Correct Answer: (c)
Splicing involves the removal of non-coding introns and the joining of coding exons. Through alternative splicing, different combinations of exons can be joined, allowing a single eukaryotic gene to code for multiple distinct mRNA transcripts and, consequently, multiple different proteins.
Q2. If you wanted to study the use of ATP during a single contraction cycle within a muscle cell, which of the following processes would you use?
Correct Answer: (b)
A twitch is a single, brief contraction and relaxation cycle of a muscle fiber in response to a single action potential. This makes it the ideal unit for studying the molecular events and energy consumption of one contraction cycle.
Q3. Mild vitamin D deficiency can lead to osteoporosis, or reduced bone mineral density. This is thought to be due to an association with increased levels of
Correct Answer: (b)
Vitamin D is necessary for calcium absorption from the gut. When Vitamin D is low, blood calcium drops, triggering the parathyroid glands to release more Parathyroid Hormone (PTH). PTH increases blood calcium by breaking down bone tissue, leading to a loss of bone density over time.
Q4. What is the relationship between mutations and evolution?
Correct Answer: (b)
Mutations are the ultimate source of genetic variation. By altering DNA sequences, they create new alleles within a population. While most mutations are neutral or harmful, occasionally some provide an advantage, and these variations serve as the raw material for natural selection and evolution to act upon.
Q5. How do the muscles move your hand through space?
Correct Answer: (d)
Muscles generate movement by contracting and by being attached to bones across joints. When a muscle contracts, it pulls one bone toward another, resulting in movement of the hand through space. Muscles do not actively lengthen; they relax.
Q6. Refer the functions of the growth hormones given below: I. Cell division, II. Cell enlargement, III. Pattern formation, IV. Tropic growth, V Flowering, VI. Fruiting, VII. Seed germination, VIII.Response to wound, IX. Response to stresses of biotic and abiotic origin. Identify the functions of growth promoters and growth inhibitors from the above.
Q7. Which part is removed or tied up in a vasectomy?
Correct Answer: (c)
In vasectomy, a small part of the vas deferens is removed or tied up.
Q8. Hybridization between incompletely isolated populations
Correct Answer: (b)
When populations that are beginning to diverge meet and hybridize, the resulting gene flow can serve as a 'genetic glue' that keeps the populations unified. Unless selection against the hybrids is strong enough to trigger reinforcement, this gene flow will typically prevent speciation.
Q9. Which of the following is a function of the kidneys?
Correct Answer: (d)
Kidneys perform multiple vital roles including removal of metabolic wastes, regulation of water balance, and maintenance of electrolyte (salt) levels. Therefore, all listed functions are correct.
Q10. Which of the following statement(s) is/are correct? (i) Animals in which the cells are arranged in two embryonic layers, an external ectoderm and an internal endoderm, are called diploblastic animals. (ii) Notochord is an ectodermally derived rod like structure formed on the ventral side during embryonic development in some animals. (iii) In some animals, the body cavity is not lined by mesoderm, instead, the mesoderm is present as scattered pouches in between the ectoderm and endoderm and such a body cavity is called pseudocoelom.
Correct Answer: (c)
Statement (ii) is incorrect; notochord is mesodermally derived and formed on the dorsal side.
Q11. With regard to phloem parenchyma, consider the following statements: 1. Plasmodesmatal connections exist between the cell walls. 2. It stores substances like resins, latex, and mucilage. Which of the statement(s) given above is/are correct?
Correct Answer: (c)
Phloem parenchyma cells are connected by plasmodesmata and serve storage functions for various organic substances.
Q12. Which of the following are not membrane-bound?
Correct Answer: (a)
Ribosomes are universally non-membrane bound organelles.
Q13. Match column-I with column-II and choose the option which shows their correct combination.
Correct Answer: (d)
All listed statements are incorrect: parasitism can drive strong defensive adaptations, involve coevolutionary arms races, and significantly affect host population dynamics.
Q15. Allopatric speciation
Correct Answer: (b)
Allopatric speciation occurs when a population is split into two or more geographically isolated groups by a physical barrier, such as a mountain range or a river. This isolation prevents gene flow, allowing the populations to diverge genetically over time until they can no longer interbreed.
Q16. Consider the following statements regarding gymnosperms and choose the correct option. (i) In gymnosperms, the male and female gametophytes have an independent existence. (ii) The multicellular female gametophyte is retained within the megasporangium. (iii) The gymnosperms are heterosporous. Of these statements
Correct Answer: (d)
In gymnosperms, gametophytes are not free-living; they remain within the sporangia on the sporophyte.
