BIO 373 1st Edition Lecture19Outline of Last Lecture I. human microbiomesa. communitiesi. subset of speciesii. structureiii. diversityiv. Shannon indexv. Commonness and rareness Outline of Current Lecture I. Communities contda. Shannon indexb. Species compositionc. Interactionsi. Direct and indirectii. Trophic cascade vs. trophic facilitationiii. Competitive networks vs. competitive hierarchiesiv. Dominant vs. keystone speciesd. Ecosystem engineerse. Context-dependenceCurrent LectureHuman Microbiomes- Communitieso Shannon indexThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. Looking at proportions of abundanceo Species composition What type of species are found in a community Want to understand and know variation of species present and species diversity between communitieso Interactions Direct interaction= two species interact with each other- A interacts with B Indirect interaction= two species share a species that they interact with- A and C do not interact but A interacts with B and C interacts with B Interactions may be positive or negative- Indirect interactions may involve both positive and negativeo Can also have direct negative interactions resulting in indirect positive interactions Trophic cascade= occurs when predators suppress abundance of prey, which helps protect a species in a lower trophic level from predation Trophic facilitation= consumer is facilitated by a species facilitating its prey (indirect)- Ex: a plant species helps another plant species grow better which helps the consumer of the planto Competitive networks vs. hierarchies Networks= indirect species interactions buffer strong, direct competition so that no one species dominates the interaction ( no none wins) Hierarchy= a species always dominates the interactiono Dominant vs. keystone species Keystone= large effects on community because of interactions rather than abundance Dominant species= dominates a community because of abundanceo Ecosystem engineers Species change characteristics of environment- Can be a dominant or keystone specieso Context- dependence Interactions of species in community can change depending on the environment- Ex: drought or flooding allows or prevents interactions and changes in
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