NCERT Solutions Class 11 Biology Chapter 10
NCERT Solutions for Class 11 Biology Chapter 10
NCERT Solutions for Class 11 Biology Chapter 10 by Extramarks will help students prepare better for the examinations. The best way to use these resources is to study the chapter, attempt NCERT textbook questions on your own and then cross-check the answers by referring to the detailed solutions prepared by subject experts. NCERT Solutions by Extramarks can also be a great resource for last-minute preparations.
NCERT Solutions for Class 11 Biology Chapter 10 – Cell Cycle and Cell Division
NCERT Class 11 Biology textbook Chapter 10 is about Cell Cycle and Cell Division. The chapter covers different phases of the Cell Cycle including the Interphase and the Mitosis and talks about the stages that take place inside the cell when it divides.
Students can refer to the NCERT Class 11 Biology Chapter 10 solutions prepared by Extramarks to get answers to the questions given at the end of the chapter in the NCERT textbook.
Access NCERT Solutions for Class 11 Biology Chapter 10 – Cell Cycle and Cell Division Biology
Students can access the NCERT Solutions for Class 11 Biology Chapter 10 right here:
Chapter 10 Biology Class 11 Cell Cycle and Cell Division NCERT Solutions
Chapter 10 Biology Class 11 is all about the cell cycle and cell division. It covers detailed phases of the cell cycle which include the Interphase and the Mitosis phase. Students will get to know some amazing facts about how cells reproduce and the series of events that lead to cell division through this chapter.
NCERT Solutions For Class 11 Biology Chapter 10 Cell Cycle and Cell Division
NCERT Class 11 Biology Chapter 10 is about the phases of cell development. Mitosis and Meiosis are discussed in detail in this chapter. Mitosis occurs in somatic cells. This process leads to the formation of two daughter cells. Meiosis occurs in germ cells and is a process that leads to the formation of four daughter cells. Cell division in mitosis occurs through asexual reproduction whereas in meiosis it occurs through sexual reproduction. Replication of chromosomes does not occur before meiotic division but occurs before mitotic division.
The significance of Meiosis is one of the important parts of this chapter. Meiosis is also called reductional division as this type of cell division decreases chromosome number by half. Meiosis is a kind of cell division that includes two sequential cycles of nuclear division, i.e. Meiosis I, and cell division, i.e. Meiosis II. At the S stage, after the parental chromosomes have produced identical sister chromatids, Meiosis I is initiated. In sexually reproducing organisms conservation of specific chromosome number of each species across generations is achieved. Genetic variability (from one generation to the next) increases in the population of organisms due to Meiosis. The process of evolution holds variations in great importance. Hence, Meiosis has quite a significance.
CBSE Class 11 Biology Chapter 10 NCERT Solutions Marks Distribution
NCERT Class 11 Biology Chapter 10 has a weightage of 15 marks in CBSE exams and 9% in NEET. Topics that are a part of Chapter 10 biology Class 11 are as follows:
- Cell Cycle
- Phases of a Cell Cycle
- M Phase
- Significance of Mitosis
- Meiosis 2
- Significance of Meiosis
Benefits of Chapter 10 Biology Class 11 NCERT Solutions
The Chapter 10 Biology Class 11 NCERT Solutions have many benefits. Detailed answers provided in these solutions will assure that all the doubts of students are addressed. These solutions are written in simple words after extensive research.
The solutions are curated by subject-matter experts to provide full support and guidance to students in the process of exam prep. Practical examples of cell division will help students learn concepts with ease and all sorts of questions that one can expect to be asked in the exams are covered in these solutions.
Q.1 What is the average cell cycle span for a mammalian cell?
The average cell cycle span for a typical mammalian cell is about 24 hours. These cells divide once every 24 hours to form two daughter cells.
