Molecular Biology Concepts, Exams of Advanced Education

Download Molecular Biology Concepts and more Exams Advanced Education in PDF only on Docsity! ETS major field test in biology questions and answers Pyrimidine dimers formed in DNA due to UV radiation can be repaired by? SOS repair Double strand break repair Mismatch repair Photoreactivation repair (nucleotide excision repair) Base excision repair - Answer -Photoreactivation repair (nucleotide excision repair) Which of the following repair mechanisms uses methyl groups to distinguish between parental and daughter strands? Answers: Mismatch repair Photoreactivation repair (Nucleotide excision repair) SOS repair Double strand break repair Base excision repair - Answer -Mismatch repair Which of the following types of molecules is always found in virions? Answers: Protein RNA Lipid DNA Carbohydrate - Answer -Protein A Barr body found within the female mammalian cell's nucleus is an example of ___ Answers: Euchromatin Polytene chromosome Pseudogenes Heterochromatin Cistron - Answer -Heterochromatin In vertebrate genes, transcription regulatory regions that contain CpG islands are inactivated by which CpG modification? Answers: Methylation Ubiquitination Acetylation Phosphorylation Myristoylation - Answer -Methylation TATA-binding protein (TBP) is a key transcription factor in eukaryotes. A schematic representation of the 240-amino acid TBP of yeast is shown in Fig. 1 below, with the positions of 2 mutations indicated. The boxed area represents the evolutionarily conserved C-terminal domain of TBP, and the shaded (dark) regions of this domain represent two repeated elements involved in DNA binding. One mutation (P65S) changes proline 65 to serine and the other I143N changes isoleucine 143 to asparagine. Fig. 2 below represents autoradiographs of gels containing RNA transcripts produced in extracts of wild type or mutant cells. Lanes 1-2 are from wild-type yeast (WT), lanes 3-4 are from the I143N mutant and lanes 5-6 are from P65S mutant, as indicated. Fig. 2A shows transcripts of a gene transcribed by RNA polymerase I (Pol I). Fig. 2B shows transcripts of a gene transcribed by RNA polymerase II (Pol II). Fig. 2C shows transcripts - Answer -Whether mutant transcription phenotypes are due to perturbation of TBP function. A set of genes from Bacillus subtilis that encode the proteins required for sporulation have conserved DNA sequences -35 and -10 nucleotides before the site of transcript initiation. However, the sequence at -35 is different from that seen in most other genes from that species. Which of the following best explains this difference? Answers: Transcription of these genes is induced by cAMP Translation of the mRNAs transcribed from these genes requires specific ribosomes that recognize a modified Shine-Dalgarno sequence A novel sigma factor is required for transcription initiation at these genes The -35 sequence is the binding site for a repressor of transcription The replication of these genes requires a specifically modified DNA polymerase. - Answer -A novel sigma factor is required for transcription initiation at these genes Which of the following repair mechanisms is often mutagenic? Answers: Mismatch repair Photoreactivation repair (Nucleotide excision repair) Base excision repair SOS repair - Answer -SOS repair The polytene chromosomes seen in Drosophila are Answers: Multiple copies of a single chromosome Chiasmata Mitotic spindle Synaptomenal complexes Secondary constrictions Centromeres - Answer -Chiasmata Hybrids between some related species are sterile because the parent plants had different chromosome numbers. Occasionally the chromosome number of such a hybrid plant doubles spontaneously. Which of the following best describes the descendants of those plants with the double chromosome number? Answers: The plant with the double chromosome would be genetically defective and have no descendants. The descendants would be at a selective advantage because of the increased ability to introgress The descendants would be reproductively successful because they could backcross with the parental species The descendants would be at a selective disadvantage because they could not reproduce asexually The descendants would regain the ability to reproduce sexually because chromosomes could pair normally - Answer -The descendants would regain the ability to reproduce sexually because chromosomes could pair normally The pedigree shows the inheritance of a human disease