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Transcript
Environmental Controls on Life • Light • Temperature • Moisture Picea glauca & 10°C July isotherm Light • Heliophytes – – sun loving (shade intolerant) – C4, CAM • Sciophytes – – shade loving (shade tolerant) – C3 Photosynthesis and Light • PS increases until maximum, then declines • Hyperbolic shape • Compensation point • Saturation point • Photoinhibition Physical Adaptations to High Light Environment • • • • • • Small and thick leaves, Thick cuticle – (covering) Curled, less surface area Reflective surface layer High number of stomata Leaf orientation (heliotropic) Physical Adaptations to Low Light Environment • • • • Large, soft leaves High amounts of chlorophyll Long-lived leaves Heliotropic leaves! Life History Adaptations to Light • Annuals versus perennials • Canopy trees flower more • Seeds require light to germinate – Loblolly pine (Pinus taeda) Physiological Adaptations to Light • Phenology – timing of changes in growth – Flowering – Leaf shedding – Leaf burst Temperature - Plants • Poikilothermic • Optimum temperature for photosynthesis - varies • EX. Circumarctic treeline – Cold stress, freezing damage Black spruce (Picea glauca) limits and July temps Plant Adaptations to Temperature • Dormancy – deciduous How do needleleaved plants survive? • Frost hardening – Chemical alteration of liquids (“antifreeze”) – Less water in cells – Cell walls deformed Plant Adaptations to Temperature • Saguaro – CAM photosynthesis – Palo Verde nurse shrubs Plant Adaptations to Temperature • Palm distribution Why can’t palms be cultivated at higher latitudes? Temperature - Animals • Poikilotherms – “cold-blooded” -1.9°C body temp OK for Antarctic icefish, 6°C lethal • Homeotherms – generate heat through metabolism – 37-47°C (10°C higher than core temps.) lethal Northern Limits of the Eastern Pheobe Adaptations to Temperature in Animals • Metabolic rates • Sweating, panting, licking • Ratio of body mass to surface area • Behavioral adaptations • Shivering • Super-cooling (gylcerol) • Hybernation • Insulation Latitude and Body Shapes • Low latitude = high surface area:volume • High latitude = low surface area: volume Allen’s Rule • Low latitude = long extremities • High latitude = short extremities Adaptations to Moisture Plants • Photosynthesis • Turgor (rigidity) • Movement of nutrients (vascular plants) • Xerophytes – dry loving • Mesophytes – moist loving • Hydrophytes – water loving Transpiration Release of water to atmosphere by plants Generally through stomata Evapotranspiration = transpiration + evaporation Water Stress and Range • Moisture deficit = evaporative demand > root absorbtion • Creosote (Larrea tridentata) = -2.0- -2.9 Mpa • Alder (Alnus spp) = -1 Mpa Lower Treeline • High elevations: – Lower evaporative demand – Higher rainfall (orographic) • Seedlings have highest sensitivity • Fig 3.9 Plant Adaptations – Moisture Stress • Water stress escapees – Annual plants • Water stress avoiders – Cacti – Drought deciduous (Fouquieria splendens –ocotillo) • Water stress tolerators – Selaginella lepidophylla “resurrection plants” Cactus Family - avoiders • • • • Fine surface root systems Enlarged stems to store water Light colored thorns reflect light CAM ps pathway (stomota open at night) • Slow growth rates Moisture - Excess • Diffusion of O2 through water is slow!! • Plantanus occidentalis (sycamore) growth declines at >50% soil moisture saturation Moisture - Animals • • • • 2/3 water by weight Mammal losses 15-20% water – fatal Water loss lower in arid dwellers Ex. Kangaroo rat (Dipodomys spectabilis) – Dry urine, feces – No sweat – Nocturnal – Water from dry food! Other Physical Factors • Chemical nutrients/environment – Nitrate, phosphorous, potassium in plants – Salinity, oxygen for aquatic orgs. • Combinations of factors Geographical Range vs. Density • Range: Area where species is found • Density : Abundance per unit area (rare versus common) • Highest densities in range center Gaussian Curve and Environmental Gradients • Physiological functioning • Density What is a niche? • Ecological concept • Species exist in a multi-dimensional space defined by various limiting factors that affect physiological functioning and abundance Generalist vs. Specialist • Generalist: wide ranges of environmental tolerances • Specialist: restricted gradient distributions Correlation Caveat • If the geographic range of a species and some climatic variable overlap, does that mean that this variable controls the range of this species? • What other factors might affect a species’ range?