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Lecture 1- Part 11-Communities and Ecosystems.docx

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McMaster University
Jurek Kolasa

Species in communities and ecosystems: What are species? Species can occupy different parts of landscapes: A population of species might be dispersed throughout the landscape A population of species might be dispersed in the island, and areas outside the island/landscape A population of certain species might only be available in the ‘part’ of the island, and another species might just be present in that one island A community comprises species: - Entirely living in it (actually living in the habitat) - Present because they are present in the surrounding habitats (arriving for food, nesting etc.) - Present only in portions of that community habitat - These are only more or less isolated subpopulations of a larger species population - How distinct they are depends on whether individuals migrate into community or are born in it (i.e. mouse species cannot really migrate, birds species are more likely to occupy different parts of that community). The bird is still part of the community (island), but they are not dependent on it due to migration, but mice are dependent on the community for survival because they cannot leave the island/community - Community is made up of species whose membership ranges from obligatory to optional (arriving from somewhere else, come in and leave types) and whose participation is not equal (some depend on it entirely, every species make different contributions in the community) What is habitat? Meaning and Structure.  Two mice populations (small animals) are unlikely to be interacting with populations even when they are only separated by a small boundary (stream). They will be genetically close due to interactions that occur once in a while, compared to faraway species which has no interaction.  Flea and a dog: Is their habitat the same? No, see below  Habitat is defined by the perception of the organism: For the flea the habitat is the warmth of the fur, safety of the fur. For the dog: The conditions in the room, temperature in the room etc.  Is habitat always different for two species living in the same location: If yes: Compare two species: -> Greater unpredictability (chance of something unexpected to happen, hunting etc. -> Food resources are another dimension -> Competitors -> Enemies (has to do with competition or predation) -> Shelter -> Physical condition (Too cold, too warm etc.) -> Dimensions vary, these are just a few possible dimensions  Although in practice (infinite dimensions are present), but only few matters Each species have a different habitat (that connects different dimensions together)  They need
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