Q17. Which of the following statements (i-iv) regarding “Splitting of water” is/are correct? (i) It is photolysis of water which provides H+ ions for synthesis of NADPH. (ii) It provides electrons for photophosphorylation & activation of NADP+. (iii) O2 is evolved during this process. (iv) It replenishes O2 consumed by living beings and combustion.
Correct Answer: (d)
All given statements correctly describe the role and outcomes of the photolysis of water in photosynthesis.
Q18. A patient with a pituitary tumor exhibits fatigue, weight loss, and low blood sugar. This is probably due to a lack of production of
Correct Answer: (b)
Adrenocorticotropic hormone (ACTH) triggers the adrenal cortex to release glucocorticoids like cortisol. Cortisol is vital for maintaining blood glucose levels. A lack of ACTH leads to low cortisol, causing hypoglycemia (low blood sugar) and chronic fatigue.
Q19. What is the basis of separation of different DNA fragments by gel electrophoresis?
Correct Answer: (b)
DNA molecules have a uniform negative charge-to-mass ratio, so they all migrate toward the positive electrode. The agarose gel acts as a molecular sieve; smaller DNA fragments move through the pores more easily and quickly than larger fragments, resulting in separation based strictly on length (size).
Q20. With reference to factors affecting the rate of photosynthesis, which of the following statements is not correct ?
Correct Answer: (b)
Statement (b) is incorrect because C4 plants actually have a higher temperature optimum than C3 plants.
Q21. Why is a heat-stable DNA polymerase required for the polymerase chain reaction (PCR)?
Correct Answer: (b)
The denaturation stage that occurs during each cycle of PCR requires high temperatures that would denature most enzymes, so a heat-stable DNA polymerase is required for PCR. Heat-stable DNA polymerases do not add DNA nucleotides at a faster rate than other DNA polymerases, so choice (A) is incorrect. PCR primers anneal to the target DNA sequence, not to the DNA polymerase, so choice (C) is incorrect. Choice (D) is incorrect because heat-stable DNA polymerases are not more accurate than other DNA polymerases.
Q22. Assertion: Methanogens are found in anaerobic sludge.
Reason: They are also present in the rumen of cattle.
Correct Answer: (a)
Both locations are correct, but one is not the explanation for the other.
Q23. Conversion of N≡N to NH3 occurs in plant cell by:
Correct Answer: (d)
The actual conversion process (nitrogen fixation) within a cell is catalyzed by the specific enzyme complex called nitrogenase.
Q24. Which of the following statements best explains the difference between nonnuclear inheritance and sex-linked inheritance?
Correct Answer: (b)
(B) Females may pass on sex-linked traits to the next generation through their X chromosomes and nonnuclear traits through their mitochondrial DNA. Since mitochondrial DNA is passed on through eggs and not sperm, males cannot pass on nonnuclear traits to the next generation, but females may pass on nonnuclear traits to the next generation. Therefore, the only true statement is choice (B), and choices (A), (C), and (D) are incorrect.
Q25. In order for mimicry to be effective in protecting a species from predation, it must
Correct Answer: (a)
In Batesian mimicry, a palatable species gains protection by resembling a distasteful or dangerous model, thereby avoiding predation.
Q26. What are those structures that appear as beads-on-string in the chromosomes when viewed under electron microscope?
Correct Answer: (c)
The basic unit of chromatin packaging is the nucleosome, which appears as 'beads-on-a-string' structure.
Q27. As you sit quietly reading this sentence, the part of the nervous system that is most active is the
Correct Answer: (c)
The parasympathetic nervous system is the 'rest and digest' division of the autonomic nervous system. It predominates during periods of relaxation and low stress, maintaining homeostatic functions and conserving energy.
Q28. Which of the following is NOT a primary meristem?
Correct Answer: (a)
Primary meristems (protoderm, ground meristem, and procambium) are derived directly from the apical meristem. The cork cambium is a lateral (secondary) meristem responsible for secondary growth.
Q29. Most carbon dioxide is
Correct Answer: (c)
Once carbon dioxide enters red blood cells, the enzyme carbonic anhydrase rapidly catalyzes the reaction between CO2 and H2O to form carbonic acid (H2CO3), which is a key intermediate step in the formation of bicarbonate for transport.