over three generations. If individual III-3 were to have a daughter, what is the probability that the daughter would receive the disease trait from her mother (III-3)? *see photo 1.00 0.33 0.25 0.00 0.5 - Answer -0.5 The pedigree shows the inheritance of a human disease over three generations. Which of the following is the most likely mode of inheritance for the disease trait? Answers: Y-linked dominant X-linked recessive Autosomal dominant Cytoplasmic - Answer -Autosomal dominant A sex-linked trait like hemophilia may be transmitted from mother to daughter and appear in the daughter's phenotype when ___ Answers: Both the mother's X-chromosomes carry the trait and the father's X-chromosome carries the trait One the mother's X-chromosomes carry the trait and the father's X-chromosome does not One of the mother's X-chromosomes carry the trait and the father's Y-chromosome carries the trait Both the mother's X-chromosomes carry the trait and the father's Y-chromosome carries the trait - Answer -Both the mother's X-chromosomes carry the trait and the father's X- chromosome carries the trait Sequences of DNA that are capable of moving and inserting themselves into a different parts of a genome are ___ Answers: Cistrons Prions Transposons Introns Transducers - Answer -Transposons In garden peas, the allele for tall plants (D) is completely dominant to the allele for dwarf plants (d) and the allele for violet flower color (W) is completely dominant to the allele for white flower color (w). In a cross between a tall violet plant, with the genotype DDWw, and a dwarf white plant, what phenotypic ratio of the progeny would be expected from this cross? Answers: All tall violet 1 tall violet: 1 tall white: 1 dwarf violet: 1 dwarf white 1 tall violet: 1 tall white 1 tall violet: 1 dwarf violet All dwarf white - Answer -1 tall violet: 1 tall white In E. coli, the inability of the lac repressor to bind an inducer would result in _____ Answers: inducible synthesis of β-galactosidase synthesis of β-galactosidase only in the absence of lactose no substantial synthesis of β-galactosidase synthesis of inactive β-galactosidase constitutive synthesis of β-galactosidase - Answer -no substantial synthesis of β- galactosidase If a male has the blood group AB, and a female has the blood group O, the blood group of any of the progeny can be __ Answers: A only B only A or B AB only O only A, B, AB or O - Answer -A or B A male fruit fly bearing linked genes that has a phenotype of normal wings and gray body mates with a female fruit fly that has a phenotype of vestigeal wings and black body. The presence of progeny with gray bodies and vestigeal wings can be explained by __ Answers: Dominance Independent assortment Crossing over Penetrance Segregation of alleles - Answer -Crossing over All the statements below are true about the trp operon attenuator EXCEPT Answers: It brings about repression of the trp operon The ribosome stalls at the attenuator It has two codons that code for tryptophan in its sequence It consists of one stem loop structure - Answer -It brings about repression of the trp operon The pedigree shows the inheritance of a rare human disease over three generations. If individual III-3 and III-6 were to have a son, what is the probability that the son would be affected with the disease? *see picture Answers: 1.00 0.5 0.25 0.00 0.75 - Answer -0.75 Which of the following most accurately explains the cause for the abnormal numbers of chromosomes during human reproduction that can result in Down's syndrome, Turner's syndrome, or Klinefelter's syndrome? Answers: The occurence of non-disjunction of homologous chromosomes during meiosis The fusion of two sperm with one egg to provide an extra set of paternal chromosomes The duplicative production of extra chromosomes during DNA replication The abnormal pairing of nonhomologous chromosomes during prophase of meiosis I Proteins destined to be secreted move through the secretory pathway in which of the following orders? Rough ER à Smooth ER à Golgi transport vesicle à Golgi cisternae à secretory vesicle à cell surface Smooth ER à Golgi transport vesicle à Golgi cisternae à secretory vesicle à cell surface Golgi cisternae à ER transport vesicle à smooth ER à secretory vesicle à cell surface Rough ER à Golgi transport vesicle à Golgi cisternae à secretory vesicle à cell surface * Golgi cisternae à ER transport vesicle à rough ER à secretory vesicle à cell surface - Answer -Rough ER à Golgi transport