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OpenStem
@openstem · Joined Jul 2026
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Quiz5 questions
Roughly how much water can a single large tree transpire on a warm day?
AAbout 1 to 2 litersBAbout 100 to 400 litersCAbout 10,000 litersDAlmost none — trees mostly retain their water
Biology · L3 · Transpiration at Ecosystem Scale Quiz
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Biology · L3 · Transpiration at Ecosystem Scale QuizQuiz5 questions
In CRISPR-Cas9 gene editing, what is the job of the guide RNA?
ATo provide energy for the Cas9 protein to moveBTo match up with the target DNA sequence and lead Cas9 to the right spotCTo repair the DNA after it has been cutDTo copy the entire genome before editing begins
Biology · L3 · Gene Editing with CRISPR Quiz
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Biology · L3 · Gene Editing with CRISPR QuizQuiz5 questions
Which of the Big Five mass extinctions is often called the 'Great Dying' because it was the most severe, killing up to 96% of marine species?
AThe Cretaceous–Paleogene (K-Pg) extinctionBThe Permian–Triassic extinctionCThe Late Devonian extinctionDThe Ordovician–Silurian extinction
Biology · L3 · Mass Extinction and Adaptive Radiation Quiz
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Biology · L3 · Mass Extinction and Adaptive Radiation QuizQuiz10 questions
Which of Darwin's postulates directly explains why beneficial traits become more common over generations?
AVariation exists among individualsBTraits are heritableCIndividuals with advantageous traits reproduce more (differential reproduction)DPopulations overproduce offspring
Biology · L4 · Ecology & Evolution — 10 Q
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Biology · L4 · Ecology & Evolution — 10 QQuiz10 questions
Which organelle is responsible for ATP production via aerobic respiration?
ANucleusBRibosomeCMitochondrionDGolgi apparatus
Biology · L4 · Cell Biology & Genetics — 10 Q
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Biology · L4 · Cell Biology & Genetics — 10 QQuiz10 questions
Where in the eukaryotic cell does glycolysis take place?
AMitochondrial matrixBInner mitochondrial membraneCCytosolDNucleus
Biology · L4 · Human Physiology & Biochemistry — 10 Q
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Biology · L4 · Human Physiology & Biochemistry — 10 QQuiz5 questions
In a rod photoreceptor, absorption of a photon by rhodopsin ultimately leads to which immediate change at the plasma membrane?
AOpening of additional cGMP-gated channels, causing further depolarizationBClosure of cGMP-gated channels as cGMP is hydrolyzed by PDE, causing hyperpolarizationCDirect opening of a ligand-gated ion channel by retinal itselfDActivation of voltage-gated Na+ channels, generating an action potential in the outer segment
Biology · L4 · Sensory Physiology Quiz
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Biology · L4 · Sensory Physiology QuizQuiz5 questions
A hormone binds a Gs-coupled receptor. Which enzyme is activated to raise intracellular cAMP?
APhospholipase CBAdenylyl cyclaseCProtein kinase CDPhosphodiesterase
Biology · L4 · Cell Signaling and Cycle Regulation Quiz
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Biology · L4 · Cell Signaling and Cycle Regulation QuizQuiz5 questions
In bacterial transcription, the primary role of the sigma (σ) factor is to:
ACatalyse phosphodiester bond formation during elongationBRecognise and bind promoter sequences to direct RNA polymerase to the correct start siteCUnwind the DNA double helix at the terminator sequenceDAdd the 5' cap to the nascent transcript
Biology · L4 · Molecular Genetics and Gene Expression — 5 Q
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Biology · L4 · Molecular Genetics and Gene Expression — 5 QQuiz5 questions
During the denaturation step of a PCR cycle, what actually happens to the DNA?
ADNA polymerase extends the primers into new strands.BThe double-stranded DNA is heated, breaking hydrogen bonds and separating the strands.CPrimers bind to their complementary sequences on the template.DThe reaction is cooled to allow the new strand to fold correctly.