Q30. Suppose that you stick your finger with a sharp pin. The area affected is very small and only one pain receptor fires. However, it fires repeatedly at a rapid rate (it hurts!). This is an example of
Correct Answer: (a)
Temporal summation occurs when a single presynaptic neuron (or receptor) fires multiple action potentials in rapid succession, resulting in the additive effect of postsynaptic potentials at the same location over time.
Q31. Which of the following pair is correctly matched ?
Correct Answer: (d)
G0 phase is known as the quiescent stage where cells remain metabolically active but no longer proliferate unless called on to do so.
Q32. Diseases in which the person’s immune system no longer recognizes its own MHC proteins are called
Correct Answer: (b)
Autoimmune diseases occur when the immune system fails to recognize self molecules, such as MHC proteins, and mounts an immune response against the body’s own tissues.
Q33. The difference between the amphibian and mammal hearts is that
Correct Answer: (c)
Amphibians have a three-chambered heart with a single ventricle, but internal ridges and channels partially separate oxygenated and deoxygenated blood, reducing mixing. Mammals, in contrast, have complete separation with a four-chambered heart.
Q34. The symbiotic association between fungi and algae is called
Correct Answer: (a)
Lichens are symbiotic associations between algae (phycobiont) and fungi (mycobiont).
Q35. Biological nitrogen fixation is the:
Correct Answer: (a)
Biological nitrogen fixation is specifically the reduction of atmospheric N2 to NH3 by certain living prokaryotes.
Q36. Which of these feature marks diplotene stage of cell cycle?
Correct Answer: (a)
The defining event of diplotene is the dissolution of the synaptonemal complex and the resulting partial separation of homologous chromosomes.
Q37. True nucleus is absent in
Correct Answer: (d) Anabaena is a cyanobacterium (prokaryote), which lacks a true membrane-bound nucleus.
Q38. Which of the following plant parts elongates directly and leads to the formation of primary roots?
Correct Answer: (b)
The radicle of the embryo elongates directly to form the primary root in dicotyledonous plants.
Q39. Convergent evolution
Correct Answer: (b)
Convergent evolution occurs when unrelated or distantly related organisms independently evolve similar traits because they are subjected to similar selective pressures in their environments, such as the streamlined bodies of dolphins (mammals) and sharks (fish).
Q40. Which of the following is correct? (i) Adoptions are one of the best methods for parenthood in India. (ii) ART requires high precision handling. (iii) MTP accounted for 1/5th of conceived pregnancies worldwide.
Correct Answer: (a)
Final observations from the ART and MTP sections.
Q41. How many meiotic divisions are required to produce 100 pollen grains ?
Correct Answer: (a)
Each meiotic division of a microspore mother cell produces 4 pollen grains. Thus, $100 / 4 = 25$ divisions are needed.
Q42. Which of the following is the primary method by which carbon dioxide is transported to the lungs?
Correct Answer: (d)
While some CO2 is dissolved in plasma or bound to hemoglobin (carbaminohemoglobin), approximately 70% of the carbon dioxide in the blood is transported in the form of bicarbonate ions (HCO3–), which are formed within red blood cells and then diffuse into the plasma.
Q43. The number of critically endangered animal and plant species in India is respectively
Correct Answer: (b)
According to Red List data (IUCN 2004/later updates relevant to the context), India had 18 critically endangered animals and 44 plants. (Ref: Answer Key Page 8).
Q44. Hyperventilation occurs
Correct Answer: (d)
Hyperventilation is breathing that is faster or deeper than necessary, which results in excessive elimination of carbon dioxide. Consequently, a hallmark state of hyperventilation is a low partial pressure of CO2 (hypocapnia) in the blood.
Q45. Which one of these is not a eukaryote?
Correct Answer: (b) Anabaena is a cyanobacterium (prokaryote). Euglena is a protist; Spirogyra is an alga; Agaricus is a fungus.
Q46. Regarding 'Infertility', which statements are true? (i) In India, the female is often blamed but the problem often lies with the male. (ii) Can be caused by drugs or psychological factors. (iii) AI is used when sperm count is low.
Correct Answer: (a)
Factors and treatments for infertility (Page 48).
Q47. Mountain climbers may have difficulty at high elevations because
Correct Answer: (a)
At high altitudes, the total atmospheric pressure is lower. Since oxygen still makes up about 21% of the air, its partial pressure (PO2) also decreases. This reduction in PO2 decreases the pressure gradient necessary to drive oxygen diffusion from the lungs into the blood.