vesicle à Golgi cisternae à secretory vesicle à cell surface Membrane carrier proteins differ from membrane channel proteins by which of the following characteristics? Carrier protein transport molecules down their electrochemical gradient, while channel proteins transport molecules against their electrochemical gradient. Carrier proteins are synthesized on free cytoplasmic ribosomes, while channel proteins are synthesized on ribosomes bound to endoplasmic reticulum Carrier proteins are glycoproteins, while channel proteins are lipoproteins Carrier proteins can mediate active transport, while channel proteins cannot Carrier proteins do not bind to the material transported, while channel proteins do. - Answer -Carrier proteins can mediate active transport, while channel proteins cannot Movement of plasma membrane receptors from the basolateral surface to the apical surface of polarized epithelial cells is by ___ Exocytosis Endocytosis Transcytosis Phagocytosis Apoptosis - Answer -Transcytosis During the translation of peptide neurohormone biosynthesis, the peptide enters the ___ Golgi apparatus Synaptic vesicle Nucleus Cytoplasm Rough endoplasmic reticulum - Answer -Rough endoplasmic reticulum Which of the following is true of an enzyme that has undergone denaturation? If the denaturation is reversible, it is incapable of spontaneously reforming its three- dimensional shape It is till able to catalyze the reaction for which it is specific It is capable of lowering the activation energy of a reaction Its primary structure is not disrupted. Its active site can still bind to a ligand - Answer -Its primary structure is not disrupted. Above 5 ng · mL-1, pig insulin exerted no further effect on glucose oxidation. Which of the following best explains this result? Such levels exceed the pig's capacity to synthesize and secrete insulin. Above this level insulin degrades itself in an autocatalytic manner. Rat fat cells show no response to insulin in concentrations greater than 5 ng· mL-1 At this level all insulin receptors in rat fat cells are bound to the hormone. Levels of insulin above 5 ng· mL-1 are toxic to rat fat cells. - Answer -At this level all insulin receptors in rat fat cells are bound to the hormone. A flourescent moelcule of 1,000 daltons injected into one cell is observed to enter an adjacent cell by passing through a ___ Hemidesmosome Desmosome Gap junction Adherens junction Tight junction - Answer -Gap junction What concentration of pig insulin produced a half-maximal effect on glucose oxidation? 0.1 ng · mL-1 1 ng · mL-1 0.5 ng · mL-1 The value cannot be determined from the data 10 ng · mL-1 - Answer -0.5 ng · mL-1 Eukaryotic cells with DNA damage often cease progression through the cell cycle until the damage is repaired. This type of control over the cell cycle is referred to as Anticyclin control Transcriptional control Checkpoint control Proteasome control Damage control - Answer -Checkpoint control Which of the following traits do prokaryotes and eukaryotes have in common? A single chromosome carries the entire genome. * Molecular weight of respective DNA is comparable ** Number of origins of replication along the chromosome is comparable*** Chromosomes are circular Replication is bidirectional - Answer -Replication is bidirectional Treatment of root tip meristem cells with the microtubule inhibitor colchicine results in all of the following EXCEPT Prevention of chromosome segregation* Induction of polyploidy Prevention of cytokinesis Cessation of DNA replication Inhibition of mitotic spindle assembly - Answer -Cessation of DNA replication Which of the following best supports the endosymbiotic theory of the evolutionary origin of mitochondria? Many mitochondrial proteins are imported across both inner and outer membranes after translation on cytoplasmic ribosomes is completed. Genes for mitochondrial pyruvate dehydrogenase subunits are found in the nuclear DNA Mitochondrial and bacterial ribosomal functions are inhibited by the same antibiotics Mitochondria, chloroplasts and prokaryotes contain electron carriers The outer mitochondrial membrane contains the protein porin - Answer -Mitochondrial and bacterial ribosomal functions are inhibited by the same antibiotics A cell expresses a transmembrane protein that is cleaved at the plasma membrane to release an extracellular fragment. The fragment binds to receptor proteins on nearby cells and activates signaling pathways resulting in altered gene expression