2019 Biology Paper 1 - Theory Exam
Complete Biology Paper 1 (Theory) examination paper from 2019 with questions covering genetics, molecular biology, ecology, evolution, and biotechnology. Includes Part I (20 marks) and Part II with Sections A, B, and C (50 marks total).
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Complete solution guide for ISC Biology 2026 examination
Created by Titas Mallick
Biology Teacher • M.Sc. Botany • B.Ed. • CTET (CBSE) • CISCE Examiner
Complete biology theory examination paper with 70 marks, covering genetics, ecology, reproduction, biotechnology, and evolution topics across multiple sections
Maximum Marks: 70
Time allowed: Three hours
(Candidates are allowed additional 15 minutes for only reading the paper. They must NOT start writing during this time.)
This paper comprises TWO PARTS - Part I and Part II.
Answer all questions.
Internal choices have been provided in two questions in Section A, two questions in Section B and in all three questions of Section C.
The intended marks for questions or parts of questions are given in brackets [ ].
Answer all questions.
(a) Answer the following questions briefly and to the point: [8×1]
(i) How many chromosomes are present in male gamete of a rat?
(ii) Why is haemophilia uncommon in females?
(iii) Name the disease-resistant variety of cowpea developed by plant breeding technique.
(iv) Define Brood parasitism.
(v) Name the vegetative propagule of Bryophyllum.
(vi) Which geological era was dominated by reptiles?
(vii) Define polygenic inheritance.
(viii) What is Dobson unit?
(b) Each of the following sub-parts, (i) to (iv) has four choices. Choose the best option in each case: [4×1]
(i) If 10 individuals in a laboratory population of 100 mice die during the period of one year, the death rate in this population will be:
(ii) The flowers which open their petals to expose their reproductive parts to allow pollination are called:
(iii) Which of the following is paired incorrectly:
(iv) The pathogen which causes Syphilis:
(c) Give one significant contribution of each of the following scientists: [2×1]
(i) F. Griffith
(ii) P. Ehrlich
(d) Expand the following: [2×1]
(i) IUI
(ii) ADA
(e) Define the following: [2×1]
(i) Biopiracy
(ii) Aneuploidy
(f) Give a reason for each of the following: [2×1]
(i) Cyanobacteria increase the productivity in paddy fields.
(ii) The shape of the pyramid of biomass in an aquatic ecosystem is inverted.
Answer all questions
Give one significant difference between the following:
(i) Linkage and crossing over
(ii) Transition and transversion
Study the graph given below and answer the questions that follow:
Population Density (N)
^
| b
| /\
| / \
| / \
| / \
|/ \
|----------\---------- (dotted line)
| \
| \
| \a
| \
+-----------------> Time (T)(i) In the absence of predators which one of the two curves would appropriately depict the prey population? Give a reason.
(ii) Time has been shown on X-axis and there is a parallel dotted line shown above. Explain the significance of this dotted line.
What is biogas? Name any two main constituents of biogas.
Explain two characteristics of cancer cells.
(a) Draw a labelled diagram of a germinating pollen grain with at least four labellings.
OR
(b) Draw a labelled diagram of a mature human ovum with at least four labellings.
What is outbreeding? How is it useful in animal breeding?
(a) What is biomagnification? Write two effects of biomagnification.
OR
(b) Write a short note on the contribution of Ahmed Khan of Bangalore.
Give three adaptations in organisms by which they avoid predation.
Answer all questions
(a) Define decomposition. Explain main steps involved in the process of decomposition.
OR
(b) Write three causes and three effects of cultural eutrophication.
(i) Write two differences between homologous organs and analogous organs.
(ii) Give one example of homologous organs and one example of analogous organs found in plants.
Describe the process of double fertilization in angiosperms. What is its significance?
What is a bioreactor? Explain important features of a Stirred tank bioreactor.
Give three significant differences between asexual reproduction and sexual reproduction.
(a) Explain the process of spermatogenesis in humans.
OR
(b) Give an account of hormonal control of oogenesis.
Answer all questions
(a) Explain the various steps involved in Recombinant DNA technology.
OR
(b) Explain the steps involved in the production of human insulin by Recombinant DNA technology.
(a) (i) Give an account of Meselson and Stahl's experiment. (ii) What is the significance of Meselson and Stahl's experiment?
OR
(b) (i) Describe the Oparin Haldane Theory of origin of life. (ii) The tadpole larva of amphibians resembles fishes. How does this observation support evolution?
(a) Draw a labelled diagram to show the life cycle of Plasmodium.
OR
(b) Draw a labelled diagram to show replication of HIV in human cells.
/Previous-Year-Questions/ISC/exam-questions/biology_paper_2020.mdx2019 Biology Paper 1 - Theory Exam
Complete Biology Paper 1 (Theory) examination paper from 2019 with questions covering genetics, molecular biology, ecology, evolution, and biotechnology. Includes Part I (20 marks) and Part II with Sections A, B, and C (50 marks total).
ISC Biology 2026 — Questions and Answers
Complete solution guide for ISC Biology 2026 examination