Class 12 ISC Biology Answer Key 2025 (Available) Live Updates: Unofficial key PDF download
For all the short-answer questions, Class 12 ISC Biology Answer Key 2025 is provided here across all set codes. Biology ISC Class 12 Exam 2025 was held on March 21.
Class 12 ISC Biology Answer Key 2025: The ISC Biology 2025 Class 12 test is set for March 21, 2025. Candidates who took the Class 12 ISC Biology 2025 exam can view the answer key by clicking this link. In particular, the CollegeDekho specialist has included the accurate Class 12 ISC Biology answers for Section A to determine the candidates' total possible marks in this part and to determine the right responses to the one-mark questions. Furthermore, keep in mind that wrong or unattempted answers will not result in a negative grade.
Also Read | Class 12 ISC Result Expected Release Date 2025
Class 12 ISC Biology Answer Key 2025
The test takers waiting to know the Class 12 ISC Biology answers can check their performance level in the exam. Check out the Class 12 ISC Biology unofficial answer key for the short questions here.
Section A: 1-2 Mark Questions
| Question Number | Correct Answers |
| Q1 (i) A sportsperson quenched his thirst by drinking some tender coconut water. Name the part of the fruit from where the liquid content is derived. | The liquid content is derived from the endosperm of the coconut fruit. |
| Q1 (ii) In a particular ecosystem, there were 1000 species at a given time. After 5 years, 200 more species were added. Calculate the growth rate of the population. | The growth rate of the population is 20% (200/1000). |
| Q1 (iii) Rachel attained puberty at the age of fourteen years. She conceived for the first time at the age of thirty years. How many primary oocytes did she lose till the time of conception? | Rachel lost approximately 620-630 primary oocytes till the time of conception (assuming 1-2 oocytes lost per month from puberty to conception). |
| Q1 (iv) How many nuclei are present in the central cell of the mature embryo sac of angiosperms before fertilisation? | There are 2 polar nuclei present in the central cell of the mature embryo sac of angiosperms before fertilisation. |
| Q1 (v) (v) A woman's first child suffered from Down's syndrome. During her second pregnancy, she wanted to find out whether her second child would be normal or not. Which method will the gynaecologist adopt to test the genetic abnormality in the embryo? | The gynaecologist will adopt Amniocentesis to test the genetic abnormality in the embryo. |
| Q1 (vi) Derive a name for a restriction endonuclease that was extracted in the 5th order from the RY13 strain of E. coli. | The name of the restriction endonuclease would be EcoRY13I, where "Eco" represents E. coli, "RY13" represents the strain, and "I" indicates it's the 5th enzyme extracted (Roman numeral for 5 would be "V", but restriction enzymes usually use "I", "II", "III", etc.). |
| Q1 (vii) A pistillate flower of a tetraploid angiosperm is pollinated by a pollen grain from a staminate flower of a diploid plant. What would be the level of the ploidy in the endosperm of seeds thus formed? | The ploidy level of the endosperm would be pentaploid (5n), as it results from the fusion of a diploid (2n) sperm and two tetraploid (4n) polar nuclei. |
| Q1 (viii) Observe the relationship between the first two words / terms and then fill in the fourth word/ term. Lipase: Candida lipolytica :: Taq polymerase: ________. | The answer is Thermus aquaticus. The relationship is that the first word is an enzyme, and the second word is the organism from which it is obtained. |
| Q1 (ix) The capacitation of sperms plays a significant role in the process of fertilisation in humans. Which of the following events are associated with the process of capacitation? I. Large quantity of Cat+2 ions enter the sperm to enhance the permeability of the acrosome. II. Antifertilisin reacts with the fertilisin protein. III. Membrane covering the sperm head and acrosome gets removed. (a) I and II only (b) I and III only (c) II and III only (d) I, II, and III | (b) I and III only |
| Q1 (x) What is the purpose of the Red Data Book? (a) To list the endangered species (b) To promote sustainable development (c) To check the growth of the animal species (d) To identify areas for conservation | (a) To list the endangered species |
