Island Biogeography
Introduced| English | Meaning |
|---|---|
| immigration/ˌɪmɪˈɡreɪʃn/ | immigration |
| extinction/ekˈstɪŋkʃn/ | The disappearance of a species when its last surviving individual dies. |
| species-area/ˈspiːsiːz ˈeərɪə/ | species-area |
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.
Large islands near the mainland hold the most species
Island biogeography says the number of species on an island is a balance between…
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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…
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Larger islands have more habitat and lower extinction, so they hold more species.
An island far from the mainland usually receives more new species than a closer one.
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False. Closer islands are easier to reach, so more species immigrate to them. Distant islands receive fewer colonists.
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.
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The species-area relationship: larger areas hold more species.
Select all true statements about island biogeography.
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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.