Abiotic Factors
• Resources
• Factors– Abiotic parameters that
influence organism’s distribution
Tolerance Range• Biological processes
are sensitive to environmental conditions and can only operate within relatively narrow ranges
Optimal Growth Temperatures Microbial Activity
Temperature
• Temperature and moisture are the 2 most limiting factors to the distribution of life on earth
• In the universe temperature varies between -273oC (absolute 0) and millions of degrees
Homeostasis• Definition
• Mechanisms
Thermoneutral Zone
Thermoneutral Zones
Microclimates• Macroclimate: Large scale weather variation.
• Microclimate: Small scale weather variation, usually measured over shorter time period.– Altitude
– Aspect
– Vegetation• Ecologically important microclimates.
Microclimates
• Ground Color– Darker colors absorb more visible light.
• Boulders / Burrows– Create shaded, cooler environments.
Microclimate
• The distribution of species and temperature contour maps do not always coincide
• This is because the temperatures organisms experience are greatly effected by numerous things.
Plant Resources
• Solar radiation (energy source)
• Water
• CO2
• Minerals (nutrients)
Saguaro cactus (Cereus giganteus)Distribution determined
by temp.Limited by temperature
remaining below freezing for 36 hr.
Dots are sites where temp. remains below freezing for 36 hr. or more. “X’s” are sites where these conditions have not been recorded. The dotted line is the boundary of the Sonoran desert.
Optimal Photosynthetic Temperatures
Plant distributions reflect the effects of all resources
C3 species C4 species
Highly sensitive to O2/ CO2
concentration. At low CO2 levels absorbs O2 instead.
Not sensitive to O2/ CO2 concentration. Higher affinity for CO2.
• Stomata– Bring CO2 in
– Allow H2O to escape
Leaf Structure• Top (e.g., trees)
– C3 leaves have chlorophyll throughout the interior of the leaf.
– CO2is found throughout the leaf allowing the CO2 to escape through open stomata
• Bottom (e.g., corn)– C4 species has nearly all its
chlorophyll in two types of cells which form concentric cylinders around the fine veins of the leaf.
– CO2 is concentrated in the bundle-sheath cells and isolated away from the stomata
C4 North American Distribution
• Percentage of C4 species in the grass floras of 32 regions in North America (Teeri and Stowe 1976)
C4 Australia Distribution
• Approximate contour map of C4 native grasses in Australia. Lines give percentages of C4 species in total grass flora for 75 geographic regions (Hattersley 1983).
Heat Exchange Pathways
Temperature Regulation by Plants
• Desert Plants: Must reduce heat storage.– Hs = Hcd + Hcv + Hr
– To avoid heating, plants have (3) options:• Decrease heating via conduction (Hcd).
• Increase conductive cooling (Hcv).
• Reduce radiative heating (Hr).
Temperature Regulation by Plants
Temperature Regulation by Plants
• Arctic and Alpine Plants– Two main options to stay warm:
• Tropic Alpine Plants– Rosette plants generally retain dead leaves,
which insulate and protect the stem from freezing.
• Thick pubescence increases leaf temperature
Yarrow (Achillea) along an altitudinal gradient
West East
Sierra-Nevada Range
Natural Selection
High temperatureHigh humidity
Low temperatureLow humidity Many
Generations
Cold genotype
Moderate genotype
Warm genotype
Animal Resources & Factors
• Temperature
• Oxygen, water
• Nutrition (energy source)
• Defense
Temperature and Animal Performance
• Biomolecular Level
• Heat Transfer
• Htot= Hc ± Hr ± Hs - He
Htot = total metabolic heat
Hc = Conductive & convective
Hr = Radiative
Hs = Storage
He = evaporation
Heat Exchange Pathways
Body Temperature Regulation• Poikilotherms
• Homeotherms
Body Temperature Regulation• Poikilotherms
• Homeotherms
Body Temperature Regulation
• Ectotherms
• Endotherms
Temperature Regulation by Ectothermic Animals
• Liolaemus Lizards– Thrive in cold
environments• Burrows
• Dark pigmentation
• Sun Basking
Temperature Regulation by Ectothermic Animals
• Grasshoppers– Some species adjust
for radiative heating by varying intensity of pigmentation during development
Temp Regulation - costs
Temperature Regulation by Endothermic Animals
• Regional Heterothermy
Countercurrent heat exchange: mechanisms allowing blood to flow to coldest part of extremity without loss of heat; related to vaso-dilation/constriction
Countercurrent Heat Exchange
Temperature Regulation
Temperature Regulation by Endothermic Animals
• Warming Insect Flight Muscles– Bumblebees maintain temperature of thorax
between 30o and 37o C regardless of air temperature
Temperature Regulation by Endothermic Animals
• Warming Insect Flight Muscles– Sphinx moths
(Manduca sexta) increase thoracic temperature due to flight activity
• Thermoregulates by transferring heat from the thorax to the abdomen
Temperature Regulation by Thermogenic Plants
• Almost all plants are poikilothermic ectotherms– Plants in family Araceae
use metabolic energy to heat flowers
– Skunk Cabbage (Symplocarpus foetidus) stores large quantities of starch in large root, and then translocate it to the inflorescence where it is metabolized thus generating heat
Surviving Extreme
Temperatures• Inactivity
• Reduce Metabolic Rate
Adaptations to Environmental
Extremes
• Dormancy
• Bergman’s Rule
• Allen’s Rule
Dormancy
• Diapause– Pausing life at a
specific stage
Temp. Regulation
• Bergmann’s Rule
– Retains heat better• Less surface area exposed to
outside environment– Volume increases as
cubed power
• Surface area increases as a squared power
• Bergmann’s Rule
• Allen’s Rule
– Increases surface area relative to volume
– Radiates heat better
Water Content of Air• Total Atmospheric Pressure
– Pressure exerted by all gases in the air.