Q.2 Distinguish cytokinesis from karyokinesis.
|Cytokinesis is the process of division of cytoplasmic contents during mitotic or meiotic division.||Karyokinesis is the division of nuclear material during the process of cell division.|
|It is the last step of cell division and requires completion of karyokinesis step.||It proceeds well before cytokinesis.|
|No well-demarcated stages are seen.||The process of karyokinesis has well-demarcated stages.|
Q.3 Describe the events taking place during Interphase.
During the course of the cell cycle, the time span a living cell spent in between two consecutive M- phase (mitotic- phase) is called Interphase. This is the metabolically active phase during which the cell grows in size, duplicating its genome (DNA) and accumulating nutrients required for mitosis. It is also called the resting phase as no change in chromatin structure is observed under the microscope during this phase. On the basis of molecular and biochemical events during Interphase, it has been divided into three sub-phases.
Gap 1 phase (G1): This is the duration between mitosis and initiation of DNA replication where the cell is metabolically active, and grow without DNA replication. This phase is marked by the increase in cell size where the cell prepares for DNA replication
Synthesis phase (S): This phase begins with DNA synthesis or DNA replication. By the end of this phase the DNA content of the cell doubles but without increase in the chromosomal number. Thus if the initial chromosomal number of a cell was 2n and DNA content was 2C, at the end of S-phase the DNA content will become 4C while chromosomal number remains the same (2n).In S-phase initiation of centriole duplication also takes place in the cytoplasm.
Gap 2 phases (G 2): In G2 phase the cell continues to grow and synthesize the regulatory proteins and enzymes necessary for mitotic phase.
Q.3 What is G0 (quiescent phase) of cell cycle?
G0 or quiescent phase of the cell cycle is the phase when the cell has come out of G1 phase to enter an inactive stage. The cells are metabolically active however do not undergo division unless required depending upon the environmental condition. It is also known as the resting phase. The adult myocardiocytes which never undergo division of cells which divide rarely to replace cells lost due to some injury or cell death remain in G0 or quiescent phase of the cell cycle.
Q.4 Why is mitosis called equational division?
Mitosis is called equational division because the two daughter cells formed at the end of mitosis acquire the same number and kinds of chromosomes as the parent cell nucleus. There is a duplication of each chromosome before the onset of mitosis and is composed of two chromatids which get separated equally during the process of mitosis. The orderly distribution of chromosomes on the mitotic spindle helps in equal separation of chromatids of each chromosome. Also, since there is no crossing over during the process of mitosis, it results in the same kinds of the chromosome as the parent cell.
Q.5 Name the stage of cell cycle at which one of the following events occur:
- Chromosomes are moved to spindle equator.
- Centromere splits and chromatids separate.
- Pairing between homologous chromosomes takes place.
- Crossing over between homologous chromosomes takes place.
- Zygotene of Meiosis I
- Pachytene of Meiosis I
Q.6 Describe the following:
Draw a diagram to illustrate your answer.
- Synapsis: It is the pairing up of duplicated homologous chromosomes (one from each parent) during the process of meiosis in such a way that the DNA of the non-sister chromatids is aligned. It takes place during the zygotene stage of prophase I of meiosis. Synapsis of homologous chromosomes is accompanied by the formation of a complex structure called synaptonemal complex.
- Bivalent: It is the complex formed by a pair of synapsed homologous chromosomes. It is a bivalent because there are two chromosomes in close association. It is also known as tetrad because bivalent contains four chromatids. Bivalents condense and become visibly distinct during the pachytene stage of prophase I of meiosis. Crossing over occurs between the non-sister chromatids of the bivalent. This results in non-identical sister chromatids of a chromosome.
- Chiasmata: It is an X-shaped structure of chromosomes formed during the diplotene stage of meiosis I. The synaptonemal complex dissolves resulting in separation of recombined homologous chromosomes of the bivalents except at the site of crossing over.
Q.7 How does cytokinesis in plant cells differ from that in animal cells?
