Ecology Unit 4 PDF

BIOL 4311 Ecology Unit 4 Factors that Limit Distributions II: Abiotic Factors (Krebs Chapter 6) Week of 02/03/25 1  Factors that Limit Distributions II...

BIOL 4311 Ecology Unit 4 Factors that Limit Distributions II: Abiotic Factors (Krebs Chapter 6) Week of 02/03/25 1  Factors that Limit Distributions II – Abiotic Factors Week of 02/03/25 2 Week of 02/03/25 3  Factors that limit distributions: temperature and moisture Temperature and physiology – Life processes on earth occur where water is liquid: between 0°C and 100°C – High temperatures → dissociation of cell membranes and nucleic acids – Low temperatures → ice destroys cell organelles Week of 02/03/25 4  Factors that limit distributions: temperature and moisture Temperature and physiology – Opposing effects of temperature on life processes Heat increases kinetic energy of molecules and accelerates chemical reactions Q10: 10°C increase in temperature → 2-4x increase in metabolic rate – poikilotherms versus homeotherms - can make & warm blooded relyon- coYdblooded T maintain heat Enzymes become less stable as temperature increases, de I outs , Terr cease to function at high temperatures  metabolic rate (beneficial) +  enzyme instability → optimal temperature range Week of 02/03/25 5  Factors that limit distributions: temperature and moisture Moisture and physiology – All life processes occur in aqueous media aquatic and marine organisms terrestrial organisms: all require some form of water in food / drink for metabolic and excretory paths – Liquid water fundamental to the way life evolved on earth Thermal properties – heat travels rapidly through water, water changes temperature slowly –  temperatures of aquatic environments and organisms are relatively constant Solvent properties – water dissolves inorganic compounds readily and makes them available to living systems Week of 02/03/25 6  Effects of temperature and moisture on distribution of species Large temperature differentials over the earth’s surface: reflection of 1) Incoming solar radiation Solar radiation hits earth Fig. 6.1 (p. 82): Distribution of energy from the sun over the earth’s surface directly at equator, obliquely at poles Less heat energy per unit area at the poles (40%) Week of 02/03/25 7  Effects of temperature and moisture on distribution of species Large temperature differentials over the earth’s surface: reflection of 2) Land masses versus water Land heats and cools rapidly → daily and seasonal fluctuations in temperature – 2-3°C flux at equator – 50°C flux in temperate zone (annually) Water heats and cools slowly, plus vertical mixing processes – 2-3°C flux at equator – 20°C flux in temperate zone (annually) Week of 02/03/25 8  Effects of temperature and moisture on distribution of species Global distribution of precipitation – Belt of highest rainfall around equator – Secondary belt of high rainfall between 45° and 55° latitude – Rainfall over oceans > land (44 versus 26 in/yr) – Rainfall on windward sides of mountains and high plateaus > leeward sides (rain shadows) Fig. 6.3 (p. 84): World distribution of mean annual Week of 02/03/25 precipitation 9  Fig. 6.4 (p. 84): Terrestrial vegetation classes plotted in relation to annual precipitation and average annual temperature Week of 02/03/25 10  Effects of temperature and moisture on distribution of species Organisms have two options for dealing with the temperature and moisture conditions of their habitats 1) Adjust physiologically → acclimation (individuals) → adaptation (population) Toneries it , if it work.. 2) Escape by some evolutionary adaptation migration hibernation Week of 02/03/25 11  Fig. 6.5 (p. 85): Hypothetical comparison of the tolerance zone of an organism to the ranges of its habitat Temp - to high Week of 02/03/25 12  Temperature restrictions Upper and lower lethal temperatures – not necessarily constant – role of acclimation – effects and ranges vary with life stage Limits on distributions through effects on a) Survival (lethal limits) b) Reproduction (within tolerance zones) c) Development of young (most sensitive) d) Competition with other species near limits of temperature tolerance (increases susceptibility to disease, predation or parasitism) Week of 02/03/25 13  Temperature restrictions What aspects of temperature are most relevant to limitations on distributions? 