Hii!
You have asked for CBSE class 12 syllabus for biology for the academic year 2020-2021. Let me tell you it has been decided by the MHRD ministry that 30% of the syllabus will be reduced.
The chapterswhich are expected to be deleted are-
* Reproduction in organism
*  Evolution
* Strategies for enhancement in food production
* Ecosystem.
However, you may visit the CBSE official website to check the same.
These chapters will be covered in other activities.
Hope this helps.
Good luck!

Hi Amar,

The revised syllabus of Class 12th CBSE Biology for the academic session 2020 - 21 is as follows:-

Unit-I Diversity of Living Organisms

• Chapter-1: The Living World
• Chapter-2: Biological Classification
• Chapter-3: Plant Kingdom
• Chapter-4: Animal Kingdom

Unit-II Structural Organization in Animals and Plants

• Chapter-5: Morphology of Flowering Plants
• Chapter-7: Structural Organisation in Animals

Unit-III Cell: Structure and Function

• Chapter-8: Cell-The Unit of Life
• Chapter-9: Biomolecules
• Chapter-10: Cell Cycle and Cell Division

Unit-IV Plant Physiology

• Chapter-13: Photosynthesis in Higher Plants
• Chapter-14: Respiration in Plants
• Chapter-15: Plant - Growth and Development

Unit-V Human Physiology

• Chapter-17: Breathing and Exchange of Gases
• Chapter-18: Body Fluids and Circulation
• Chapter-19: Excretory Products and their Elimination
• Chapter-20: Locomotion and Movement
• Chapter-21: Neural Control and Coordination
• Chapter-22: Chemical Coordination and Integration

Refer here for full detailed syllabus of Biology - http://cbseacademic.nic.in/web_material/CurriculumMain21/revisedsyllabi/SrSecondary/REVISEDBiology_2020-21.pdf

Feel free to ask doubts in the Comment Section.

I hope this information helps you.

Good Luck!