In animal cells, a furrow develops in the plasma membrane. This cleavage furrow deepens gradually and ultimately joins in the centre resulting in the division of the cell cytoplasm into two halves. However, the plant cells are surrounded by a rigid and inextensible cell wall due to which no cell furrow formation takes place. The process of cytokinesis is very different in plant cells as compared to that of animal cells. The major differences are:
- Cell plate formation: The cell wall formation begins with the precursor called cell plate at the centre of the cell.
- Extension of cell plate: The cell plate extends outwardly in all direction and ultimately unites with the exiting lateral wall and thus function as middle lamella between the walls of two adjacent cells
- Deposition of cell wall components: Once the cell plate is fused to the cell wall of the cell, deposition of cell wall components such as cellulose takes place to make a proper cell wall.
Q.8 Find examples where the four daughter cells differ from meiosis are equal in size and where they are found unequal in size?
An example where equal-sized daughter cells are formed at the end of meiosis: Spermatogenesis results in the production of equal-sized haploid sperms.
An example where unequal sized daughter cells are formed at the end of meiosis: During the process of oogenesis, unequal sized daughter cells are formed at the end of meiosis.
Q.9 Distinguish anaphase of mitosis from anaphase I of meiosis.
|Anaphase of Mitosis||Anaphase I of Meiosis|
|Centromere joining the sister chromatids splits and the two daughter chromatids (produced during the S phase), now referred to as chromosomes segregate to opposite poles.||The homologous chromosome separate to the opposite poles while the sister chromatids remain attached as there is no splitting of the centromere.|
|This separation maintains the DNA content and the chromosome number in the daughter cells.||This separation results in the reduction of chromosome number to half as the homologous chromosome separate to opposite poles.|
Q.11 List the main differences between mitosis and meiosis.
|Mitosis is a process of cell duplication during which one cell gives rise to two daughter cells.||Meiosis is a division of a germ cell involving two divisions of the nucleus and giving rise to four gametes, or sex cells, each possessing half the number of chromosomes of the original cell.|
|The steps of mitosis are Interphase, Prophase, Metaphase, Anaphase, Telophase and Cytokinesis||The steps of meiosis are Interphase, Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II and Telophase II.|
|Single division results in the formation of two diploid daughter cells.||A series of two divisions result in the formation of four haploid daughter cells.|
|Daughter cells are genetically identical to the mother cell.||Daughter cells are not genetically identical to the mother cell.|
|Since the number and kind of chromosomes remain the same as mother cells, it is also known as equational division.||Since the number of chromosomes reduces to half at the end of meiosis I, it is known as reductional division.|
|The pairing of homologous chromosomes does not occur.||The pairing of homologous chromosomes and cross-over of chromosomes occurs.|
|Crossing over does not occur.||Crossing over between non sister chromatids occurs.|
|Mitosis takes place during cellular reproduction & general growth and repair of the body.||Meiosis takes place during sexual reproduction.|
|It occurs in all kinds of cells except sex cells.||It occurs only in sex cells resulting in the formation of gametes.|
|It occurs in all organisms.||It is a characteristic feature of Humans, animals, plants, fungi.|
Q.12 What is the significance of meiosis?
Significance of meiosis:
- Since gametes in sexually reproducing organisms are produced by the process of meiosis (resulting in the reduction of chromosome number to half), it helps in conserving the specific chromosome number of each species across generations.
- It also increases genetic variability due to the process of crossing over happening during the process. This results in gaining new characteristics by the population over generations. Such variations help in the process of evolution.
Q.13 Discuss with your teacher about
(i) Haploid insects and lower plants where cell-division occurs, and
(ii) Some haploid cells in higher plants where cell-division does not occur.
(i) Cell division occurs in insects and lower plants, like algae (Spirogyra and Chlamydomonas), bryophytes and pteridophytes. Haploid gametes are produced through mitosis and the zygote formed after fertilisation undergoes meiosis to produce haploid organisms.