| Q1 (xi) Given below are two statements marked Assertion and Reason. Read both the statements carefully and choose the correct option. Assertion: The eyes of octopus and horse are evidence of convergent evolution. Reason: Eyes of both the organisms have the same structure and serve the same function. (a) Both Assertion and Reason are true and Reason is the correct explanation for Assertion. (b) Both Assertion and Reason are true but Reason is not the correct explanation for Assertion. (c) Assertion is true and Reason is false. (d) Both Assertion and Reason are false. | (c) Assertion is true and Reason is false. |
| Q1 (xii) Given below are two statements marked Assertion and Reason. Read both the statements carefully and choose the correct option. Assertion: In a pond ecosystem, pyramid of biomass shows a sharp decrease in the biomass at higher trophic levels. Reason: Primary producers convert only 10% of the energy of sunlight into net primary productivity. (a) Both Assertion and Reason are true and Reason is the correct explanation for Assertion. (b) Both Assertion and Reason are true but Reason is not the correct explanation for Assertion. (c) Assertion is true and Reason is false. (d) Both Assertion and Reason are false. | (c) Assertion is true and Reason is false. |
| Q1 (xiii) A forest has a GPP of 20,000 kcal/m²/year, and 40% of this energy is used for respiration. Calculate the amount of energy available as NPP. | NPP = 12,000 kcal/m²/year. |
| Q1 (xiv) Ryan used a synthetic hair dye to colour his hair. Within a day of dyeing, red rashes appeared on his face causing constant itching. What condition do these symptoms indicate? | Allergic contact dermatitis |
| Q1 (xv) Answer the following questions. (a) Name the scientist who is considered the Father of Indian Ecology. (b) Expand the abbreviation SSBP. | (a) Dr. Ramdeo Misra (b) Solid State Biochemistry |
| Q1 (xvi) A transformed bacterial cell contains a transgene that can produce one molecule of protein 'X' per cell. This bacterium duplicates every 20 minutes. It is cultured in a nutrient medium for 3 hours. How many molecules of protein 'X' will be produced by the end of the culture? | X = 512 |
| Q1 (xvii) Which drug is extracted from the leaves shown in the image shown below? | Cannabis |
| Q1 (xviii) Give a reason for the following. (a) The period of lactational amenorrhoea is marked by the absence of menstruation. | (a) Breastfeeding delays the resumption |
Class 12 ISC Biology Exam Analysis 2025 Link
The candidates can also find out the Class 12 Biology exam analysis 2025 here, which has been made based on the student's feedback.
Class 12 ISC Subject-Wise Answer Key 2025 |
| Name of Subject | Answer Key 2025 Links |
| English Language | Class 12 ISC English Language Answer Key 2025 |
| English Literature | Class 12 ISC English Literature Answer Key 2025 |
| Economics | Class 12 ISC Economics Answer Key 2025 |
| Chemistry | Class 12 ISC Chemistry Answer Key 2025 |
| Mathematics | Class 12 ISC Mathematics Answer Key 2025 |
| Business Studies | Class 12 ISC Business Studies Answer Key 2025 |
| Physics | Class 12 ISC Physics Answer Key 2025 |
| Commerce | Class 12 ISC Commerce Answer Key 2025 |
| Accounts | Class 12 ISC Accounts Answer Key 2025 |
| Biology | Class 12 ISC Biology Answer Key 2025 |
Class 12 ISC Biology Answer Key 2025 Live Updates
Mar 21, 2025 11:00 PM IST
ISC Class 12 Biology Answer Key 2025: Section A Question 1 (ix) Answer
Ques: The capacitation of sperms plays a significant role in the process of fertilisation in humans. Which of the following events are associated with the process of capacitation?
I. Large quantity of Cat+2 ions enter the sperm to enhance the permeability of the acrosome.
II. Antifertilisin reacts with the fertilisin protein.
III. Membrane covering the sperm head and acrosome gets removed.
(a) I and II only
(b) I and III only
(c) II and III only
(d) I, II, and IIIAns: (b) I and III only
Mar 21, 2025 10:40 PM IST
ISC Class 12 Biology Answer Key 2025: Section A Question 1 (viii) Answer
Ques: Observe the relationship between the first two words / terms and then fill in the fourth word/ term.
Lipase: Candida lipolytica :: Taq polymerase: ____.Ans: The answer is Thermus aquaticus. The relationship is that the first word is an enzyme, and the second word is the organism from which it is obtained.
