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Biology · 2019

CBSE Class 12 Biology 2019 — Previous-Year Question Paper

CBSE Class XII Board 2019 · Set 57/2/1

Real board examination⚠ Old pattern · pre-2020 syllabus
Sets

This paper has 6 questions on a topic removed in CBSE’s 2023-24 syllabus update (each marked Not in syllabus). It’s kept for historical accuracy — the exam really asked it that year — but isn’t in the current syllabus and doesn’t count toward a concept’s importance. Switch to to focus on what’s still examinable.

About this paper

The real Class-12 board examination held in 2019. Every question below is solved the concept-first way. Sample papers are labelled honestly — never shown as a past exam.

Total marks
70
Questions
27
Duration
180 min
Sections
4

The marks / questions / duration above are the official exam pattern. We currently have 27 of this paper’s questions (100% of the full paper), with 27 fully solved. Questions we couldn’t yet extract or verify are held — never shown as complete.

Sections & marks

SectionTypeQuestionsMarks eachTotal
ASection AVery short answer515
BSection BShort answer I7214
CSection CShort answer II12336
DSection DLong answer3515
Total2770

The question paper

The questions we hold for this paper, laid out by section. Solutions are on the Answers tab.

Board Examination

Biology

CBSE Class XII Board 2019 · Set 57/2/1

Series/Set: 57/2/1Roll No. ________
Time Allowed: 3 hoursMaximum Marks: 70

General Instructions

  1. This question paper contains 27 questions divided into 4 sections — A, B, C, D.
  2. Section A comprises 5 questions of 1 mark each (Very short answer).
  3. Section B comprises 7 questions of 2 marks each (Short answer I).
  4. Section C comprises 12 questions of 3 marks each (Short answer II).
  5. Section D comprises 3 questions of 5 marks each (Long answer).

Above is the official exam pattern. The questions printed below are those we currently hold for this paper.

Section A

Very short answer · 1 mark each · 5 of 5 shown

Q1.
Give one reason to justify statutory ban on amniocentesis.
[1]
Q2.
Name a human genetic disorder due to the following :
  • (a) An additional X-chromosome in a male
  • (b) Deletion of one X-chromosome in a female
(OR)
State what does aneuploidy lead to.
[1]
Q3.
Mention one example each from plants and animals exhibiting divergent evolution.
[1]
Q4.
Name any two physiological barriers that provide innate immunity.
(OR)
Select two disease resistant crop varieties from the list of crop varieties given below : Himgiri, Pusa Gaurav, Pusa Komal, Pusa A-4
[1]
Q5.
Give two reasons as to why a weed such a Calotropis flourishes in abandoned fields.
⚠ This question is not in the current syllabus — Organism and its Environment (Adaptations) (removed 2023-24)
[1]
Page 1 of 5
Section B

Short answer I · 2 marks each · 7 of 7 shown

Q1.
Mosses and frogs both need water as a medium for fertilisation. Where does syngamy occur and how is it ensured in both these organisms ? OR Write the basis of categorising animals as oviparous or viviparous, giving one example of each.
⚠ This question is not in the current syllabus — Reproduction in Organisms (removed 2023-24)
[2]
Q2.
(a) You are given castor and bean seeds. Which one of the two would you select to observe the endosperm ? (b) The development of endosperm precedes that of embryo in plants. Justify.
[2]
Q3.
A segment of DNA molecule comprises of 546 nucleotides. How many cytosine nucleotides would be present in it if the number of adenine nucleotides is 96 ?
[2]
Q4.
How is 'somatic hybridization' carried out ? Mention one example of a somatic hybrid.
⚠ This question is not in the current syllabus — Strategies for Enhancement in Food Production (removed 2023-24)
[2]
Q5.
How are DNA fragments visualised during gel-electrophoresis ? What is elution ?
[2]
Q6.
A corn farmer has perennial problem of corn-borer infestation in his crop. Being environmentally conscious he does not want to spray insectides. Suggest solution based on your knowledge of biotechnology. Write the steps to be carried out to achieve it.
[2]
Q7.
State 'two' observations made by German naturalist, Alexender von Humboldt during his extensive explorations in South American jungles. OR If in a population of size 'N' the birth rate is represented as 'b' and the death rate as 'd', the increase or decrease in 'N' during a unit time period 't' will be : dN/dt = (b – d)N The equation given above can also be represented as : dN/dt = rN, where r = (b – d) What does 'r' represent ? Write any one significance of calculating 'r' for any population.
[2]
Page 2 of 5
Section C

