
reticulum. These characteristics allow an observer to classify the
cells on Slide 2 as eukaryotic.
Prokaryotic cells are unicellular, and they lack membrane-bound
organelles and a membrane-bound nucleus. Although eukaryotic
organisms may be unicellular or multicellular, most eukaryotic cells
have a membrane-bound nucleus and membrane-bound organelles.
The presence of these characteristics in the cells on Slide 3 allows an
observer to classify these cells as eukaryotic.
Prokaryotic cells have a relatively simple structure and lack
membrane-bound organelles, such as mitochondria. In general, they
range in size from 0.1 micrometers to 5.0 micrometers. Although
eukaryotic cells vary in size, they typically have a complex structure
and have membrane-bound organelles, including mitochondria. The
presence of these characteristics in the cells on Slide 4 allows an
observer to classify these cells as eukaryotic.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
12
Option D is correct
Organisms with a cell wall made of cellulose are plants. Almost all
organisms in kingdom Plantae are autotrophs. Organisms with a
cell wall made of chitin are fungi. Fungi are heterotrophs.
Option A is incorrect
While plants are multicellular, fungi can also be multicellular.
Option B is incorrect
Plants are multicellular, but fungi can be unicellular or
multicellular.
Option C is incorrect
Although some plants are heterotrophs, no fungi are autotrophs.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
13
The endocrine
system releases
hormones into the
bloodstream, and
the circulatory
system carries
them to the target
location.
Although both the nervous system and endocrine system send
messages over a long distance, the nervous system does not directly
produce hormones, and its messages are carried to a target location
by cells of the nervous system. In contrast, the endocrine system
releases hormone messengers into the circulatory system, which
transports these messages to specific cells of other systems. Although
certain cells of the immune system can produce hormones, these
hormones are produced on-site as immune cells move to a specific
location.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
14
Option D is correct
This is a mutualistic relationship, so both organisms benefit. Thus,
Trichonympha improve the survival of termites.
Option A is incorrect
Unlike in some parasitic relationships, Trichonympha do not
eventually kill the host termites."
Option B is incorrect
Unlike a parasite, Trichonympha do not cause infection in the host
termites.
Option C is incorrect
Unlike parasites, Trichonympha do not steal resources from the
host termites.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
15
Option B is correct
Phylum is a higher, or more broad, level of classification than
order. Therefore, two organisms that share the same order would
also share the all the same classifications that are higher or
broader than order. They would have the same kingdom, phylum,
and class, as well as order.
Option A is incorrect
Family is a more specific level of classification than order, so two
organisms in the same order do not necessarily belong to the same
family.
Option C is incorrect
Genus is a more specific level of classification than order, so two
organisms in the same order do not necessarily belong to the same
genus.
Option D is incorrect
Species is a more specific level of classification than order, so two
organisms in the same order are not necessarily members of the
same species.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
16
Option C is correct
Transfer RNA transports amino acids to the ribosome for protein
synthesis; the ribosome is composed of rRNA; and mRNA carries
the genetic information from DNA to the ribosomes, where
translation occurs.
Option A is incorrect
Transfer RNA does not carry genetic information from the nucleus
to the ribosome; mRNA does that task.
Option B is incorrect
Ribosomal RNA does not bring amino acids to growing
polypeptides; tRNA does that task.
Option D is incorrect
Messenger RNA is not a component of ribosomes; rRNA is.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
17
Option A is correct
The process in the diagram shows DNA replication, which takes
place during interphase.
Option B is incorrect
The process in the diagram does not show protein synthesis and
does not take place during prophase.
Option C is incorrect
The process in the diagram does not show crossing over and does
not take place during metaphase.
Option D is incorrect
The process in the diagram does not show cytokinesis and does
not take place during anaphase.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
18
Option C is correct
The roots will continue to grow so that the plant can access
water, while the stem and leaf growth will decrease to minimize
water usage and water loss.
Option A is incorrect
Leaf and stem production will both be slowed or stopped to limit
the use and loss of water, while root growth will continue so that
roots are able to grow deeper into the soil to access water.
Option B is incorrect
While root growth will continue to allow roots to grow deeper into
the soil to access water, leaf growth will be slowed to limit the
loss of water to the environment and stem growth will be slowed
to limit the use of water in cellular respiration.
Option D is incorrect
While root growth will increase and stem growth will decrease,
leaf growth will decrease to limit the movement of water from the
roots to shoots through the xylem.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
19
2 pts.
The student identifies that Mutation 2 would have the most
significant impact because it would cause a frameshift mutation in
which the existing codon sequence (AAA GGC CAC) would be
replaced by a different sequence (AAG GCC AC), resulting in the
production of a different amino acid sequence.
1 pt.
