BIO120H1 Lecture Notes - Lecture 13: Montane Ecosystems, Habitat, Atmospheric Circulation

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12 Jul 2017
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BIO120: Species Ranges and Limiting Factors; Climate (Lecture 13)
Where Does BIO120 Fit Conceptually?
-why questions
-answers tend to be evolutionary answers
-how does the world work
-interested in these questions considering levels of whole organisms and up
questions have to do with how whole organisms are doing
-reproductive biology: one of the two things that characterize life on earth
life only persists through reproduction
-second characteristic: life is short, all things die
death is another aspect of our existence, why do we die?
Ecology
-science of ecology: science of distribution and abundance of organisms
-why do we find organisms where they are, why are some of them numerous and some
rare?
Habitats and Organisms Patchy at All Scales
-global:
Middle East: deserts, dry, hot, stresses
Asia: lush vegetation, animals depend on this
-regional:
low-elevation sage brush and short grassland
coniferous forests (spruce and fir trees, on sides of mountains)
tundra vegetation (on tops of mountains)
-habitat:
sub-alpine meadow: grasslands, flowering plants, trees are all one species (low
elevation)
higher elevation: trees replaced by spruce forest
-microhabitat:
desert, but wet winter, annual plants
non-random patchiness of plants
-smaller microhabitat
lichens: slow-growing symbiotic combinations of algae and fungus
distributed in non-random way
Abiotic (Physical/Chemical) Factors: Resources and Conditions
-resources are exhaustible: nutrients, space, etc.
chemical things that organisms use up
-conditions are not exhaustible: temperature, pH, salinity, etc.
more physical than chemical, adjust behaviour and how you live to adjust to changes
-conditions vary across space and time; we envision gradients of conditions
no physical factors are evenly spread across face of world
-organisms perform best at certain levels (i.e. at certain portions of a gradient)
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organisms distributed across gradients in particular ways that relate to organisms range
of tolerance for each of these factors
Species Have High Ranges of Tolerance along Environmental Gradients
-gradient of some resource like temperature that runs from low to high on the x-axis
-graph how well particular species of organism can perform along different points of
gradient
-performance graph: range of tolerance
-typically bell-shaped
how much of bell you see depends on how much of gradient sample represents
-sweet spot where organism thriving, conditions very good: reproductive zone
-between those levels, organisms can survive and grow, and reproduce
harvesting enough resources and doing well enough
-more marginal habitats: first thing that drops out is ability to reproduce, but organisms
may still be able to survive
-farther: may be able to survive, but not grow
-outside S, zones where organisms can’t survive (dead/lethal zones)
-hierarchy of survival, growth, reproduction
What Factors are Most Important
-factors that determine ranges of tolerance, different for plants and animals
-for terrestrial plants (in order of importance):
temperature
soil moisture
nutrients (N most important, then P, K); other trace elements needed in small quantities
disturbance (especially fire, also windstorms, floods, landslides); can wipe out plant in
one place, may take a long time for it to recover
interactions with other organisms: herbivory, diseases, pollinators, seed dispersers,
mycorrhizal fungi
-for aquatic plants: add salinity, remove moisture and fire, P is key
-for terrestrial animals:
food and water
temperature
habitat quality (cover, nesting sites)
predation, disease
-for aquatic animals: add salinity/osmotic pressure
-animals will tend to follow plants
found in particular places where plant able to support them
overall dryness of habitat isn’t as important
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