Environmental Science 1001
Environmental Science 1001 EVR 1001
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This 10 page Class Notes was uploaded by Samantha Estis on Sunday October 2, 2016. The Class Notes belongs to EVR 1001 at Florida State University taught by Dr. Rob Spencer in Fall 2016. Since its upload, it has received 5 views. For similar materials see Introduction to Environmental Science in Natural science at Florida State University.
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Date Created: 10/02/16
Environ Science lecture 9/29/16 Sustaining life on earth requires more than individuals, species, or populations Ecosystem – biological community of interacting organisms and their physical environment o Interactions of many organisms functioning together Ecosystems have fundamental characteristics o Structures Comprised of living and non-living par o Processes Cycling elements Flow of energy Ecosystem chemical cycling o For complete recycling of chemical elements, several species must interact Photosynthetic organisms produce sugar from carbon dioxide and water From sugar and inorganic compounds, they make other organic compounds (protein, woody tissue, etc.) Need decomposers to return material to inorganic compounds At its simplist, each community will have o At least one species that is producer o At least one species that is a decomposer o Plus a fluid medium (air, water, or both) Ecological community definitions o A set of interacting species found in the same place and functioning together to maintain life In practice, it is difficult to identify the interacting species (and it is likely that they are all interacting o All the species found in area, whether or not they interact Species: group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding Population: group of organisms of one species that interbreed and live in the same place at the same time Ecological communities and food webs Trophic level: number of feeding levels away from original source of energy First trophic level o Primary producers o Use energy from sun and carbon dioxide from air to photosynthesize o Green plats, algae, other bacteria Second trophic level o Primary consumer o Herbivores o Organisms that feed on autotrophs Third trophic level o Feed directly on herbivores o Carnivores o Secondary consumers Fourth tropic levels o Feed on carnivores o Tertiary consumers Decomposers o Feed on waste and dead organisms of all trophic levels o Trophic level may vary based on the structure of ecosystems o Include scavengers, fungi, microorganisms, termites, etc. Organisms at each trophic level transform a fraction of what they eat into biomass o This biomass is then available to higher trophic levels o The % of energy that is converted to biomass (and made available to higher trophic levels) is known as its gross growth efficiency or trophic level efficiency Typically, about 10% for land animals Higher for many small marine organisms The inefficiency of organisms leads to energy loss at each trophic level Thus less energy is available to each successive trophic level This puts a limit on the number of organisms that an ecosystem can support at any given trophic level That limit depends on total production All life requires energy – the ability to do work Ecosystem energy flow o Movement of energy through an ecosystem from external environment through a series of organisms and back to the external environment Energy must be continually added to an ecological system in a usable form o because it is inevitably degraded into heat o Net flow of energy is a one-way flow Second law of thermodynamics o No use of energy is ever 100% efficient o energy is lost as heat Biological production Biomass o total amount of organic matter on Earth or in any ecosystem or area o measured as amount per unit surface area Primary production o autotrophs conduct photosynthesis o make their own organic matter from an energy source and inorganic compounds respiration o use of energy from organic matter by most heterotroph and autotrophic organisms opposite of photosynthesis organic matter Ecological interactions: competition Competition o Interactions among organisms who compete for limited, shared resources o Intraspecific competition Members of the same species pursue shared resources o Interspecific competition Organisms from diff species also compete for shared resources Interspecific competition o If you remove a competitor the remaining species will have greater access to resources Light Nutrients Prey o Remaining species o Competitive exclusion principle Two species that differently compete for essential resources cannot coexist One species will eventually displace the other o Competitors coexist? Fundamental (or