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Lecture 15

BIO205 Lecture 15 (Oct 29, 2012).doc

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University of Toronto Mississauga
Christoph Richter

BIO205 Lecture 15 - Ecological and evolutionary effects of herbivory and competition on plant communities at Silwood Park, England - Goals o Ecological importance of plant competition and herbivory o Field techniques o Complexity of field ecology methods and results o Interrelatedness of ecology and evolution - Outline o Plant competition o Plant herbivore interactions o Grasslands of Silwood Park o Ecological effects of competition o Ecological effects of herbivory o Evolutionary effects of herbivory - Species interactions o Competition and parasitism - Plant competition o dominant form of competition in the ecological system o evolve to compete better with other plants o tall trees are always competing for light o desert plants are always competing for water o in tropical rainforests, competition for light because it’s so condensed o there’s competition for food we eat; we grow crops selectively  teosinte corn (choose it for growing straight up and bigger kernels) - Plant herbivore interactions o dominant species interactions o 300 thousand species of plants o 1 million species of herbivores o create diversity of life and form food webs o lots of organisms eat plants directly o In Australia, they introduced rabbits in this area and they exploded and started to eat everything  A fenced area to show the differences between side with rabbits and one side without o A picture showing yellow goldenrods plots where one side has insecticides and the other side is natural  With insecticides, goldenrods grow more abundantly  Similar with other plant species o Plant herbivore coevolution  coevolution: reciprocal evolutionary change between one species to the another  animals pick and select traits in plants and then plants evolution change to affect the animals and then on and on it goes o herbivory and agriculture  infested corn - Grasslands of Silwood Park o On campus in England o Acid grassland and it’s sandy o 30 species or so - Ecological effects of competition o Studying plant competition  greenhouse experiments  growing a plant in a pot  growing a plant with competition in a pot  how long it survive (biomass); if there's competitors, the plant has lower biomass o plant competition experiment  Hypothesis: grasses competitively exclude herbs within plant communities  Herbs (all plants other than grasses)  Grass herbicides to kill all the grasses  To compare the conditions of when grass are there and when it’s not  Results • whole bar is the biomass of all plants and then broken down • left bar is when grass isn't there and it increases the biomass, which is strange because grass is the dominant species; maybe grass use up too much nitrogen so that when there's no grass, the other plants can grow better • usually grass makes up half the community (biomass) on the right bar • grasses are huge component of reducing herbs; suppresses their growth - ecological effects of herbivory o herbivore removal experiment  hypothesis: herbivory by insects and molluscs shape composition of plant communities  using similar plots and looking at plant communities  4
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