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CBSE Class 12 Biology Additional Practice Paper 2023-24

CBSE Class 12 Biology Additional Practice Paper 2023-24 has been published on the official website of CBSE @cbse.academic.nic.in. Students can download the questions from CBSE’s website!
authorImageKrati Saraswat9 Feb, 2024
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CBSE Class 12 Biology Additional Practice Questions Paper 2023-24

CBSE Class 12 Biology Additional Practice Paper 2023-24: The Central Board of Secondary Education has issued the CBSE Class 12 Biology Additional Practice Paper 2023-24. This is for students in Class 12 who have chosen science as their main subject. To get this paper, students can visit the official CBSE website at www.cbseacademic.nic.in.

Those getting ready for the CBSE Class 12 Board exam in 2024 are encouraged to use the CBSE Class 12 Biology Additional Practice Paper 2023-24. It's beneficial to thoroughly practise these papers as it helps students become familiar with the recently updated CBSE paper pattern. All students should be aware that starting this session, there won't be term exams, and instead, a single examination will be held by the Central Board.

CBSE Class 12 Biology Additional Practice Paper 2023-24 Overview

The recently published CBSE Class 12 Biology Additional Practice Paper for the academic year 2023-24 covers the entire syllabus. Students preparing for the CBSE Class 12 Biology exam in 2023 can get the biology sample paper from the official CBSE website or read it in our article, where we've included the complete CBSE Class 12 Biology Additional Practice paper with solutions. Now, let's go over some important instructions that students should be aware of before taking the exam.
CBSE Class 12 Biology Additional Practice Paper Download Here
CBSE Class 12 Biology Additional Practice Paper Solution Download Here

The CBSE Class 12 Biology Additional Practice Paper 2023-24 is divided into five sections with 33 questions in total. All 33 questions are mandatory, but some questions offer internal choices. In those cases, students need to attempt only one of the alternatives. The examination will have a duration of 3 hours for students to complete.
  1. In Section A: There are 16 questions Carrying 01 mark each;
  2. In Section B: Consists of 05 questions of 02 marks each;
  3. In Section C: There are 07 questions of 03 marks each;
  4. In Section D: Contains 02 case-based questions of 04 marks each; and
  5. In Section E: Carries 03 questions of 05 marks each;
  6. Wherever necessary, the students are required to draw neat and properly labelled diagrams.
CBSE Sample paper Class 12

CBSE Class 12 Biology Additional Practice Paper 2023-24

Here we have discussed all the questions of the Biology Additional Practice Paper 2023-24 with their solutions.

Section A

Question 1. In the process of making pollen grains, the generative cell splits to create the two male gametes.

What is the ploidy of the generative cell?

  1. n
  2. 2n
  3. 3n
  4. 4
Ans: (a) n Question 2. Kiwi is a dioecious plant. Which of the following methods can be ruled out for sure as a possible way of pollination in its situation? 1. cleistogamous autogamy 2. chasmogamous autogamy 3. geitonogamy 4. xenogamy
  1. Only 1 and 3
  2. Only 1 and 2
  3. Only 2 and 4
  4. Only 1, 2, and 3
Ans: (d) only 1, 2 and 3 Question 3. Arun believes it's hard to find the exact mRNA sequence from the protein sequence. Is he right, and if so, why?
  1. No, as the genetic code is universal.
  2. Yes, as the genetic code is degenerate.
  3. No, as the mRNA is translated into a protein sequence.
  4. Yes, as the mRNA contains introns which are non-coding sequences.
Ans: (b) Yes, as the genetic code is degenerate. Question 4. Crickets are bugs that use XO sex determination. Which of these statements is always correct about this kind of sex determination?
  1. Eggs that have an O chromosome will give rise to a male cricket.
  2. Eggs that have an X chromosome will give rise to a female cricket.
  3. Sperms that have an X chromosome will give rise to a male cricket.
  4. Sperms that have an O chromosome will give rise to a male cricket.
Ans: (d) Sperms that have an O chromosome will give rise to a male cricket. Question 5. Oysters usually come in either dark or light colours. Dark oysters do well in dark places, and light oysters do well in bright places. Oysters with colours in between face difficulties because they don't blend in effectively in either setting.

Which type of natural selection does this phenomenon exemplify?

