How do closed populations differ from open populations in ecology?

In population ecology, the distinction between closed and open populations is defined by the presence or absence of migration.1

• Closed Populations: These are geographically isolated groups where no immigration or emigration occurs. Consequently, changes in population size are determined exclusively by the balance of births and deaths. The population at the end of a time interval is calculated as:213
  $${\text{Population}}_{\text{end}}={\text{Population}}_{\text{start}}+\text{Births}-\text{Deaths}$$1

• Open Populations: These populations are connected to others, allowing for the movement of individuals into or out of the area. Because migration is a factor, the population size is influenced by four components: births, deaths, in-migration, and out-migration. The calculation for an open population is:21
  $${\text{Population}}_{\text{end}}={\text{Population}}_{\text{start}}+\text{Births}-\text{Deaths}+\text{In-migrants}-\text{Out-migrants}$$1

While some species occupy clearly defined geographic boundaries, such as islands, many others exist as open populations with varying degrees of connectedness across broader landscapes.2