Скачать или смотреть Unit 4 | L1 | Part (2-3) | Cell Division | Science | Prep.3 | First Term | 2022

ساينس تالتة اعدادي - ترم اول 2022
ساينس الصف الثالث الاعدادي - الفصل الدراسي الاول 2022
علوم لغات 2022

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   • Unit 4 | L1 | Part (1-3) | Cell Division |...  

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In This part we will study :
Meiosis
Meiosis occurs in living organisms that reproduce by gametes.
Occurrence :
In humans and animals, Its important this division occurs in the testis to produce the
male gametes ( sperms) and in the ovary to form t he female gametes ( ova).
in flowering plants this division occurs in the anther to produce the pollen grains and in the flower ovary to form an egg.
Importance :production of male gametes and females gametes to complete the sexual reproduction.
Phases of meiosis:
1 – First meiotic division
2 – Second meiotic division.
First meiotic division
Prophase 1 , Metaphase 1 , Anaphase 1 and Telophase 1
The crossing over phenomenon
At the end of prophase I, some parts of the two inner chromatids of each tetrad are exchanged to produce new genetic arrangements. This process is called the crossing over phenomenon.
Crossing over phenomenon
It is a phenomenon that takes place at the end of prophase 1 and in which some parts of the two inner chromatids of each tetrad are exchanged to produce new genetic arrangements.




Motion in One Direction .
Graphic Rep. of Moving in a Straight Line
Physical Quantities, Scalars and Vectors
Mirrors Lenses
The Universe and the Solar System
cell division - sexual

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