(ii) In higher plants, antipodals and synergids of the embryo sac are haploid and do not undergo cell division.
Q.14 Can there be mitosis without DNA replication in ‘S’phase?
No, mitosis cannot take place without DNA replication in ‘S’phase. Mitosis is an equational division resulting in the production of two genetically identical daughter cells. This is achieved because the DNA of each chromosome duplicates by the process of replication during the S or synthetic phase of the cell cycle. The amount of DNA per cell doubles. This is followed by segregation of the two chromatids of each chromosome during the anaphase stage of mitosis bringing the DNA content identical to that of the parent cell.
Q.15 Can there be DNA replication without cell division?
Yes, there can be DNA replication without cell division. Endoreplication is the replication of DNA of the cell without the cell division. This results in a large number of copies of the same DNA molecule(s) within the cell nucleus resulting in polyploidy. One example is polytene chromosomes of the salivary glands of fruit flies. The repeated division of chromosomes without any cell division results in a large number of sister chromatids tightly bound to each other. DNA replication without cell division is a common phenomenon in plants.
Q.16 Analyze the events during every stage of cell cycle and notice how the following two parameters change
- Number of chromosomes (N) per cell
- Amount of DNA content (C) per cell
Mitotic Cell Cycle:
- The number of chromosomes (N) per cell: Number of chromosomes (N) per cell never changes in the mitosis. If the cell has diploid (2n) number of chromosomes, even after the synthetic phase where the DNA replication occurs, the chromosome number remains 2n.
- Amount of DNA content (C) per cell: During the S phase (synthetic) of interphase in mitosis, DNA synthesis or replication takes place. It results in duplication of the amount of DNA per cell i.e. from the initial amount of 2C, it becomes 4C. It is during the anaphase that the sister chromatids separate due to splitting of the centromere, thereby bringing the DNA content per cell back to 2C amount.
Meiotic Cell Cycle:
- The number of chromosomes (N) per cell: Meiosis results in the reduction of the number of chromosome per cell to half. The cell starts with a 2N number. Before meiosis, the DNA replication occurs and each chromosome gets 2 sister chromatids. It is during the anaphase I of meiosis I that homologous chromosomes segregate reducing the chromosome number to N. There is no further reduction in the chromosome number in meiosis II.
- Amount of DNA content (C) per cell: Amount of DNA content per cell is also reduced to half during the process of meiosis. Let us assume the initial DNA content is to be 1C per cell before the onset of meiosis. During the replication process before the onset of meiosis I, each chromosome undergoes replication thereby doubling the DNA content (2C). During anaphase I, homologous chromosomes segregate to opposite poles however there is no splitting of the centromere. The DNA content of the 2 daughter cells produced becomes 1C again. It is during the anaphase II in meiosis that the centromeres split resulting in separation of sister chromatids further into 4 daughter cells. This results in a reduction of DNA content to half as compared to the parent cell.
FAQs (Frequently Asked Questions)
1. What are the phases of a cell cycle?
Cell cycle has two phases;
- G1 Stage (Gap 1)
- S Stage (Synthesis)
- G2 Stage (Gap 2)
- M phase
2. What are the stages involved in Meiosis I & II?
Stages involved in Meiosis are as follows;
- Meiosis I
- Prophase I (This phase is longer than that of the mitosis prophase)
- Metaphase I
- Anaphase I
- Telophase I
After Telophase once Cytokinesis has occurred, Meiosis II Prophase will begin.
- Meiosis II
- Prophase II
- Metaphase II
- Anaphase II
- Telophase II
3. How Many Changes Take Place in Chromosomes and Amount of DNA Content per Cell During Every Part of the Cell Cycle?
DNA replication can take place during the cell cycle’s G1 phase. The number of chromosomes stays the same as before and each chromosome is framed by one chromatid. Two sister chromatids joined at the centromere form the chromosome in the S stage. In the G2 stage, comparative conditions proceed. M stage has the sister chromatids acting independently and moving to various cells. In Mitosis, the number of chromosomes stays equivalent. In the cell, DNA content quantity stays the same as before during the G1 stage, however, in the S1 stage, it doubles. It stays double in the G2 stage but in the M phase of the cycle, it splits.
