Note4Students
From UPSC perspective, the following things are important :
Prelims level: Wallace Line
Why in the News?
In the 19th century, English naturalist Alfred Russel Wallace observed a sharp shift in biodiversity as he moved from Asia to Australia, leading him to propose the Wallace Line—an imaginary boundary separating species from both regions.
About the Wallace Line:
- It is a bio-geographical boundary separating Asia and Australia’s eco-zones.
- It was identified by Alfred Russel Wallace in 1863 during his explorations.
- It is an imaginary line running through the Lombok Strait (between Bali and Lombok) and the Makassar Strait (between Borneo and Sulawesi).
- Distinct evolutionary histories:
- West of the line (Asia): Tigers, elephants, and orangutans.
- East of the line (Australia): Kangaroos, marsupials, and cockatoos.
- A very few species cross the line, particularly birds and mammals.
- This is a barrier for land species but not marine life.
- Its formation:
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- Continental drift: Australia separated from Antarctica and moved toward Asia (~35 million years ago). This created a deep-water channel, preventing species migration.
- Pleistocene Epoch Influence: Lower sea levels exposed land bridges but deep waters maintained the boundary.
Scientific Relevance:
- Wallace Line is more of a gradient than a strict boundary.
- Understanding biogeography helps predict species adaptation to climate change.
Note:Weber Line more accurately defines the balance point where the influence of Asian and Australian species is nearly equal, whereas the Wallace Line marks a sharper divide. |
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