Short answer II · 3 marks each · 12 of 12 shown

Q1.
When and where do tapetum and synergids develop in flowering plants ? Mention their functions. OR Where are the following structures present in a male gametophyte of an angiosperm ? Mention the function of each one of them. (a) Germ pore (b) Sporopollenin (c) Generative cell
[3]
Q2.
Construct a flow chart exhibiting sequential events of oogenesis.
[3]
Q3.
Draw L.S. of an embryo of grass and label its parts. OR Draw a diagrammatic sectional view of a seminiferous tubule (enlarged) in humans and label its parts.
[3]
Q4.
(a) How does mutation occur ? (b) Differentiate between point mutation and frameshift mutation.
[3]
Q5.
''Use of heavy isotope of nitrogen by Meselson and Stahl demonstrated semi-conservative mode of replication of a DNA molecule.'' Explain how did they arrive at this conclusion. OR Explain the mechanism of translation that occurs in the ribosomes in a prokaryote.
[3]
Q6.
According to Darwinian theory of natural selection the rate of appearance of new forms is linked to the life-cycle or the life-span of an organism. Explain with the help of an example.
[3]
Page 3 of 5
Q7.
(a) Name the causative agents of pneumonia and common cold. (b) How do these differ in their symptoms ? (c) Mention two symptoms common to both. OR (a) Write the scientific names of the causative agent and vector of malaria, and write its symptoms. (b) Name any two diseases spread by Aedes sp.
[3]
Q8.
(a) Differentiate between inbreeding and outbreeding. (b) List any three advantages and one important disadvantage of inbreeding practice in animal husbandry.
⚠ This question is not in the current syllabus — Strategies for Enhancement in Food Production (removed 2023-24)
[3]
Q9.
Name the most commonly used bioreactor in biotechnology labs. Mention the most essential components this bioreactor must have so as to provide the optimum conditions to the culture medium, resulting in production of large volume of desired product.
[3]
Q10.
A child is born with ADA-deficiency. (a) Suggest and explain a procedure for possible life-long (permanent) cure. (b) Name any other possible treatment for this disease.
[3]
Q11.
Differentiate between an 'Expanding age pyramid' and a 'Stable age pyramid'. Substantiate your answer with diagrams.
[3]
Q12.
Analyse the effects of 'Alien species invasion' on the biodiversity of a given area. Provide two examples.
[3]
Page 4 of 5
Section D

Long answer · 5 marks each · 3 of 3 shown

Q1.
Mendel crossed a homozygous pea plant having yellow and round seeds with another pea plant bearing green and wrinkled seeds. He found that in some of the F2 population new combination of parental characters were observed. How will you explain the appearance of a new combination of parental characters in F2-offsprings ? Support your answer with the help of Punnett square. OR Describe S.L. Miller's experiment. Comment on the observations he made and his contribution towards the origin of life on Earth.
[5]
Q2.
(a) Differentiate between active and passive immunity. (b) Comment on the role of vaccination and immunization in keeping human population healthy. OR Describe the process of secondary treatment given to municipal waste water (sewage) before it can be released into fresh waterbodies. Mention another benefit provided by this process.
⚠ This question is not in the current syllabus — Environmental Issues (removed 2023-24)
[5]
Q3.
A plastic sack manufacturer in Bengaluru, Ahmed Khan has managed to find an ideal solution to the problem of plastic waste. Explain in five steps the efforts of Ahmed Khan to meet the challenges of solid waste management. OR (a) What does an ecological pyramid represent ? State any two limitations that these pyramids have. (b) Describe an inverted pyramid of biomass with the help of an example.
⚠ This question is not in the current syllabus — Environmental Issues (removed 2023-24)
[5]
Page 5 of 5