Class 11 Biology Notes | Chapter 7: Protists and Fungi (FBISE, Best for Exams)

 Protists and Fungi| Best 11th Class Biology Notes | Federal Board 

Chapter 6 : 

Protists and Fungi 

7. PROTISTS AND FUNGI

7.1 Protists – Evolutionary Relationships

• Eukaryotic cells: Nucleus + membrane-bound organelles (mitochondria, plastids)
• Polyphyletic origin: No single common ancestor; grouped for convenience
• Diversity:
  • Size: Microscopic (e.g., Amoeba) → 60m (e.g., kelps)
  • Body forms: Unicellular, colonial, coenocytic, multicellular (simple tissues)
  • Nutrition: Autotrophic (algae), heterotrophic (protozoa, slime molds), parasitic
  • Locomotion: Pseudopodia, cilia, flagella
  • Habitat: Mostly aquatic (plankton), symbiotic (mutualism/parasitism)
• Reproduction:
  • Asexual (common) + Sexual (meiosis + syngamy)
  • No multicellular sex organs/embryos

7.2 Major Groups of Protists

Protozoa (Animal-like)

• Examples: Amoeba, Paramecium, Plasmodium, Trypanosoma
• Locomotion:
  • Pseudopodia (Amoeba)
  • Flagella (Trypanosoma)
  • Cilia (Paramecium)
• Structures: Contractile vacuoles, shells (e.g., foraminifera)
• Reproduction: Asexual (cyst formation), sexual

Algae (Plant-like)

• Groups:
  1. Euglenoids (e.g., Euglena): Mixotrophic (chloroplasts/absorption)
  2. Dinoflagellates: Cellulose plates; red tides (neurotoxins)
  3. Diatoms: Silica shells; major oceanic producers
  4. Brown Algae (e.g., kelps): Cool marine habitats
  5. Red Algae: Warm seawater; agar production
  6. Green Algae (e.g., Volvox, Spirogyra): Freshwater/land; ancestral to plants

Fungi-like Protists

• Myxomycota (Slime Molds):
  • Plasmodial stage → sporangia (meiosis → spores)
  • Resemble fungi/amoebae
• Oomycota (Water Molds):
  • Cellulose cell walls (unlike fungi)
  • Zoospores (2 flagella); oospores (sexual)
  • Example: Phytophthora infestans (potato blight)

7.3 General Characteristics of Fungi

• Structure: Mycelium (hyphae network); septate/coenocytic hyphae
• Nutrition: Heterotrophic (absorption); cell walls (chitin)
• Reproduction:
  • Asexual: Spores (conidia), budding (yeast)
  • Sexual: Zygospores (Zygomycota), ascospores (Ascomycota), basidiospores (Basidiomycota)
• Nuclear mitosis: Envelope remains intact

7.4 Diversity Among Fungi

Zygomycota (e.g., Rhizopus)

• Asexual: Sporangia → spores
• Sexual: Conjugation → zygospores (thick-walled)

Ascomycota (e.g., yeast, Penicillium)

• Asexual: Conidia (conidiophores)
• Sexual: Ascus (8 ascospores); ascocarps (fruiting bodies)

Basidiomycota (e.g., mushrooms)

• Structure: Basidiocarp (cap + gills + stalk)
• Life cycle: Dikaryotic hyphae → basidiospores (meiosis)

Deuteromycota (Imperfect Fungi)

• Examples: Aspergillus, Alternaria
• Reproduction: Only asexual (parasexuality)

7.5 Importance of Fungi

Benefits

• Food: Mushrooms, truffles, yeast (bread/beer)
• Medicine: Antibiotics (penicillin, cyclosporins)
• Industry: Single-cell protein (SCP), enzymes

Ecological Roles

• Decomposition: CO₂ release, humus formation
• Mutualism: Lichens (algae + fungi), mycorrhizae (plant roots + fungi)

Pathogens

• Plants: Rusts, smuts, blights (e.g., Phytophthora)
• Animals/Humans:
  • Superficial (ringworm, athlete’s foot)
  • Systemic (histoplasmosis, candidiasis)
  • Toxins (aflatoxins, ergotism)