The student answers half of the question correctly.
0 pts.
The response is incorrect or irrelevant.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
20
Option B is correct
The insertion of DNA from other species of salamanders into their
own DNA would increase the genetic diversity of the Ambystoma
population.
Option A is incorrect
A decrease in mutations would decrease the genetic diversity of
the Ambystoma population.
Option C is incorrect
An increase in similarity of DNA across the population would
decrease the genetic diversity of the Ambystoma population.
Option D is incorrect
The creation of many genetically identical individuals would
decrease the genetic diversity of the Ambystoma population.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
21
Option D is correct
The endocrine, digestive, excretory, and skeletal systems are all
represented in the feedback-loop diagram for blood calcium
homeostasis.
Option A is incorrect
The respiratory system and muscular system are not represented
in the feedback-loop diagram for blood calcium homeostasis.
Option B is incorrect
The respiratory system, immune system, and reproductive system
are not represented in the feedback-loop diagram for blood
calcium homeostasis.
Option C is incorrect
The integumentary system and muscular system are not
represented in the feedback-loop diagram for blood calcium
homeostasis.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
22
Option C is correct
The diagram shows movement of glucose through the transport
protein after insulin binds to the receptor.
Option A is incorrect
The diagram does not provide information about the role of white
blood cells in the removal of glucose from the blood.
Option B is incorrect
Although a cell membrane is shown, there is not information
provided in the diagram to suggest that the flexibility of the cell
membrane might change as glucose moves through it.
Option D is incorrect
No information in the diagram suggests that, during this process,
energy is used to create more glucose.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
23
Option B is correct
While the DNA sequences of the plant and animal differ, these
sequences do contain the same types of bases (adenine, guanine,
cytosine, thymine).
Option A is incorrect
Only closely related organisms share an identical genetic
sequence for a given gene.
Option C is incorrect
While the lizard may consume the bluebonnet, the bluebonnet’s
DNA will not alter the DNA within the cells of the lizard and does
not account for any similarity between the two DNA sequences.
Option D is incorrect
Although mutations do randomly occur in the genetic code, the
differences in the organisms' gene sequences are due not to
recent random mutations, but to the fact that the organisms are
only distantly related.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
24
Option B is correct
Viruses hijack the host cell’s DNA, use it to make copies of viral
genetic material, and then lyse the cell, spreading the infection.
Option A is incorrect
Viruses are not able to reproduce without a living host, so two
viruses cannot reproduce with each other.
Option C is incorrect
Viruses are nonliving and cannot obtain energy from food since
they do not consume food.
Option D is incorrect
Vaccines enable hosts to initiate an immune response to counter
a viral invasion; the virus does not compete with the host cells
for water.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
25
Option A is correct
Soil organisms use nitrogen to decompose wood, so adding
sawdust to the soil will cause a nitrogen deficiency in the soil and a
disruption of the nitrogen cycle. Because plants need nitrogen for
biological processes such as transcription and translation, loss of
all available nitrogen will cause the growth of plants to cease.
Option B is incorrect
Limiting nitrogen limits the growth of plants.
Option C is incorrect
Disruption of the nitrogen cycle will be harmful to both existing
plants and plants moving into the environment.
Option D is incorrect
The plants in this location will be unable to grow and reproduce, as
nitrogen is essential to the process of transcription and
translation. It is unlikely that a subset of plants in the environment
have mutations that allow these processes to take place in the
absence of nitrogen. Without such variation in the population,
selection for such a trait will not take place.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
26
Option C is correct
Crossing-over is the process that occurs between Step 2 and Step 3
and creates more genetic diversity in the resulting cells.
Option A is incorrect
Chromosome nondisjunction would cause the cells in Step 4 to
contain different numbers of chromosomes. However, all the cells
in Step 4 have the same number of chromosomes.
Option B is incorrect
Genome replication occurs during interphase, which is not
illustrated in the diagram.
Option D is incorrect
Chromosome deletion would cause a change in the size of one or
more of the chromosomes shown in Step 4. Although they have a
different makeup than those in Step 1, all the chromosomes
shown in Step 4 are the same size as those in Step 1.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
27
Option C is correct
The pattern of evolution described is called punctuated
equilibrium.
Option A is incorrect
Convergent evolution is the independent evolution of similar
features in organisms that are not closely related. Convergent
evolution creates analogous structures that have similar form or
function but were not present in the last ancestor that the two
species had in common.
Option B is incorrect
Differentiation is a cellular process by which less-specialized cells
develop, or mature, to become more distinct in form and function.
Option D is incorrect
Gradualism refers to changes that are continual and slow rather
than periodic and rapid, as in punctuated equilibrium.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
28
Option B is correct
The function of an enzyme is to reduce the activation energy and
speed up the rate of the reaction.
