Lecture 12 - 3/1/2011 Announcements Tutorial # 3 posted and...

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Unformatted text preview: 3/1/2011 Announcements Tutorial # 3 posted and will run next week Midterms marks will be posted by Mon Mar 7th, and returned next week in tutorial Final Exam: Tuesday April 26, 2-5pm A-Sc: EX200 Se – Z: EX100 Environment Career Day Ecosystems ENV200H1S – March 1, 2011 1 Outline Biomes – geographic variation (p.162(p.162188, Supp 57-65) 57Ecosystems Services (p. 205) Ecological Niches Ecological Interactions (p.146-152, Supp p.146-152, 3535-40) HART HOUSE, GREAT HALL THUR, MARCH 3rd , 10-3 10http://careerday.environment.utoronto.ca/ Review: Introduction to Ecosystems Characteristics of ecosystems Abiotic factors Biotic factors Thur Mar 3: Evolution & Natural Selection (p.188(p.188192, Supp 21-33) 21Tues Mar 8: Biological Diversity (Ch 7, Supp 40-41) 40Thur Mar 10: Biogeography and Conservation Biology (Supp 46-57) 463 Geographic Variation 2 4 Figure. 6.1 – The World’s Terrestrial Biomes variation in kinds and #s of species found on the Planet as a function of geographic variation biomes can be classified by a system corresponding to latitude (temperature) and humidity Community, ecosystem, landscape, biomes Characteristic assemblage of plants and animals that have adapted and evolved to specific climatic conditions 5 6 1 3/1/2011 Variation across Canada’s 49th parallel Figure 6.2 – How Climate Shapes Terrestrial Biomes 7 8 In aquatic systems, moisture is irrelevant but temperature, light, nutrients and a variety of biological interactions remain important variables regulating species distributions Designating large areas as biomes is somewhat of an oversimplification given the 3 dimensional structure of landscapes 9 10 Ocean nutrient levels (oxygen, phosphorus and light) Ecosystem Services (p.205) (p.205) 11 Environmental benefits provided by ecosystems Often taken for granted 31 2 3/1/2011 How Ecosystems Organize Themselves Niches: How Species Coexist Competition exclusion principle – two species that have exactly the same requirements cannot coexist in the exactly the same habitat Habitat complexity Ecological niche – what an organism does for a living (profession) Measured as set of all environmental conditions under which species can persist and carry out its life function Fundamental vs. realized vs. niches However having a wide tolerance range (a wide fundamental niche) niche) does not ‘guarantee’ a species will occupy the whole of the niche Biological interactions with other species may restrict organisms to a realized niche that is ‘smaller’ than their fundamental niche. work by Robert MacArthur These 5 wood warbler species could utilize the whole tree (fundamental niche), but do not. Why? 13 Interactions Between Species Symbiosis Symbiosis - Mutualism Symbiosis Benefits both Parasitism (predation): • benefits one but detrimental to the other 14 A relationship between two organisms from which both benefit Competition • Outcome negative for both pollination mutualisms 15 More mutualisms 16 Speaking of mutualisms! The large fruits of the Saguaro cactus provide food for the whitewhitewinged dove The bird consumes the fruit, ingesting the cactus' seeds cactus seeds The bird then flies off, and later deposits the seeds in a new location (with a nice dose of fertilizer to boot!) A dispersal mutualism EEB 303H: Tropical Ecology and Evolution La Selva National Park, Costa Rica www.marietta.edu/~biol/biomes/symbiosis.htm 17 1. The leafcutter ant on the left is tending the fungus Leucocoprinus Leucocoprinus in the ants’ underground nest. The ants eat this fungus exclusively while the fungus is completely dependent on the ants for its survival in the nest. 2.The 2. The ants bring in nutrients (leaf bits of specific plants), prune the fungus, transfer it to new bits of it bit leaves leaves (and even to new ant nests). 3.The 3. The ants enlist a second symbiont – a Streptomyces bacteria – that Streptomyces bacteria the ants grow in specially modified areas of their own exoskeletons. 