ISC Class 12 Biology Half Yearly Sample Paper 2025: Download PDF for FREE

Board

ISC

Class

12

Subject

Biology

Full Marks

70

Total Section

Section A, B, C & D

Exam Duration

3 Hours 15 Mins

Question 1 : Answer the following questions briefly.

(i) The types of gametes formed by the genotype RrYy are__,__,__,__ [1]    

(ii) Arrange the following terms in the correct developmental sequence: [1]  

(iii) Define spermiogenesis. [1]

(iv) According to Darwin, reproductive fitness helps organisms to better fit in an environment and  leave more progeny than others (True/False). [1]  

(v) A chimpanzee can hold objects with its hand whereas the elephant can hold the object by its  trunk. How would you classify the organs--hand and trunk based on evolution ? [1]    

(vi) In the blue and white selection method, a fluorescent substrate is used to differentiate  recombinant cells. (Rewrite the statement by changing the underlined word). [1]  

(vii) Give the scientific term for the proteins secreted by virus-infected cells. [1]

(viii) How many chromosomes are present in the egg and Primary Endosperm Nucleus of a plant  which has 32 chromosomes in its sporogenous cell. [1]  

(ix) Dragon flies are employed as biocontrol agents to get rid of: [1]  

(a) Aphids  

(b) Mosquitoes  

(c) Caterpillar of butterflies  

(d) Cotton bollworms  

(x) A biologist studied the population of rats in a barn. He found that the average mortality 120,  average natality 130, immigration 20 and emigration 30. The net increase in the rat population  mentioned above is: [1]  a) 20 b) 10 c) 5 d) Zero

(xi) Answer the following questions: [2]  

(a) In DNA structure G is always equal to C and A is always equal to T, this concept was  given by which Scientist?  

(b) Expand -IMR  

(xii) Assertion: The inner cell mass of blastocyst gets attached to the endometrium during  embryonic development in humans. [1]  Reason: The blastomeres in the blastocyst gets arranged into trophoblast and inner cell  mass.  

(a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion 

(b) Both Assertion and Reason are true, but Reason is not the correct explanation of  Assertion.  

(c) Assertion is true but Reason is false.  

(d) Both Assertion and Reason are false.  

(xiii) A DNA molecule is 160 base pairs long. It has 30 %Guanine. How many Adenine bases are  present in this DNA molecule: [1]  

(a) 48  

(b) 64  

(c) 96  

(d) 32

(xiv) Observe the diagram and identify the type of evolution shown in it. [1]

(xv) Identify the structure. Name the hormone secreted by it. [1]

(xvi) State two characteristics of Cro- Magnon man. [1]    

(xvii) A human protein alpha -1 antitrypsin is used for the treatment of __________. [1]

(xviii) Give a reason for each of the following. [2]  

(a) Once a person starts taking alcohol or drugs, it is difficult to get rid of this habit.

(b) Cleistogamy favours autogamy.

Question 2 : In a population that is in Hardy Weinberg equilibrium, the frequency of the recessive homozygous  genotype of a certain trait is 0.16. What is the percentage of individuals homozygous for the dominant  allele?

Question 3 : Expand GEAC. Give it two roles.

Question 4 : Study the given pedigree chart and answer the questions that follow:  

(a) Is the trait recessive or dominant?

(b) Is the trait sex linked or autosomal?  

(c) Give the genotype of the parents shown in generation I and of the third and fourth child in   generation II. 

Question 5 : (a) Discuss gene therapy -with reference to ADA disease.  

OR  

(b) Give the objectives of developing Transgenic organisms.

Question 6 : Draw a well labelled diagram of an antibody.

Question 7 : Enlist any two narrowly utilitarian and broadly utilitarian of species diversity to the ecosystem.

Question 8 : The following graph is of relative concentrations of the four hormones present in the blood plasma of  a woman during her menstrual cycle. Identify the hormones A, B, C &D.  

Question 9 : Many plant and animal species are on the verge of extinction because of loss of forest land by  indiscriminate use by humans. As a biology student, what methods you would suggest along with  its advantages that can protect such threatened species from getting extinct.

Question 10 : Give the scientific name of the causative agent and a symptom of each of the following diseases:  Typhoid, Dengue, Filariasis.

Question 11 : Describe Hershey and Chase experiment. Write the conclusion drawn by the Scientists after their  experiment.

Question 12 : (a) How does Modern synthetic theory explain evolution of new species?  

(b) Differentiate between substitution and frame shift mutation.

Question 13 : Explain the process of spermatogenesis.

Question 14 : (a) How Insulin is prepared by rDNA technology? Enlist its steps. 

 OR  

(b) Describe RNAi (interference)with reference to Meloidogyne incognita

Question 15 : Study the graph given below and answer the questions that follows:  

 (i) Write the status of food and space in the curves A and B.  

(ii) In the absence of predators, which one of the two curves would approximately depict the prey  population ?  

(iii) Time has been shown on the X axis and there is a parallel dotted line above it. Give the significance  of this dotted line.

Question 16 : Describe the events that take place from time of entry of human sperm into the ovum till fertilisation is  complete

Question 17 : Answer the following questions:  

(i) 1. Give the common and scientific name of the plant shown above.

2. Name the drug obtained from the plant shown above.  

(ii) Arun has become a habitual drinker. As a friend, make him aware of its ill effects on his health  (mention any two).  

(iii) Differentiate between cannabinoids and barbiturates.  

(iv) Despite the statutory warning on cigarette packets against smoking and its injurious effect on  health, smoking is more prevalent in society. Enumerate two important health hazards to a smoker.

Question 18 : (a) (i) What is central Dogma?  

(ii) How does replication of the DNA molecule occur? Explain the mechanism.  

OR  

(b) (i) What are the properties of genes?  

(ii) Describe the experiment that helped demonstrate the semi conservative mode of DNA  replication.

CHECK:ISC Class 12 Biology Half Yearly Sample Paper 2025, Download PDF