theoretical) niche – the complete range of environmental conditions (temp, food, water) over which the species might possibly exist Realized niche – range of conditions over which a species actually occurs o Niche differentiation Potential competitors are able to coexist because they divide up the fundamental niche o Exploitation competition: competition for a shared resource One species of desert plant taking up all the water One pride of loins eating all the zebras One undergrad consuming everything in the cafeteria o Successful competitors are able to take up or utilize resources more efficiently o Interference competition: aggressive actions deigne to drive off a competitor Scavengers fighting over remains of animal Plants release chemicals that inhibit other plants o Herbivores use several different feeding strategies Some of these feeding strategies are beneficial to plants Fructivores: feed on fruits Gramnivores: feed on seeds Many insects feed on pollen and nectar o Herbivores use seeral different feeding strategies Grazers: feed directly on the leaves and young stems of plants Feeding challenges associated with chemical nature of food Leaves and stems are formed of cellulose (glucose polymer) that is resistant to breakdown Many grazers keep specialized microbes in their guts o Coevolution: organisms can evolve in combination Plants evolve defenses against herbivores Thorns, irritating hairs, distasteful or toxic chemicals Natural selection favors herbivores with adaptations that allow them to thwart these defenses, or even take advantage of them Milkweed produces chemicals (alkaloids) that are toxic to most animals Caterpillars (of monarch butterflies) are resistant to those chemicals and even store them in their own bodies to protect against predation Coevolution can also lead to species benefiting each other Insects and flowering plants o Predation Capture, kill, and consume other animals Two basic feeding strategies Filter feeding – webs or net-like structures used to filter a predator’s environment (spider webs, blue whales, krill) Hunting – stalk and capture their prey Coevolution significantly affects the evolution of predators and prey Predator-prey population cycles When distinct two species predator-prey relationships exist they will often undergo cycles of high and low abundance High prey abundance leads to growth of the predator High predator abundance leads to decrease in the prey Low prey abundance leads to decrease of the predator o Parasites Live and feed in or on other organisms (hosts) Usually do not kill host But do harm it and may lead to its death Virus, tick, tape worm o Vectors – organisms that carry parasites but not affected by them Some parasites have complex life cycles that involve many hosts and vectors o Factors affecting spread of parasites Abundance of hosts Bubonic plague linked to growth of cites Accessibility of parasites to locate viable hosts can depend on species on species diversity o Transmission rates of parasites Compare common cold to HIV o Length of life of an infected host Highly virulent parasites that quickly immobilize or kill their hosts limit the opportunities for the parasites to reproduce and spread (Ebola) o Habitat expansion When climatic or other environmental conditions change, parasites can move into a new area o Symbioses – intimate interdependencies between species Parasitism Mutualism o Mutualism – both organisms benefit Flowering plants and pollinators o Commensalism – one species benefits, the other is unaffected Hermit crab lives in shells of marine snails (but only after they die) o Ecosystems are dynamic – always changing o Primary succession Establishment and development of an ecosystem where one didn’t previously exist o Ecosystems are dynamic – always changing Secondary succession o Reestablishment of an ecosystem following disturbance o Remnants of previous biological community (soil, seeds, organic material, etc.) o When succession occurs it follows certain general patterns Dune succession o Early succession plant characteristics Small size Grow well in bright light Withstand harshness of environment Environ Sci lecture 9/27/16 The hydrologic cycle Transfer of water from oceans to the atmosphere At the regional and local level, the fundamental unit of the landscape is the drainage basin - The area that contributes surface runoff to a particular stream or river - Vary greatly in size - Usually named for main stream or river Why do we care about watersheds? - Precipitation above a watershed directly affects water levels throughout that watershed - Water flows in the watershed transport nutrients and pollutants across watershed - Water falling outside the watershed will not be transported into the watershed - Catchments are