Mar 21, 2025 10:20 PM IST
ISC Class 12 Biology Answer Key 2025: Section A Question 1 (vii) Answer
Ques: A pistillate flower of a tetraploid angiosperm is pollinated by a pollen grain from a staminate flower of a diploid plant. What would be the level of the ploidy in the endosperm of seeds thus formed?
Ans: The ploidy level of the endosperm would be pentaploid (5n), as it results from the fusion of a diploid (2n) sperm and two tetraploid (4n) polar nuclei.
Mar 21, 2025 10:00 PM IST
ISC Class 12 Biology Answer Key 2025: Section A Question 1 (vi) Answer
Ques: Derive a name for a restriction endonuclease that was extracted in the 5th order from the RY13 strain of E. coli.
Ans: The name of the restriction endonuclease would be EcoRY13I, where "Eco" represents E. coli, "RY13" represents the strain, and "I" indicates it's the 5th enzyme extracted (Roman numeral for 5 would be "V", but restriction enzymes usually use "I", "II", "III", etc.).
Mar 21, 2025 09:40 PM IST
ISC Class 12 Biology Answer Key 2025: Section A Question 1 (v) Answer
Ques: A woman's first child suffered from Down's syndrome. During her second pregnancy, she wanted to find out whether her second child would be normal or not. Which method will the gynaecologist adopt to test the genetic abnormality in the embryo?
Ans: The gynaecologist will adopt Amniocentesis to test the genetic abnormality in the embryo.
Mar 21, 2025 09:20 PM IST
ISC Class 12 Biology Answer Key 2025: Section A Question 1 (iv) Answer
Ques: How many nuclei are present in the central cell of the mature embryo sac of angiosperms before fertilisation?
Ans: There are 2 polar nuclei present in the central cell of the mature embryo sac of angiosperms before fertilisation.
Mar 21, 2025 09:00 PM IST
ISC Class 12 Biology Answer Key 2025: Section A Question 1 (iii) Answer
Ques: Rachel attained puberty at the age of fourteen years. She conceived for the first time at the age of thirty years. How many primary oocytes did she lose till the time of conception?
Ans: Rachel lost approximately 620-630 primary oocytes till the time of conception (assuming 1-2 oocytes lost per month from puberty to conception).
Mar 21, 2025 08:40 PM IST
ISC Class 12 Biology Answer Key 2025: Section A Question 1 (ii) Answer
Ques: In a particular ecosystem, there were 1000 species at a given time. After 5 years, 200 more species were added. Calculate the growth rate of the population.
Ans: The growth rate of the population is 20% (200/1000).
Mar 21, 2025 08:20 PM IST
ISC Class 12 Biology Answer Key 2025: Section A Question 1 (i) Answer
Ques: A sportsperson quenched his thirst by drinking some tender coconut water. Name the part of the fruit from where the liquid content is derived.
Ans: The liquid content is derived from the endosperm of the coconut fruit.
Mar 21, 2025 08:00 PM IST
ISC Class 12 Biology Answer Key 2025: Student Reviews March 21, 2025, 20 PM
Some students opined that the paper was of moderate difficulty, with Section A being the easiest among all. The questions were from the syllabus only, and came from the previous year's question paper. The paper was a little time-consuming but could be managed.
Mar 21, 2025 07:40 PM IST
ISC Class 12 Biology Answer Key 2025: Was the paper time-consuming?
As per the student reviews, the paper was a little time-consuming.
Mar 21, 2025 07:20 PM IST
ISC Class 12 Biology Answer Key 2025: Expected Good Score
According to the candidates, the overall expected good score can be 50+.
Mar 21, 2025 07:00 PM IST
Class 12 ISC Biology Answer Key 2025: Which was the lengthiest section?
Based on the initial feedback, the lengthiest section in the question paper was Section D.
Mar 21, 2025 06:45 PM IST
Class 12 ISC Biology Answer Key 2025: Difficulty Level of Section D
Based on the initial feedback, the difficulty level of Section D is Moderate.
Mar 21, 2025 06:30 PM IST
Class 12 ISC Biology Answer Key 2025: Difficulty Level of Section C
Based on the initial feedback, the difficulty level of Section C is Moderate.
Mar 21, 2025 06:15 PM IST
Class 12 ISC Biology Answer Key 2025: Difficulty Level of Section B
Based on the initial feedback, the difficulty level of Section B is Moderate.
