3 - Ecology - Fors - Earth’s Ecological Layers •...

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Unformatted text preview: Earth’s Ecological Layers • Atmosphere: gas layer Troposphere – to 17 km (11 mi.) Stratosphere – 17­48 km (11­30 mi.) • Hydrosphere: water layer • Lithosphere: crust/upper mantle; land • Ecosphere: layer where life can exist 1 Ecology: the science (or study of) of the relationships between organisms and their environments ­the relationship between organisms and their environment Organism: an individual form of life, such as a plant, animal, bacterium, protist, or fungus ­a body made up of organs, organelles, or other parts that work together to carry on the various processes of life 2 Levels of Organization Species: related organisms capable of interbreeding Population: all the organisms that constitute a specific group or occur in a specified habitat (often it refers to only one species) Community: a group of plants and animals living and interacting with one another in a specific region under relatively similar environmental conditions at the same time 3 Levels of Organization Ecosystem: an ecological community together with its environment, functioning as a unit ­exist as 2 interacting components: biotic (living) and abiotic (non­living) Biosphere: the part of the earth and its atmosphere in which living organisms exist or that is capable of supporting life 4 Relevant Scientific Principles Matter: something that occupies space and can be perceived by one or more senses Organic: matter composed primarily of carbon, hydrogen and oxygen (living) Inorganic: matter consisting of mineral­based substances (non­living) Law of Conservation of Matter: matter can be changed from one form to another but cannot be created or destroyed by ordinary physical or chemical means 5 Relevant Scientific Principles Energy: is the ability to do work Potential: energy in object at rest (e.g., oil, coal, timber) Kinetic: energy of motion (gasoline engine, waterwheel) 6 Relevant Scientific Principles First Law of energy: energy cannot be created or destroyed but can be converted from one form to another Second Law of energy: conversions result in energy lost as heat (no conversion is 100% efficient (20­ 40% at best)) Entropy: the tendency for all matter and energy in the universe to evolve toward a state of inert uniformity (or disorder) 7 Flow of energy through ecosystems Solar Energy: virtually all energy in the biosphere comes from the sun Photosynthesis: major life­sustaining process ­solar energy (light) captured by green plants (chlorophyll) converting chemical energy into glucose molecule and releasing oxygen Solar energy + 6CO2 + 6H2O > C6H12O6 + 6O6 Cellular respiration: breakdown of sugars by plants and animals to produce energy C6H12O6 + 6O6 > 6CO2 + 6H2O + energy 8 Flow of energy through ecosystems Primary Production: organic matter produced by plants 1. Gross primary production (GPP): total biomass produced by plants 2. Net Primary Production (NPP): biomass that remains after plants use their share 9 Flow of energy through ecosystems Producers (autotrophs): green plants Consumers (heterotrophs): organisms (generally animal) ­capture solar energy; convert (“produce”) chemical energy ­consume stored energy Food Webs vs. Food Chains 10 10 Ecosystem structure Detritus feeder: organisms that obtain their energy and nutrients from waste material and the dead bodies of plants and animals (bacteria, fungi, scavengers) ­bacteria and fungi break large complex molecules into smaller, usable compounds that plants absorb Detritus food web: any food web that has its base in the dead remains of plants and animals Trophic level: a group of organisms that occupy the same position in a food chain / web 11 11 Matter and energy flow in ecosystems Energy vs. Biomass Pyramid Only 10% transfer of energy and matter 12 12 Why only 10% transfer of energy and matter? 1) Not all organisms in one trophic consumed by the next ­organism may die of “natural causes” and feed into the detritus food web 2) Not all parts of an organism are digestible (cellulose, bone, hair, etc.) 3) Not all material is accessible (roots of a plant) 4) Respiration: loss of energy through heat and loss of carbon through CO2 13 13 Nutrient cycles Nutrients re­circulate in the ecosystem, travel from living to dead components and then back to living (“recycle”) The circular flow of an element from nonliving (abiotic environment: rocks, air, water) into the bodies of living organisms and then back into the nonliving environment; also called biogeochemical cycle 14 14 Nutrient cycles ­­major ones: carbon, nitrogen, phosphorus, water ­­nutrient cycles are closed systems (energy systems are open) ­­note: 96% of living organisms are C, H, O and N 15 15 Nutrient cycles ­­have been in relative equilibrium for eons ­­in the past 200 years anthropogenic activities have knocked some of these cycles out of equilibrium ­­dis­equilibrium results in higher (or lower) concentrations