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Review of Population Topics Biodiversity: Species diversity: combination of: species richness - the number of different species it contains species evenness - abundance of individuals within each of those species Biggest threat to Biodiversity is habitat loss Biodiversity Species richness: Equal – both have 10 species But clearly B is far less diverse….because 1 species is dominant – have to look at evenness Species evenness: For A: 10 species with 10 indiv each For B: 1 species has 82 indiv 9 species have 2 indiv Invasive species Nonnative (Introduced) • They lower biodiversity – The can outcompete the native species – This displaces / kills native species • The can adapt very quickly to local habitats • They have no/few natural predators • They can reproduce very quickly Importation of Species • Ex. The Chinese chestnut had a fungus that spread & virtually eliminated the American chestnut. • Kudzu Keystone Species: Major Players • Keystone species help determine the types and numbers of other species in a community thereby helping to sustain it. Figures 7-4 and 7-5 Keystone Species • Keystone species- a species that plays a role in its community that is far more important than its relative abundance might suggest. Succession • Succession is a series of changes that occur as an ecosystem develops – Initial species are called pioneer species – they set the stage for the appearance of other species – eventually resulting in a climax or mature community. • Primary – Starts with bare rock – ex.: volcanic flows, glacier movement • Secondary – Soil already there, after a major ecological disruption – Ex: post mining, post fire, post flood Tragedy of the Commons Be prepared to explain & give examples