Star Testing Practice Biology
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Questions and Answers
- 1.
A computer model of cellular mitosis can simulate the aspects of cellular division quite well. However, microscopic observation of actual cellular mitosis can improve understanding because actual observations
- A.
May reveal greater unknown complexities
- B.
Are easier than a computer model to view
- C.
Are the same each time
- D.
May provide division events in sequence.
Correct Answer
A. May reveal greater unknown complexitiesExplanation
Microscopic observation of actual cellular mitosis may reveal greater unknown complexities because computer models can only simulate the aspects of cellular division based on the information and assumptions programmed into them. Actual observations can provide new insights and unexpected findings that may not have been accounted for in the computer model. Therefore, observing cellular mitosis under a microscope can improve understanding by uncovering hidden complexities that were not previously known or considered.Rate this question:
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- 2.
The cell membrane of the red blood cell will allow water, oxygen, carbon dioxide, and glucose to pass through. Because other substances are blocked from entering, this membrane is called
- A.
Perforated
- B.
Semi-permeable
- C.
Non-conductive
- D.
Permeable.
Correct Answer
B. Semi-permeableExplanation
The cell membrane of the red blood cell is referred to as semi-permeable because it allows certain substances like water, oxygen, carbon dioxide, and glucose to pass through while blocking other substances from entering. This selective permeability is essential for maintaining the cell's internal environment and regulating the movement of molecules in and out of the cell.Rate this question:
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- 3.
There are many different enzymes located in the cytoplasm of a single cell. How is a specific enzyme able to catalyze a specific reaction?
- A.
Different enzymes are synthesized in specific areas of the cytoplasm.
- B.
Most enzymes can catalyze many different reactions
- C.
An enzyme binds to a specific substrate (reactant) for the reaction catalyzed
- D.
Enzymes are transported to specific substrates (reactants) by ribosomes.
Correct Answer
C. An enzyme binds to a specific substrate (reactant) for the reaction catalyzedExplanation
Enzymes are able to catalyze specific reactions because they have a specific binding site that is complementary to the shape and chemical properties of their specific substrate. This allows the enzyme to bind specifically to the substrate and form an enzyme-substrate complex. The enzyme then facilitates the conversion of the substrate into the desired product by lowering the activation energy required for the reaction to occur. This specificity is crucial for the efficient functioning of metabolic pathways and ensures that each reaction occurs at the right time and place within the cell.Rate this question:
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- 4.
Maltose can be broken down into glucose molecules by the enzyme maltase. Which of the following would slow the reaction rate
- A.
Adding maltase
- B.
Adding maltose
- C.
Removing glucose
- D.
Diluting with water
Correct Answer
D. Diluting with waterExplanation
Diluting with water would slow the reaction rate because it would decrease the concentration of maltose, reducing the chances of maltase enzyme molecules coming into contact with maltose molecules. This would result in fewer successful collisions between the enzyme and substrate, leading to a slower rate of reaction.Rate this question:
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- 5.
A food chain is shown below. Grass -- crickets -- field mice -- hawks For the food chain shown, which of the following changes would have the most severe consequences?
- A.
A drastic decrease in rainfall, causing drought
- B.
The poaching of predatory hawks by game hunters
- C.
The introduction of a second predator that eats field mice
- D.
A parasitic infestation that reduces the cricket population
Correct Answer
A. A drastic decrease in rainfall, causing drought -
- 6.
The first stage of photosynthesis in a chloroplast is
- A.
Light-dependent.
- B.
temperature-dependent
- C.
Glucose-driven.
- D.
ATP-driven
Correct Answer
A. Light-dependent.Explanation
The first stage of photosynthesis in a chloroplast is light-dependent because it requires light energy to initiate the process. During this stage, light energy is absorbed by chlorophyll molecules in the chloroplasts, which then converts it into chemical energy in the form of ATP and NADPH. These energy-rich molecules are crucial for the subsequent stages of photosynthesis, where they are used to produce glucose and other organic compounds. Without light, this initial stage cannot occur, making light-dependency the correct answer.Rate this question:
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- 7.
The plasma membrane of a cell consists of
- A.
Protein molecules arranged in two layers with polar areas forming the outside of the membrane
- B.
Two layers of lipids organized with the nonpolar tails forming the interior of the membrane
- C.