Q48. Which of the following is an example of a density-dependent effect on population growth?
Correct Answer: (c)
Density-dependent effects intensify as population density increases. Limited access to cool burrows when population size is high directly links survival to population density.
Q49. In prokaryotes, chromatophores are
Correct Answer: (d)
Chromatophores are pigment-containing membranous extensions in photosynthetic prokaryotes like cyanobacteria.
Q50. Which one of the following is not used for construction of ecological pyramids?
Correct Answer: (c)
Ecological pyramids are built based on numbers, energy, or biomass. For biomass, dry weight is preferred over fresh weight because fresh weight varies with water content.
Q51. In 1986, the quail population in Golden Gate Park in San Francisco was 140 birds. Hunting by feral cats reduced the number of quail to 32 birds by 2016. If the birth rate of quail over this period averaged 20.4 quail/year, what was the average death rate of quail during this period?
Correct Answer: (c)
(C) dN/dt = B (birth rate) – D (death rate). So the average death rate would be D = B – dN/dt. The death rate is D = 20.4 quail/year – ((32 – 140) quail / 30 years) = 20.4 – (–3.6) = 20.4 + 3.6 = 24 quail/year.
Q52. The genome of a newly discovered virus has the following nucleotide composition: 22% guanine, 16% cytosine, 34% adenine, and 28% uracil. Based on the nucleotide composition, the genome of this virus is most likely made of which of the following?
Correct Answer: (c)
(C) Since the question states that the virus’s genome contains uracil, choices (C) and (D) are possibilities since RNA contains uracil and DNA does not; thus, rule out choices (A) and (B). However, since the percentage of guanine does not equal the percentage of cytosine and the percentage of adenine does not equal the percentage of uracil, it cannot be a double-stranded virus, so choice (C) is the best answer.
Q53. Which of the following represents the correct combination without any exception?
Characteristics
Class
(a) Mouth ventral, gills without operculum; skin with placoid scales; persistent notochord
Chondrichthyes
(b) Sucking and circular mouth; jaws absent, integument without scales; paired appendages
Cyclostomata
(c) Body covered with feathers; skin moist and glandular; fore-limbs form wings; lungs with air sacs
Aves
(d) Mammary gland; hair on body; pinnae; two pairs of Limbs
Mammalia
Correct Answer: (a)
Combination (a) is correct without exceptions. Cyclostomes can lack paired appendages; birds have air sacs but not 'moist skin'; some mammals lack pinnae.
Q54. Five kingdom system of classification suggested by R.H. Whittaker is not based on
Correct Answer: (a)
While cell type is a factor, the fundamental distinction between prokaryotes and eukaryotes (nucleus presence) was already used; the unique focus of his system was the criteria of nutrition, body organization, and reproduction.
Q55. Why, at higher light intensities, gradually photosynthesis rate does not show further increase?
Correct Answer: (d)
Once light is no longer the limiting factor, the rate is restricted by other variables such as CO2 concentration or temperature.
Q56. The charged molecule which is electrically neutral is known as
Correct Answer: (b)
A zwitterion is an ion that has separate positive and negative charges but a net charge of zero.
Q57. In alcoholic fermentation:
Correct Answer: (b)
NADH produced during glycolysis (triose phosphate oxidation) donates electrons to acetaldehyde, reducing it to ethanol.
Q58. In terms of studying gene function, what is the main benefit that genome editing has over RNAi?
Correct Answer: (a)
RNA interference (RNAi) is a 'knockdown' technology that degrades mRNA or blocks translation, resulting in reduced protein levels but often leaving some function intact. Genome editing (like CRISPR/Cas9) creates permanent changes in the DNA sequence, allowing for a complete 'knockout' or total elimination of the gene's function.
Q59. What potential problems must be considered in creating a transgenic bacterium with the human insulin gene isolated from genomic DNA to produce insulin?
Correct Answer: (b)
Human insulin is synthesized as a precursor (proinsulin) that requires eukaryotic-specific post-translational modifications, including the formation of disulfide bonds and the enzymatic cleavage of the C-peptide in the Golgi apparatus. Bacteria lack these organelles and specialized processing enzymes, so they cannot produce active insulin from a simple genomic gene sequence without additional engineering.
Q60. Members of phycomycetes are found in (i) Aquatic habitats (ii) On decaying wood (iii) Moist and damp places (iv) As obligate parasites on plants
Correct Answer: (d)
Phycomycetes are found in aquatic habitats, on decaying wood in moist/damp places, and as obligate parasites on plants.
