Ecology-Week Four Bio317
Virginia Commonwealth University
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This 8 page Class Notes was uploaded by Jayda Abrams on Friday September 23, 2016. The Class Notes belongs to Bio317 at Virginia Commonwealth University taught by Dr. Bissett in Fall 2016. Since its upload, it has received 9 views. For similar materials see Ecology in Biology at Virginia Commonwealth University.
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Date Created: 09/23/16
Ecology- Week Four 9/21/2016 9/23/2016 Chapter 6 Water Relation Water availability- Tendency of water to move down concentration gradient, from more concentrated to less concentrated. The microclimate determines if organisms lose or gain water. What happens if there is not enough water? Plants Animals Cannot do photosynthesis Limited physiological processes Can over heat Waste and solute build up Reduce evaporative cooling Reduce cooling potential potential Embolism- Strong pull of water that creates an air bubble in the column. This makes plants collapse. What happens if there is excess water? Plants Animals Physiological damage due to Drowning anaerobic conditions Can build up hydrogen sulfide Lose nesting site and ammonia Loss of insulation Water Content of the Air Relative Humidity- Completely dependent on the temperature Relative Humidity is calculated as follows: 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. Warm air holds more water than cold air! Evaporation Water Loss Arthropods have cuticles that makes them water proof and limits them from losing lots of water. They can move easily from wet land to dry land. Plants in warm environments lose more to the atmosphere and plants in cold environments lose less to the atmosphere. Plants and Soil Down a water potential gradient. Water Potential- Capacity to do work (ψ) Pure water ψ = 0 Negative pressure! Ψ soluteasures the reduction in due to dissolved substances. SPAC has to be unbroken for the water column to work, plants to survive, water to move and photosynthesis to occur! Dry air has the most negative water potential. With 100% humidity in the rainforest the air isn’t imposing water from plants. The plants can’t do photosynthesis, and they are not sucking up water. Ψ plant = ψ solute+ψ matric + ψ pressure Matric Forces- Water’ s tendency to adhere to walls. ΨPressure is the reduction in water potential due to negative pressure created by water evaporating from leaves. As long as ψ plant < ψ soil, water flow from the soil to the plant. Water movement can be used to measure water stress. In big plants, with big leaves and a dry atmosphere lots of negative pressure sneaks in intercellular spaces and creates air bubbles that get caught in the water column. Plants at high altitudes have the same issues. Scholander-type Pressure Chamber (AKA pressure bomb)- applies pressure and observes when water comes back to the surface. Guttation- Root pressure can force excess water out! It can be active or passive. This can also be known as dew. Guttation can give indications about photosynthesis and evaporation rates. Water Acquisition by Plants Extent of plant roots develops and often reflects differences in water and water availability. Deep roots are found in dry environments so the plants can reach the deep and stable water. (Ex: Phreatophytes) Hydraulic Lift- Like guttation, water potential builds up and pressure builds so much that the water can come through roots laterally. This is also known as hydraulic redistribution and it occurs on small community scales. Water Regulation for Land Plants Plant Adaptation Avoidance/ Tolerance Mechanism Input: Absorb by roots Short growth cycle- Grow, flower, reproduce, die Output: Evapotranspiration Dormancy (ex: resurrection ferns) Regulation: Stomal Control Succulence (ex: Cacti)- CAM photosynthesis Leaf adaptations: 1. Thick cuticle 2. Leaf rolling 3. Sunken stomates 4. Pubescence Water use efficiency Dissimilar Organisms with Shared Approach Camels Can stand 20% of water loss Face the sun Grows thick hair that makes them sweat Saguaro Cactus Stores water with a shallow dense root network Reduces heat gain by exposing top to the sun 2 Arthropods’ Desert Life Scorpions: Slow down and conserve water Stay out of the sun Long lived Low metabolic rates Cicadas: Active on hot days Perch on branch tips (cool microclimates) Feed on xylene (Exposed to free flow water supply in plants) How do plants and animals lose water? Plants lose water through transportation and animals lose water through evaporation. How do plants and animals gain water? Plants gain water by using their roots and animals gain water with feeding and drinking. Can plants take water from the atmosphere? Currently we don’t know, research is still being done. Kangaroo Rats Not much water loss due to dry feces and strong concentrated urine Nocturnal behavior Mouth pouch is dry Stores seeds underground to hydrate Metabolic water comes from seeds Little Pocket Mouse Builds a stone mound every night and knocks it down every morning. Why? It is checking for water to harvest that condensed on the cool rocks during the night. Water Regulation for Land Plants Water and Salt Balance in Aquatic Environments Marine Fish and Invertebrates Isosmotic 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. Freshwater fish and invertebrates Hyperosmotic organisms that excrete excess internal water via large amounts of dilute urine. Replace salts by absorbing sodium and chloride at base of gill filaments by ingesting foods. Animal Adaptation Water balance Avoidance/ Tolerance Mechanism Input: Drinking, eating, metabolism Migration, dormancy, nocturnal activities Output: Urine, feces, breathing Reduce sweat glands Regulation: Excretion- Changing the Surface area/volume- acclimation concentration of water in urine and changes in shape/weight with feces. temperature or behavior. In general… …Most adaptations to drought are avoidance, not tolerance. …Adaptations to conserve moisture often conflict with adaptations to remain cool in warm weather. …It is difficult to separate adaptations for water regulations from temperature regulation. (Temperature and water are very interrelated.) Chapter 7 Ecological Importance of Light (nutrient and energy relations) Energy sources- Different energy levels and trophic levels can be used to classify organism. Autotrophs- Use inorganic sources of carbon and energy Photosynthetic- Plants Chemosynthetic- Underwater plants Heterotrophs- Use organic molecules for sources of carbon and energy. Trophic diversity: Bacteria can be anything! (Figure 7.2) Photosynthetic Autotrophs- Light propagates through space as a wave: Photon: Particle of light bears energy IR (infrared): Longwave, low energy, interacts with matter, shows heat and motion UV (ultra violet): Short wavelength, high energy can destroy biological machinery. Photosynthetic Active Radiation (PAR): Falls between the two extremes and contains visible light at 400-700nm. PPFD is the new PAR. UV IR Visible Mutation Sight Sight Sight Heat Photosynthesis Energy balance Energy balance Leaf Area index (LAI) is calculated as follows: A single layer of leaves = an LAI of 1 Photosynthesis requires two linked process. Energy conversion from light to phosphorus compounds is known as light reactions or light dependent reactions. The building of carbohydrates from CO2, water, phosphorous compounds and other elements is known as dark/light independent reactions. Photosynthetic Pathways C3 Photosynthesis: Most common CO2 and ribulose bisphosphates make a three carbon acid To fix carbon, plants have to open their stomata to let CO2 in however water may be lost this way. Everything happens in the mesophyll cells Works in lots of environments and has many different rates Leaf anatomy is not specialized C4 Photosynthesis: Second most common Reduces internal CO2 concentration and increases the rate of CO2 diffusion inward Needs fewer stomata to open and conserves water Acids produced during carbon fixation is diffused to specialized cells surrounding bundle sheath. Distributed widely but grasses that grow in hot or dry places use this the most. Specialized leaf anatomy is Kranz Efficient use of CO2 Its stable compound has four carbon high rates of photosynthesis (stuff that grows fast)
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