  1. directional
  2. stabilising
  3. disruptive
  4. (The phenomenon described does not exemplify natural selection.)
Ans: (c) disruptive Question 6. A group of archaeologists discovered the fossilised remains of a creature similar to humans, and it had a brain size of over 700cc. The structure and other findings suggest that this creature was able to use tools for hunting. Which stage of human evolution is this creature NOT from?
  1. Homo erectus
  2. Homo habilis
  3. Neanderthal Man
  4. Australopithecines
Ans: (d) Australopithecines. Question 7. Which of the following statements is RIGHT about how DNA moves on an agarose gel and why?
  1. P
  2. Q
  3. R
  4. S
Ans: (d) S Question 8. What is the LOWEST chance of a dominant trait showing up in the offspring following a test cross?
  1. 25%
  2. 50%
  3. 75%
  4. 100%
Answer: (b) 50% Question 9. What process causes the alcohol percentage in whisky to go up after fermentation?
  1. malting
  2. dilution
  3. distillation
  4. maturation
Ans: (c) distillation.

Section B

Question 10. Kavya mentions that the placenta makes relaxation, and this is important during pregnancy.
  1. Is she correct? Justify.
  2. Name TWO other hormones secreted by the placenta during pregnancy.
Ans: (a) 0.5 marks each for the following: – No, she is not correct. – Relaxin is produced by the ovaries and not the placenta. (b) 0.5 marks each for any two of the following: – human chorionic gonadotropin (hCG) – human placental lactogen (hPL) – estrogens – progestogens Question 11. Thalassemia is a genetic disorder where an individual experiences anaemia. When we look at a blood sample from a person who carries one affected gene, the blood cells appear small, light in colour, and not regularly shaped, alongside the usual red blood cells.
  1. State the genotypic and phenotypic ratios of offspring born to a carrier mother and a thalassemic father.
  2. Does the allele for thalassemia exhibit codominance? Justify.
Ans: (a) 0.5 marks for each of the following: – Genotypic ratio: 1:1 ratio of carriers: affected – Phenotypic ratio: 50% will not show major symptoms while 50% will show the symptoms. (b) 0.5 marks for each of the following: – Yes – Since both proteins are produced/both types of RBCs are visible, it is codominance. [Accept any other valid answer.] Question 12. Explain any TWO reasons why the treatment of AIDS is only partially effective. Ans: 1 mark each of any two of the following: – HIV has a high mutation rate and genetic variability making it difficult to target. – HIV can be latent for more extended periods of time, making it difficult to diagnose the disease. – HIV replicates in immune cells of the human body and targeting them might pose a risk to the individual’s immune system and safety. Question 13. Rati aims to cultivate a type of lactobacillus bacteria in a bioreactor. Lactobacillus is a kind of bacteria that doesn't need oxygen and is often used to start the process in making dairy products. Below is a picture of the bioreactor she has in her lab.
  1. Identify ONE component that should definitely NOT be present in the reactor to grow the lactobacillus spps. Justify.
  2. Explain TWO quantities that the sensors in the bioreactor should monitor.
Ans: (a) 0.5 marks each for the following: – The air inlet/sparger should be absent. – Since lactobacillus is anaerobic, it may not thrive well if oxygen is present. (b) 0.5 marks each for any two quantities such as: – A sensor should monitor temperature as bacteria are likely to die if the temperature fluctuates. – Dissolved oxygen should be measured to ensure anaerobic conditions are maintained. [Accept any other valid answer.]

