ECOLOGY Part 2 What is Ecology? The study of biological organization at and above the level of the organism. (one definition) What are levels of organization? Biosphere Ecosystem Community Population Organism Organ Tissue Cell Organelle Molecule 2-7 Ecology Note: species is not on this list Ecosystem Population 1 Pop 2 Pop 3 etc. Abiotic Environment Light, nutrients, substrate, etc. Community Organism (sp. 1) 23 Similar species can co-exist more readily if they utilize different portions of shared niche axes have different niches (determined by traits) So, an organisms integrated traits (genes) allow success or determine failure of a population in any particular ecosystem Both the possibilities and limits for survival Populations/Communities Coastal wetland What organizes biology above the level of the population? Communities & Ecosystems - Primarily the interactions of populations with each other and the abiotic environment (another definition of ecology). Most common interaction? Eating. Communities In economics follow the money, in ecology, follow the food 2-16/2-18 A marine food web Communities are analyzed by the network of eating interactions, ultimately the overall food web or trophic structure. Communities Community the array of interacting populations in a place. Major insight to a large extent, the question is - who eats who? Species Interactions classified by pairwise effects (+,-, 0) Competition (-/-) use same resource, depletion or combat Predation (+/-) one eats(kills) the other Parasitism (+/-) one eats (partially) the other Mutualism (+/+) each benefits from the other Commensalism (+/0) hard to verify, e.g. epiphytes (0,0) meaningless, seldom see (-,0) why? Eating still the key underlying theme competition, predation, parasitism obvious. 4-4/4-2 Even mutualism often about eating (or not being eaten) usually involves a trade (food, defense) Plants major mutualisms - nutrition myccorhizae (fungus), nitrogen fixers (bacteria), trade nutrient and carbohydrate Flowers mutualism? Angiosperm flowers attract insects with rewards, often food (nectar, pollen), gain reproduction In some flowers, the rewards are questionable Many mutualisms reveal these kinds of subtle antagonisms when studied closely. A food web consists of a complex set of interconnected transformations. Similar in this way to a biochemical pathway. Communities A food web consists of a complex set of interconnected transformations. Similar in this way to a biochemical pathway. One important difference is, there is currently no evidence that natural selection operates on the overall food web as it does on whole organisms. A community is more like a free market economy, structured only by the interactions. Communities Communities are assembled by the component species Note potential for re-assembly Around my barn - Dillon Bustin When the hound begins to howl And Ive not heard a hooting owl When the chickens begin to squawk Thats the time Ill take a walk Refrain: around my barn, around my barnyard Could be the wind in the trees Could be a rabbit or a groundhog sneeze Eating the peppers in my garden spot Hed better hope that I am not Around my barn, around my barnyard Could be a cloud across the moon Could be a fox or a sly raccoon Coming down to make a meal He dont know the way I feel About my barn, about my barnyard You ask me whats dirty trick Skinny old weasel in among the chicks And when hes done gnawing their legs An old skunk come and hell suck the eggs That are left in my barn, left in my barnyard Down in the cornfield see the deer Each one chewing on a yellow ear And every squirrel thats ever been born Wants to make a living off the little corn That I get to my barn, get to my barnyard All the milk that my milk cow makes Gets drunk up by a long milk snake You may not believe what I say is true But he aint eating mice Im telling you Out in my barn, out in my barnyard Lindy tells me treat them like brothers I told her let them eat each other Its what they done before I come What theyll do before Im done With my barn, done with my barnyard Well I never expected life to be Simple or easy or completely free But I did not think that Id have to fight To get one drink or a single bite Of food from my barn, food from my barnyard Types of eating: Major insight different food webs share a general structure, with photosynthesizers as the foundation The rest of the food web depends on the photosynthesizers Communities Herbivory plant eating Carnivory meat eating Omnivory mixed diets Detritivory eating dead stuff Photosynthesis sun eating This led to the concept of ecosystem Simplified web food chain Ecosystem ecologists aggregate (simplify) webs to focus on key dynamics and system properties Communities/Ecosystems Photosynthesizers called producers, herbivores & carnivores called consumers 2-15/2-17 Ecosystems Generalization called attention to a major component of the ecosystem previously ignored - decomposers The unasked question: where does all the dead stuff go? and incidentally what are plants eating? 