Mar 21, 2025 06:00 PM IST
Class 12 ISC Biology Answer Key 2025: Difficulty Level of Section A
Based on the initial feedback, the difficulty level of Section A is Easy to Moderate.
Mar 21, 2025 05:45 PM IST
Class 12 ISC Biology Answer Key 2025: Overall Difficulty Level of the Paper
Based on the initial feedback, the overall difficulty level of the paper is Moderate.
Mar 21, 2025 05:30 PM IST
Class 12 ISC Biology Answer Key 2025 to be Updated Soon!
The unofficial Class 12 ISC Biology Answer Key 2025 for the Section A questions will be provided shortly as the exam has now concluded. The CollegeDekho team is now collecting the question papers to prepare the answer key.
Mar 21, 2025 05:15 PM IST
Class 12 ISC Biology Exam 2025: Student Reviews
As per the first-hand reviews available from the students who have just departed from the exam hall, the Class 12 ISC Biology exam 2025 was moderate in level of difficulty. The detailed analysis will be available soon.
Mar 21, 2025 05:00 PM IST
Class 12 ISC Biology Exam 2025 Ends; Answer Key soon!
The exam timing for the Class 12 ISC Biology Exam 2025 ends, and the collection of answer sheets have begun. Students will be departing soon, and reviews and Class 12 ISC Biology Answer Key 2025 will be updated here soon.
Mar 21, 2025 04:40 PM IST
Class 12 ISC Biology Exam 2025 to end soon!
The last few minutes of the Class 12 ISC Biology Exam 2025 are left. Students should by now start to wrap up their answer sheets for submission.
Mar 21, 2025 04:20 PM IST
Class 12 ISC 2025 Result Date
The official result date for ISC Class 12 exam 2025 has not been announced yet, but it is expected to be released on May 2025 by experts, following the previous years' patterns.
Mar 21, 2025 04:00 PM IST
Where to find Class 12 ISC Biology Answer Key 2025 for Subjective questions?
The Subjective-type questions are opinion-based, so determining a particular answer is not possible. So, for subjective-type questions, Class 12 ISC Biology Answer Key 2025 will not be available here. However, students may refer to their notes, or ask their seniors or teachers for the best answers.
Mar 21, 2025 03:40 PM IST
Class 12 ISC Biology Answer Key 2025: Objective Questions Only
Students should be aware that the Class 12 ISC Biology Answer Key 2025 here will only include the answers to the objective type questions or 1 marks questions only.
Mar 21, 2025 03:20 PM IST
Is Objection to Class 12 ISC Biology Answer Key 2025 available?
Due to the nature of the Class 12 ISC Biology Answer Key 2025 being unofficial, claims or objections will not be entertained. Students will have to refer to the answer key for answers only and may not file objections to it.
Mar 21, 2025 03:00 PM IST
Is the Class 12 ISC Biology Answer Key 2025 definitive?
Yes, the Class 12 ISC Biology Answer Key 2025 is authentic and definitive, as it is prepared by subject experts. Although it is unofficial in nature, students may rely on the answer key to check their answers.
Mar 21, 2025 02:40 PM IST
Class 12 ISC Biology Answer Key 2025 Release Time
Soon after the end of the exam, the Class 12 ISC Biology Answer Key 2025 will be released. Although the exact release time may not be predicted, students should be assured that as soon as the question paper is available to our experts, the answer key will be updated here!
Mar 21, 2025 02:20 PM IST
Class 12 ISC Biology Exam 2025: Writing Time Starts!
Students appearing for the Class 12 ISC Biology exam 2025 are now allowed to write. Students shouldn't waste any time and start to attempt the paper with confidence.
Mar 21, 2025 02:00 PM IST
Class 12 ISC Biology Exam 2025 Begins!
The Class 12 ISC Biology exam 2025 begins with the question paper's distribution. Students will be given 15 minutes to read through the question paper. After the completion of 15 minutes, students will be allowed to start writing the exam.
Mar 21, 2025 01:40 PM IST
Class 12 ISC Biology Exam 2025: Last-minute Checklist
Before entering the exam hall for the Class 12 ISC Biology exam 2025, here is the last-minute checklist:
- Class 12 ISC Hall Ticket 2025 and valid ID proof.