Section C

Question 14. A biologist observes the cells in a cross-section of the seminiferous tubule and the nearby tissues. The biologist then tallies the different types of cells. Spermatozoa, Spermatid, Primary spermatocyte, Secondary spermatocyte, Leydig cells, Sertoli cells, Spermatogonium. From these cells, identify the cells:
  1. that are diploid.
  2. that can produce hormones and their names.
Ans: (a) 0.5 marks for each type of cell: – Leydig cells – Sertoli cells – Spermatogonium – Primary spermatocyte (b) 0.5 marks for each of the following: – Leydig cells – produces androgens Question 15. A couple is trying to conceive and start a family.
  1. If the lady's monthly period, which comes regularly, is expected to begin on July 19, what was the approximate date when ovulation occurred in the last cycle?
  2. List the four crucial reproductive hormones and mention whether their concentrations will be elevated or reduced on the specified date in (a).
Ans: (a) 5th July (b) 0.5 marks for each for the following: Oestrogen – The highest level Progesterone – The lowest level FSH – The highest level LH – The highest level [Do not award marks if the level is not mentioned.] Question 16.
  1. State any FOUR phenomena in which the Hardy-Weinberg theorem may not hold true.
  2. A group of 100 beings has 0.3 for the A gene and 0.7 for the A gene. The Aa gene mix (heterozygous) happens at 0.49. Is this bunch following the Hardy-Weinberg balance? Explain why or why not.
Ans: (a) 0.5 marks for any FOUR of the following: – gene migration – genetic drift – mutation – genetic recombination – natural selection (b) For the population to be in Hardy-Weinberg equilibrium, the expected frequency of the heterozygous genotype (Aa) has to be Since the frequency of the heterozygous genotype (Aa) is 49%, it deviates from the Hardy-Weinberg equilibrium/the population is not in Hardy-Weinberg equilibrium. [0.5 marks].

Section D

Question 17. Here is a cloning vector 'Z' that Kamla plans to use for making a recombinant vector containing her gene of interest. The vector has spots for three restriction enzymes: ScaI, HindIII, and EcoRI. The gene of interest also has spots for these same enzymes. It has two ‘ori’ sequences, one for replicating in Escherichia coli and another for replicating in Zymomonas mobilis. Additionally, the vector contains two antibiotic resistance genes—one for tetracycline (tet) and another for chloramphenicol (CML).
  1. What are the benefits of having two 'ori' sequences in one vector? Provide a scenario where this would be especially helpful.
OR
  1. If the vector gets sliced with HindIII, what will be found in colonies growing on a medium with tetracycline for sure?
  2. Recommend which of the three restriction enzymes would be appropriate for adding the gene of interest. Provide TWO benefits of using the enzyme you selected.
  3. Mention one drawback of using the two other restriction enzymes not selected in (b).
Ans: (a) 0.5 marks each for the following: – It helps the vector replicate in different hosts. – When putting the genes from bacteria that you're interested in into plant vectors, having origins (ori's) that assist the same genetic structure to copy itself in both bacteria and plants would make the gene cloning process easier. [Accept any other correct response.] OR (a) The vector that hasn't been modified with the gene of interest. [1 mark] [Deduct 0.5 marks if a student describes the relegated vector without including a gene of interest]. (b) EcoRI would be ideal to use [1 mark] 0.5 marks each for any TWO advantages such as: – It has only one restriction site, so you'll get either the product with the gene of interest or without it, and there won't be multiple products. – The site where restriction occurs is located in the chloramphenicol resistance gene. When it becomes inactive due to insertion, it aids in choosing recombinant vectors. [Feel free to suggest any other correct alternative.] (c) Using ScaI and/or HindIII might create several end products or fragments, making it challenging to choose the recombinant vector. Question 18. The wild cat in the picture, called Predator Y, lives in the forests and mainly hunts prey X, which are plant-eating animals. The information below displays their population changes over time.
  1. What could be the reason for the pattern observed in the populations of prey and predators over the years?
  2. If, let's say, all the predators in the forests disappear, what would happen to the plants in the forest?
  3. Imagine a scenario where a different kind of predator species moves into the forest. What is expected to occur over time and why?
Ans: (a) 0.5 marks each for the following: – As prey X is the main food for prey Y, when the number of prey goes up, the number of predators also increases. – More predators consume the prey causing the prey population to drop. – When the number of prey goes down, predators don't have sufficient prey, causing their population to decrease as well. – When this happens, the prey population increases again. (b) The vegetation will also slowly disappear. (c) 0.5 marks each for the following: – Both types of animals will vie for the same food, and the weaker one may be removed over a period. – As they both eat the same prey, there's not enough for both, leading to the removal of the weaker predator. [Feel free to offer any acceptable alternative.] OR Juglone is a substance made by the black walnut tree in various parts of itself. When the tree drops, this substance goes into the ground. It causes a lot of other plants near the black walnut to die. Determine the kind of interaction happening between the black walnut and the nearby plants. Explain why. Ans: 0.5 marks each for the following: – amensalism – The black walnut is neither harmed nor benefitted while the plants surrounding it are harmed.