Lipid molecules positioned between two carbohydrate layers
- D.
Protein molecules with polar and nonpolar tails
Correct Answer
B. Two layers of lipids organized with the nonpolar tails forming the interior of the membraneExplanation
The correct answer is two layers of lipids organized with the nonpolar tails forming the interior of the membrane. The plasma membrane is composed of a phospholipid bilayer, which consists of two layers of lipids. The lipids have a polar head and a nonpolar tail. In the bilayer, the nonpolar tails are oriented towards the interior of the membrane, while the polar heads face the aqueous environment both inside and outside the cell. This arrangement creates a hydrophobic barrier that regulates the movement of substances into and out of the cell.Rate this question:
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- 8.
Which of the following is a function of the nervous system?
- A.
Releasing ATP into contracting muscle tissues
- B.
Signaling muscle tissues to contract
- C.
Producing lactic acid in fatigued muscle tissues
- D.
Increasing cellular respiration in muscle tissues
Correct Answer
B. Signaling muscle tissues to contractExplanation
The nervous system is responsible for transmitting signals throughout the body, including to muscle tissues. These signals, known as nerve impulses, stimulate the muscle fibers to contract, allowing for movement and coordination. Therefore, signaling muscle tissues to contract is a function of the nervous system.Rate this question:
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- 9.
Which of the following is a function of the nervous system?
- A.
Releasing ATP into contracting muscle tissues
- B.
Signaling muscle tissues to contract
- C.
Producing lactic acid in fatigued muscle tissues
- D.
Increasing cellular respiration in muscle tissues
Correct Answer
B. Signaling muscle tissues to contractExplanation
The correct answer is signaling muscle tissues to contract. The nervous system is responsible for transmitting signals from the brain to various parts of the body, including muscle tissues. These signals stimulate the muscle fibers to contract and produce movement. This function of the nervous system allows for voluntary and involuntary muscle actions, such as walking, talking, and breathing.Rate this question:
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- 10.
What is the greatest danger to a patient who has had damage to the skin?
- A.
Loss of oils produced by the skin
- B.
Excessive muscle contractions in the damaged area
- C.
Infections in uncovered tissues
- D.
Damaged tissue entering the blood stream
Correct Answer
C. Infections in uncovered tissuesExplanation
When a patient has damage to the skin, the greatest danger they face is the risk of infections in uncovered tissues. When the skin is damaged, it creates an opening that allows bacteria and other pathogens to enter the body, leading to infections. These infections can range from mild to severe and can cause complications and delays in the healing process. Therefore, it is crucial to keep the damaged area covered and clean to minimize the risk of infections.Rate this question:
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- 11.
A small population of chimpanzees lives in a habitat that undergoes no changes for a long period. How will genetic drift probably affect this population?
- A.
It will accelerate the appearance of new traits
- B.
It will promote the survival of chimpanzees with beneficial traits
- C.
It will increase the number of alleles for specific traits
- D.
It will reduce genetic diversity
Correct Answer
C. It will increase the number of alleles for specific traitsExplanation
Genetic drift is the random change in allele frequencies in a population due to chance events. In a small population that undergoes no changes for a long period, genetic drift is likely to occur. Over time, genetic drift can lead to an increase in the number of alleles for specific traits in the population. This is because certain alleles may become more or less common purely by chance, leading to an increase in the overall number of alleles for specific traits in the population. This can result in an increase in genetic diversity for those specific traits.Rate this question:
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- 12.
In fruit flies, the gene for red eyes (R) is dominant and the gene for pink eyes (r) is recessive. What are the possible combinations of genes in the offspring of two red-eyed heterozygous flies (Rr)?
- A.
RR only
- B.
Rr only
- C.
Rr and rr only
- D.
RR, Rr, and rr only
Correct Answer
D. RR, Rr, and rr onlyExplanation
The possible combinations of genes in the offspring of two red-eyed heterozygous flies (Rr) are RR, Rr, and rr only. This is because the gene for red eyes (R) is dominant, so even if only one parent has the dominant gene, there is a chance that the offspring will inherit it. The recessive gene for pink eyes (r) will only be expressed if both parents contribute the recessive gene. Therefore, the possible combinations are RR (red-eyed), Rr (red-eyed), and rr (pink-eyed).Rate this question:
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- 13.
