NCERT Solutions for Class 11 Biology Chapter 10
NCERT Solutions for Class 11 Biology Chapter 10 Cell Cycle and Cell Division free download in PDF files for or to Study online without downloading files updated for new academic session 2020-21.
Download CBSE Offline Apps based on NCERT Solutions of other subjects and study notes related to all chapters. Ask your queries in Discussion Forum to share your knowledge with the others.NCERT Solutions for Class 11 Biology Chapter 10
Class: | 11 |
Subject: | Biology |
Chapter 10: | Cell Cycle and Cell Division |
Class 11 Biology Chapter 10 Solutions in English
NCERT Solutions for Class 11 Biology Chapter 10 in PDF format to download free for new academic session 2020-21 based on latest NCERT Books 2020-2021. Offline Apps are also updated for new session following the latest CBSE Syllabus 2020-2021. Join the Discussion Forum to ask your doubts and discuss your educational problems. NIOS board provides you directly class 12 (after passing 10th) without doing 11th.
Chapter 10 Cell Cycle and Cell Division Solutions
Important Notes on Cell Cycle and Cell Division
MEIOSIS
Specialised kind of cell division that reduces the chromosomes number by half, hence it is called reductional division.
Occurs during gametogenesis in plants and animals.
Involves two sequential cycles of nuclear and cell division called Meiosis I and Meiosis II.
It results in 4 haploid daughter cells.
Interphase occurs prior to meiosis which is similar to interphase of mitosis except the S phase is prolonged.
SIGNIFICANCE OF MEIOSIS
Format ion of gametes: In sexually reproducing organisms.
Genetic variability: Variations are very important for evolution.
Maintenance of chromosomal number: By reducing the chromosome number in gametes. Chromosomal number is restored by fertilisation of gametes.
Mitosis
Since the number of chromosomes in the parent and progeny cells is the same, it is called as equational division. Mitosis is divided into four sub stages.
1. Prophase
Replicated chromosomes, each consisting of 2 chromatids, condense and become visible.
Microtubules are assembled into mitotic spindle.
Nucleolus and nuclear envelope disappear.
Centriole moves to opposite poles.
2. Metaphase
Spindle fibres attached to kinetochores (small disc-shaped structures at the surface of centromere) of chromosomes.
Chromosomes line up at the equator of the spindle to form metaphase plate.
3. Anaphase
Centromeres split and chromatids separate.
Chromatids move to opposite poles due to shortening of spindal fibres.
4. Telophase
Chromosomes cluster at opposite poles.
Nuclear envelope assembles around chromosomes clusters’.
Nucleolus, Golgi Complex, E.R. reforms.
Significance of Mitosis
Growth-addition of cells.
Maintenance of surface/volume ratio. Maintain Nucleo-cytoplasmic ratio.
Maintenance of chromosomes number.
Regeneration.
Reproduction in unicellular organisms, lower plants and some insects.
Repair and wound healing.
Vegetative reproduction in plants takes place by mitosis.
Important Questions on 11th Biology Chapter 10
G1 phase:
It is the stage during which the cell grows and prepares its DNA for replication. In this phase, the cell is metabolically active.
S phase:
It is the stage during which DNA synthesis occurs. In this phase, the amount of DNA (per cell) doubles, but the chromosome number remains the same.
G2 phase:
In this phase, the cell continues to grow and prepares itself for division.
The proteins and RNA required for mitosis are synthesised during this stage.
(b) Oogenesis or the formation of ovum in human beings occurs by the process of meiosis. It results in the formation of four daughter cells which are unequal in size.
Significance of meiosis
Meiosis maintains the chromosome number from generation to generation. It reduces the chromosome number to half so that the process of fertilisation restores the original number in the zygote.
Variations are caused by the cross-over and the random distribution of homologous chromosomes between daughter cells. Variations play an important role in evolution.
Chromosomal mutations are brought about by the introduction of certain abnormalities. These chromosomal mutations may be advantageous for an individual.
(ii) The phenomenon of polyploidy can be observed in some haploid cells in higher plants in which cell division does not occur. Polyploidy is a state in which cells contain multiple pairs of chromosomes than the basic set. Polyploidy can be artificially induced in plants by applying colichine to cell culture.