Q61. Identify correct statements for 'Biofertilisers': (i) They enrich the nutrient quality of the soil. (ii) Rhizobium fixes atmospheric nitrogen into organic forms. (iii) Mycorrhiza absorbs phosphorus from the soil.
Correct Answer: (a)
Standard functions of biofertilisers (section 8.6).
Q62. Which of the following is true about lipophilic hormones?
Correct Answer: (b)
Lipophilic hormones do not dissolve well in the aqueous environment of the blood plasma. Therefore, they must travel through the circulatory system bound to specialized transport proteins to remain in solution until they reach their target cells.
Q63. A species facing extremely high risk of extinction in the immediate future is called
Correct Answer: (c)
Critically Endangered is the highest risk category assigned by the IUCN Red List for wild species.
Q64. Bananas can be prevented from over ripening by:
Correct Answer: (c)
Antioxidants like ascorbic acid can sometimes be used to slow down the oxidative processes associated with ripening and browning. (Wait, check Key: 71(c)).
Q65. You study a gene known to be important in the early stages of heart development. Loss of the gene is also suspected to play a role in triggering lung cancer. What kind of transgenic mouse would you use to study your gene in vivo?
Correct Answer: (c)
A traditional knockout mouse lacks the gene from conception, which would likely result in embryonic lethality if the gene is essential for heart development. A conditional knockout allows the researcher to delete the gene at a specific time or in a specific tissue (such as the lungs of an adult mouse), allowing the study of its role in cancer without stopping development.
Q66. Most abundant protein in human body is
Correct Answer: (a)
Collagen is the most abundant structural protein in the human body, found in skin, bone, and connective tissues.
Q67. Which one of the following statement is correct for botanical garden?
Correct Answer: (c)
Botanical gardens and seed banks are essential for the ex-situ conservation of plant species and their genetic material.
Q68. Which of the given statement can be assigned to the gametophytic phase in the alternation of generation life cycle?
Correct Answer: (a)
The gametophyte is the haploid phase that produces gametes by mitosis.
Q69. To make 100 molecules of glucose, how many molecules of ATP & NADPH are required?
Correct Answer: (a)
Synthesis of 1 glucose molecule requires 18 ATP and 12 NADPH. Therefore, 100 glucose molecules require $100 imes 18 = 1800$ ATP and $100 imes 12 = 1200$ NADPH.
Q70. Select the option which arranges the following steps in a correct sequence as per Gram's staining technique: Treatment with 0.5% iodine solution (1), washing with water (2), treatment with absolute alcohol/ acetate (3), staining with weak alkaline solution of crystal violet (4).
Correct Answer: (a)
The correct sequence is: Crystal Violet (4) -> Iodine (1) -> Water wash (2) -> Alcohol/Decolorizer (3).
Q71. Japanese four o’clocks that are red and tall are crossed to white short ones, producing an F1 that is pink and tall. If these genes assort independently, and the F1 is self-crossed, what would you predict for the ratio of F2 phenotypes?
Correct Answer: (d)
Color shows incomplete dominance (1 red : 2 pink : 1 white) and height shows simple dominance (3 tall : 1 short). Using the product rule: (1 Red + 2 Pink + 1 White) × (3 Tall + 1 Short) = 3 Red Tall, 1 Red Short, 6 Pink Tall, 2 Pink Short, 3 White Tall, 1 White Short. Sorting these leads to choice D.
Q72. How would plant development change if the functions of the genes SHOOTMERISTEMLESS (STM) and MONOPTEROUS (MP) were reversed?
Correct Answer: (c)
STM is required for shoot development at the apical end, while MP is required for root development at the basal end. Reversing their functional domains would flip the identity of the poles, reversing the root-shoot axis.
Q73. Which one of the following acts as the “alarm signal” to activate the body’s adaptive immune system by stimulating helper T cells?
Correct Answer: (b)
Interleukin-1 is a cytokine released by macrophages and antigen-presenting cells. It functions as an alarm signal by activating helper T cells, thereby linking innate immunity to adaptive immunity.
Q74. Pineapple can be made to flower in off season by
Correct Answer: (c)
Application of NAA (synthetic auxin) is a standard practice to induce flowering and fruit set in pineapple plantations.
Q75. Which of the following pair is not correctly matched ?
Correct Answer: (a)
Fungi are heterotrophs (decomposers/saprotrophs), not autotrophs. Autotrophs are mostly green plants.