• Water Vapor Pressure– Partial pressure due to water vapor.
• Saturation Water Vapor Pressure– Pressure exerted by water vapor in air saturated by
water.
• Vapor Pressure Deficit– Difference between WVP and SWVP at a particular
temperature.
Water Content of Air• Relative Humidity:
Water Vapor Density
Saturation Water Vapor Density (x 100)
• Water vapor density is measured as the water vapor per unit volume of air
• Saturation water vapor density is measured as the quantity of water vapor air can potentially hold– Temperature dependent
Water Availability
• The tendency of water to move down concentration gradients, and the magnitude of those gradients, determine whether an organism tends to lose or gain water from its environment.– Must consider an organism’s microclimate in
order to understand its water relations.
Water Content of Air• Evaporation =
much of water lost by terrestrial organisms– As water vapor in
the air ,water concentration gradient from organisms to air is reduced, thus evaporative loss
– Evaporative coolers work best in dry climates
Water Movement in Aquatic Environments
• Water moves down concentration gradient– freshwater vs. saltwater
• Aquatic organisms can be viewed as an aqueous solution bounded by a semi-permeable membrane floating in an another aqueous solution
Water Movement in Aquatic Environments
• If 2 environments differ in water or salt concentrations, substances move down their concentration gradients– Diffusion
• Osmosis: Diffusion of water through a semi-permeable membrane.
Water Movement in Aquatic Environment
• Isomotic: – [Salt]– body fluids = external fluid
• Hypoosmotic: – [Salt] <– body fluids > external fluid– Water moves out
• Hyperosmotic: – [Salt] >– body fluids < external fluids– Water moves in
Water Regulation on Land
• Terrestrial organisms face (2) major challenges:– Evaporative loss to environment.– Reduced access to replacement water.
Water Regulation on Land - Plants
Water Regulation on Land - Plants
• Wip= Wr + Wa - Wt - Ws
• Wip= Plant’s internal water
• Wr =Roots
• Wa = Air
• Wt = Transpiration
• Ws = Secretions
Water Regulation on Land - Animals
Water Regulation on Land - Animals
• Wia= Wd + Wf + Wa - We - Ws
• Wia= Animal’s internal water
• Wd = Drinking
• Wf = Food
• Wa = Absorbed by air
• We = Evaporation
• Ws = Secretion / Excretion
Water Acquisition by Plants
• Extent of plant root development often reflects differences in water availability.– Deeper roots often help plants in dry
environments extract water from deep within the soil profile.
• Park found supportive evidence via studies conducted on common Japanese grasses, Digitaria adscendens and Eleusine indica.
Xerophyte adaptation – deep roots
http://usda-ars.nmsu.edu/JER/Gibben4.gif
•Chihuahuan Desert plants showing deep root systems
Water Acquisition by Animals
• Most terrestrial animals satisfy their water needs via eating and drinking.– Can also be gained via metabolism through
oxidation of glucose:• C6H12O6 + 6O2 6CO2 + 6H2O
– Metabolic water refers to the water released during cellular respiration.
Water and Salt Balance in Aquatic Environments
• Marine Fish and Invertebrates– Isomotic organisms do not have to expend energy
overcoming osmotic gradient.• Sharks, skates, rays - Elevate blood solute concentrations
hyperosmotic to seawater.– Slowly gain water osmotically.
• Marine bony fish are strongly hypoosmotic, thus need to drink seawater for salt influx.
Water Conservation by Plants and Animals
• Many terrestrial organisms equipped with waterproof outer covering.
• Concentrated urine / feces.• Condensing water vapor in breath.• Behavioral modifications to avoid stress times.• Drop leaves in response to drought.• Thick leaves• Few stomata• Periodic dormancy
Figure 3.17
Kangaroo rat, in SW USA, forages for food at night; benefit of cooler air temps. Water conserved via condensation in large nasal passages and lungs.
Loop of Henle in mammal kidney
Dissimilar Organisms with Similar Approaches to Desert
Life• Camels
• Saguaro Cactus– Trunk / arms act as water storage organs.– Dense network of shallow roots.– Reduces evaporative loss.
• Temperatures above thermoneutrality