In aerobic respiration, the Krebs cycle (citric acid cycle) takes place in
- A.
Chloroplasts
- B.
Nuclei
- C.
Lysosomes
- D.
Mitochondria
Correct Answer
D. MitochondriaExplanation
The Krebs cycle, also known as the citric acid cycle, is a part of aerobic respiration that occurs in mitochondria. Mitochondria are the powerhouse of the cell and are responsible for generating energy in the form of ATP. This cycle takes place in the mitochondrial matrix, where it oxidizes acetyl-CoA and produces NADH, FADH2, and ATP. Therefore, the correct answer is mitochondria.Rate this question:
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- 14.
Which cellular organelle is responsible for packaging the proteins that the cell secretes
- A.
Cytoskeleton
- B.
Cell membrane
- C.
Lysosomes
- D.
Golgi Apparatus
Correct Answer
B. Cell membraneExplanation
The cell membrane is responsible for packaging the proteins that the cell secretes. The cell membrane contains specialized structures called vesicles that transport proteins from the endoplasmic reticulum to the Golgi apparatus. These proteins are then modified, sorted, and packaged into new vesicles in the Golgi apparatus. These vesicles are then transported to the cell membrane, where they fuse with the membrane and release their contents outside the cell. Therefore, the cell membrane plays a crucial role in the packaging and secretion of proteins.Rate this question:
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- 15.
Which of the following best describes meiosis?
- A.
It is carried out in all tissues that require cell replacement
- B.
It occurs only in cells in the reproductive structures of the organism
- C.
It happens in all tissues except the brain and spinal cord
- D.
It is the first stage of mitosis.
Correct Answer
B. It occurs only in cells in the reproductive structures of the organismExplanation
Meiosis is a type of cell division that specifically occurs in the reproductive structures of an organism. It is responsible for the production of gametes (sperm and eggs) and involves two rounds of division, resulting in the formation of four genetically unique daughter cells. Unlike mitosis, which occurs in various tissues for growth and repair, meiosis is limited to the reproductive organs and is essential for sexual reproduction.Rate this question:
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- 16.
Which of these organisms are most helpful in preventing Earth from being covered with the bodies of dead organisms
- A.
Herbivores
- B.
Producers
- C.
Parasites and viruses
- D.
Fungi and bacteria
Correct Answer
D. Fungi and bacteriaExplanation
Fungi and bacteria are most helpful in preventing Earth from being covered with the bodies of dead organisms. Fungi and bacteria are decomposers that break down dead organic matter, such as dead plants and animals, into simpler substances. They play a crucial role in the nutrient cycling process by breaking down complex organic compounds and releasing nutrients back into the environment. Without the activity of fungi and bacteria, dead organisms would accumulate and not be recycled, leading to the Earth being covered with bodies of dead organisms.Rate this question:
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- 17.
Eukaryotic cells are differentiated from prokaryotic cells because eukaryotic cells
- A.
Are much smaller.
- B.
Have permeable membranes
- C.
Have a higher rate of reproduction
- D.
Have nuclei.
Correct Answer
D. Have nuclei.Explanation
Eukaryotic cells are differentiated from prokaryotic cells because they have nuclei. Unlike prokaryotic cells, which lack a true nucleus, eukaryotic cells have a distinct membrane-bound nucleus that houses the cell's genetic material. This nucleus allows for more complex genetic control and regulation of cellular processes.Rate this question:
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- 18.
Two students were testing the amount of fertilizer that would best promote the growth of strawberries in a garden. Which of the following could be an unavoidable source of experimental error?
- A.
Length of the study
- B.
Variation in the strawberry plants
- C.
The cost of watering the plants
- D.
Fertilization during the study
Correct Answer
B. Variation in the strawberry plantsExplanation
An unavoidable source of experimental error in testing the amount of fertilizer that would best promote the growth of strawberries in a garden could be the variation in the strawberry plants. This means that the strawberries used in the experiment may have different genetic traits, growth rates, or health conditions, which could affect their response to the fertilizer. This variation could introduce confounding factors and make it difficult to determine the true effect of the fertilizer on the growth of the strawberries.Rate this question:
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- 19.
