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Lecture

BIOL 215 Lecture Notes - Soil Fertility, Transpiration, Terrestrial Ecosystem


Department
Biology (Sci)
Course Code
BIOL 215
Professor
Neil Price

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BIOL215 Lecture 22 Notes
A classic question in ecology first posed by Andrewartha and Birch
in 1954 is what is the relationship between species distribution and
abundance
The pattern shows that most species have fairly small range sizes and
that fairly few species have large range sizes. This pattern can be seen for
birds, plants, or even animals, all showing the same distribution
Rapoport's rule shows that geographic range size of particular taxa
increases with latitude. What that shows is that in low latitude regions,
range size of mammals tend to be small and in high latitude regions,
range size of mammals is almost a factor of 10 larger, so much greater
range
Range size on a map is really looking at the geographic area that
encompasses the perimeter of a species' habitats
Rapoport's rules don’t apply to all species or situations. The ecological
explanation includes climatic variability (greater at high latitudes,
organisms should have greater tolerance to temperature survival),
product of glaciation (as glaciers retreated, new habitats became
available and the organisms who lived close to ice edge now could disperse and move into the new
habitat - only organisms who could disperse to greatly can go to new habitat), lack of competition in
polar communities (species diversity is much lower in polar than tropical habitat, thus competition is
less intense which does not force species to occupy a portion of the range which they would
otherwise occupy)
Topography (mountains vs. lowlands) interacts with latitude in affecting range size
Range size and population - abundance are positively correlated - Hanski's Rule. Essentially, the
greater the population abundance, the greater the range size and vice-versa
What mechanism is responsible for generating the positive relationship between distribution and
abundance:
Sampling issue (if abundance is low, it's difficult to observe those rare individuals in nature so it's
hard to determine the range in comparison to more abundant species)
Ecological specialization (some species are specialists. They use one or two resources and can
occupy only a narrow range of environmental conditions. Other species are generalists who have
multiple resources and can occupy a wide range of environmental conditions. You also have
species in between specialist and generalist
Local population model (populations exist as metapopulations which are separated one from the
other in a matrix of habitat that is inhospitable - those species which can traverse and disperse
across the inhospitable region to a hospitable region have more range size because they are able
to sample a much larger area)
Read chapter 22
Sun energy is what drives the operation of ecosystem. Sun energy is taken through photosynthetic
organisms (autotrophs) --> converts to chemical bond energy which are eaten by herbivores which
are eaten by carnivores. However, some of the energy from the primary producers is used by
decomposers and at each step, some of the energy is lost as waste through heat
Nutrients through decomposers will be recycled for primary producers
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