3. z
CERTIFICATE
This is to certify that Swarnav Miahra of class XI of Kendriya
Vidyalaya,Boudh has completed his BIOLOGY PROJECT under my
supervision and has taken proper care and displayed utmost sincerity in
completion of this project.
His project is up to the standard both in respect of its contents as per CBSE
norms and this is his original work as per my knowledge.
Ms. Rajalaxmi Biswal
(Subject teacher)
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4. z
ACKNOWLEDGEMENT
The success and final outcome of this project required a lot of guidance
and assistance from many people and I am extremely privileged to have
got this all along the completion of my project. All that I have done is
only due to such supervision and assistance and I would not forget to
thank them.
I respect and thank Rajalaxmi Biswal ma’am, for providing me an
opportunity to do the project work in Kendriya Vidyalaya,Boudh and
giving me all support and guidance which made me complete the project
duly. I am extremely thankful to her for providing such a nice support
and guidance, although she had busy schedule.
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5. z MITOSIS
It is a type of cell division that produces two
similar daughter cells.
→The daughter cells have the same number of
chromosomes as the parent cell.
→The chromosome number remains unaltered,
and it is conserved in parents and progeny..
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6. z SIGNIFICANCE OF MITOSIS
Meiosis is responsible for the formation of sex cells or gametes that are
responsible for sexual reproduction.
It activates the genetic information for the development of sex cells and
deactivates the sporophytic information.
It maintains the constant number of chromosomes by halving the same.
This is important because the chromosome number doubles after
fertilization.
In this process independent assortment of maternal and paternal
chromosomes takes place. Thus the chromosomes and the traits controlled
by them are reshuffled.
The genetic mutation occurs due to irregularities in cell division by meiosis.
The mutations that are beneficial are carried on by natural selection.
Crossing over produces a new combination of traits and variations.
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8. z A. KARYOKINESIS
1. PROPHASE
• It is the first phase of karyokinesis.
• It is the longest phase in terms of the time taken
forcompletion.
• The chromatin fibres start condensing into a mass
during the early prophase.
• Since it resembles a condensed ball of wool, early
prophase is also known as the spireme stage (tangle
or coil of filament). • They further condense as
prophase continues to form the chromosomes.
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9. z
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• Prophase also includes nuclear membrane
degeneration and disappearance of the
nucleolus.
• Disintegration of endoplasmic reticulum
and Golgi apparatus takes place.
• The centrosomes with replicated centrioles
start moving towards the opposite poles.
• Each centrosome radiates microtubules
known as asters. Aster rays help the
centrioles to hold their place in the cytoplasm.
• The centrioles form spindle fibres.
10. z
2.METAHASE
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• The complete degradation of the nuclear
membrane marks the start of metaphase.
• The chromosomes come to lie in the equatorial
plane (equidistant from the two poles).This
process is known as congression.
• Congression occurs with the assembly of the
mitotic spindle that mediates the microtubule-
chromosome interactions required for the
movement of chromosomes.
• The spindle fibres attach to the kinetochore of
thechromosomes
Chromosomes are observed to be the thickest
and the shortestat this stage. • This is the best
time to do thefollowing: →Study the morphology
of each chromosome →Count their numbers
11. z
3. ANAPHASE
The centromere splits.
• The sister chromatids separate into two
identical and independent chromosomes.
• Each chromatid now has its own centromere.
• The spindle fibres pull the chromatids along
with the centromere towards their
respectivepoles.
• The chromatids move to opposite poles (Half
of them reach one pole and the other
halfreach the other).
• During migration, the centromere of
chromosomes face towards the poles. The
chromatids or arms of chromosomes trail
behind.
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12. z 4. TELOPHASE
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• Chromosomes cluster at opposite
poles.
• They start decondensing into
chromatin fibres and their individuality
is lost as discrete elements.
• The nucleolus, ER, and Golgi
apparatusreappear.
• The nuclear envelope develops
around the chromatin at each pole,
forming two daughter nuclei.
13. z
B. CYTOKINESIS
Cell furrow formation →In animal cells,
cytokinesis is achieved by the formation of a
furrow. →Furrow appears in the plasma
membraneand deepens towards the centre
in a centripetal fashion. →Furrows from both
the sides join at thecentre, dividing the
cytoplasm into two. →The formation of cell
furrow is aided by microfilaments and
microtubules.
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14. z
Cell plate formation
→In plant cells, wall formation starts at the centre of the cell and
growsoutwards.
→The formation of the new cell wall begins with the formation of a cell plate.
→Fragments from the Golgi complex, which are known as vesicles, fuse
together to formcell plates.
→The cell plate is laid in a centrifugal manner.
→The cell plate represents the middle lamella between the walls of twoadjacent
cells.
→Mitochondria and plastids get distributed between the twodaughter cells.
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