Mendel hypothesized that reproductive cells have only one factor for each inherited trait. This hypothesis is supported by the observation that
- A.
Haploid cells are produced by mitosis
- B.
Diploid cells are produced by mitosis
- C.
Haploid cells are produced by meiosis.
- D.
Diploid cells are produced by meiosis
Correct Answer
C. Haploid cells are produced by meiosis.Explanation
Mendel hypothesized that reproductive cells have only one factor for each inherited trait. This hypothesis is supported by the observation that haploid cells are produced by meiosis. Meiosis is a type of cell division that results in the formation of haploid cells, which contain only one set of chromosomes. This supports Mendel's hypothesis that reproductive cells have only one factor for each inherited trait, as each haploid cell produced through meiosis carries only one allele for each trait.Rate this question:
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- 20.
A signal that the bladder is full is sent to the central nervous system by
- A.
Feedback loops.
- B.
Sensory neurons
- C.
Nephron tubules
- D.
Receptor proteins
Correct Answer
B. Sensory neuronsExplanation
Sensory neurons are responsible for transmitting signals from the bladder to the central nervous system when it is full. These neurons are specialized to detect changes in the bladder's stretch receptors and send this information to the brain. This signal triggers the sensation of needing to urinate, allowing the individual to be aware of their bladder's fullness and take appropriate action.Rate this question:
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- 21.
Which of these best illustrates natural selection?
- A.
An organism with favorable genetic variations will tend to survive and breed successfully.
- B.
A population monopolizes all of the resources in its habitat, forcing other species to migrate.
- C.
A community whose members work together utilizes all existing resources and migratory routes.
- D.
The largest organisms in a species receive the only breeding opportunities
Correct Answer
A. An organism with favorable genetic variations will tend to survive and breed successfully.Explanation
An organism with favorable genetic variations will tend to survive and breed successfully is the best illustration of natural selection because it highlights the concept of individuals with advantageous traits being more likely to survive and pass on their genes to the next generation. This process leads to the gradual accumulation of beneficial traits in a population over time, resulting in the adaptation of the species to its environment.Rate this question:
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- 22.
A cell from heart muscle would probably have an unusually high proportion of
- A.
Lysosomes
- B.
Mitochondria
- C.
MRNA
- D.
Golgi Bodies
Correct Answer
B. MitochondriaExplanation
Heart muscle cells, also known as cardiomyocytes, require a large amount of energy to constantly contract and pump blood. Mitochondria are the powerhouses of the cell, responsible for producing the energy molecule ATP through cellular respiration. Therefore, it is expected that heart muscle cells would have an unusually high proportion of mitochondria to meet their high energy demands.Rate this question:
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- 23.
Which of the following sequences represents chromosome number during fertilization?
- A.
N+n→2n
- B.
2n →n+n
- C.
N → n
- D.
2n →2n
Correct Answer
A. N+n→2nExplanation
During fertilization, the chromosome number is doubled. This is represented by the sequence "n+n→2n", where "n" represents the haploid number of chromosomes and "2n" represents the diploid number of chromosomes.Rate this question:
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- 24.
Based only on the sex chromosomes in typical human egg and sperm cells at fertilization, the probability of producing a female is
- A.
25%
- B.
50%
- C.
75%
- D.
90%
Correct Answer
B. 50%Explanation
The probability of producing a female is 50% because the sex of a human is determined by the presence of either an X or a Y chromosome. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). During fertilization, the egg can contribute an X chromosome, and the sperm can contribute either an X or a Y chromosome. Since there is an equal chance of the sperm carrying either an X or a Y chromosome, the probability of producing a female is 50%.Rate this question:
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- 25.
In certain breeds of dogs, deafness is due to a recessive allele (d) of a particular gene, and normal hearing is due to its dominant allele (D). What percentage of the offspring of a normal heterozygous (Dd) dog and a deaf dog (dd) would be expected to have normal hearing?
- A.
0%
- B.
25%
- C.
50%
- D.
100%
Correct Answer
C. 50%Explanation
When a normal heterozygous (Dd) dog mates with a deaf dog (dd), there is a 50% chance for each offspring to inherit the dominant allele (D) from the heterozygous parent, resulting in normal hearing. The other 50% chance is for the offspring to inherit the recessive allele (d) from both parents, resulting in deafness. Therefore, 50% of the offspring would be expected to have normal hearing.Rate this question:
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- 26.
