Ecology, Week 2
Ecology, Week 2 LIFE 320
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This 7 page Class Notes was uploaded by Rheanna Gimple on Monday September 19, 2016. The Class Notes belongs to LIFE 320 at Colorado State University taught by Dale R Lockwood in Fall 2016. Since its upload, it has received 8 views. For similar materials see Ecology in Biology at Colorado State University.
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Date Created: 09/19/16
Organism's adaptations for energy Ecology, like all life, starts in the Sun 4H -> He + 2 photons at 13.6 million degrees o Other fusion reactions produce heavier elements o Light travels 150 million km to earth takes 8 minutes Light is harnessed by photosynthesis o Light warms objects on the earth's surface Light drives climate patterns Uneven heat creates complexity to the planet o Plant light absorption Plants with a lot of chlorophylls absorb red and blue - reflect green Plants with a lot of carotenoids absorb green and reflect red and blue Light intensity varies o Solar constant: 1400 watts per square meter at top of atmosphere o Varies with: Time of day Latitude Season Clouds/fog Water depth o Plant growth can be limited by light, water or temperature Flow of energy o It is primarily chemical energy flow among organisms o Ultimate source of energy is the sun o Basic energy transfer: Chemical energy transfers Respire to do work Energy stored in chemical bonds Photosynthesize to store energy Energy + 6CO + 2H O = 2 H O +6612 6 2 Animals need to eat to gain energy (no photosynthesis) Energy terms: o Autotroph: Assimilate complex organic compounds from inorganic molecules using energy from sunlight or from chemical reactions Photoautotroph Photosynthesis Converts CO in2o sugars Chemoautotroph Aerobic oxidation of Methane Sulfur Iron Ammonia H, N, etc. o Heterotroph: obtains carbon from organic sources using energy of organic chemical Bonds Land plants: o CO diffuses into stomate 2 o CO 2oncentration about 0.03% o Lose water in process of transpiration o Water loss is greater than its CO 2ain Aquatic plants o Bicarbonate chemically dissolves 100x more than the amount of CO 2 absorbed + - CO 2 H O2->H CO2->H3+HCO 3 o Aquatic plants can use both CO an2 HCO but n3t equally fast o Diffusion slows the uptake of Carbon Gas Movement o Gases often move by diffusion Diffusion: Random movement of substances Allows movement from regions of high concentration to low concentration o Velocity of gas movement is 10000x slower in water than in air Due to density of water o Aquatic organisms can become O starved 2 o O 2as low solubility in water 21% concentration in air Max 1% in H O 2 Low rate of diffusion in H2O Sediments and wet soils become "anoxic" Photosynthetic adaption o Compensation point: light intensity where photosynthesis gains = respiration loss Rate of photosynthesis changes the greatest at this point Can dip below this as long as has stores of sugars i.e. trees in winter o Saturation point: above which photosynthesis no longer increases with light Most CO2 intake at this point o Shade plants adapted to lower light Photosynthetic pathways o C3 photosynthesis most common o Drought-resistant photosynthesis C4 - grasses CAM = cacti, euphorbs C3 photosynthesis o CO2 + RuBP = two 3PG o Rubisco has low CO2 affinity, so make lots: 30% of leaf dry weight o Rubisco catalyzes reverse reaction at high O2 and low CO2 (photorespiration) o Net photosynthesis Slowed at low CO2 and high light o How to overcome RuBP probs. Concentrating CO2 Moving site of C-fixation away from site of O2 production C4 photosynthesis o Occurs in warm season grasses o Enzyme PEP carboxylase has high affinity for CO2 o CO2 fixed to PEP in mesophyll o Calvin cycle segregated to bundle sheath cells where O2 concentration is lower o Cost: less leaf tissue active in Ps CAM photosynthesis o Some succulent plants (e.g. cacti) o Use C4-like metabolism o Only open stomates at night o Fix CO2 into PEP during night o Calvin cycle during day to move carbon from OAA to sugars Thermal environment o Heat created, transferred (long wavelength energy) Important for metabolism Maintain body temp. in optimal range Radiation, conduction, convection (define) Lichens use conduction for energy Reptiles, cactus use heat for metabolism Evaporation Cooling mechanism Sweating o Heat control Heat budget related to metabolic budget Gain heat = metabolism - evaporation +/- (radiation, conduction, convection) Some orgs. Control temp. by varying physiology Some with behavior Some "go with the flow" Limited living environment Larger organisms have more stable metabolism Smaller more metabolic response to environment o Organisms limited to certain environments Enzymes, thus organisms, have optimal conditions Some optima are fixed genetically Some biochemical systems can acclimate Constant internal environment o Homeostasis: ability of org. to maintain constant internal conditions Costly Limited by physiology and food supply Can choose partial homeostasis Animals vary in size, surface area Surface of sphere: = 4pi r^2 Volume of sphere: = 4/3 pi r^3 Surface to volume ration: 1/(3r) Smaller you are = more contact with environment o Homeothermy: maintaining a constant internal temp. o Poikilothermy: internal tem. Follows environment temperature o Ectotherms: gain heat from enviro o Endotherms: generate heat internally o Cold tolerance Ice in cells break through cell membrane Antifreeze proteins Keep water from forming ice "super cooling" Other strategies Fat, fur, metabolism