2020 Biology EOCT Practice Items (from study/resource guide)

Students modeled the changes in cells during mitosis, using paper plates, flat wooden sticks, cotton

swabs, and construction paper. * Which statement correctly uses the model to explain how mitosis maintains genetic continuity?

• The chromosomes in cell 1 are the same as in cells 6 and 7.

• Crossing-over occurs in cell 4, which increases the genetic diversity in cells 6 and 7.

• When the nuclear membrane reforms in cell 5, each nucleus becomes diploid in number.

• The independent assortment that is represented in cell 2 ensures that cell 3 has the correct number of

  chromosomes.

Answer explanation

The correct answer is choice (A) The chromosomes in cell 1 are the same

as in cells 6 and 7. Choice (B) is incorrect because crossing-over does not occur in mitosis. Choice (C) is

incorrect because the chromosomes in step 5 are haploid, not diploid as shown in the picture. Choice (D)

is incorrect because it is not an independent assortment.

The scientists claimed that the growth and stability of the phytoplankton populations were affected by

the viruses. Using the information given, which TWO arguments support this claim?

• The phytoplankton population was unable to absorb the light necessary for growth because the viruses

  covered the surface of the water.

• The phytoplankton population was affected by the viruses because the viruses were competitors for the

  food sources in the environment.

• As the phytoplankton population increased, the number of viruses began to increase because the

  phytoplankton were consumed by the viruses.

• As the phytoplankton population reached capacity, the number of viruses began to increase because

  the phytoplankton were the hosts to the viruses and replicated the viruses’ genome.

• The phytoplankton population decreased as the number of viruses increased because the cells of

  the phytoplankton were destroyed as the viruses used them to increase the number of viruses in the

  environment.

Answer explanation

Choice (A) is incorrect because nothing in the graph indicates that the viruses are able to block sunlight.

Choice (B) is incorrect because viruses do not require a food source. Choice (C) is incorrect because the

viruses do not eat phytoplankton.

Portions of the protein sequence alignments for a group of ciliates are shown in the image. * Which of the following cladograms BEST represents these data?

• 
• 
• 
• 

Answer explanation

The correct answer is choice (C). Choice (A) is incorrect

because the organisms are not equally related. Choice (B) is

incorrect because one ciliate is duplicated in the cladogram.

Choice (D) is incorrect because one ciliate is omitted.

The ribosome of the bacterium E. coli includes the ribosomal protein L4 (rpl4). The rpl4 gene carries

the instructions for making rpl4 protein. Which of the following arguments provides support for the

claim that E. coli has a common ancestor with all other organisms?

• Every organism depends on proteins to carry out essential cellular processes. Ribosomes are needed

  by all organisms to synthesize proteins such as rpl4.

• Every organism possesses in its ribosome a protein that is similar to rpl4. This protein has an amino

  acid sequence that is similar to the sequence of E. coli’s rpl4.

• Every organism contains a structure that is similar to a ribosome. This structure helps convert the

  instructions from the rpl4 gene into amino acids.

• Every organism has proteins made of amino acids. The code for amino acids is the same in E. coli

  because the instructions for amino acids come from the DNA. DNA contains the same components in

  all organisms.

Answer explanation

The correct answer is choice (B) Every organism possesses in

its ribosome a protein that is similar to rpl4. This protein has

an amino acid sequence that is similar to the sequence of

E. coli’s rpl4. Choice (A) is incorrect because just the fact

that all organisms make proteins does not support a common

ancestor. Choice (C) is incorrect because sharing ribosomes

does not indicate a common ancestor. Choice (D) is incorrect

because having common amino acids is not support for a

common ancestor.

Organisms can be organized by their similarities and differences. The incomplete cladogram shows the relationship between some invertebrates based on their body structures. * The development of six legs should be placed at letter ___ on the cladogram because the body structure is present only in organisms _____ that point on the cladogram.

• A; before

• B; after

• B; before

• C; at

Answer explanation

“B” is the correct response for the first drop-down menu and “after” is the correct response for the second

drop-down menu because the worm does not have legs, the spider has eight legs, and all the organisms

on the cladogram after B have six legs, a key trait distinguishing between arachnids and insects. In this

cladogram, all the organisms are related because they all possess a segmented body. They must be

further distinguished from each other by other distinctive traits. The development of the trait for six legs

occurred after the evolution of spiders and before the evolution of ants.

Hemoglobin is a protein found in the red blood cells of vertebrates and in the plasma of many

invertebrates. The function of this protein is to transport oxygen throughout the body and to bring

carbon dioxide back to be expelled from the organism. If the amino acid sequence of the protein is

altered, the mutated protein is not as efficient at carrying oxygen as is the normal hemoglobin. Which

argument is supported by this information?

• The mutated hemoglobin protein can still carry carbon dioxide to be expelled from the organism.

• Hemoglobin must be a simple molecule because it is found in both vertebrates and invertebrates.

• Structural changes of hemoglobin affect its ability to carry oxygen, indicating that the shape of a

  protein is important to its function.

• Normal hemoglobin must be a larger molecule than the mutated hemoglobin since it has sufficient

  space to attach to and carry both oxygen molecules and carbon dioxide molecules.