Mutations within a DNA sequence are
- A.
Natural processes that produce genetic diversity
- B.
Natural processes that always affect the phenotype
- C.
Unnatural processes that always affect the phenotype
- D.
Unnatural processes that are harmful to genetic diversity.
Correct Answer
A. Natural processes that produce genetic diversityExplanation
Mutations within a DNA sequence are natural processes that produce genetic diversity. This is because mutations are changes in the DNA sequence that can result in new variations of genes. These variations can lead to differences in traits and characteristics, which contribute to genetic diversity within a population. Mutations can occur spontaneously or be induced by external factors such as radiation or chemicals. They can be beneficial, neutral, or harmful to an organism, but overall, they play a crucial role in evolution by introducing new genetic variations that can be selected for or against in different environments.Rate this question:
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- 27.
Striking the tendon just below the kneecap causes the lower leg to jerk. Moving an object quickly toward the face can cause the eyes to blink shut. These are examples of
- A.
Learned responses
- B.
Short-term memory.
- C.
Reflex reactions
- D.
Sensory overload
Correct Answer
C. Reflex reactionsExplanation
The given examples of striking the tendon below the kneecap and moving an object quickly towards the face causing the legs to jerk and eyes to blink shut respectively are both reflex reactions. Reflex reactions are involuntary responses to specific stimuli, which occur without conscious thought. In both cases, the body automatically reacts to protect itself from potential harm.Rate this question:
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- 28.
Which of these secretes a hormone that regulates the rate of metabolism of the body?
- A.
Spleen
- B.
Cerebrum
- C.
Thyroid
- D.
Kidney
Correct Answer
C. ThyroidExplanation
The thyroid secretes a hormone called thyroxine, which plays a crucial role in regulating the body's metabolism. This hormone helps control the rate at which the body uses energy, affects growth and development, and regulates body temperature. The thyroid gland is located in the neck and is responsible for producing and releasing this hormone into the bloodstream.Rate this question:
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- 29.
Which of the following require a host cell because they are not able to make proteins on their own?
- A.
Blue-green alage
- B.
Bacteria
- C.
Protozans
- D.
Viruses
Correct Answer
D. VirusesExplanation
Viruses require a host cell because they are not able to make proteins on their own. Unlike other organisms such as blue-green algae, bacteria, and protozoans, viruses lack the necessary cellular machinery to synthesize proteins. Instead, they rely on infecting host cells and hijacking their protein synthesis machinery to produce the proteins they need for replication and survival. This dependence on a host cell is a defining characteristic of viruses.Rate this question:
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- 30.
5' ATCAGCGCTGGC 3' The above sequence of DNA is part of a gene. How many amino acids are coded for by this segment?
- A.
4
- B.
8
- C.
12
- D.
20
Correct Answer
A. 4Explanation
The given DNA sequence is 12 nucleotides long. Each amino acid is coded by a sequence of three nucleotides called a codon. Therefore, the number of amino acids coded for by this segment would be equal to the number of codons in the sequence. Since there are four codons in the sequence (ATC, AGC, GCG, TGG), the number of amino acids coded for is 4.Rate this question:
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- 31.
Rabbits introduced into Australia over 100 years ago have become a serious pest to farmers. Rabbit populations increased so much that they displaced many native species of plant eaters. What is the most logical explanation for their increased numbers?
- A.
Rabbits have a high death rate
- B.
There are few effective predators
- C.
Additional rabbit species have been introduced
- D.
There is an increase in rabbit competitors.
Correct Answer
B. There are few effective predatorsExplanation
The most logical explanation for the increased numbers of rabbits in Australia is that there are few effective predators. This means that there are not enough natural enemies to control the rabbit population, allowing them to reproduce and thrive. Without predators to keep their numbers in check, rabbits can quickly multiply and become a serious pest to farmers and a threat to native species.Rate this question:
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- 32.
Some snake venoms are harmful because they contain enzymes that destroy blood cells or tissues. The damage caused by such a snakebite could best be slowed by
- A.
Applying ice to the bite area
- B.
Drinking large amounts of water.
- C.
Inducing vomiting
- D.
