Abiotic Factors. Tolerance Range. Optimal Growth Temperatures Microbial Activity

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1 Abiotic Factors Resources Abiotic factors organism must assimilate to survive and reproduce Factors Abiotic parameters that influence organism s distribution Limiting Factor Difference may only exist for a particular organism i.e., solar radiation is a factor for animals but is a resource for plants. Tolerance Range Biological processes are sensitive to environmental conditions and can only operate within relatively narrow ranges Homeostasis Organisms will reproduce, grow and perform best in an optimum environment Optimal Growth Temperatures Microbial Activity 1

2 Temperature Temperature and moisture are the 2 most limiting factors to the distribution of life on earth In the universe temperature varies between -273 o C (absolute 0) and millions of degrees Body temperature of animals usually falls between about -2 o C and 45 o C Aquatic Temperatures Riparian vegetation influences stream temperature by providing shade. Definition Maintenance of constant internal environment despite varying external conditions Mechanisms Physiological Behavioral Homeostasis 2

3 Thermoneutral Zone LETHAL TEMPERATURE RELATIONS FOR TWO SPECIES OF FISH. ENCLOSED AREA OF EACH TRAPEZIUM IS THE ZONE OF TOLERANCE Thermoneutral Zones 3

4 Microclimates Macroclimate: Large scale weather variation. Microclimate: Small scale weather variation, usually measured over shorter time period. Altitude Higher altitude - lower temperature. Aspect Offers contrasting environments. 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. Behavior of animals North-facing & south-facing slopes 4

5 Plant Resources Solar radiation (energy source) Water CO 2 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 5

6 Plant distributions reflect the effects of all resources C 3 species C 4 species Highly sensitive to O 2 / CO 2 concentration. At low CO 2 levels absorbs O 2 instead. Not sensitive to O 2 / CO 2 concentration. Higher affinity for CO 2. Stomata Bring CO 2 in Allow H 2 O to escape Leaf Structure Top C 3 leaves have chlorophyll throughout the interior of the leaf. CO 2 is found throughout the leaf allowing the CO 2 to escape through open stomata Bottom C 4 species has nearly all its chlorophyll in two types of cells which form concentric cylinders around the fine veins of the leaf. CO 2 is concentrated in the bundle-sheath cells and isolated away from the stomata 6

7 C 4 North American Distribution Percentage of C 4 species in the grass floras of 32 regions in North America (Teeri and Stowe 1976) C 4 Australia Distribution Approximate contour map of C 4 native grasses in Australia. Lines give percentages of C 4 species in total grass flora for 75 geographic regions (Hattersley 1983). Heat Exchange Pathways 7

8 Temperature Regulation by Plants Desert Plants: Must reduce heat storage. H s = H cd + H cv + H r To avoid heating, plants have (3) options: Decrease heating via conduction (H cd ). Increase conductive cooling (H cv ). Reduce radiative heating (H r ). Temperature Regulation by Plants Temperature Regulation by Plants Arctic and Alpine Plants Two main options to stay warm: Increase radiative heating (H r ). Decrease Convective Cooling (H cv ). Tropic Alpine Plants Rosette plants generally retain dead leaves, which insulate and protect the stem from freezing. Thick pubescence increases leaf temperature 8

9 Sierra-Nevada Range West East Yarrow (Achillea) along an altitudinal gradient Cold genotype Moderate genotype Warm genotype Natural Selection Low temperature Low humidity Many Generations High temperature High humidity 9

10 Animal Resources & Factors Temperature Oxygen, water Nutrition (energy source) Defense Intraspecific competition Temperature and Animal Performance Biomolecular Level Most enzymes have rigid, predictable shape at low temperatures Heat Exchange Pathways Heat Transfer H tot = H c ±H r ±H s -H e H tot = total metabolic heat H c = Conductive & convective H r = Radiative H s = Storage H e = evaporation What values can H tot assume? 10

11 Body Temperature Regulation Poikilotherms Body temperature varies directly with environmental temperature Homeotherms maintain a relatively constant internal environment Body Temperature Regulation Poikilotherms Body temperature varies directly with environmental temperature Homeotherms maintain a relatively constant internal environment Body Temperature Regulation Ectotherms Rely mainly on external energy sources Endotherms Rely heavily on metabolic energy 11

12 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 12

13 Temperature Regulation by Endothermic Animals Regional Heterothermy Appendages = poorly insulated; used to shunt heat during activity or prevent heat loss (via countercurrent exchange) Countercurrent heat exchange: mechanisms allowing blood to flow to coldest part of extremity without loss of heat; related to vasodilation/constriction - close arrangement of arteries & veins Countercurrent Heat Exchange 13

14 Temperature Regulation rete mirabile 14

15 Temperature Regulation by Endothermic Animals Warming Insect Flight Muscles Bumblebees maintain temperature of thorax between 30 o and 37 o 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 Thermoregula tes 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 15

16 Surviving Extreme Temperatures Inactivity Seek shelter during extreme periods Reduce Metabolic Rate Hummingbirds enter a state of torpor when food is scarce and night temps are extreme Hibernation - Winter Estivation - Summer Adaptations to Environmental Extremes Dormancy Diapause Torpor Hibernation Estivation Bergman s Rule Allen s Rule Diapause Pausing life at a specific stage Dormancy 16

17 Temp. Regulation 17

18 Bergmann s Rule Body size (volume) increases with latitude 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 Length of appendages decreases with latitude Increases surface area relative to volume Radiates heat better 18

19 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. Relative Humidity: Water Content of Air 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. 19

20 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 Content of Air 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 semipermeable 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 semipermeable membrane. 20

21 Water Movement in Aquatic Environment Isomotic: body fluids = external fluid Hypoosmotic: body fluids > external fluid Hyperosmotic: body fluids < external fluids Water Regulation on Land Terrestrial organisms face (2) major challenges: Evaporative loss to environment. Reduced access to replacement water. Water Regulation on Land - Plants 21

22 Water Regulation on Land - Plants W ip = W r + W a -W t -W s W ip = Plant s internal water W r =Roots W a = Air W t = Transpiration W s = Secretions Water Regulation on Land - Animals Water Regulation on Land - Animals W ia = W d + W f + W a -W e -W s W ia = Animal s internal water W d = Drinking W f = Food W a = Absorbed by air W e = Evaporation W s = Secretion / Excretion 22

23 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 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: C 6 H 12 O 6 + 6O 2! 6CO 2 + 6H 2 O Metabolic water refers to the water released during cellular respiration. 23

24 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. 24

25 Loop of Henle in mammal kidney Dissimilar Organisms with Similar Approaches to Desert Life Camels Can withstand water loss up to 20%. Face into sun to reduce exposure. Thick hair: Increased body temperature lowers heat gradient. Saguaro Cactus Trunk / arms act as water storage organs. Dense network of shallow roots. Reduces evaporative loss. 25

26 Temperatures above thermoneutrality Become hyperthermic by raising T B to near T A, thereby reducing water loss and continuing dry heat transfer e.g., many desert mammals 26