CBSE Class 12 Biology Previous Year Question Paper 2012
This is the CBSE Class 12 Biology Previous Year Question Paper from 2012, focusing on the topic of Fertilisation, Pregnancy & Embryonic Development. The paper includes questions carrying 1 mark and 2 marks, testing fundamental concepts of human reproduction. For instance, it asks about the mechanism ensuring single sperm entry into the ovum, the function of the trophoblast, the embryonic stage implanted in the uterine wall, the hormonal regulation of parturition, and the protective role of colostrum. It also delves into the detailed events of fertilisation, including its location and the process of zygote formation. Solving this board question paper provides valuable practice for students preparing for their CBSE examinations, helping them understand the exam pattern and reinforce their knowledge of reproductive biology.
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Quick info
| Board | CBSE |
|---|---|
| Class | 12 |
| Subject | Biology |
| Session | 2012 |
| Language | English |
| Type | Previous Year Question Paper |
| Exam type | Board Exam |
Paper pattern
The paper includes 1-mark and 2-mark questions covering topics related to fertilisation, pregnancy, and embryonic development.
Topics covered
Paper topics
- Fertilisation
- Pregnancy
- Embryonic Development
- Human Reproduction
- Ovum
- Sperm
- Zygote
- Trophoblast
- Colostrum
- Parturition
Important topics
- Mechanism of single sperm entry
- Function of trophoblast
- Implantation stage
- Hormonal control of parturition
- Role of colostrum in immunity
- Events of fertilisation
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Question paper text
Fertilisation, Pregnancy & Embryonic Development
1 Mark Questions
- How is the entry of only one sperm ensured into an ovum during fertilisation in humans? [All India 2012]
Ans. During fertilisation, a sperm comes in contact with the zona pellucida layer of the ovum and induces changes (depolarisation) in the membrane that blocks the entry of additional sperms. This ensures that only one sperm can fertilise an ovum
2.Mention the function of trophoblast in human embryo.[Delhi 2011]
Ans. Trophoblast is the outer layer of blastocyst which helps in attachment of blastocyst to the endometrium of the uterus.
- Name the embryonic stage that gets implanted in the uterine wall of a human female. [All India 2011] Ans. Blastocyst gets implanted in the uterine wall.
- What stimulates pituitary to release the hormone responsible for parturition? Name the hormone.[All India 2011]
Ans. Foetal ejection reflex stimulates pituitary to release the oxytocin hormone, which is responsible for parturition.
- How does colostrum provide initial protection against diseases to newborn infants? Give one reason. [Delhi 2009]
Ans. Colostrum contains necessary antibodies (IgA) that provide protection against diseases to newborn infants.
2 Marks Questions
- Where does fertilisation occur in humans? Explain the events that occur during this process. [All India 2014]
Ans. In humans, the fertilisation of ovum takes place in ampullary-isthmic junction of Fallopian tube.
The events that occur during the process of fertilisation are:
- The sperm reaches the junction of ampulla and isthmus and comes in contact with zona pellucida layer of ovum.
- Acrosome of sperm head release sperm lysin enzymes that dissolves corona radiata and digests zona pellucida layer and enters cytoplasm.
- Entry of sperm stimulates secondary oocyte to complete its suspended second meiotic
division, thus producing haploid egg or ovum and second polar body.
- Nucleus of sperm and of ovum fuses to form a diploid zygote.
7. Explain the events that occur during fertilisation of an ovum in humans. How is it that only one sperm enters the OVUm? [All India 2014 C]
Ans.(i) In humans, the fertilisation of ovum takes place in ampullary-isthmic junction of Fallopian tube.
The events that occur during the process of fertilisation are:
- The sperm reaches the junction of ampulla and isthmus and comes in contact with zona pellucida layer of ovum.
- Acrosome of sperm head release sperm lysin enzymes that dissolves corona radiata and digests zona pellucida layer and enters cytoplasm.
- Entry of sperm stimulates secondary oocyte to complete its suspended second meiotic division, thus producing haploid egg or ovum and second polar body.
- Nucleus of sperm and of ovum fuses to form a diploid zygote.
- During fertilisation, a sperm comes in contact with the zona pellucida layer of the ovum and
Frequently asked questions
What is this document?
This is a CBSE Class 12 Biology Previous Year Question Paper from 2012, focusing on Fertilisation, Pregnancy & Embryonic Development.
What topics are covered in this paper?
The paper covers key concepts like fertilisation, the role of the trophoblast, implantation, parturition, colostrum, and the detailed events of fertilisation in humans.
What is the benefit of solving this previous year paper?
Solving this previous year question paper helps students understand the CBSE exam pattern, identify important topics, and improve their marks in Biology.
What is the marking scheme for these questions?
The paper includes questions carrying 1 mark and 2 marks, as indicated in the text.
How can students best use this resource?
Students should solve this paper under timed conditions to simulate the actual exam and then review the answers to understand concepts better and identify areas for improvement.
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