Biology · L4 · Biotechnology and Recombinant DNA Quiz
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Biology · L4 · Biotechnology and Recombinant DNA QuizQuiz5 questions
In a Hardy-Weinberg population, the dominant allele frequency is p = 0.6. What is the expected frequency of homozygous dominant individuals?
A0.36B0.48C0.6D0.16
Biology · L4 · Population Genetics Quiz
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Biology · L4 · Population Genetics QuizQuiz5 questions
A ventricle has a stroke volume of 80 mL and a heart rate of 75 beats per minute. What is the cardiac output?
A800 mL/minB5,000 mL/minC6,000 mL/minD155 mL/min
Biology · L4 · Cardiovascular Physiology
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Biology · L4 · Cardiovascular PhysiologyQuiz5 questions
According to Boyle's law, what happens to the pressure inside the lungs when the thoracic cavity expands during inhalation?
APressure increases because the same amount of gas is compressedBPressure decreases because the gas occupies a larger volumeCPressure stays constant because volume and pressure are unrelatedDPressure oscillates unpredictably as volume changes
Biology · L4 · Respiratory Physiology
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Biology · L4 · Respiratory PhysiologyQuiz5 questions
Glomerular filtration rate (GFR) is best defined as:
AThe volume of blood flowing through both kidneys per minuteBThe volume of filtrate formed by both kidneys per minuteCThe volume of urine excreted per dayDThe rate of blood flow through the renal artery
Biology · L4 · Renal Physiology — 5 Q
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Biology · L4 · Renal Physiology — 5 QQuiz5 questions
A hormone binds a receptor located inside the cytoplasm, and the hormone-receptor complex then binds DNA directly to alter gene transcription. Which hormone class does this describe?
ASteroid hormoneBPeptide hormoneCCatecholamineDGlycoprotein tropic hormone
Biology · L4 · Endocrine Physiology — 5 Q
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Biology · L4 · Endocrine Physiology — 5 QQuiz5 questions
According to the size principle, which motor units are recruited first when a muscle produces a small, light-intensity force?
ASmall, low-threshold Type I motor unitsBLarge, high-threshold Type IIx motor unitsCAll motor units are recruited simultaneously regardless of sizeDOnly motor units with the highest innervation ratio
Biology · L4 · Musculoskeletal Physiology — 5 Q
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Biology · L4 · Musculoskeletal Physiology — 5 QQuiz5 questions
A bacterial cell takes up naked DNA released into the environment by a lysed neighboring cell. This process is called:
ATransformationBTransductionCConjugationDTransposition
Biology · L4 · Microbial Genetics and Pathogenesis Quiz
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Biology · L4 · Microbial Genetics and Pathogenesis QuizQuiz5 questions
A shoot bends toward a light source coming from one side. Which explanation best accounts for this phototropic response?
AAuxin is redistributed to the shaded side, causing those cells to elongate more than the illuminated sideBChlorophyll on the illuminated side is destroyed by excess light, stopping growth thereCCytokinin accumulates on the illuminated side, causing rapid cell divisionDEthylene diffuses away from the light source, inhibiting elongation on the shaded side
Biology · L4 · Plant Physiology and Hormones Quiz
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Biology · L4 · Plant Physiology and Hormones QuizQuiz5 questions
Sea otters preying on sea urchins keep kelp forests intact by limiting urchin grazing. This describes the role of otters as a:
APioneer speciesBKeystone speciesCClimax speciesDInvasive species
Biology · L4 · Community and Ecosystem Ecology Quiz
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Biology · L4 · Community and Ecosystem Ecology QuizQuiz5 questions
An enzyme has a very low Km for its substrate compared to a second enzyme acting on the same substrate. What does this indicate?
AThe low-Km enzyme has a higher affinity for the substrate and reaches half-maximal rate at a lower substrate concentrationBThe low-Km enzyme has a lower affinity for the substrate and requires more substrate to become saturatedCThe low-Km enzyme necessarily has a higher Vmax than the second enzymeDKm provides no information about substrate affinity
Biology · L4 · Enzyme Kinetics and Metabolism Quiz
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Biology · L4 · Enzyme Kinetics and Metabolism QuizQuiz5 questions
Where on an antibody monomer is the antigen-binding site located?