Answer explanation

The correct answer is choice (C) Structural changes of

hemoglobin affect its ability to carry oxygen indicating that

the shape of a protein is important to its function. Choice (A)

is incorrect because nothing in the information indicates

the ability or inability of the altered hemoglobin to carry

carbon dioxide. Choice (B) is incorrect because nothing in

the information indicates whether the molecule is simple or

complex. Choice (D) is incorrect because hemoglobin changes

shape not size.

Bromothymol blue (BTB) is a pH indicator that is also used to detect carbon dioxide (CO2). BTB is blue

when pH is basic and CO2 is low. BTB is yellow when pH is acidic and CO2 is high. BTB is green when

pH is neutral. A group of students are planning to perform an investigation in which they will place

either a stalk of the aquatic plant elodea or a snail in a test tube that contains water with a neutral

pH of 7 and BTB. The students will also include a test tube that contains elodea and a snail. Observing

color change once the tubes have been placed under a growth light for several hours will allow the

students to answer which TWO of the following questions?

• B. Does elodea produce oxygen during photosynthesis?

• C. Do snails respire faster when placed in a tube with elodea?

• D. Do snails use the CO2 produced by elodea to produce oxygen?

• E. Does photosynthesis performed by elodea remove CO2 from the water?

• F. Does cellular respiration occur at a higher rate than photosynthesis in the tube with only elodea?

Answer explanation

Choice (B) is incorrect because there is no way

to measure oxygen with this setup. Choice (C) is incorrect

because there is no way to measure this and because the rate

of respiration should not vary. Choice (D) is incorrect because

this question cannot be answered using this investigation.

Ruby-throated hummingbirds are found throughout eastern North America. They are omnivores, feeding

on nectar, pollen, tree sap, insects, and spiders. They get all the water they need from nectar. Most

nests are in forested areas, citrus groves, marshes, and scrubland. The hummingbirds breed in the

spring and the summer, and females raise one to three broods per breeding season. Most of the

hummingbirds migrate to Mexico or Central America for the winter. Many fly nonstop for 20 hours to

cross the Gulf of Mexico. However, increasing numbers of the hummingbirds have begun to winter north

of the gulf. Researchers have documented that the hummingbirds’ winter range has expanded northward

by about 300 kilometers in recent years.

Which explanation BEST predicts the ability of the hummingbirds to survive their first winter in this

new environment?

• Finding suitable nesting materials and sites is the most important task the hummingbirds must

  accomplish because they must produce offspring.

• Finding a sufficient supply of flowering plants, flowering trees, and insects is the most important task

  for the hummingbirds because they need food to survive.

• Finding bodies of water is the most important task for the hummingbirds because they need to

  supplement the supply of nectar if it is inadequate to provide all the calories the hummingbirds need

  to survive.

• Finding mates to allow the hummingbirds to lay fertile eggs and have two parents to feed the new

  hatchlings is the most important task for the hummingbirds because they need to ensure there is a

  new generation of hummingbirds in the region.

Answer explanation

The correct answer is choice (B) Finding a sufficient supply

of flowering plants, flowering trees, and insects is the most

important task for the hummingbirds because they need food

to survive. Choice (A) is incorrect because most of the south will

have adequate places and materials for nesting, although there

might be some areas with sparse vegetation, the birds would

be able to winter in wooded areas, marshes, citrus groves, etc.

Choice (C) is incorrect because they do not need to drink water,

which contains no calories, since they get the water they need

from nectar. Choice (D) is incorrect because finding a mate is

not as important as finding food and shelter.

Students studied Mendel’s laws of segregation and independent assortment. They created a

Punnett square to show a cross between a homozygous furred mouse (FF) and a homozygous furless

mouse (ff). The students then created a second Punnett square for a cross between two heterozygous

F1 mice. ** WHICH QUESTION COULD BE ANSWERED USING THE INFORMATION FROM THE PUNNETT SQUARES

• Can furred mice produce furless mice?

• How many mice will be produced in the F1 generation?

• Will fewer furless mice survive to adulthood than furred mice?

• Are furred mice the best organism to use for this investigation?

Answer explanation

The correct answer is choice (A) Can furred mice produce

furless mice? Choices (B), (C), and (D) are incorrect because

the question cannot be answered using the Punnett square.

The model shows part of a process that uses tRNA. *Which description explains the role of the tRNA in the process shown in this model?

• The tRNA delivers amino acids to the ribosome so that they can be added to the developing peptide.

• The tRNA recognizes the stop codon of a developing peptide so that no new amino acids are added.

• The tRNA signals the release of the peptide from the ribosome once all of the amino acids have been

  added.

• The tRNA scans the developing peptide to make sure that the sequence of the amino acids matches

  the mRNA.

Answer explanation

The correct answer is choice (A) The tRNA delivers amino

acids to the ribosome so that they can be added to the

developing peptide. Choice (B) is incorrect because the tRNA

does not recognize the stop codon. Choice (C) is incorrect

because tRNA is not responsible for releasing the polypeptide.

Choice (D) is incorrect because quality control is not a

function of tRNA.