1) Maximum temperature 2) Minimum temperature Fig. 7.6 (p. 91): Winter distribution of the Eastern phoebe, 1962-1972 (blue line is the -4°C isotherm) 3) Average temperature 4) Variability in temperature 5) Weather migrants Eastern phoebe winter bird species in Freeze Houston Week of 02/03/25 14  Temperature and moisture adaptations in plants Distribution of native vegetation around the globe is the result of local climate, primarily due to adaptations to water availability – Drought resistance WW – Flooding tolerance Comparison of drought resistance in plants (specific survival time relates to plant’s ability to conserve the water it has stored in its leaves) Week of 02/03/25 15  Drought resistance in plants Frost drought versus soil drought Resistance facilitated by – Improved uptake – Decreased water loss stomatal closure reduction of leaf surface water storage Deciduous trees < conifers Drought resistant plants: xerophytes Week of 02/03/25 16  Fig. 6.6 (p. 87): Natural distribution limits and calculated climatic limits for loblolly pine Lost Pines Week of 02/03/25 17  Flooding resistance: growth of seedlings of water tupelo and sycamore from the southern U.S. (84 days at 4 water levels) Week of 02/03/25 18  Altitudes of timberlines in North America Week of 02/03/25 19  Fig. 6.8 (p. 88): Alpine treeline and snowline in relation to latitude for 150 sites around the world Week of 02/03/25 20  Determinants for tree lines Lack of soil Desiccation of leaves in cold weather Short growing season Lack of snow, exposing plants to winter drying Excessive snow lasting through the summer Mechanical aspects of high winds Rapid heat loss at night Excessive soil temperatures during the day Drought Week of 02/03/25 21  Genetic adaptations in plants Ecotypic variation across distribution (Clausen, Keck and Heisey 1948) – Yarrow (Achillea lanulosa): ecotypic races from western N. America Fig. 6.11 (p. 91): Ecotypes of Achillea lanulosa  altitude →  average grown in a common garden at Stanford University temperature,  number days < freezing, winter dormancy Sierra Nevada ecotype: small growth form, late blooming, cold adapted Week of 02/03/25 22  Genetic adaptations in plants Ecotypic variation across distribution (Clausen, Keck and Heisey 1948) – Transplant experiments among the different races were unsuccessful – Seeds from various ecotypes all grown in greenhouse under identical conditions: ecotype growth form characteristics remained same Week of 02/03/25 23  Genetic adaptations in plants Cold hardiness: resistance in temperate zone perennials to winter temperatures – Dependent on not growing – Use day-shortening in fall to start metabolic changes that give cold resistance Shed leaves Dormant metabolism Shift water to outside cells of bind it up chemically to prevent intracellular freezing Week of 02/03/25 24  Temperature and moisture adaptations in animals Poikilotherms must acclimate to seasonal climate changes – Involves increasing upper lethal temperature limit in summer and/or decreasing lower lethal temperature limit in winter Zones of tolerance: acclimation versus lethal temperatures for two species of fish – Acclimation ability Some species cannot acclimate (e.g., chum salmon) Some species acclimate well to temperature changes (e.g. bullhead) Week of 02/03/25 25  Seasonal variation in the upper lethal temperature of the bullhead (Ameiurus nebulosis) in Ontario Week of 02/03/25 26  Fig. 7.9 (p. 95): Distribution of species on a barnacle- dominated slope in a rocky intertidal zone Week of 02/03/25 27  Water balance in terrestrial animals Adaptations to prevent water loss – Arthropods Insects: exoskeleton of hard chitin covered by waxy cuticle Crustaceans, centipedes, millipedes – lose water through integument – behavioral adaptations Week of 02/03/25 28  Water balance in terrestrial animals Adaptations to prevent water loss – Arthropods Metabolic waste elimination 1) Ammonia in water: