Theory of Island Biogeography waxaa laga yaabaa in ay tahay qaybtii ugu muhiimsaneyd ee fahamka sayniska ee labada geedi socodka iyo sida loo cabbiro heerka noocyada dabar go'a. Heerka dabar go'a asalka ah ee hadda jira waxaa lagu qiyaasaa inuu yahay hal nooc dhowrkii sanoba. Cabbirka luminta noocyada socda ayaa ka sii murugsan xaqiiqda ah in inta badan noocyada Dunida aan la sharraxin ama la qiimeyn. Qiimeyntu aad ayey u kala duwan yihiin inta nooc ee dhab ahaantii jira (qiimeyn: 3,600,000-111,700,000) illaa inta ay heleen nooc dhab ah (qiimeyn: 1.5-8 milyan oo xayawaan).
Noocyada aan la qeexin ama aan la qiimeyn