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