IDEA FOUND // IDEA 251
Island Biogeography
“An island's species count reflects a moving balance between arrival and disappearance.”
01 / PLAINLY
What it means, plainly
The theory links species richness with immigration, extinction, area size, and isolation.
02 / CONTEXT
A little more
Large islands generally support larger populations and more habitats; nearby islands receive colonists more easily. The predicted equilibrium is dynamic: species identity changes even when count remains similar.
03 / WHY IT MATTERS
Why it matters
It offers hypotheses for real islands and habitat fragments and has shaped conservation study design.
04 / EXAMPLE
A familiar example
A small remote islet may receive fewer species and lose populations more often than a large nearby island.
05 / LIMIT
What it does not mean
The basic model alone does not capture local evolution, species differences, landscape matrix, or human history.
06 / NOTICE
Notice it in your day
Draw four islands combining large/small and near/far. Rank expected immigration and extinction.
FINAL NOTE
The idea worth keeping
Separate area and isolation effects and treat equilibrium count as an expectation, not a fixed census.
QUESTIONS / 02
Questions people still have
Can an urban park behave like an island?
Sometimes. A fragment surrounded by a hostile matrix shares processes, although the analogy depends on the organism.
Does equilibrium mean nothing changes?
No. Immigration and extinction continue; an approximate count can persist while composition changes.