Increasing blood flow to the area
Correct Answer
A. Applying ice to the bite areaExplanation
Snake venoms contain enzymes that destroy blood cells or tissues, leading to damage in the affected area. Applying ice to the bite area can help slow down the spread of venom and reduce swelling by constricting blood vessels. This can help minimize the damage caused by the snakebite and provide some relief to the victim. Drinking large amounts of water, inducing vomiting, or increasing blood flow to the area would not be effective in slowing down the damage caused by the venom.Rate this question:
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- 33.
If a corn plant has a genotype of Ttyy, what are the possible genetic combinations that could be present in a single grain of pollen from this plant?
- A.
Ty, ty
- B.
TY, ty
- C.
TY, Ty, ty
- D.
Ty, ty tY, TY
Correct Answer
A. Ty, tyExplanation
The given genotype Ttyy indicates that the corn plant has one dominant allele (T) for one trait and one recessive allele (y) for another trait. In a single grain of pollen, there can be two possible genetic combinations: Ty and ty. The dominant allele (T) can combine with the recessive allele (y) to form the combination Ty, and the recessive allele (y) can combine with itself to form the combination ty.Rate this question:
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- 34.
Which of these would most likely cause a mutation?
- A.
The placement of ribosomes on the endoplasmic reticulum
- B.
The insertion of a nucleotide into DNA
- C.
The movement of transfer RNA out of the nucleus
- D.
The release of messenger RNA from DNA
Correct Answer
B. The insertion of a nucleotide into DNAExplanation
The insertion of a nucleotide into DNA is most likely to cause a mutation because it alters the sequence of the DNA molecule. Mutations occur when there are changes in the genetic material, and inserting a nucleotide can disrupt the normal sequence of DNA bases. This can lead to changes in the resulting protein or gene expression, potentially causing a variety of genetic disorders or abnormalities.Rate this question:
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- 35.
A healthy individual is a carrier of a lethal allele but is unaffected by it. What is the probable genotype of this individual?
- A.
Two dominant normal alleles
- B.
One recessive lethal allele and one dominant lethal allele
- C.
One recessive lethal allele and one dominant normal allele
- D.
One dominant lethal allele and one recessive normal allele
Correct Answer
C. One recessive lethal allele and one dominant normal alleleExplanation
This individual is unaffected by the lethal allele, which means they must have at least one dominant normal allele to mask the effects of the lethal allele. Additionally, they are a carrier of the lethal allele, which means they must also have one recessive lethal allele. Therefore, the probable genotype of this individual is one recessive lethal allele and one dominant normal allele.Rate this question:
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- 36.
Fossil evidence suggests that a number of members of one fish species from an ancient lake in Death Valley, California, became several isolated species. Each of these new species lived in a different pond. Which of the following best explains the cause of this speciation?
- A.
Episodic isolation
- B.
Temporal isolation
- C.
Geographic isolation
- D.
Behavioral isolation
Correct Answer
C. Geographic isolationExplanation
The fossil evidence suggests that the members of one fish species from an ancient lake in Death Valley, California, became several isolated species. This indicates that the cause of speciation was geographic isolation. Geographic isolation occurs when a population of organisms becomes physically separated by a geographic barrier, such as a mountain range or a body of water. This physical separation prevents gene flow between the populations, leading to genetic divergence and the formation of new species.Rate this question:
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- 37.
The Sabin vaccine is a liquid containing weakened polio viruses. Vaccinated individuals become protected against polio because the weakened viruses
- A.
Prevent further viral invasion
- B.
Induce an inflammatory response
- C.
Promote production of antibodies.
- D.
Are too weak to cause illness.
Correct Answer
C. Promote production of antibodies.Explanation
The Sabin vaccine is a liquid containing weakened polio viruses. When individuals are vaccinated with this vaccine, the weakened viruses stimulate the immune system to produce antibodies. These antibodies can then recognize and attack the polio virus if the person is exposed to it in the future, providing protection against polio. The weakened viruses are not strong enough to cause illness, but they do trigger the production of antibodies.Rate this question:
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- 38.
The bacterium Agrobacterium infects plants, and a portion of its DNA is inserted into the plant’s chromosomes. This causes the plant to produce gall cells, which manufacture amino acids that the bacterium uses as food. This process is a natural example of
- A.
Polyploidy
- B.