crustaceans, centipedes, millipedes 2) Ammonia gas (virtually no water): isopods 3) Insoluble uric acid and guanine (no water at all): insects, spiders Week of 02/03/25 29  Water balance in terrestrial animals Adaptations to prevent water loss – Vertebrates E.g., kangaroo rat (Dipodomys), SW US deserts – lives indefinitely on air-dried food with no drinking water – eliminates dry feces – scavenges moisture from air through nostrils Week of 02/03/25 30  Water balance in terrestrial animals Adaptations to prevent water loss – Vertebrates Physiological and behavioral adaptations – nocturnal; inhabit cool, deep, moist burrows during day – do not store water through drinking – no sweat glands – produce very concentrated urine (little water) – low water content in feces – obtain water from food: oxidation of food → metabolic water Week of 02/03/25 31  Water balance in terrestrial animals Adaptations to prevent water loss – Vertebrates Reptiles: most successful desert vertebrates – dry skin protected by scales:  water loss – excrete uric acid without water – behavior Week of 02/03/25 32  Temperature adaptations in animals Adaptations for extreme heat – Nocturnal lifestyle Mammals, reptiles, insects – Evaporative cooling Mammals Not for desert dwellers – Storage of heat Raise body temperature during the day, lower it at night to dissipate the heat Camels: body temperature flux from 35-40°C (95-104⁰F) Week of 02/03/25 33  Temperature adaptations in animals Adaptations for cold environments – Antarctic fish (notothenioid) Inhabit waters full of ice crystals Glycoprotein molecules in tissue fluids  freezing points to below -1.9°C Dissostichus mansonii Trematomus hansoni Week of 02/03/25 34  Temperature adaptations in animals Adaptations for cold environments – Birds Fluff outer contour Decrease metabolic rate and feathers → trap air next to body temperature at rest body (e.g., hummingbirds and Legs and feet of some other small bird species) species have no muscles, Black-capped chickadee sits on a branch with snow on it. nerves or blood vessels, therefore do not freeze CVV CVV Black-capped chickadees can go into regulated hypothermia, dropping their normal daily body temperatures by 12–15°F? This helps the birds conserve energy and store fat over the winter. Week of 02/03/25 35  Temperature adaptations in animals Adaptations for cold environments – Mammals Thicker fur coats during winter months Hollow hairs in winter coats Arctic fox: summer Arctic fox: winter Week of 02/03/25 36  Other factors that limit distributions Light Nutrients Soil type Salinity Oxygen availability Fire regime Week of 02/03/25 37  Light as a limiting factor Function of light in ecosystems 1) Stimulus for timing of circadian rhythms in plants and animals Diurnal: feeding and activity cycles Seasonal (photoperiodism) – reproduction – migration – dormancy Week of 02/03/25 38  Light as a limiting factor Function of light in ecosystems 2) Photosynthesis CO2 + H2O + sunlightvis → CnH2nOn + O2 Inefficient: 0.5 – 1% of incoming radiation captured and stored by photosynthesis Rate measured by uptake of CO2 Week of 02/03/25 39  Energy for photosynthesis Week of 02/03/25 40  Photosynthesis pigments Week of 02/03/25 41  Chemical reactions of photosynthesis Week of 02/03/25 42  Light as a limiting factor: terrestrial Photosynthesis strategies in plants – C3 photosynthesis (C3 plants) usual form of photosynthesis, no special adaptations one of the critical compounds in the reaction is a 3-carbon sugar – C4 photosynthesis (C4 plants) uses an enzyme to attach carbon from CO2 to a 4-carbon sugar makes plants better able to absorb CO2 from atmosphere, no photorespiration high light, temperature, periodic drought, salinity – Crassulacean acid metabolism (CAM plants) further refinement of C4 metabolism plants open stomata for short time only at night large water storage capacity extreme desert plants Week of 02/03/25 43  Fig. 6.13 (p. 93): Comparison of C3 and C4 photo- synthesis in Atriplex species Week of 02/03/25 44  Light as a limiting factor: terrestrial Shade tolerance: stratification and light extinction in a forest Week of 02/03/25 45  Light as a