AAt the base of the constant region stemBAt the tips of the variable regions, where a heavy and light chain pairCAlong the entire length of the heavy chainDWithin the disulfide bonds linking the two heavy chains
Biology · L4 · Immunology
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Biology · L4 · ImmunologyQuiz5 questions
Which channel opens first to produce the sharp depolarizing upstroke of the action potential, and what ion carries the current?
AVoltage-gated K+ channels; K+ effluxBVoltage-gated Na+ channels; Na+ influxCLigand-gated Ca2+ channels; Ca2+ influxDThe Na+/K+ pump; simultaneous Na+ and K+ movement
Biology · L4 · Neurobiology Quiz
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Biology · L4 · Neurobiology QuizQuiz5 questions
What is the immediate functional consequence of the cortical reaction following fertilization?
AIt restores the diploid chromosome number by fusing the sperm and egg nucleiBIt blocks additional sperm from fertilizing the egg (block to polyspermy)CIt initiates the first mitotic cleavage divisionDIt establishes the anterior-posterior axis of the embryo
Biology · L4 · Developmental Biology Quiz
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Biology · L4 · Developmental Biology QuizQuiz5 questions
A herring gull chick pecks more at an artificial bill with an exaggerated red spot than at a real parent bill. This demonstrates:
AHabituation to a repeated stimulusBA supernormal stimulus exploiting the rules of a sign-stimulus releasing mechanismCOperant conditioning through reinforcementDLatent learning expressed without reward
Biology · L4 · Animal Behavior and Ethology Quiz
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Biology · L4 · Animal Behavior and Ethology QuizQuiz5 questions
A group of closely related freshwater fish, with very poor tolerance for salt water, is found on continents now separated by ocean. This distribution is best explained by:
ADispersal across the open oceanBVicariance, with the lineage splitting as the continents drifted apartCConvergent evolution producing similar but unrelated fish independentlyDThe equilibrium theory of island biogeography
Biology · L4 · Biogeography Quiz
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Biology · L4 · Biogeography QuizQuiz5 questions
Most vertebrate limb muscles (e.g. the biceps at the elbow) operate as which type of lever, and what functional tradeoff does this represent?
AFirst-class lever; maximizes static holding forceBSecond-class lever; always favors mechanical advantage greater than 1CThird-class lever; sacrifices mechanical advantage for greater speed and range of motionDNo lever system is involved in limb movement
Biology · L4 · Biomechanics and Animal Locomotion Quiz
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Biology · L4 · Biomechanics and Animal Locomotion QuizQuiz5 questions
AB blood type, in which both A and B antigens are fully and separately expressed on red blood cells, is an example of:
AIncomplete dominanceBCodominanceCEpistasisDGenomic imprinting
Biology · L4 · Classical Genetics and Inheritance Patterns Quiz
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Biology · L4 · Classical Genetics and Inheritance Patterns QuizQuiz5 questions
The wings of a bat and the wings of an insect are best described as:
AHomologous, because both function for flightBAnalogous, because they evolved independently from non-homologous ancestral structuresCVestigial in both lineagesDSerially homologous within each individual animal
Biology · L4 · Comparative Vertebrate Anatomy Quiz
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Biology · L4 · Comparative Vertebrate Anatomy QuizQuiz5 questions
A small population loses genetic diversity through drift, suffers inbreeding depression, declines further, and becomes even more vulnerable to further genetic loss and stochastic events. This self-reinforcing decline is called:
AA genetic bottleneckBAn extinction vortexCThe edge effectDAssisted migration
Biology · L4 · Conservation Biology Quiz
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Biology · L4 · Conservation Biology QuizQuiz5 questions
Pepsinogen is converted to active pepsin primarily by:
ABicarbonate secreted by the pancreasBThe acidic environment of the stomach, with pepsin then autocatalytically activating more pepsinogenCBile salts released from the gallbladderDEnteropeptidase in the duodenum
Biology · L4 · Digestive Physiology Quiz
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Biology · L4 · Digestive Physiology Quiz