small drainage basins within a larger watershed The rock cycle consists of numerous processes that produce rocks and soils depend on tectonic cycle for energy and hydrologic cycle for water rocks classified as o igneous – formed through cooling and solidification of magma or lava o sedimentary – formed by sediment that is deposited over time and compressed (glued together) into layers of rock (limestone, sandstone, etc.) o metamorphic – formed from another rock that has been altered due to high temperature and pressure (ex. Limestone to marble) Physical weathering (freeze, thaw) produces sediment such as gravel, sand, silt Chemical weathering occurs when weak acids in water dissolve chemicals from rocks The initial chemical composition and specifics of formation (temperature and pressure) determine the chemical nature of the rocks The chemical and physical nature of the rocks in turn affects the elements released during weathering The carbon cycle Carbon is the element that anchors all organic substances Carbon has a gaseous phase o Enters atmosphere (CO2 and CH4) through respiration, fires, and diffusion Removed from the atmosphere by photosynthesis Carbon enters the biota through photosynthesis and then is returned by respiration or fire o When organisms die, decomposition of their remains releases carbon o If buried under certain conditions, carbon is not released Transformed into fossil fuel Clear cutting and burning of tropical rain forests releases carbon from biota into the atmosphere Most of the carbon stored in living biomass is found in terrestrial organisms o 560 Pg C o 560,000,000,000,000,000 grams of carbon o most of it is in plants o soil contains an additional 1500 Pg C terrestrial (land) carbon cycle oceans, lakes, and rivers contain 38,000 Pg C o much, much more than in terrestrial biota carbon occurs in the ocean in several forms o dissolved into CO2 carbonate (CO3^-2), and bicarbonate (HCO3^-) o dissolved organic carbon (sugars, etc.) o marine organisms and their products (ex. CaCO3) Carbon enters oceans by o Diffusion from atmosphere and then dissolves in the ocean o Transfer from land in rivers as dissolved carbon Carbon leaves the ocean by o Diffusion of gases out of the ocean o Sinking (sedimentation) of particles to the bottom of the ocean o Transport by organisms (ex. Seabirds) that feed in the ocean The carbon silicate cycle The cycling of carbon is intimately involved with the cycling of silicon Weak caronic acid falls as rain and weathers silicate rich rocks o Releases Ca2+ and HCO3- o Transferred to oceans and used by marine phytoplankton o Organisms sinking to sea floor become part of sedimentary rock layer Affects the level of CO2 and O2 in the atmosphere Net reaction is CaSiO3 + CO2 <- -> CaCO3 + SiO2 The nitrogen cycle Nitrogen (N) is essential to life because it is necessary for the production of proteins and DNA Free N2 (Nitrogen Gas) makes up 78% of the atmosphere o But most organisms can’t use it directly o Relatively unreactive N2 gas must be converted to NO3- or NH4+ Nitrogen fixation: processs of converting atmospheric N2 to NO3- or NH4+2 Denitrification: process of releasing fixed nitrogen back to gaseous N2 Almost all organisms depend on nitrogen-converting bacteria o Some have formed symbiotic relationships in the roots of plants (like soybeans), stomachs of animals, or inside tiny phytoplankton cells Industrial processes can now convert molecular nitrogen (N2 Gas) into compounds usable by plants (Haber process) o Main component of N fertilizers o N in agricultural runoff is a potential source of eater production N combines with O at high temperature Human activities have doubled the rate of nitrogen exchange The phosphorous cycle Phosphorus (P) is one of the “big six” required for life o Often limiting factor for plant and algae growth o Needed for ATP (short term energy storage) and DNA and RNA Does not have gaseous phase o IS abundant in Earth’s crust (minerals known as apatite or calcium phosphate) o Rate of transfer is slow Enters biota through uptake as phosphate by plants, algae, and some bacteria o Returns to soil when plants die or is lost to oceans via runoff o Phosphate is particularly important in lake and ocean environments where P (in the form of PO4^3-) is often the limiting nutrient for the growth of Algae Phosphorous mining creates environmental problems o Mined from sedimentary rocks o Guano is also used as a fertilizer Overabundance of phosphorous in runoff causes pollution problems o Unwanted growth of photosynthetic bacteria and algae in rivers, ponds, estuaries, and the coastal ocean o Oceanic dumping of organic materials high in N & P has produced several hundred “dead zones”
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