2-13/2-14Why do decomposers exist? The most general concept of ecosystem includes decomposers as main component Ecosystems 2-14/2-15 Also chemicals, or nutrients (since this is mostly food for the producers) Note the difference in emphasis compared to the food web Energy flows through the ecosystem, driving Material cycles within Resource use by individuals (eating) drives these dynamics Ecosystems This is a dynamic equilibrium (outputs inputs) Components may stay fairly stable, but This is a basic picture of an ecosystem Producers Nutrients Decomposers Consumers Sun Energy Materials Both energy and materials are transferred together except here Heat Plants Nutrients Bacteria & Fungi Animals Sun Algae & Cyanobacteria Nutrients Bacteria & Fungi Animals & Protists Sun To a decent first approximation, you can stick our kingdoms into this basic picture of ecosystems Terrestrial (land-based) Aquatic (water-based) This suggests a deep connection between evolution and ecology Ecosystems nutrient cycling Terrestrial ecosystems - soil Rock particles & organic matter Aquatic systems Dissolved organic matter (DOM) & Sediments 7-A/2-22 Decomposers are a complex of many species in an OM matrix Soils & sediments can take 100s of years to develop Ecosystems nutrient cycling What are nutrients? In addition to CO 2, light and water, producers also need various other essential elements Nitrogen (N), Phosphorus (P), Potassium (K), Magnesium (Mg), Calcium (Ca) and various others (Iron, Boron, Nickel, etc.) Why? Chlorophyll What controls nutrients? Ecosystems nutrient cycling Nutrient Cycling Reservoirs. Most elements originally come from rock the earths crust, via weathering. Except Nitrogen - atmosphere In most systems, most elements used by producers come from decomposition which recycles the nutrients. Nutrients have both long and short term cycles Long term (slow) from system to reservoir, back to system Short term (fast) community to dead organic matter (detritus; OM) via decomposition to the nutrient pool back to community Producers Nutrients Decomposers OM Consumers Reservoir Ecosystems nutrient cycling In addition to water and carbon cycles, life creates cycles within ecosystems of essential nutrients for producers Phosphorus cycle is typical of most elements rock reservoir, organic matter derived available pool (also K, Ca, Mg, etc.) 2-22/2-28 Producers Nutrients Decomposers OM Consumers Reservoir Ecosystems nutrient cycling Nitrogen Cycle Reservoir N 2 gas in atmosphere 79% Nitrogen fixation (certain bacteria) converts N 2 to organic form energetically expensive Decomposition releases nitrogen to available forms (ammonium (NH 4 ) and nitrate (NO3)) Producers take up available N so convert it back to organic Nitrogen completing the short cycle N 2 => OrgN => Available N Producers Nutrients Decomposers OM Consumers Reservoir Some bacteria use NO 3 for energy, releasing N 2 gas Denitrification. This is the cause of our N 2 atmosphere Percent Composition of the Atmosphere CO 2 O 2 N 2 Venus96.5trace3.5 Mars Earth (w/o life) Earth (w/ life) This creates the longer cycle N 2 => OrgN => Available N => N 2 Ecosystems nutrient cycling Producers Nutrients Decomposers OM Consumers Reservoir 2-21/2-27 Ecosystems nitrogen cycling Producers Nutrients Decomposers OM Consumers Reservoir These nutrient cycles can be added to the water and carbon/oxygen cycles covered earlier. 2-19/ /2-26 Together they describe the global fluxes of major materials regulating ecosystem production photosynthesis CH 2 O respiration O2O2 CO 2, H 2 O Ecosystems nutrient cycling Producers Nutrients Decomposers OM Consumers Reservoir Ecosystems Trophic Structure The energy pyramid Energy flows through the ecosystem from sun to space Energy is transformed by photosynthesis from light to chemicals (e.g., sugar) Energy of chemicals is transformed from producers to consumers and to decomposers -Respiration (can be >90% of energy taken in) -The energy transformations are not 100% efficient Producers Nutrients Decomposers Consumers Sun Energy is lost in all transformations as heat, generating EM waves Heat Ecosystems - energy 2-17/2-19 The flow of energy up is a diminishing one Only a portion of energy flowing into a trophic level is transferred to the next higher level. Ecological Efficiency about 10% (2-40%) This limits trophic levels to 4 or 5 Ecosystems Primary Productivity Ecosystems depend on producers for energy Primary productivity is variable throughout the world What controls this variability? Global chlorophyll levels winter 2004 Ecosystems - productivity Net Primary Productivity (NPP) = Gross Primary Productivity (GPP) Respiration (R) NPP measures the ecosystems capacity to support life (producers, consumers, decomposers) Units: kcal/m 2 /year energy/area/time Ecosystems - productivity Ecosystems differ in NPP area of systems not shown (e.g., ocean) 2-18/2-21 Why? Globally, there is a strong correlation between NPP, total plant biomass, and precipitation. We know that NPP is dependent on temperature, water, light, CO 2 and many nutrients. Why is water so important? Biomes Result: Water is both a resource and a controller of CO 2 and nutrients. More rain has several benefits. How plants work: Leaf light, CO 2 Root water, nutrients air soil But water is lost in taking up CO 2 more water = more CO 2 And water increases decomposition rate in soil more water = more nutrients Temperature? higher temp = more water lost per C lower temp = shorter growing season (less liquid water) Biomes In general: NPP controlled by light and water. Light is relatively un-varying; water is variable Variation in NPP primarily due to water Biomes Distribution of climates. So precipitation and temperature are the master controllers of plant production (NPP) Precipitation and temperature = climate Biomes Distribution of chlorophyll Climate controls NPP Biomes 3-6/3-7 niche diagram Ecology summary 1.The biosphere consists of diverse linked ecosystems 2.Eating by individual organisms, including photosynthesis, drives primary production, trophic structure, and decomposition. The balance of nature reflects a balance of conflicting interests of individuals. 3.Ecosystems consist of 4 main components: producers, consumers, decomposers, nutrients. Fit of kingdoms to these compartments suggests a deep connection of evolution and ecology. 4.Energy flows from the sun through the ecosystems and into space, powering materials (elemental) cycles within ecosystems. 5. In terrestrial systems, variation in climate controls variation in NPP, and therefore biome distribution. End Ecology