Genetic manipulation
- C.
Grafting
- D.
hybridization
Correct Answer
B. Genetic manipulationExplanation
The process described in the question involves the bacterium Agrobacterium inserting a portion of its DNA into the plant's chromosomes, causing the plant to produce gall cells that manufacture amino acids for the bacterium. This process is an example of genetic manipulation because it involves the intentional modification of an organism's genetic material by an external agent, in this case, the bacterium.Rate this question:
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- 39.
In most stable freshwater environments, populations of Daphnia are almost entirely female and reproduce asexually. However, males are observed in low oxygen environments or when food is scarce. Based on these observations, a researcher suggests that male Daphnia develop in response to unfavorable environmental conditions. This is an example of a
- A.
Result
- B.
Theory
- C.
Procedure
- D.
Hypothesis
Correct Answer
D. HypothesisExplanation
The researcher's suggestion that male Daphnia develop in response to unfavorable environmental conditions is a hypothesis. A hypothesis is a proposed explanation or prediction based on observations or evidence. In this case, the researcher is proposing that the presence of males in low oxygen or scarce food environments is a response to these unfavorable conditions. This hypothesis can be tested through further research and experimentation to determine its validity.Rate this question:
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- 40.
Semi-conservative replication of DNA refers to the idea that
- A.
DNA molecules need to unwind before duplication begins
- B.
Each new DNA molecule contains two new single RNA strands.
- C.
The two strands of DNA molecules run in opposite directions.
- D.
Each half of the original DNA molecule is joined with a new complementary DNA strand.
Correct Answer
D. Each half of the original DNA molecule is joined with a new complementary DNA strand.Explanation
In semi-conservative replication of DNA, each half of the original DNA molecule is joined with a new complementary DNA strand. This means that during replication, the two strands of the DNA molecule separate and each strand serves as a template for the synthesis of a new complementary strand. As a result, each new DNA molecule formed contains one original strand and one newly synthesized strand. This process ensures the preservation of the original genetic information while allowing for the creation of identical copies of the DNA molecule.Rate this question:
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- 41.
Earth has undergone some catastrophic changes from time to time. Which of these most likely explains why life on Earth continued following these catastrophes?
- A.
Dominant species had a slow mutation rate.
- B.
Many species filled the same niche
- C.
A strong species had many different characteristics.
- D.
A wide diversity of species existed.
Correct Answer
D. A wide diversity of species existed.Explanation
A wide diversity of species existed. This means that there were many different types of organisms living on Earth. When catastrophic changes occurred, some species may have become extinct, but others were able to survive and adapt to the new conditions. The wide diversity of species allowed for a greater chance of survival and the continuation of life on Earth.Rate this question:
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- 42.
What causes tomatoes to ripen much more slowly in a refrigerator than they do if left on a table at room temperature?
- A.
Tomatoes need sunlight to ripen
- B.
Humidity accelerates the ripening process
- C.
Low temperatures reduce the action of ripening enzymes.
- D.
Enzymes produced by bacteria inhibit ripening.
Correct Answer
C. Low temperatures reduce the action of ripening enzymes.Explanation
Low temperatures reduce the action of ripening enzymes. When tomatoes are kept in a refrigerator, the cold temperature slows down the activity of enzymes responsible for ripening. This inhibits the natural ripening process and causes tomatoes to ripen much more slowly compared to when they are left on a table at room temperature.Rate this question:
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- 43.
If a human baby boy inherits a recessive allele from his mother, in which circumstance would he most likely show the trait coded for by the recessive allele?
- A.
The baby inherits the dominant allele from his father
- B.
The allele is on an autosomal chromosome and the baby is a twin.
- C.
The allele is on the X chromosome.
- D.
The allele is on the Y chromosome
Correct Answer
C. The allele is on the X chromosome.Explanation
This is because if the recessive allele is on the X chromosome, the baby boy only needs to inherit one copy of the allele from his mother to show the trait. Since males have one X chromosome and one Y chromosome, they do not have another X chromosome to mask the effects of the recessive allele.Rate this question:
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- 44.
Individuals with HIV sometimes contract a pneumonia infection that is rare in the rest of the population because people with HIV
- A.
Are unable to fight off these pneumonia causing organisms.
- B.
