This a previous year sample paper., High school final essays of Biology

Download This a previous year sample paper. and more High school final essays Biology in PDF only on Docsity! CBSE ADDITIONAL PRACTICE QUESTIONS Biology (044) Class XII| 2023–24 Max Marks: 80 Time: 3 hours General Instructions: (i) All questions are compulsory. (ii) The question paper has five sections and 33 questions. All questions are compulsory. (iii) Section–A has 16 questions of 1 mark each; Section–B has 5 questions of 2 marks each; Section– C has 7 questions of 3 marks each; Section– D has 2 case-based questions of 4 marks each; and Section–E has 3 questions of 5 marks each. (iv) There is no overall choice. However, internal choices have been provided in some questions. A student has to attempt only one of the alternatives in such questions. (v) Wherever necessary, neat and properly labeled diagrams should be drawn. Section A Q.Nos. Questions Marks 1 During the pollen grain formation, the generative cell divides to give rise to the two male gametes. What is the ploidy of the generative cell? (a) n (b) 2n (c) 3n (d) 4n 1 2 Kiwi is a dioecious species. Which of the following methods can be definitely RULED OUT as a possible mode of pollination in its case? P) cleistogamous autogamy Q) chasmogamous autogamy R) geitonogamy S) xenogamy (a) only P and R 1 (b) only P and Q (c) only Q and S (d) only P, Q and R 3 Arun thinks that identifying the exact mRNA sequence from the protein sequence is difficult. Is he correct and why? (a) No, as the genetic code is universal. (b) Yes, as the genetic code is degenerate. (c) No, as the mRNA is translated into a protein sequence. (d) Yes, as the mRNA contains introns which are non-coding sequences. 1 4 Crickets are insects that follow the XO type of sex determination. Which of the following statements is ALWAYS TRUE about this type of sex determination? (a) Eggs that have an O chromosome will give rise to a male cricket. (b) Eggs that have an X chromosome will give rise to a female cricket. (c) Sperms that have an X chromosome will give rise to a male cricket. (d) Sperms that have an O chromosome will give rise to a male cricket. 1 5 Oysters are generally either dark or light in colour. Dark oysters excel in dark environments, while light oysters thrive in bright environments. Intermediate-coloured oysters are disadvantaged, lacking effective camouflage in either setting. Which type of natural selection does this phenomenon exemplify? (a) directional (b) stabilising (c) disruptive (d) (The phenomenon described does not exemplify natural selection.) 1 6 A team of archaeologists found a fossilized skeleton of a human-like creature with a brain capacity of more than 700cc. The structure and its associated findings also show evidence that this creature could use tools for hunting. Which stage of human evolution is this creature NOT from? (a) Homo erectus 1 Section B 17 Kavya says that the placenta produces relaxin which plays a crucial role during pregnancy. (a) Is she correct? Justify. (b) Name TWO other hormones secreted by the placenta during pregnancy 2 18 Thalassemia is an autosomal recessive disorder that causes anaemic conditions in an individual. A blood smear from a heterozygous individual shows blood cells that are small, pale and irregularly shaped along with normal RBCs. (a) State the genotypic and phenotypic ratios of offspring born to a carrier mother and a thalassemic father. (b) Does the allele for thalassemia exhibit codominance? Justify. 2 19 Explain any TWO reasons why the treatment of AIDS is only partially effective. 2 20 Rati wants to grow a variant of the lactobacillus spps. in a bioreactor. Lactobacillus is an anaerobic bacterium commonly used as a starter culture for diary products. Shown below is a bioreactor she had in her laboratory. (a) Identify ONE component that should definitely NOT be present in the reactor to grow the lactobacillus spps. Justify. (b) Explain TWO quantities that the sensors in the bioreactor should monitor. 2 21 Shown below is a food chain. (a) Millipedes have a hard exoskeleton whose composition is different from that of the leaves. Considering all other conditions to remain the same, which step is likely to be slower between A to B and B to C and why? (b) What would be the direction of the flow of energy in this food chain? OR (a) A coral reef can be regarded as an ecosystem. Mention any TWO reasons why. (b) The net primary productivity (NPP) of a coral reef is approximately 2000 g C/m2/year and the gross primary productivity (GPP) is 4000 g C/m2/year. Calculate the respiration losses (R) of this ecosystem. 2 2 Section C 22 A biologist sees the following cells in a cross-section of the seminiferous tubule and its surrounding tissues and counts the number of various kinds of cells. Spermatozoa, Spermatid, Primary spermatocyte, Secondary spermatocyte, Leydig cells, Sertoli cells, Spermatogonium. From these cells, identify the cells: (a) that are diploid. (b) that can produce hormones and their names. 