patterns in the nearby cells. What form of intercellular signaling does this represent? Contact-dependent signaling Endocrine signaling Synaptic signaling Paracrine signaling Autocrine signaling - Answer -Paracrine signaling Science is considered to be hypothesis driven. A researcher wants to determine the effect of prune juice on the growth of human liver cells. Which of the statements below would be a valid alternative hypothesis. None of the options are correct All the options are correct Does prune juice promote the growth of human liver cells? Prune juice has no effect on the growth of human liver cells Initiate elongation of ciliary and flagellar subnuits by causing the addition of new protein at the base of the axomene. Organize the microtubules into a 9+2 arrangement and gives rise to the doublet microtubules. Organize the microfilaments into a 9+2 arrangement and gives rise to the doublet microfilaments. assemble α-tubulin and β-tubulin molecules into heterodimers and arrange them into protofilaments Assemble actin molecules into actin filaments and arrange them into a double-strand helix - Answer -Organize the microtubules into a 9+2 arrangement and gives rise to the doublet microtubules. Which one of the following statements is true about the Golgi apparatus? Transit of a secretory protein occurs in a direction from its trans face to its cis face.* It is oriented in the cytoplasm so that its cis face is closest to the endoplasmic reticulum*** Glycosylation of certain secretory proteins occur prior to the protein's entry into its lumen. Its composite flattened cisternae are continuous with one another It is typically associated with small secretory vesicles located near its cis face ** - Answer -It is oriented in the cytoplasm so that its cis face is closest to the endoplasmic reticulum In contrast to transporters, which of the following statements is true about channel proteins, like ion channels, in cellular membranes channel proteins can only mediate passive transport. channel proteins form pores that are always open channel proteins interact strongly with the solute(s) that they transport. channel proteins undergo a conformational change every time they transport a solute - Answer -channel proteins can only mediate passive transport The assembly of pure brain tubulin into microtubules in vitro can be followed by using a spectrophotometer to measure light scattering (absorbance at 350 nm). The total mass of microtubule polymer is proportional to the amount of light scattered. Polymerization is initiated by warming the sample buffer, containing tubulin and an excess of GTP, to 37°C. In the experiment whose results are show above, soluble tubulin at 1.6 mg/mL was used for both sample X and sample Y. A small volume of eukaryotic basal bodies was added to sample X only. ASsume that the basal body sample did not significantly affect the volume or the initial tubulin concentration of sample X. Which of the following statements best describes the situation at 50 minutes in both sample X and sample Y? The rate of tubulin subunit addition to microtubules equals the rate of tubulin loss from microtubules All tubulin is in the polymeric form**** The numb - Answer -The rate of tubulin subunit addition to microtubules equals the rate of tubulin loss from microtubules Consider the membrane transporter that is shown below. The direction of transport of Na+ and K+ ions is demonstrated by the ion in the box near the corresponding arrow. Which of the following is true about the transport of Na+ ions? The transport of Na+ ions is by active transport The transport of Na+ ions is in the opposite direction to the transport of the K+ ions. The transport of Na+ ions is mediated by diffusion The transport of Na+ ions is by passive transport - Answer -The transport of Na+ ions is by active transport Which of the following is a reason that geneticists use mitochondrial DNA (mtDNA) to study the relatedness of animal populations? - Answer -mtDNA is passed from mother to child and is free from recombination that occurs between pairs of chromosomes RNA is thought to have played an important role in the evolution of life for which of the following reasons? It occurred in great quantities on early Earth. It can self-replicate via a complementary chain. It can catalyze some cellular functions. - Answer -ii and iii Which of the following statements about fungi is NOT true? - Answer -some are photosynthetic A prokaryote that is thermophilic