4.The Streptomyces produces 4. The Streptomyces produces an “antibiotic” that inhibits the growth of a second fungi, Escovopsis , Escovopsis which can invade the nest, overgrow and destroy the Leucocoprinus Leucocoprinus fungus fungus that the ants feed on. 18 3 3/1/2011 parasitism A relationship between two organisms where one benefits and one is harmed. Some parasites have little contact with their “hosts” The brown-headed cowbird, a brood or nest parasite Wasp (parasitoid) larva on a caterpillar (an ecoparasite) Evolutionarily, “cowbirds” lived in association with buffalo, whose migratory lifestyle did not leave sufficient time to raise chicks. The adaptation? Leave your eggs for somebody else to raise and follow the herd! Parasitism is not all that different from predation – it’s exploitative 19 20 Another example: freshwater flatworms or Planaria Planaria Competition: Recall the wood warblers and the difference between their fundamental and realized niches Where niches overlap, species could be in ‘competition’ for the same resource 21 22 There appears to be an “advantage” to “co“co-existing” or avoiding competition: optimizing allocation of energy Why does it matter whether species compete for the same resource? Feeding Basal metabolism Reproduction Predator avoidance This vs. this Sleep How do organisms “divideup” the habitat and why? 23 If an organism can avoid spending time competing with other organisms, it can spend more time (and devote more energy) to finding a mate, reproducing and caring for young (increasing the chances that its genes will persist into the next generation in the form of more offspring) Perhaps at the expense of the organisms who spend more of their time competing 24 4 3/1/2011 Rather than competing, these 5 species of warblers avoid competition by partitioning their habitat or by “co-existing” (over long “coevolutionary time, each has developed a unique approach to feeding) The species of organisms we see coexisting today may be the result of th competitive competitive interactions that took place thousands or millions of years ago (the ghost of (the competition past) past) Plants also exhibit strategies to avoid competition over nutrients, water, light or pollinators (i.e. co-exist) coPlants with different shaped leaves can both obtain light permitting them to coexist Plants with fibrous roots may coexist with plants with taproots as each is drawing water and nutrients from different soil horizons 25 Species of wood warblers or planaria or plants represent examples of avoidance of interspecific competition. However organisms might also compete with other members of their own species (intraspecific (intraspecific competition) with similarly negative results Differentiation between larvae and adult, e.g. larval adult, e.g. larval caterpillars and adult moths or butterflies, is assumed to be a mechanism to avoid intraspecific competition Territoriality is another mechanism for avoiding intraspecific competition Wood wren 27 Here’s how the “story” goes: Imagine Imagine a situation where 2 species of warblers “compete” for insects on a spruce tree (e.g. spending time and energy chasing each other from a particular place in the tree) Now Now imagine a behavioural change (likely driven by a random mutation) by by which some individuals move to a unique unique area of the tree to feed Now Now the warbler neither has to chase away others (or be chased), it has more time to gather insects than individuals who are still competing With With more energy available to devote to reproduction, it raises more chicks than the individuals who are still competing 26 stuart mcdonald (FlickR) Over time (a long time!), the population will come to be dominated by the individuals with the unique feeding behaviour 29 28 Over Over time (and assuming a reasonably stable environment), environment), random genetic changes (mutations) could confer on some individuals an increased ability to better exploit a narrower segment of the resource gradient. These These individuals thus avoid niche overlap and potential competition (whether intra or inter). IF IF this proves “successful” (i.e. the individuals with with this characteristic leave more offspring than individuals without the characteristic), then over time more and more individuals of that species will come to possess the characteristic over time The The result is that the population will be ever more finely tuned to its environment! 30 5 3/1/2011 The “original” situation Over time, in reasonably time in reasonably stable/predictable environments, populations are expected to exhibit progressively narrower realized niches, i.e. to become more specialized The long term outcome 31 6 ...
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