BIO 373 1st Edition Lecture20Outline of Last 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-dependenceOutline of Current Lecture I. Communities contda. Changes in communitiesi. Agents of change1. Abiotic2. Bioticii. Succession1. Primary and secondary successionThese 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.2. Early modes of succession3. Connel and Slatyer’s 3 modes of successiona. Facilitation modelb. Tolerance modelc. Inhibition modelCurrent LectureCommunities Contd- Changes in communitieso Can be caused by human impactso Agents of change in communities Abiotic- Fire, storms, earth quakes, tsunamis- Disturbance= abiotic events that injure or kill individuals and create opportunities for other individuals- Stress= an abiotic factor that reduces growth and reproduction of individuals but does not injure or kill them Biotic- Competitive networks and hierarchy - Pests and disease- Predator/prey interactiono Succession Deterministic factors Succession= change in (usually dominant) species composition in communities over time Primary succession= low frequency and high intensity of disturbance—very few communities Secondary succession= intermediate frequency and intensity of disturbance Little succession= can be low or high frequency, low intensity Trajectory of succession- Succession progresses through various stages that include a climaxstageo =stable end point that changes little- If catastrophic, pioneer stage formed through primary succession- Secondary succession will occur after a disturbance alters a community greatly but does not destroy all life Early modes- Space for time substitution- Clements= believed plan communities are like superorganisms—group of species working together towards a deterministic end (climax stage)- Gleason= communities are the random product of fluctuating environmental conditions acting on individual species Connell and Slatyer 3 modes of Succession- Facilitation modelo (Clements) early species modify environment in ways that benefit later species—species facilitations leads to climax community- Tolerance modelo Assumes earliest species modify environment but in neutral ways- Inhibition modelo Early species modify environment negatively and inhibit later
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