limiting factor: aquatic Theoretical attenuation of solar radiation with depth of water Euphotic zone Compensation point (1% full light) Aphotic zone Week of 02/03/25 46  Nutrients as a limiting factor Nutrient Function Nitrogen (N) Structural component of proteins and nucleic acids Phosphorus (P) Structural component of nucleic acids, phospholipids, bone Potassium (K) Major solute in cells Sulfur (S) Structural component of many proteins Calcium (Ca) Regulator of cell permeability, structural component of bone, material between woody plant cells Magnesium (Mg) Structural component of chlorophyll; involved in function of many enzymes Iron (Fe) Structural component of hemoglobin and many enzymes Sodium (Na) Major solute in extracellular fluids of animals Silica (Si) Structural component of diatom tests Week of 02/03/25 47  Nutrients as a limiting factor All natural waters contain dissolved nutrients – lakes and rivers: 0.01 – 0.02% – oceans: 3.5% – inland salt seas: >10% Nutrient composition of natural waters – freshwater:  Ca2+, SO42-, CO3- – seawater:  Na+, Cl- Nutrient composition of living organisms – blood plasma:  Na+, Cl- – cells:  K+ Week of 02/03/25 48  Soil type as a limiting factor Soil composition Variables – Clay – Physical / chemical – Silt nature of soil – Sand – Water holding – Organic detritus capacity of soil Week of 02/03/25 49  Soil type pyramid Best soil for agriculture Week of 02/03/25 50  Soil type as a limiting factor Serpentine soils – Sterile, unproductive soil over unusual geologic formations – High in Mg, Fe, Si – Often low in Ca, N, P – Specialized vegetation Bogs – Low pH (high acidity) – Low in N – Specialized plants adapted to low N conditions (e.g., sphagnum) or are N-fixers Week of 02/03/25 51  Salinity as a limiting factor Salt balance in organisms – Marine: must constantly excrete salts – Freshwater: must constantly take up salts Salinity classification of organisms – Stenohaline (“narrow salt”) stenohaline marine stenohaline freshwater – Euryhaline (“wide salt”) Week of 02/03/25 52  Salinity as a limiting factor Osmosis – Water diffuses to regions of high ion (salt) concentrations * * *without any kind of salt regulation Week of 02/03/25 53  Salinity as a limiting factor Salinity adaptation mechanisms – Osmoregulators: excrete or concentrate salts as needed – Osmoconformers: cannot adapt to salinity at all – Ion (volume) regulators: osmoconformers that can use a free amino acid pool to regulate volume, can not regulate salt Week of 02/03/25 54  Oxygen availability as a limiting factor Oxygen required for metabolism; requirements and consumption relative to organism size Oxygen concentrations – Air: 21% – Water: 0.6 – 0.9% (salinity and temperature dependent) O2 availability often restricts distribution of certain aquatic species Week of 02/03/25 55  Fire regime as a limiting factor Natural establishment of jack pines and lodgepole pines – Serotinous cones require heat of forest fire to release seeds – Seedlings appear only after forest fires Week of 02/03/25 56  Fire regime as a limiting factor Chaparral areas of California Week of 02/03/25 57  Fire regime as a limiting factor North American prairies – Frequent fires prevent establishment of large tree species – Additional role of drought Week of 02/03/25 58  The major grasslands of North America, and the air masses influencing the climate of the central grasslands Week of 02/03/25 59  Effect of climate change on distributions of species Indicators will be changes in plant species distributions Changes in plant species distributions will occur very slowly – Long-lived species: will survive quite a while in places that become unsuitable seed production decreases until no viable seedlings are produced – Short-lived species: dependent on dispersal capacity Week of 02/03/25 60  Effect of climate change on distributions of species Effect of ecotypic variation? If time permits, species will change their distribution limits as the climate changes Animal species? Week of 02/03/25 61  Fig. 6.16 (p.96): Predicted change in distribution of balsam fir in E. US due to climate change through 2100 Week of 02/03/25 62