Class 11 Biology | Biological Classification - XVII

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In this final video of Chapter 2 – Biological Classification (Page 17), we’ll study Viroids and Lichens — fascinating biological entities that connect the plant, fungal, and viral worlds.
This topic often appears in NEET Biology and CBSE Class 11 exams, so watch till the end for complete clarity!

📚 Topics Covered (Page 17):

🧬 1️⃣ Viroids:

Discovered by T.O. Diener (1971) while studying Potato Spindle Tuber Disease

Smaller than viruses; infectious RNA particles without a protein coat

Cause several plant diseases

Represent the simplest form of infection-causing agents

Example: Potato Spindle Tuber Viroid (PSTVd)

🍃 2️⃣ Lichens:

Symbiotic association between Algae (or Cyanobacteria) and Fungi

Algal component – Phycobiont (photosynthetic partner)

Fungal component – Mycobiont (provides shelter & minerals)

Found on tree bark, rocks, walls, and soil surfaces

Ecological importance:

Indicators of air pollution

Help in soil formation by breaking rocks

Examples: Usnea, Cladonia, Parmelia

💡 Highlights:

Final concept of Biological Classification

Based on Nectar Education Class 11 Biology Book & NCERT Biology

Must-watch summary for NEET 2025 & CBSE revision

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📺 Previous Video: Structure of Viruses (Page 16 – Biological Classification)

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