Lecture 1 - 23 and Nature article readings

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12 Dec 2012
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Lecture 1 Content
Abiotic Factors (for success)
Resources (are exhaustible): nutrients and space
Conditions (are not exhaustible): Temperature, pH
o Vary across space and time
All organisms perform best at certain levels.
o We expect organisms need a range of tolerance
o From Survival Growth Reproduction
Most important factors that limit distribution?
For terrestrial Plants (most important to least):
o Temperature (this and soil are most important)
o Soil moisture
o Nutrients (N most important, then P, K)
o Disturbances (esp. fire)
o Disease, pollinators, etc etc)
For Terrestrial animals
o Food and water
o Temperature
o Habitat quality
o Predation, disease
o Tend to follow plants
Variations in the Above Factors
Temperature is a function of latitude
o High latitude are colder, and seasons depend on temperature
o Lower latitudes are warmer, and seasons depend on rainfall
Rainfall depends on atmospheric circulations
Lecture 2 Content
Heat Balancing
Size
o SA:Volume ratio
o SA determines the equilibration rate
o Volumes provides the inertia
o THUS, big things with huge ratios will equilibrate slowly compared to smaller
things
o Bergmann’s rule
Homeotherms are larger at higher latitudes (colder)
Duh, cause you don’t want the outside environment affecting their
inner environment quickly. Low SA:V ratio
Shape
o Allen’s rule
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Appendages (anything outside the body) is reduced in cold climates
So technically why isn’t everything a sphere? Lowest possible SA:V
Well we need some SA for function
Hot environments you want to lose heat therefore want large SA, you
typically find flat animals in hot environments
(flying snake)
(pika’s very minimum SA:V ratio as they form a sphere and curl
up into a ball, small ears as well, good for cold habitats so you
don’t lose heat as quickly)
Insulation (more important than size/shape)
o Hairs, feathers, blubber
Vascularization
o Like the hare, can use blood vessels in ear to dump heat into the environment
Countercurrent circulation
o Used to conserve heat
o So if you have a small distance from arteries and veins, (appressed vessels) then
returning blood can be warm due to gradient
If vessels are not appressed then returning blood is chilled
Convection and Evaporation
Lecture 3 Content
Why doesn’t natural selection produce perfect species?
Weasel body shape
o NS does not produce perfection
o Short furred, but very long and thin
High SA:V, and they curl to a flat disk (higher SA compared to balls)
Yet they live in cold climates Why?
o Remember, Constraints and Tradeoffs
Weasels trade off a low SA:V shape/size so that they can fit in narrow
burrows to get food
Like the pocket gopher
Basically, being thin has more fitness gains, then the fitness cost of an
expensive metabolism to staying warm due to higher SA:V ratio
o THUS, NS can’t maximize everything, but gives you the best option
2 reasons
o 1) Tradeoffs
Being good at (x) doesn’t mean being bad at (y)
o 2) Constraints
NS can only build on what is already there
Example: can’t just make wings out of nothing for humans
NS can tinker, but cant redesign
Kangaroo Rats
Osmotic Balance (conserving water in hot dry envivronments)
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o 1) Bipedal, thus less heat gain from conduction from the ground
o 2) Super efficient kidneys and metabolic sufficient
Can make fat into water so they don’t need to go drink water, just need fat
as a food source
o 3) Nocturnal
Spends hot days underground
o 4) Cache seeds
They put seeds underground that recapture water vapor from exhalation
from the k-rats!
When Physiological Stress becomes Overwhelming
Enter dormant stage with minimal metabolism (refer to Torpor)
Hibernate
Store Food
Migrate
Both migration and Hibernation are driven by food supply than abiotic stress
Lecture 4 Content
Plant Ecophysiology of Carbon Balance
Autotrophs depend on net photosynthesis
o CO2 + H2O  Carbohydrates + O2
o Must take in light, gases and water into photosynthetic tissue
Requires a range of temperature, osmotic balance, enzymes, and nutrients
from soil (N,K,P)
o Ultimately, the anatomy and physiology of plants will reflect constraints
Plant Structure
Photosynthetic structures
o Normally the leaves, but can be stems
o Leaf size and shape
Are thin and flat (thus high SA:volume ratio)
Benefits, would be great SA for photosynthesis
Costs, would be bad for overheating, and water lost
Can also influence gas exchange through laminar flow vs. turbulent flow
Plants don’t want stream line flow (laminar) because there is a
boundary layer, that decreases the velocity of air
Want turbulent flow so you get eddies, that eliminate the boundary
layer
Thus, keeps the plant cool and lots of gases for exchange
You’ll see leafs with holes, used for turbulance
o Stomata
Will open and close
Closes so that the leaf won’t lose water, but then it can’t cool the
leaf either. Shuts off all photosynthesis
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