Labs / Biology
Island Biogeography
New species keep paddling out from the mainland while species already on the island keep dying out. Drag the island closer or farther, resize it, and add a land bridge — the balance point between arrivals and losses (S*) is the number of species the island can hold.
S 6S* 0colonized 0extinct 0
What to try
- Slide the island far out to sea. Why does the immigration line sag, and where does S* end up?
- Shrink the island to a speck. Which curve moves, and what happens to the extinction rate?
- Can you find a near, tiny island and a far, huge one that hold the same number of species?
- Flip on the land bridge. Why does connecting to the mainland push S* higher on both counts?
- The species count keeps twitching even at equilibrium — if arrivals equal losses, why is the list never the same species?