Island Biogeography
Introduced| English |
|---|
| immigration/ˌɪmɪˈɡreɪʃn/ |
| extinction/ekˈstɪŋkʃn/ |
| species-area/ˈspiːsiːz ˈeərɪə/ |
Why islands are special
- An island is a patch of land cut off by water.
- New species can only reach it by crossing the sea.
- This makes islands natural laboratories for studying biodiversity.
- The number of species they hold follows clear rules.
A balance of arrivals and losses
- Species reach an island by immigration 移入 — arriving from elsewhere.
- Species are lost by extinction 灭绝 — dying out on the island.
- The number of species settles where these two balance.
- More arrivals or fewer losses means more species overall.
Island biogeography says the number of species on an island is a balance between…
Species number balances immigration (arrivals) against extinction (losses) on the island.
Bigger islands, more species
- A larger island offers more habitat and more resources.
- More habitat means lower extinction rates.
- So larger islands hold more species — the species-area 物种-面积 relationship.
- Double the area and you gain a predictable jump in species.
Bigger islands hold more species
Plot island size against species number - larger islands support more species (the species-area relationship).
Compared with a small island, a large island usually has…
Larger islands have more habitat and lower extinction, so they hold more species.
An island closer to the mainland usually receives more new species.
Closer islands are easier to reach, so more species immigrate to them.
Closer islands, more arrivals
- An island near the mainland is easier for species to reach.
- So closer islands receive more immigration.
- Distant islands get fewer arrivals and hold fewer species.
- Size and distance together predict an island's biodiversity.
The link between island size and species number is called the species-____ relationship.
The species-area relationship: larger areas hold more species.
Select all true statements about island biogeography.
Island size strongly affects species number. The other three are correct.
These rules do not apply only to real islands. A patch of forest surrounded by farmland is an "island" too. Making habitat patches smaller and more isolated — as humans often do — reduces the number of species they can hold, exactly as island biogeography predicts.
Designing a nature reserve:
- Island biogeography guides how to protect species.
- A single large reserve usually holds more species than several tiny scattered ones.
- Connecting patches with corridors raises immigration and lowers extinction — keeping more species alive.
Island biogeography explains the number of species on an island as a balance between immigration (arrivals) and extinction (losses). Larger islands hold more species (the species-area relationship), and closer islands receive more arrivals. The same rules apply to isolated habitat patches on land.