of key nutrients in certain components of the cycle…harmful to humans and organisms 16 16 Nitrogen (N) cycle ­­N is essential component of many biological molecules (e.g., DNA, chlorophyll) ­­biotic N comes ultimately from atmosphere N2, which is very abundant (80% of atmosphere) but inert for most organisms ­­N2 needs to be fixed before it can be used by plants and passed onto to heterotrophs 17 17 Nitrogen (N) cycle Nitrogen Fixation 1) Atmosphere fixation: lightening or sunlight convert N2 to nitrate NO3 in atmosphere; washed to earth 2) Biological fixation: bacteria in soil and water convert N2 to ammonia (NH3); absorbed by plants ­N­fixing bacteria also live in the roots of many plants (e.g., legumes); produce usable N 18 18 Nitrogen (N) cycle Nitrogen Fixation 3) Industrial fixation: combine N2 with hydrogen (H) to form ammonia (NH3), converted to salts to be used as fertilizer ­ increase in use since WWII ­use animal and human waste as fertilizer; concentrates N 19 19 Nitrogen (N) cycle Anthropogenic effects 1) Pesticides: can be detrimental to N­fixed bacteria 2) Fertilizer: too much N disrupts cycle 3) Fossil fuels: burning produces NO2, adds N to system 20 20 Carbon (C) cycle ­­key element of organisms (49% of human dry weight) ­­reservoirs: atmosphere, organisms, ocean, sediment and calcium carbonate (CaCO3) ­­atmospheric and organismic reservoirs are not large but flow rate is high 21 21 Phosphorous (P) cycle ­about 1% of dry weight of body, key component of DNA ­anthropogenic activity (soaps, fertilizer) has increased the amount of P in aquatic systems ­creates algal blooms that die, sink to the bottom, decay, bacteria use up O2, creating anoxic zones 22 22 Principles of Ecology Law of Tolerance ­survival depends on interaction of many factors (e.g., moisture, temperature, etc.), which can vary greatly ­for each factor, a given species has a range of tolerance, or a range of conditions it can tolerate ­if environmental conditions exceed upper or lower limit of tolerance, death can result 23 23 Principles of Ecology Habitat: the area or environment where an organism or ecological community normally lives or occurs ­often thought of as simple (e.g., trout: fresh water stream) but is usually complex (e.g., trout – water, DO, temp, pH, food…) Niche: the function or position of an organism or population within an ecological community ­the particular area within a habitat occupied by an organism 24 24 Principles of Ecology Competitive exclusion principle ­if 2 species occupy same habitat and have the same role (ecological niche), then one will drive other to extinction ­extinction at least in the local area (extirpation) Carrying capacity ­number of individuals an ecosystem can support ­determined by food, water, nesting sites, cover, climate, space, much more. ­dynamic – changes seasonally and yearly 25 25 Principles of Ecology Population growth: increase when favorable, decrease when not Biotic potential: maximum reproductive rate (e.g., maximum # offspring produced per litter, per year, or per lifetime) ­ genetically determined but environmentally controlled Environmental resistance: biotic and abiotic factors that reduce growth 26 26 Principles of Ecology Biological succession: orderly and often predictable replacement of one community by another in the absence of a disturbance Primary succession: succession that occurs in areas not previously occupied by organisms Secondary succession: succession that occurs in areas previously occupied by organisms ­occurs when an ecosystem is disturbed ­quicker, soil already established 27 27 Biomes ­ large terrestrial community characterized by its climate and unique assemblage of plants & animals Tundra: extends from the timberline to perpetual ice in the north (10% of earth) ­limiting factors are solar radiation and cold temperatures Northern coniferous forest (taiga): extensive forest (pines) just south of tundra, around most of the world ­reasonable rainfall and productivity Deciduous forest: deciduous forest in NA, China, 28 28 Japan and Australia Biomes Tropical rain forest: equatorial regions, lots of rain ­high species diversity but rapid cutting and destruction Tropical savannah: warm­climate grassland with scattered trees (SA, Africa, India and Australia) ­wet and dry seasons, low species diversity (but large, hoofed herbivore populations) Grassland: large area of land dominated by grasses (prairies of NA, SA, Eurasia and Africa) ­cultivated by humans 29 29 Biomes Desert: found throughout the world, receive < 25 cm of rain (organisms have to be specialized to handle low water) ­tend to be leeward side of prominent mountains Altitudinal biomes: with altitude you see changes in the biomes, at much smaller scale 30 30 ...
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This note was uploaded on 03/22/2009 for the course FORS 1100 taught by Professor Warren during the Spring '09 term at University of Georgia Athens.

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