- Check pockets to ensure no objectionable things are there.
- Stay calm and composed throughout the examination.
- Quickly and carefully read through the entire question paper at the beginning to avoid wastage of time.
Mar 21, 2025 01:20 PM IST
Class 12 ISC Biology Exam 2025: Students reach exam hall
With the exams to begin at 2 PM, students appearing for the Class 12 ISC Biology Exam 2025 have started to reach the exam hall. The exams will begin soon, so, students are seen doing their last-minute go through for the exams.
Mar 21, 2025 01:00 PM IST
Class 12 ISC Biology Revision Questions 2025 (8)
Refer to the Class 12 ISC Biology Revision Questions 2025 here:
Question: Robert was suffering from chronic renal failure. At the doctors’ recommendation of transplantation of kidney received from a healthy donor, Robert underwent a kidney transplant. However, after two weeks, the transplanted kidney was rejected by the immune system of Robert.
(i) Identify and define the type of immune response that is responsible for the rejection of the grafted organ.
(ii) Suggest a clinical method by which the rejection of the transplanted organ can be prevented.
Question: The red panda has been listed as an endangered species on the IUCN Red List since 2015. Regional captive breeding programmes have been established in zoos around the world to protect the red panda from extinction.
(i) Classify the biodiversity conservation programme referred to above.
(ii) Mention any other two methods of conservation which belong to the same category.
Mar 21, 2025 12:45 PM IST
Class 12 ISC Biology Revision Questions 2025 (7)
Refer to the Class 12 ISC Biology Revision Questions 2025 here:
Question: Answer the following questions.
- What are ZIFT and GIFT?
- All STDs do not affect the genital organs. Justify the statement.
Mar 21, 2025 12:30 PM IST
Class 12 ISC Biology Revision Questions 2025 (6)
Refer to the Class 12 ISC Biology Revision Questions 2025 here:
- Draw a well-labelled diagram of RNA.
- Draw a well-labelled diagram of nucleosome.
Mar 21, 2025 12:15 PM IST
Class 12 ISC Biology Revision Questions 2025 (5)
Refer to the Class 12 ISC Biology Revision Questions 2025 here:
Question: Answer the following questions.
(a) Why are some molecules called bioactive molecules?
(b) Mention the respective source and state the specific use of any two bioactive molecules.
Mar 21, 2025 12:00 PM IST
Class 12 ISC Biology Revision Questions 2025 (4)
Refer to the Class 12 ISC Biology Revision Questions 2025 here:
Question: Answer the following questions.
(a) Why are the biocontrol agents preferred over the chemical pesticides?
(b) Explain the role of any two biocontrol agents by mentioning their target pests.Mar 21, 2025 11:45 AM IST
Class 12 ISC Biology Revision Questions 2025 (3)
Refer to the Class 12 ISC Biology Revision Questions 2025 here:
- The black colour on the beak of finches dominates over the yellow colour. There are 210 individuals with the genotype DD, 245 individuals with the genotype Dd and 45 individuals with the genotype dd. Deduce the frequency of individuals with dominant, heterozygous, and recessive traits.
- Enumerate the cause and the characteristic symptom of PKU.
Mar 21, 2025 11:30 AM IST
Class 12 ISC Biology Revision Questions 2025 (2)
Refer to the Class 12 ISC Biology Revision Questions 2025 here:
- Name the technique used to detect the presence of HIV in the body of an individual, Justify the principle associated with this technique.
- Name any two factors responsible for the loss of biodiversity in a geographical region.
Mar 21, 2025 11:15 AM IST
Class 12 ISC Biology Revision Questions 2025 (1)
Refer to the Class 12 ISC Biology Revision Questions 2025 here:
- Name the pollinating agent of a flowering plant with large and coloured flowers with sticky stigma. State one characteristic feature of the pollen grains produced in such flowers.
- What happens to an inferior competitor if:
(i) a superior competitor is present in the same environment?
(ii) the superior competitor is removed from the environment?
Mar 21, 2025 11:00 AM IST
Class 12 ISC Biology Exam 2025: Date and Time
The Class 12 ISC Biology Exam 2025 is scheduled to be held today, March 21, 2025, at 2 PM at all the exam centres across the country.