Ecology, Week 1
Ecology, Week 1 LIFE 320
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This 4 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 9 views. For similar materials see Ecology in Biology at Colorado State University.
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Date Created: 09/19/16
Ecology Divided in to hierarchy of subdivisions From Greek for study of and house Organism in their environment o Adaptations to pressure in their environment o Environment can be biological or physical Populations o Changes in number of individuals in population o Behavior of individuals in group o Evolution shapes populations over time Community Eco o Interactions among populations Simplest form is two population interactions Can be Beneficial, harmful or neutral Competition, predation and mutualism Species interact with many other populations Forms of food webs Ecosystems: energy and element cycles o Community of organisms with biotic and abiotic interactions o Ecosystem behavior gives the context for individual organisms Human dimensions o Climate & environmental change - human driven o Species and habitat loss Ex: deforestation, over fishing o Ecological benefits to humans We benefit from ecology Need natural resources to survive o Sustainability of managed systems Ecology o Basically about change and how it often happens in networks I.e. Food webs o About our world The Physical Environment: Adaptations for water and nutrients Physical Environment o Gives boundaries and opportunities for organisms in area o Life must be able to survive in their environment or die o Adaptations are driven by changes in environment Aspects of physical environment o Nature of water Water needed for all life as we know it o Nutrients (food) Water: o Makes up 50-95% of an organism’s mass o Biochemistry happens in water Cellular level functions o Organisms must replenish water loss o Chemical properties of water Dipole makes water bind together (surface tension) Ionizes to make effect Dissolves polar substances Neutral pH (7) Critical to life o Water is a habitat Physical properties High heat capacity Temperatures tend to be consistent Helps homeostasis Extends to coastal regions Beach areas tend to have more stable temperatures year round Ice floats If sank temperate lakes would not support life It would freeze solid and fish would die More viscous than air Requires streamlined body shapes Commonly liquid at earth's temperatures o Things dissolve in it Key ions: + Na, K, Ca, Mg (-)Cl, SO4, HCO3 (bicarbonate) Nutrients: N (NO3-, NH4+), P (PO42-) o Water sticks to soil particles Smaller soil grains = more surface area Potential: strength of forces holding water to soil particles Rocky soils drain better and don’t hold water much Water potential is abbreviated as and measured in unites of megapascals (Mpa) More negative values attract water Field capacity: amount of water held by matric potential against gravity Wilting point: Minimum amount of water in soil needed so plants don’t wilt o o Osmotic potential: force of solution to attract water Osmosis: movement of water from regions of high to low concentration across a semipermeable membrane In osmotic membranes water moves to equalize solute pressures on either side osmotic potential of solution proportional to number of dissolved molecules Osmotic potential is also called solute potential 1 molar solution = -21 atm osmotic potential o Water moves by Soil matric potential Osmotic forces Transpiration o Transpiration and water uptake Water potential of dry air: -133 Mpa @ 20C Vascular plants move water long internal distances Tension-cohesion theory Force required to move water within xylem elements is generated when water moves from the vascular vessels to leaf cells replacing transpiration losses Transpirational pull is facilitated by cohesion of water molecules to each other and cohesion of water molecules to cell walls Literally pulled from roots to leaves o Adaptations to arid environments Stomate modifications Open and close in response to plant water potential Internal structures slow air movement Leaf modifications Increased surface area for heat dissipation Pubescence (leaf hairs) thicken moisture boundary layer Formation of waxy cuticle to reduce water loss Ions o Nutrients more dilute in environment than in plant o Active transport across root membrane o Symbiosis with fungi Hyphae pulls nutrients in plant o Often limited by root surface area, so alter root: shoot ratio Salt o Osmoregulation is crucial for survival o Plants, protists, invertebrates and vertebrates all have different adaptations for dealing with salt at different levels Cellular level Structural level Organ level o Vertebrates deal with salt Osmotic pressure varies among environments: Ocean = -2.5 Mpa Fresh water = 0 Mpa Most vertebrates around -.3 to -.5 o Hyperosmotic: tend to gain water and/ or lose solutes to environment Marine fish gain salt Loss of water across gills Many fish drink water to make up for losses Kidneys work hard to excrete salt, gills too o Hypo-osmotic: tend to lose water and/ or gain solutes Freshwater fish lose ions Loss of ions through gills to fresh water These fish urinate the extra water they gain Kidneys selectively retain ions Gills tot can selectively gain ions o Terrestrial organisms and salt Transpiration loss of water leads to salt accumulation in all leaves Terrestrial animals lose salt in urine, gain from food Desert animals develop super-kidneys: urine up to 25x salty as blood Marine birds have salt glands (formerly tear-ducts) to eliminate brine o Water (and air) and movement Organisms have adaptations to deal with movement in fluid environments Physics is key to understanding dynamics Reynolds number (Re) is dimensionless rationale of inertial forces vs. viscous forces Larger number means the organism doesn't really feel fluid they are moving through and can move quickly through it o Flying through air or fighting molasses A small Re implies viscous force dominates Ex: Planktonic larvae are pushed around by water Large Re implies inertial forces dominate Ex: Dolphins can speed through water
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