Are more often exposed to these pneumonia causing organisms.
- C.
Release pheromones that attract the pneumonia-causing organisms
- D.
Release substances that increase the strength of the pneumonia-causing organisms
Correct Answer
A. Are unable to fight off these pneumonia causing organisms.Explanation
Individuals with HIV have a weakened immune system, which makes it difficult for them to fight off infections, including pneumonia. This is why they are unable to fight off these pneumonia-causing organisms, leading to a higher risk of contracting pneumonia compared to the general population.Rate this question:
-
- 45.
Sweat and skin secretions contain a mixture of molecules that kills or limits the growth of many types of microbes. This control of microbes is an example of
- A.
A nonspecific defense against infection.
- B.
An enzyme-catalyzed biochemical reaction
- C.
A feedback loop to maintain homeostasis.
- D.
A specific immune response to infection by microbes.
Correct Answer
A. A nonspecific defense against infection.Explanation
Sweat and skin secretions contain molecules that have antimicrobial properties, meaning they can kill or inhibit the growth of many types of microbes. This defense mechanism is considered nonspecific because it does not target specific pathogens, but rather acts against a wide range of microbes. It is a general defense mechanism that helps protect the body from infection.Rate this question:
-
- 46.
Which of these organisms would most likely be found at the top of an energy pyramid?
- A.
Clams
- B.
Sardines
- C.
Shark
- D.
Kelp
Correct Answer
C. SharkExplanation
The shark would most likely be found at the top of an energy pyramid because it is a top predator in the marine food chain. As a carnivorous predator, the shark feeds on other organisms, such as smaller fish and marine mammals, which are lower in the food chain. Being at the top of the pyramid means that the shark has fewer predators and consumes a large amount of energy from the organisms it preys upon.Rate this question:
-
- 47.
Which of the following is the correct order of organization of structures in living things, from simplest to most complex?
- A.
Organ systems, organs, organism, tissues, cells
- B.
Tissues, cells, organs, organism, organ system
- C.
Cells, tissues, organ systems, organs, organism
- D.
Cells, tissues, organs, organ systems, organism
Correct Answer
D. Cells, tissues, organs, organ systems, organismExplanation
Living things are made up of cells, which are the basic building blocks of life. Cells come together to form tissues, which are groups of cells that work together to perform a specific function. Organs are made up of different types of tissues and work together to perform a specific function in the body. Organ systems are groups of organs that work together to carry out a particular function in the body. Finally, an organism is made up of all the organ systems working together to support life. Therefore, the correct order of organization of structures in living things, from simplest to most complex, is cells, tissues, organs, organ systems, organism.Rate this question:
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- 48.
Refer to the diagram above. Which of these best completes this concept map?
- A.
An animal cell
- B.
A prokaryotic cell
- C.
A virus
- D.
A plant cell
Correct Answer
D. A plant cellExplanation
A plant cell would be the best completion for this concept map because it is a type of cell that is distinct from the other options listed. The diagram likely shows a comparison or classification of different types of cells, and including a plant cell would provide a comprehensive representation of the different cell types.Rate this question:
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- 49.
Which statement about enzymes is not correct?
- A.
Enzymes are composed of polypeptide chains.
- B.
Enzymes form a temporary association with a reactant
- C.
Enzymes are destroyed when they are used and must be synthesized for each reaction
- D.
Enzymes are specific because of their shape and catalyze only certain reactions.
Correct Answer
C. Enzymes are destroyed when they are used and must be synthesized for each reactionExplanation
Enzymes are not destroyed when they are used and do not need to be synthesized for each reaction. Enzymes are catalysts that facilitate chemical reactions by lowering the activation energy required for the reaction to occur. They are not consumed or altered during the reaction and can be reused multiple times. Therefore, enzymes are not destroyed and do not need to be synthesized for each reaction.Rate this question:
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- 50.
The number of autosomes and type of sex chromosome normally present in a human egg cell is
- A.
44 + XY
- B.
44 + XX
- C.
22+X
- D.
22+ Y
Correct Answer
C. 22+XExplanation
The correct answer is 22+X. This is because a human egg cell contains 22 autosomes, which are chromosomes that are not involved in determining sex, and one X sex chromosome. The presence of the X chromosome determines the individual's biological sex as female.Rate this question:
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