Q76. If you are asked to classify the various algae into distinct groups then which of the following characters you should choose for the classification?
Correct Answer: (d)
The primary basis for the classification of algae into Chlorophyceae, Phaeophyceae, and Rhodophyceae is the type of pigments they contain.
Q77. An important function of the excretory system is to eliminate excess nitrogen produced by metabolic processes. Which of the following organisms is most efficient at packaging nitrogen for excretion?
Correct Answer: (c)
Iguanas excrete nitrogen primarily as uric acid, which is relatively non-toxic and requires very little water for elimination. This makes uric acid the most efficient form of nitrogen packaging among the options given.
Q78. Which one of the following reactions is an example of oxidative decarboxylation?
Correct Answer: (c)
The conversion of pyruvate to Acetyl-CoA involves both the loss of CO2 (decarboxylation) and the reduction of NAD+ (oxidation of the substrate).
Q79. Inhibitory neurotransmitters
Correct Answer: (a)
Inhibitory neurotransmitters typically open ligand-gated Cl– or K+ channels. This results in the membrane potential becoming more negative (hyperpolarization), which makes it more difficult for the postsynaptic neuron to reach the threshold for an action potential.
Q80. A forensic scientist cuts DNA from a crime scene and DNA from a suspect with the same enzyme. Which tool should the scientist use to separate the DNA fragments according to their size?
Correct Answer: (c)
Gel electrophoresis separates fragments of DNA according to their size. Bacterial transformation involves the uptake and expression of foreign DNA by bacteria, so choice (A) is incorrect. CRISPR-Cas9 is used for gene editing, so choice (B) is incorrect. PCR amplifies specific sequences of DNA, so choice (D) is also incorrect.
Q81. A threatened species category includes
Correct Answer: (d)
The broad category of 'threatened' species includes those that are critically endangered, endangered, and vulnerable.
Q82. Which of the following statements best describes the sliding filament mechanism of muscle contraction?
Correct Answer: (a)
During muscle contraction, the individual protein filaments (actin and myosin) maintain their original length. The sarcomere shortens because the thin actin filaments are pulled over the thick myosin filaments, increasing the degree of overlap.
Q83. In a vertical section of a dorsiventral leaf, the protoxylem in its midrib bundle
Correct Answer: (a)
In dicot leaves, xylem is oriented towards the adaxial (dorsal/upper) side of the leaf.
Q84. The measure of the ability of the plant to produce new plant material is referred as:
Correct Answer: (a)
The relative growth rate, which expresses the growth of a system per unit time as a percentage of the initial parameter, is often called the efficiency index.
Q85. The Ti plasmid of Agrobacterium usually induces tumors called galls on infected plants. When Agrobacterium is used to make transgenic plants, why does no gall form?
Correct Answer: (b)
To use Agrobacterium as a vector, the Ti (tumor-inducing) plasmid is 'disarmed.' This involves genetically engineering the plasmid to remove the T-DNA genes that cause tumor formation (galls) and replacing that space with the specific transgene the scientist wishes to introduce into the plant.
Q86. Vernalization induces flowering following exposure to
Correct Answer: (c)
Vernalization is the acquisition of a plant's ability to flower in the spring by exposure to the prolonged cold of winter. This ensure that reproductive development occurs at an appropriate time.
Q87. Sedimentary cycle having a small gaseous component is found in
Correct Answer: (d)
Sulfur is primarily sedimentary but has gaseous forms like SO2 and H2S in its cycle. Phosphorus has no significant gaseous phase.
Q88. Assertion: Cleavage refers to the mitotic divisions of the zygote.
Reason: It results in daughter cells called blastomeres.
Correct Answer: (b)
Both are true, but the formation of blastomeres is the result, not the 'reason' for the division being called cleavage.
Q89. Problems with the biological species concept include the fact that
Correct Answer: (a)
The biological species concept relies on the criteria of interbreeding and sexual reproduction. Because asexual organisms do not interbreed, the concept cannot be applied to them. Furthermore, it is often difficult to apply to fossils or to populations that are geographically separated (allopatric).
Q90. Imagine that you are doing an experiment on the movement of ions across neural membranes. Which of the following plays a role in determining the equilibrium concentration of ions across these membranes?
Correct Answer: (d)
The electrochemical gradient is the combined force of the chemical concentration gradient and the electrical gradient (charge difference) across a membrane. Together, these factors determine the direction and equilibrium of ion movement.