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Lecture 9

Biology Lecture 9 Article 1.docx

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University of Toronto St. George
Scott Browning

BIOLOGY LECTURE 9 Successional Changes in Communities *Change in community comp over time = SUCCESSION o Community comp changes because of succession, this change that can be influenced by environ, abiotic factors, biotic interactions, and dispersal - Exploited by humans with manipulation of habitat to promote abundance of certain plant/animal species for our benefit History of Study of Succession  Cowle! Defined laws of underlying the patterns in community change  Recognized plant communities as being dynamic  Basic idea = plant communities of different ages in sand dunes reflected how communities changed over time  Used the chronosequence approach to better understand succession *Sere: Stage in successional sequence  Succession is ubiquitous aka happens errrwhere Types of Succession Succession is categorized into 2 types, based on properties of habitat where they happen: 1) Primary Succession: colonization of habits devoid of life, happens in new habitats with no vegetation - New lands made by things that make species colonize are from outside: volcanism, dune and barrier island forms, glaciation - Rate tends to be slow cause of arduous process of soil development 2) Secondary succession: reestablishment of a community where most, but not all, orgs are destroyed Occurs in habitats following a disturbance which leaves seeds, spores of plants present *Disturbance = change the availability of resources and composition/densities of species Rate = faster because habitat readily successible Another differ = soil development In primary, takes thousands of years In secondary, usually fully developed  *Pioneer community: initial inhabitants (early serial stage)  *Climax community: final stage Models of Succession Clement: succession = deterministic + orderly sequence of seres that end with climax community Climax community characterizes habitat = “expression of the climate”  Each stage composed of a group of species viewed as a SUPPER ORG working together and developing site that was replaced by another stage Gleason: DIFFERENT VIEW  Emphasized individualistic traits (abiotic tolerance/dispersal) of species and their interactions with environment  They occur together as result of their abiotic tolerances, not because they are a “super org”  Less deterministic and more reliance on chance dispersal event  Consequence = potential for different successional trajectories = alternate climax communities Tansley: criticized Clements  illuminated view regarding individualis
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