4. Why is DNA Replication important?
DNA replication is a process that involves the duplication of the DNA inside a cell. This occurs during cell division. An equal amount of identical replicas of DNA is given to every daughter cell. DNA carries information that is crucial for the repair, growth, and regeneration of tissues.
5. What are the Events Taking Place During Interphase? Also, Define the Stage that G0 is.
The Interphase has 3 basic stages that are categorized on the basis of how much a cell progresses.
G1 Stage (Gap 1) – In this stage, though the cell is metabolically active and DNA is being developed and readied for replication, DNA replication does not take place.
S Stage (Synthesis) – DNA synthesis or replication takes place in this phase. The DNA quantity doubles in this phase while the chromosome quantity remains unchanged.
G2 Stage (Gap 2) – This is the stage between the S stage and the M phase. This is where the cell prepares itself for the process of cell division. RNA and proteins that are needed for mitosis are produced in this stage.
G0 Stage- This is a stage where neither is a cell being divided nor is it preparing to divide. In adult animals, some cells do not show cell division while some that do divide, do it occasionally only when there is an occurrence of loss of cells caused due to cell death or injury. The cells not dividing exit the G1 phase and enter the G0 stage or the quiescent stage. In the G0 stage, cell division does not occur but the cell is metabolically active.
6. What are the important topics of NCERT Class 11 Biology Chapter 10 Cell Cycle And Cell Division?
The important topics of NCERT Class 11 Biology Chapter 10 Cell Cycle And Cell Division are:
- The span of cell cycle
- Mitosis and Meiosis
- Cytokinesis and Karyokinesis
- DNA replication
7. What can I learn from Chapter 10 of NCERT Class 11 Biology?
Cell Cycle and Cell Division are discussed in detail in the Chapter 10 Biology Class 11 NCERT textbook. Stages in cell division, the change of DNA and chromosomes in the cell, the difference between mitosis and meiosis, and events during the interphase are the topics that are encompassed in the chapter. Referring to the explanations given in the NCERT Solutions Class 11 for Biology Chapter 10 will boost the confidence of the students and will help them tackle any kind of question in the exam.
8. What type of questions can be expected from Chapter 10 of NCERT Class 11 Biology?
One can expect the following type of questions:
- Explain the cell cycle.
- What event occurs during the cell cycle?
- Differentiate between Mitosis and Meiosis.
- What is the importance of meiosis?
- Differentiate between cytokinesis and karyokinesis.
- Explain the events during the interphase.
- What is the significance/ importance of DNA replication?
- What is the change in DNA content in each cell?
- How does the number of chromosomes change in the cell cycle?
- 5 mark long answers are to be written in detail with relevant points covered in the answer. If the answer has diagrams as a part of it students must illustrate the same even if it is not specified in the question.
- Marks can be obtained easily through diagram questions so students are advised to practise the same.
- MCQs carrying 1 mark are expected to be asked and to get these right a thorough preparation has to be done by students.
9. Which tissue of plants and animals undergoes meiosis?
The sex cells of both female and male reproductive organs of plants, as well as animals, have meiosis occurring in them. Male and female gametes (which take part in sexual reproduction) are produced by them.
10. What are the benefits of NCERT solutions for Class 11 Biology Chapter 10?
NCERT solutions have multiple benefits such as:
- They are framed while adhering to CBSE guidelines.
- Solutions are provided chapter-wise in a systematic manner.
- The solutions are easy to comprehend as they are written in a simple language with in-depth explanations.
- Experts in the field with relevant experience have prepared the solutions.