3 23 A couple is trying to conceive and start a family. (a) If the woman's period, which is regular, is scheduled to start on July 19, what was the estimated date of ovulation for the previous cycle? (b) Name the four important reproductive hormones and state whether their levels will be high or low on the date identified in (a). 3 24 As part of assisted reproductive technologies (ART), (a) What is the destination for blastomeres with a count of less than 8 cells and more than 8 cells? (b) What could be the reason behind transferring to the destinations identified in (a)? (c) What techniques are used to transfer the blastomeres to the destinations identified in (a)? 3 25 (a) State any FOUR phenomena in which the Hardy-Weinberg theorem may not hold true. (b) A population of 100 individuals has a frequency of allele A of 0.3 and a frequency of allele a of 0.7. The frequency of the heterozygous genotype (Aa) is 0.49. Is this population in Hardy-Weinberg equilibrium? Justify. 3 26 State whether each of these statements given below is/are true or false. Justify your answer. (a) Flocs reduce the pollution in water by increasing its BOD. (b) Mycorrhiza is a type of parasitic relationship in which only the plants benefit from fungi. 3 27 Erythropoietin is a glycoprotein hormone that is otherwise naturally produced in the kidney when the body becomes anaemic. However, this does not happen in the case of chronic renal diseases where kidney function is lost. Epoetin alfa is a human erythropoietin produced in cell culture using recombinant DNA technology. The cell culture used is called Namalwa cells, a human cell culture. There are eight exons and seven introns in a single gene that encodes the hormone, whose sequence is known. Explain the step-by-step process that should be followed for producing human erythropoietin in culture. OR Today, many genetic disorders can be detected using a single cell from an embryo. This helps in planning the child's health care in advance, and in some cases even treating the disorder while the baby is still in the womb. (a) Identify a biotechnological technique that can be used for this purpose. Give a reason to support your answer. (b) Can the technique identified in (a) be used to detect the presence of RNA viruses? Justify. 3 28 In a study comparing two continents - Antarctica and Asia, the species-area relationship was investigated using the following data: Parameter Antarctica Asia Area 14 x 106 km2 44 x 106 km2 Regression coefficient 1 1 Y-intercept 5 10 3 OR Amey and Lalita are expecting their first child, with Lalita being in her second month of pregnancy with no known complications. Amey's family has a history of cystic fibrosis while Lalita's family has a history of Down's syndrome, leading to a concern that the baby may have one of these conditions. (a) Suggest and explain a way of testing if their baby is at risk for any genetic disorders. (b) In case of the presence of one or both of the abnormalities and posing a risk to the mother's health, mention one possible option for them to consider. (c) Is the process mentioned in (b) safe for Lalita at the current gestational age? Justify. (d) Under what conditions is the process mentioned in (b) illegal? 32 Shown below is a pedigree of an individual X who is suffering from ocular albinism which results in permanent vision loss. Use the pedigree to answer the questions that follow: (a) Complete the following statement about this disease: The trait for the disease is linked to ___________ (X-chromosome/Y- chromosome/autosome) and is __________ (dominant/recessive). (b) Give a reason to support your answer to (a). (c) Identify the genotypes of individuals P, Q, R and S marked in the pedigree. OR 5 Shown below is a nucleotide sequence and the genetic code. 5' - ATGCGTAGACTCGTA - 3' (a) Identify the protein sequence formed by this sequence. (b) Draw the tRNA molecule for the third codon with its polarity labelled. Give a reason to support the polarity identified. (b) The first guanine base in the nucleotide sequence changes to cytosine. Identify the type of mutation caused by this change. (c) Will the mutated sequence form an mRNA and protein? Justify. 33 (a) Classify the following scenarios as active/passive immunity and justify your answer. (i) A fetus receives antibodies from its mother through the placenta. (ii) A person accidentally gets cut by a blade and later receives a tetanus shot. (iii) A person receives a blood transfusion from a donor who has been vaccinated against a disease. (b) Zoya is bitten by an infected Anopheles mosquito in the morning. In the evening, another non-infected Anopheles mosquito bites Zoya and then bites Zaheer immediately. How likely is Zaheer to get malaria? Justify your answer. OR A patient is suffering from fatigue, high fever, and weight loss, and has been observing an increasing number and size of lumps in various regions of her body over a very short time. 5 (a) What could she be suffering from? (b) Mention FOUR ways in which the disease identified in (a) is caused and FOUR techniques that can be used to diagnose it.