and methanogenic and has isoprenylglycerol ethers in its membrane instead of phospholipids is most likely - Answer -An archaeon Based on the phylogenetic tree above, which statement best describes a relationship between the common ancestor and the other organisms? - Answer -The common ancestor shares DNA with each of the other organisms How do cyanobacteria differ from green unicellular algae? - Answer -Cyanobacteria have no nuclei. The membranes of mitochondria, chloroplasts and bacteria are involved with all of the following except: - Answer -catalyze the reaction of the Krebs cycle In the formation of the earliest cells, which of the following components most likely arose first? - Answer -Plasma membrane In one taxonomic classification, Archaea, Eukarya, and Bacteria represent the three major domains of life. Eukarya utilize the general transcription factors TBP (TATA- binding protein) and TFIIB in transcription, whereas Bacteria do not. At least one member of Archaea has a protein similar to TBP and a protein similar to TFIIB. Based on this observation, which of the following scenarios is most likely? - Answer -Archaea and Eukarya diverged after their common ancestor diverged from Bacteria Which of the following statements are true about fossils - Answer -Fossils are the preserved remains of once-living organisms that can be found in amber, Siberian permafrost, dry caves, rocks etc Which of the following statements are true about finding the age of fossils? - Answer - Dating methods that use the decay of Uranium to Lead can provide the age of fossils that were on earth millions of years ag Which of the following facts was established prior to 1859, the year in which Charles Darwin published On the Origin of Species ? - Answer -There exist fossilized remains of species that have become extinct Barley seeds are divided in half, as shown in the diagram, and the halves containing only endosperm and aleurone are then treated with different concentrations of gibberellin. After 8 hours of incubation, reducing sugars appear and a calibration curve is developed for the relation between gibberellin concentration and the production of reducing sugars. The most important reason for removing the embryo of the seeds used in the experiment is to ____ prevent the seeds from germinating during the experiment- prevent the inhibition of gibberellin activity facilitate the absorption of gibberellin into the cut seeds- remove the glucose contained in the embryo- remove the natural source of gibberellin - Answer -remove the natural source of gibberellin Secondary growth that is observed in angiosperms is promoted by ____ Inflorescence meristems Apical meristems Lateral meristems Intercalary meristems - Answer -Lateral meristems In angiosperms, once the embryo completes development, it must become dormant until the conditions for germination are favorable. This dormancy is mainly promoted by ___ Auxin Gibberellin Cytokinin Leaves Root Shoot - Answer -Root An organism with a lobed thallus, rhizoids, and gemmae is a Fern Filamentous mold Moss Mushroom Liverwort - Answer -Liverwort All of the following are true of monocots EXCEPT Their vascular bundles are arranged in a circle A bundle sheath encloses their vascular bundles Their cortex and pith are not clearly defined They generally do not undergo secondary growth Their vascular tissue extends through the length of the stem - Answer -Their vascular bundles are arranged in a circle Which of the following tissues in an actively photosynthesizing plant would have the highest rate of oxygen production? Endodermis Cortex Vascular cambium Palisade mesophyll Epidermis - Answer -Palisade mesophyll The tissue in plants that is made of undifferentiated cells that give rise to various tissues and organs of a plant is ____ Meristems Node Xylem Phloem Petiole - Answer -Meristems A stem-boring beetle has laid its eggs in the center of a 5-year-old wood twig, and the eggs have matured into larvae. In proper order (inside to outside), what tissues and tissue regions would the larvae encounter as they eat their way toward the outside of the twig? (For simplicity, assume that the epidermis has already fallen off completely. Pith; primary xylem; secondary xylem; vascular cambium; secondary phloem; cortex; primary phloem Pith; secondary xylem; primary xylem; vascular cambium; secondary phloem; primary phloem; cortex Pith; secondary xylem; primary xylem; vascular cambium; primary phloem; secondary phloem; cortex