Final answer:
The number of species on an island is determined by the theory of island biogeography, which describes a balance between species immigration and extinction, affected by island size and isolation.
Step-by-step explanation:
Island Biogeography
The theory of island biogeography postulates that the number of species on an island represents a dynamic equilibrium between the immigration of new species and the extinction of previously established species. This equilibrium is influenced by factors such as the island's isolation, with islands farther from the mainland having lower immigration rates, leading to a lower equilibrium number of species. Likewise, smaller islands, being harder to find and supporting smaller populations, also suffer from lower immigration rates and higher probabilities of extinction, contributing to the dynamic balance of biodiversity on these 'islands.'
Optimal preserve design is based on these principles as conservationists aim to maintain biodiversity, particularly in fragmented habitats that function like metaphorical islands surrounded by developed land. Such fragmented landscapes mimic the condition of real islands and can be managed using insights from island biogeography.