Option A is incorrect
The function of an enzyme is not to raise the temperature of the
system, although an increase in temperature may be one effect of
the reaction.
Option C is incorrect
The function of an enzyme is to aid in the conversion of a
substrate molecule into one or more product molecules, not to
increase the amount of substrate added.
Option D is incorrect
The function of an enzyme is to help form a product, not to change
the type of product.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
29
Option C is correct
Transcription copies the code of DNA onto a single-stranded RNA
molecule that can then leave the nucleus.
Option A is incorrect
Transcription is not able to correct mutations on the DNA strand;
it simply copies DNA’s code.
Option B is incorrect
Replication is the process of making an exact copy of the DNA
molecule. In contrast, transcription makes a copy of a portion of
a DNA molecule using a different set of nucleotides.
Option D is incorrect
Transcription copies DNA’s code and makes it possible for tRNA
to translate the code and direct the formation of the protein.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
30
Option D is correct
The fungus is harming the corn plant while benefiting from the
relationship. A relationship between organisms where one
benefits and the other is harmed is known as parasitism.
Option A is incorrect
Competition occurs when two species are competing for limited
resources, not when one species uses another as a food source.
Option B is incorrect
Commensalism is a relationship in which one organism benefits
from the relationship and the other is unaffected. Here, the
fungus benefits and the plant is harmed.
Option C is incorrect
Predation is a relationship in which a consumer kills and eats
another organism. Although the fungus is extracting nutrients
from the corn and may be considered a primary consumer, the
fungus does not kill the plant before consuming its resources.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
31
Option A is correct
Cancer cells lack functioning checkpoints, which results in
uncontrollable cell division.
Option B is incorrect
Regulated gene expression happens in noncancerous cells.
Option C is incorrect
Noncancerous cells can respond to outside stimuli.
Option D is incorrect
Most eukaryotic cells contain mitochondria.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
32
Option C is correct
The sequence of nucleotides in a DNA molecule determines the
sequence of amino acids that are combined to make a protein.
Option A is incorrect
Although the temperature of a cell may affect the rate at which
cellular processes take place and can also affect the folding of
amino acids into a protein, temperature will not directly affect the
types of amino acids that combine to produce a protein.
Option B is incorrect
The loss of the chromosomes containing the gene for albumin
would result in no translation of albumin, not an albumin
molecule with a different amino-acid sequence.
Option D is incorrect
Although translation, like other cellular processes, requires
energy, the lack of energy would result in no translation, not the
translation of protein with a different amino-acid sequence.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
33
Option C is correct
The pattern of succession shown in the table best represents
secondary succession, as large plants are found soon after the
disturbance. Plowing a field does not remove all the existing soil
and vegetation from the area; thus, if a field were abandoned after
being plowed, existing vegetation would quickly regrow.
Option A is incorrect
The retreat of a glacier would result in the creation of new soil that
would undergo primary succession.
Option B is incorrect
The formation of a volcanic island would produce bare rock that
would undergo primary succession.
Option D is incorrect
The formation of a new sand dune would produce bare sand that
would undergo primary succession.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
34
Option B is correct
Using the standard taxonomic system to name the snake species
would help avoid confusion since there are a variety of species.
Option A is incorrect
The taxonomic system is not related to whether organisms appear
in the fossil record.
Option C is incorrect
The standard taxonomic system does not use habitat to classify
organisms into groups; it uses the organisms’ physical
characteristics.
Option D is incorrect
The impact of ecosystem changes is not quantified by the
taxonomic system; the names are based on each organism’s
physical characteristics.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
35
Option A is correct
A community has two or more populations of species interacting
with each other, not one individual of a species interacting with
other individuals of the same species.
Option B is incorrect
Communities of organisms can be in small, indoor areas as well as
in large, outdoor areas.
Option C is incorrect
Living (biotic) and nonliving (abiotic) components interact together
within an ecosystem.
Option D is incorrect
A community may be multigenerational, but this characteristic is
not a requirement of a community.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
36
Option C is correct
Dolphin embryos develop hind limbs as embryos because they
share genetic information with early ancestors that had hind
limbs.
Option A is incorrect
Populations, not individual organisms, adapt to changes in the
environment.
Option B is incorrect
The genes that control the development of hind limbs are
regulated, not destroyed, during the development process.
Option D is incorrect
The disappearance of hind limbs does not support the claim that
dolphins are evolving to become terrestrial animals.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
37
Option C is correct
The phases of mitosis occur in this order: prophase (Z), metaphase
(X), anaphase (W), and telophase (Y).
Option A is incorrect
Z, Y, X, W is not the correct order of the phases of mitosis.
