Biogeographical Regions
Geography & ENVS
World Biogeographical Regions
Basis of Identifying Regions
- Species Composition and Endemism: The presence of species found nowhere else. E.g., ~80% of Australian mammals are endemic.
- Species Turnover (Beta Diversity): How rapidly species change across boundaries. E.g., The Wallace Line marks a dramatic boundary between Asian and Australasian species.
- Shared Evolutionary History: Organisms evolving together over millions of years.
- Physical Barriers: Oceans, mountain ranges, and deserts prevent gene flow.
Geographical Forces of Development
- Continental Drift: The breakup of Pangaea isolated populations, allowing independent evolution (e.g., Neotropical fauna evolving after separating from Africa).
- Oceans as Barriers: The Atlantic separates the Nearctic from the Palearctic.
- Mountain Ranges: The Himalayas protect the warm Indomalayan realm from cold Central Asian air.
- Climate Zonation: Tropical zones yield rainforests; subtropical zones yield deserts.
The Eight Realms: Overview
| Realm | Key Characteristics | Flagship Species |
|---|---|---|
| Nearctic | North America; Boreal forests, prairies. Shared affinities with Palearctic (Holarctic). | Bison, Bald eagle, Grizzly bear |
| Neotropical | South/Central America. Highest biodiversity on Earth (~10% in Amazon). | Jaguar, Macaw, Poison dart frog |
| Palearctic | Largest realm. Europe, North Africa, Northern Asia. | Brown bear, Siberian tiger |
| Afrotropical | Sub-Saharan Africa, Madagascar. Extreme endemism in Madagascar. | Elephant, Lion, Lemur |
| Indomalayan | India, SE Asia. Separated from Australasia by Wallace Line. | Bengal tiger, Orangutan |
| Australasian | Australia, NZ. Highest proportion of endemic species (marsupials, monotremes). | Kangaroo, Platypus, Emu |
| Oceanian | Pacific islands. Low species richness but very high endemism. Dominated by birds. | Hawaiian honeycreeper |
| Antarctic | Smallest, most isolated. No land mammals/reptiles. Rich marine food web. | Emperor penguin, Blue whale |
Self-Assessment: Set 1
Topics: Identification Basis, Geographical & Biological Reasons.
Rules: 15 Questions. 15 Minutes. Submit to see your score.
Self-Assessment: Set 2
Topics: The Eight Biogeographical Realms, Flora & Fauna.
Rules: 15 Questions. 15 Minutes. Submit to see your score.
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