Behavior Countercurrent heat exchange Keep core warm via circulatory system Physical Variations Context for life on earth o From map you can determine Latitude, continental vs. maritime, mountain effects, elevation, geology Can predict - seasonality, rainfall, temperature, regime, soil properties Wind patterns, mountains and location of continent drives U.S. weather patterns (rainfall) o Context for plant and animal adaptations Problems with water, ions, nutrients energy flow, CO2 uptake, temperature, movement, dispersal, etc. Variation in time and space o Land and soil o Past climate o Heat input/redistribution o Moisture distribution Heat input/redistribution o Solar radiation Varies with latitude Sun's rays are more spread out over polar areas than in tropics Varies seasonally Due to 23.5 degree tilt of earth Like moving 23.5 N or S with seasons Oaxaca almost exactly 23.5 degrees S of here Reykjavik, Iceland almost 23.5 degrees N of here Drives variation in day length Temp. variations greater at poles than tropics Moisture distribution o Air convention redistributes heat Hadley cells Warm moist air rises at equator, Rain Diverges to N and S Sinks when cooler and farther from equator Cycles about every 30 degrees lat. Surface flow replaces rising air, deserts Deserts 30 degrees N and S equator Polar cell falling air Ferrel cells at mid-latitudes Coriolis(?) effect due to wind patterns No winds in doldrums o How well does Hadley circulation predict vegetation? Wind patterns, geography, and latitude contribute to formation of deserts, wet areas o Tropics: 1 or 2 rainy seasons Solar zenith = solar equator Latitude where sun is directly overhead Migrates over equator Location of maximum rain Equatorial regions get 2 rainy periods Points near 20 degrees N&S get one rainy period o El Niño southern oscillation El Nino: Christmas-time appearance of warm waters off the coast of Peru Upwelling is depressed along the west coast of S. America Pulls surface water away from east coasts, cold water rises - pushes warm waters east Affects the Humboldt current Fisherman's catches go down - less nutrient rich water Southern oscillations: high pressure at Darwin, Australia and low pressure at Tahiti Thermal year (La Nina) warm water is pushed westward - opposite flow from El Nino year ENSO phenomenon associated with global temp. and rainfall changes Rainfall and sea-surface temperatures correlate generally Upwelling zones high biological productivity occur where winds move surface waters away from continental margin Occur on west coasts N or S of equator o Elevation and Temperature o Lapse rate: temp. change with elevation, average 6 degrees C per 1000m (3.6 F per 1000 ft) (PV=nRT) o Air masses moving over mountains lose their moisture as rain and snow Decrease T as elevation increases Rain shadow: one side of mountains has more moisture and vegetation, other side more desert ecosystem o Ecological systems experience different climate across elevation changes o As T increases atmosphere holds more water Basics of soils o Soil: layer of chemically and biologically altered material overlaying rock on the surface of the earth o Differences among soils driven by "state factors" Hans Jenny's state factors Regional Climate- how warm and dry Organism pool- available organisms Relief (topography)- how flat land is: drainage Parent material- bedrock underneath Time- how long has soil been there S=f(Cl,O,R,P,T,…) Soil is function of state factors Weathering of soil minerals o Weathering: physical and chemical alteration of rock material near earth's surface Physical breaking into smaller pieces Wind and water erosion Displacement of elements in rock minerals leads to "secondary" mineral formation and loss of some elements from the rock to the soil water Weathering more important feature of tropics Lot of water flow - poor soil Nutrients from dead plants on top of soil Soil physical structure o horizons: Horizontal layers of soil with similar characteristics Decrease in organic matter content with depth Less light More like "parent material" (i.e. source rock) with depth Shift from biologically active to bed rock composition o Soil and climate go hand in hand Climate in the past o Physical environment varies with time Daily, seasonal variation is part of our experience Decadal, ocean currents can cycle changing T and nutrient flows El Niño events Century to millennial scales recorded in human history Natural or things we may have caused Natural archives of past Lake bottom sediments record Pollen, charcoal Organism bodies and chemicals Tree rings - "good" years and "bad" Ice cores (poles, alpine glaciers) Trapped atmospheric gases isotopes Snow, dissolved ions and particulates Ocean sediments Phytoliths Can determine C3 or C4 Local ecology Important info about past What was climate like Glacial periods and interglacial periods correlate with concentrations of O2 isotopes Concentration drop during glacial period How were organism distributed Fossil records Can hint how continental drift occurred When climate changed how fast could organisms respond Pollen and lake bed samples can tell this for plants Ex: pulse of strontium (large fires) change pine and spruce forest to Oak and Hornbeam o Context for life on earth From map Latitude, continental v. maritime, mountain effects, elevation, geology Can predict Seasonality, rainfall, T regime, soil properties Plant and animal adaptations Problems with water, ions, energy flow, CO2 uptake, T
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