Option B is incorrect
X, W, Z, Y is not the correct order of the phases of mitosis.
Option D is incorrect
X, Z, Y, W is not the correct order of the phases of mitosis.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
38
Option C is correct
The question, “How does the eye span of stalk-eyed flies compare
from one generation to the next?” indicates that the student is
thinking about how traits change over time.
Option A is incorrect
This question compares traits within two groups of a current
population and does not examine how traits in a population
change over time.
Option B is incorrect
This question compares traits that currently exist in a population
and does not examine how traits within a population change over
time.
Option D is incorrect
This question does not focus on the change in eye span in stalk-
eyed flies.
2023 STAAR Grade Bio Science Rationales
Item
#
Rationale
39
Part A
Option D is correct
Carbohydrates are transported to the fungi from the plant through
the phloem.
Option A is incorrect
The xylem transports water, minerals, and nutrients from the soil to
all the plant parts.
Option B is incorrect
The phloem transports carbohydrates produced by photosynthesis
to plant tissues.
Option C is incorrect
The xylem transports water, minerals, and nutrients from the soil to
all the plant parts.
Part B
Option B is correct
The phloem transfers glucose throughout the plant.
Option A is incorrect
The xylem transports water, minerals, and nutrients, not
carbohydrates.
Option C is incorrect
The xylem transports water, minerals, and nutrients, not
carbohydrates.
Option D is incorrect
The phloem and xylem are tissues that move material throughout
the plant. These tissues do not connect within or near the root of
the plant.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
40
Option A is correct
The introduction of Texas pumas into the Florida panther
population increased the genetic diversity of the Florida
population as new genes were introduced into the breeding
population. The introduction of the Texas puma added new alleles
into the gene pool of the Florida panther.
Option B is incorrect
Hunting and habitat loss do not produce gene flow. Gene flow
increases variation.
Option C is incorrect
Artificial selection is the selection of organisms by humans for
mating, not the introduction of alleles into a population.
Option D is incorrect
Hunting and the loss of habitat do not result in artificial selection.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
41
Option B is correct
Differences in temperature affect the gender of American alligator
hatchlings because different genes are expressed at different
temperatures.
Option A is incorrect
Gene repair does occur differently at different temperatures, but
the ability to repair DNA does not explain how temperature affects
the gender of alligator hatchlings.
Option C is incorrect
Different genes within the embryo's DNA are turned on or off at
different temperatures, not deleted.
Option D is incorrect
Different genes within the embryo's DNA are turned on or off at
different temperatures, not duplicated.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
42
Option D is correct
Chitin, like other carbohydrates, provides support to the organism.
Chitinase, like certain other proteins (enzymes), breaks down
other molecules.
Option A is incorrect
Chitinase is an enzyme and therefore does not store genetic
information.
Option B is incorrect
Chitinase is an enzyme and therefore does not have a structural
role, such as insulation of an organism.
Option C is incorrect
Chitin is a carbohydrate and therefore does not store genetic
material. Chitinase is an enzyme and therefore does not have a
structural role, such as providing support and protection.
2023 STAAR Grade Bio Science Rationales
Item
#
Rationale
43
Option A is correct
Based on the key, both the red-winged blackbird and the hairy
woodpecker do not have a crest.
Option C is correct
Based on the key, both the red-winged blackbird and the hairy
woodpecker do not have a short beak.
Option B is incorrect
“Is the bird blue?” is a question that differentiates between blue
jays and northern cardinals.
Option D is incorrect
“Does it have a reddish coloration?” is a question that
differentiates between rose-breasted grosbeaks and American
goldfinches.
Option E is incorrect
“Is it mostly black and white?” is a question that differentiates
between the red-winged blackbird and the woodpeckers.
Option F is incorrect
“Do its tail feathers have dark spots?” is a question that
differentiates between the downy woodpecker and hairy
woodpecker.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
44
Option D is correct
The grasses would have the largest amount of energy available,
and because of the inefficiency of energy transfer, there is a
dramatic difference in available energy at each trophic level as
energy is transferred up the chain to the coyotes.
Option A is incorrect
Energy transfer would not be this efficient in the ecosystem. Only
about 10% of the available energy is transferred from one trophic
level to the next.
Option B is incorrect
Top predators do not have the most energy in a food chain.
Option C is incorrect
Coyotes would not have the most energy in this food chain, as
they are top predators.
2023 STAAR Grade Bio Science Rationales
Item #
Rationale
45
Option C is correct
Guanine (G) pairs with cytosine (C), and thymine (T) pairs with
adenine (A). Only Option C shows the complete pairing between
the two strands of DNA.
Option A is incorrect
A does not pair with G.
Option B is incorrect
G does not pair with G.
Option D is incorrect
T does not pair with G.
