Chapter 13.1 — Biodiversity 🎉

1. A Quick Tour of Life’s Amazing Variety 🌏

  • Earth wows us with 20 000 + ants, 300 000 + beetles, 28 000 + fishes and ~20 000 orchids – and that’s just a teaser! :contentReference[oaicite:21]{index=21}
  • Biodiversity is the total variety found at every level of biology – from molecules 🔬 to whole biomes. :contentReference[oaicite:22]{index=22}

2. Three Levels to Remember 📚

  1. Genetic diversity – e.g., Rauwolfia vomitoria makes different amounts of reserpine in separate Himalayan ranges; India alone boasts 50 000 rice strains and 1 000 mango varieties. 🍚🥭 :contentReference[oaicite:23]{index=23}
  2. Species diversity – the Western Ghats shelter more amphibian species than the Eastern Ghats. 🐸 :contentReference[oaicite:24]{index=24}
  3. Ecological diversity – deserts, rain-forests, mangroves, coral reefs, wetlands, estuaries, alpine meadows… India has them all! 🌵🌊🏔️ :contentReference[oaicite:25]{index=25}

3. How Many Species Are There? 🔍

  • 1.5 million species are formally described so far. :contentReference[oaicite:26]{index=26}
  • Robert May’s careful estimate: ≈ 7 million species exist worldwide. :contentReference[oaicite:27]{index=27}
  • Animals dominate ( > 70 %), plants ~22 %. Seven out of every ten animals are insects! 🐞 :contentReference[oaicite:28]{index=28}
  • India owns just 2.4 % of land but a hefty 8.1 % of global species (≈ 45 000 plants + > 90 000 animals recorded). 🇮🇳 :contentReference[oaicite:29]{index=29}

4. Patterns of Biodiversity 🗺️

4.1 Latitudinal Gradient ☀️

Species richness drops from equator to poles. Example:

  • Colombia (~0°) → 1 400 bird species
  • New York (41° N) → 105 species
  • Greenland (71° N) → 56 species

The Amazon rainforest tops the charts with 40 000 + plants, 3 000 fishes, 1 300 birds and more! 🌳🦜 :contentReference[oaicite:30]{index=30}

Why more in the tropics?

  1. Longer, uninterrupted evolutionary time ⏳
  2. Stable, predictable climate 📆
  3. Higher solar energy → greater productivity ☀️

4.2 Species–Area Relationship 📈

Humboldt discovered that species richness rises with area but only to a limit. On a log scale it’s a straight line:

\( \log S \;=\; \log C + Z \log A \)

  • Typical slope \( Z \) ranges 0.1 – 0.2 for local areas.
  • For huge scales (whole continents) \( Z \) steepens to 0.6 – 1.2; frugivorous birds + mammals show \( Z = 1.15 \). :contentReference[oaicite:31]{index=31}

5. Why Lots of Species Matter ⚖️

  • Experiments show plots with more species swing less year-to-year and produce more biomass. 🌱💪 :contentReference[oaicite:32]{index=32}
  • Rivet-Popper Analogy ✈️ – lose too many “rivets” (species) and ecosystem “plane” risks collapse. :contentReference[oaicite:33]{index=33}

6. Loss of Biodiversity 😢

We are in the Sixth Mass Extinction; extinction rates today are 100 – 1 000 × faster than pre-human times. 💔 :contentReference[oaicite:34]{index=34}

6.1 The Evil Quartet 👿👿👿👿

  1. Habitat loss & fragmentation – tropical rain-forests now cover < 6 % of land (was 14 %). 🌳 :contentReference[oaicite:35]{index=35}
  2. Over-exploitation – e.g., Steller’s sea-cow, passenger pigeon. 🎣 :contentReference[oaicite:36]{index=36}
  3. Alien species invasion – Nile perch in Lake Victoria wiped out > 200 native cichlids; water-hyacinth chokes waterways. 🌿🐟 :contentReference[oaicite:37]{index=37}
  4. Co-extinctions – lose a host and its obligate partners vanish too (hosts ↔ parasites, plant ↔ pollinator). 🔗 :contentReference[oaicite:38]{index=38}

7. (Brief) Why We Should Care 🌟

  • Narrow utilitarian – food, fibres, drugs (25 % of modern medicines are plant-derived). 💊🌾 :contentReference[oaicite:39]{index=39}
  • Broad utilitarian – ecosystems regulate climate, cleanse water, pollinate crops, cycle nutrients. 🌧️🐝 :contentReference[oaicite:40]{index=40}
  • Ethical – every form of life has a right to live; we’re stewards, not owners. 🤝

🌟 High-Yield NEET Nuggets 🌟

  1. Three Levels of Biodiversity (Genetic, Species, Ecological) plus Indian examples.
  2. Latitudinal Gradient: equator > poles + reasons (time, stability, energy).
  3. Species–Area Equation \( \log S = \log C + Z \log A \) and typical \( Z \) values.
  4. Evil Quartet: four major human-driven causes of extinction.
  5. Rivet-Popper Hypothesis: link between species richness and ecosystem stability.

Keep exploring – biodiversity is not just a chapter, it’s our life-support system! 🌍💚