Section E

Question 19. A Non-Government Organisation (NGO) aims to increase awareness against STDs.
  1. What could be the ideal target age group for the NGO?
  2. List two possible enduring health issues that can arise from untreated STDs, which the NGO should inform the target age group about.
  3. Mention ONE contraceptive method that provides protection against the STD. Justify.
  4. Mention TWO birth control methods that don't guard against STDs, which they can inform the group about.
Ans: (a) 15-24 years [Accept any other valid answer that includes a nearby age group] (b) 1 mark each for the following: – Chronic pain and discomfort in various body organs – Infertility in some STDs – Lower immunity levels and increased risk of other infections – Higher risk of transmitting the diseases to others. [Accept any other valid answer] (c) 0.5 marks each for the following: – condoms – They act as a barrier preventing the mixing of body fluids. (d) 0.5 marks each for any two of the following: – Oral Contraceptive Pills – Vasectomy or Tubectomy – IUDs OR Amey and Lalita are looking forward to their first baby. Lalita is two months pregnant, and everything seems fine so far. Amey's family has a background of cystic fibrosis, and Lalita's family has a history of Down's syndrome. This raises some worry that the baby might have one of these conditions.
  1. Suggest and explain a way of testing if their baby is at risk for any genetic disorders.
  2. If there are any abnormalities present that could be risky for the mother's health, suggest one option for them to think about.
  3. Is the process mentioned in (b) safe for Lalita at the current gestational age? Justify.
  4. Under what conditions is the process mentioned in (b) illegal?
Ans: (a) Amniocentesis – It involves taking a sample of the amniotic fluid and testing it for genetic abnormalities. [0.5 marks each for suggesting the name of the method and explaining it] (b) Medical Termination of Pregnancy (MTP) (c) Yes, it is currently safe [1 mark] This option should be considered before the completion of the first trimester, as it might be riskier after this period. [1 mark] (d) MTP is illegal in cases involving determining the gender of the unborn child and female foeticide. Question 20. Below is a family tree of a person named X dealing with eye albinism, causing lasting vision problems. Use the family tree to respond to the upcoming questions. a. Complete the following statement about this disease: The trait for the disease is linked to ___________ (X-chromosome/Ychromosome/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. Ans: (a) 0.5 marks each for the following: 1.0 – X-chromosome – recessive (b) 1 mark each for the following: – It happens in both guys and girls, but it's more common in guys, where only one X chromosome is needed for the trait to show up. – The trait shows up in only a few kids or a small group, so it's probably a recessive trait. [Accept any other valid answer.] (c) 0.5 marks each for the following: – P: XY – Q: X0X – R: X0X – S: XY OR Shown below is a nucleotide sequence and the genetic code. 5′ – ATGCGTAGACTCGTA – 3′
  1. Find the protein sequence created by this set of codes.
  2. Sketch the tRNA structure for the third codon and mark its direction. Explain why the direction is chosen.
  3. The initial guanine in the genetic code turns into cytosine. Determine the mutation type resulting from this alteration.
  4. Will the mutated sequence form an mRNA and protein? Justify.
Ans: (a) TYR ALA SER GLU HIS [1 mark] (b) Correct drawing with anticodon 3′ -AGA – 5′ [1 mark] Reason: The mRNA sequence is translated in the 5′ to 3′ direction so the anticodon has to be in the 3′ to 5′ direction [1 mark]. (c) point mutation [0.5 marks]. (d) 0.5 marks each for the following: – mRNA will be formed – protein will not be formed – The first codon is a stop codon due to which translation will not happen.
Cheat Sheets of CBSE Class 12
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CBSE Class 12 Biology Additional Practice Paper 2023-24 FAQs

Can practising with the paper improve my exam performance?

Yes, regular practice with the questions can significantly boost your confidence and improve your overall performance in the board exams.

Are there success stories from students who used the practice paper?

Yes, the blog includes testimonials and success stories, showcasing how students have benefited from the additional practice questions.

Can I find explanations for the answers in the practice paper?

Yes, detailed explanations for each question are provided, allowing you to understand the concepts and reasoning behind the correct answers.

How can I analyse my mistakes effectively?

The blog offers guidance on analysing mistakes, emphasising the importance of understanding the root cause and learning from them.

Is it advisable to take regular mock tests?

Absolutely, incorporating regular mock tests into your study routine helps simulate exam conditions and enhances your exam-taking skills.
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