Pith; primary xylem; secondary xylem; vascular cambium; primary phloem; secondary phloem; cortex Pith; primary xylem; secondary xylem; vascular cambium; secondary phloem; primary phloem; cortex - Answer -Pith; primary xylem; secondary xylem; vascular cambium; secondary phloem; primary phloem; cortex Which of the following is a correct statement about the cohesion-tension theory for the ascent of water in the xylem? The cohesion of water molecules is responsible for the formation of embolisms (air bubbles) in the water column The evaporation of water from leaf mesophyll cells generates tension in the water column. Turgor pressure prevents the collapse of xylem cells that are under tension Water moves from a source region with high hydrostatic pressure to a sink region with low hydrostatic pressure. Living cells of the xylem provide the main conduit for an ascent of water - Answer -The evaporation of water from leaf mesophyll cells generates tension in the water column. Which of the following sets of reactions occurs in the stroma of the chloroplast in plant cells? Krebs cycle Fermentation Calvin cycle Decarboxylation - Answer -Calvin cycle Water is used in photosynthesis to ______________ To combine with ribulose 1,5 bisphosphate and produce oxygen Provide electrons to the chlorophyll in the reaction center of photosystem II To produce NADH Provide electrons to the chlorophyll in the reaction center of photosystem I - Answer - Provide electrons to the chlorophyll in the reaction center of photosystem II The red and purple colors in leaves that are seen in fall season are due to the production of Chlorophyll Anthocyanins Isoflavones Carotenoids - Answer -Anthocyanins The hormone that promotes phototropism in stems is ______ Gibberellin Cytokinin Auxin Ethylene - Answer -Auxin Two xylem plant cell types that provide support and conduct water and minerals are the Collenchyma and sclerenchyma Parenchyma and collenchyma Sieve tubes members and companion cells Vessel elements and companion cells Tracheids and vessel elements - Answer -Tracheids and vessel elements Which of the following plant cells undergoes programmed cell death to become functional? Xylem vessel member Phloem sieve tube member Bundle sheath cell Stomatal guard cell Root cap cell - Answer -Xylem vessel member In eukaryotic photosynthetic cells, which of the following occurs when electrons flow cyclically through the electron transport chain associated with photosystem I? Release of O2 Reduction of NADP+ to NADPH Reduction of CO2 to sugar Formation of H2O Synthesis of ATP - Answer -Reduction of NADP+ to NADPH C4 and CAM plants employ physiological and biochemical strategies to reduce photorespiration. Which of the following is an accurate comparison of the two strategies? C4 plants fix CO2 in the mesophyll but carry out the Calvin cycle in the bundle sheath, while CAM plants fix CO2 and carry out the Calvin cycle in the mesophyll. C4 plants fix CO2 as the 4-carbon acid oxaloacetate, while CAM plants fix CO2 as the 5-carbon acid ribulose 1, 5-bisphosphate. C4 plants fix CO2 in the bundle sheath but carry out the Calvin cycle in the mesophyll, while CAM plants fix CO2 and carry out the Calvin cycle in the bundle sheath. C4 plants store CO2 as phosphoglycolate, while CAM plants store CO2 as oxaloacetate. C4 plants carry out photosynthetic electron transport in the daytime, while CAM plants carry out photosynthetic electron transport at night. - Answer -C4 plants fix CO2 in the mesophyll but carry out the Calvin cycle in the bundle sheath, while CAM plants fix CO2 and carry out the Calvin cycle in the mesophyll. Which of the following is the symplastic pathway for the movement of sucrose from the site of photosynthesis in mesophyll cells into the phloem? Bundle sheath, companion cell, fibers, sieve tube Bundle sheath, phloem parenchyma, companion cell, sieve tube Companion cells, phloem parenchyma, fibers, sieve tube Which of the following best describes the ionic currents at the peak (see arrow) of the action potential from neuron B? The outward potassium current is equal to the inward sodium current The outward calcium current is greater than the inward sodium current The inward sodium current is equal to the outward chloride current x The outward sodium current is greater than the inward potassium current The inward chloride current is equal to the inward sodium current - Answer -The outward potassium current is equal to the inward sodium current Which of the following are anamniotes? Birds Fish Birds and mammals Reptiles Mammal - Answer -Fish The lens of the vertebrate eye develops only after the head ectoderm comes in contact with the optic cup. This is an example of __ Differentiation Determination Pattern formation Induction Plasticity - Answer -Induction Cleavage arising from early cell divisions that occur at an oblique angle to the polar axis is known as Superficial cleavage Spiral cleavage Incomplete cleavage Radial cleavage Meroblastic cleavage - Answer -Spiral cleavage Mouse sperm contain receptor proteins that bind to a glycoprotein (ZP3) in the zona pellucida of mouse eggs. Binding of ZP3 receptors to ZP3 initiates the sperm's acrosomal reaction. All of the following experimental observations would be expected EXCEPT Injecting eggs with antibodies that bind to ZP3 blocks in vitro fertilization Coating synthetic beads with ZP3 leads to sperm aggregation on the beads Incubating sperm with purified ZP3 prior to mixing sperm and eggs blocks in vitro fertilization. Coating synthetic beads with a different glycoprotein, ZP2, fails to lead to sperm aggregation on the beads- Incubating eggs with antibodies that bind to ZP3 blocks in vitro fertilization - Answer - Injecting eggs with antibodies that bind to ZP3 blocks in vitro fertilization Bromodeoxyuridine (BrdU) is used to label cells in the S phase of the cell cycle. Lobsters were exposed to BrdU during six 4-hour periods during the 24-hour day. The number of labeled neurons in the brain was counted for each 4-hour labeling period, and the means of these counts were plotted as histograms relative to time of day for animals maintained on the normal light/dark cycle (Figure 1: Normal LD) and on the reversed light/dark cycle (Figure 2: Reversed LD). The shaded bars indicate the sampling period at dawn and dusk, which also are shown in the table below. The horizontal bar at the top of the graph indicates illumination conditions (white = light; black = dark; arrows = subjective dusk). The dawn/dusk data for LD and DD (dark/dark conditions) are summarized in Table 1 below. The graphs of mean counts of BrdU-labeled neurons proliferating at different times of day in the lobster brain demonstrate that neur - Answer -the greatest number of neurons proliferate at subjective dusk The siphon of a bivalve serves primarily to secrete calcium carbonate Propel the bivalve through water seize and grasp prey release sperm cells filter sediment from ingested water - Answer -filter sediment from ingested water Which of the following would increase the rate at which a gas diffuses between the alveoli of the lung and the blood within a pulmonary capillary? Increasing the total surface area available for diffusion Decreasing the solubility of the gas in water Decreasing the partial pressure gradient of the gas Decreasing the rate of blood flow through the pulmonary capillary Increasing the thickness of the respiratory membrane - Answer -Increasing the total surface area available for diffusion The malpighian tubules of the grasshopper provide the same function as which of the following in an earthworm? Gizzard Crop Ganglia Esophagus Nephridia - Answer -Nephridia The nematocysts of cnidarians is used for Locomotion Excretion Respiration Support Feeding - Answer -Feeding The tracheae of insects is used for Locomotion Support Excretion Feeding Respiration - Answer -Respiration The ability of the brain to detect differences in stimulus intensity is best explained by the fact that which of the following varies with the stimulus intensity? The threshold potential The final destination of the action potential The number of action potentials per second The number of synapses crossed The amplitude of the action potential - Answer -The number of action potentials per second the radula of molluscs is used for Feeding Respiration Excretion Support Locomotion - Answer -Feeding The sight organs of crustaceans and insects contain ommatidia, which can make up the individual visual units of the Binocular eye Simple eye Compound eye Eyespot Pit organ - Answer -Compound eye The spicules of sponges is used for Feeding Excretion Support Respiration Locomotion - Answer -Support Monoclonal antisera are distinguished from polyclonal sera in which of the following ways A monoclonal antiserum contains antibodies secreted from the descendants of a single B lymphocyte; a polyclonal antiserum contains antibodies secreted from the descendants of both B and T lymphocytes