Communities What organizes biology above the level of the population?

Transcription

1 ECOLOGY part 2

2 Populations/Communities Similar species can co-exist more readily if they utilize different portions of shared niche axes have different niches (determined by traits) Coastal wetland So, an organism s integrated traits (genes) allow success or determine failure of a population in any particular ecosystem Both the possibilities and limits for survival

3 Communities What organizes biology above the level of the population? Communities & Ecosystems -Primarily the interactions of populations with each other and the abioticenvironment (another definition of ecology). Most common interaction? In economics follow the money, in ecology, follow the food

4 Communities Community the array of interacting populations in a place. Major insight to a large extent, the question is -? Communities are analyzed by the network of eating interactions, ultimately the overall food web or structure A marine food web

5 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.

6 Even often about eating (or not being eaten) usually involves a (food, defense) Plants major mutualisms -nutrition myccorhizae ( ), nitrogen fixers ( ), trade nutrient and carbohydrate 4-2

7 Flowers mutualism? Angiosperm flowers attract insects with rewards, often food (, pollen), gain In some flowers, the rewards are questionable Many mutualisms reveal these kinds of subtle antagonisms when studied closely.

8 Communities A food web consists of a complex set of interconnected transformations. Similar in this way to a

9 Communities A food web consists of a complex set of interconnected transformations. Similar in this way to a 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, structured only by the interactions. Communities are assembled by the component species Note potential for re-assembly

10 Communities Types of eating: Herbivory plant eating Carnivory meat eating Omnivory mixed diets Detritivory eating dead stuff Photosynthesis sun eating Major insight different food webs share a general structure, with photosynthesizers as the The rest of the food web depends on the photosynthesizers This led to the concept of ecosystem

11 Communities/Ecosystems Simplified web food chain Photosynthesizers called, herbivores & carnivores called 2-15/2-17 Ecosystem ecologists aggregate (simplify) webs to focus on key dynamics and system properties

12 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?

13 Why do decomposers exist? 2-13/2-14

14 Ecosystems The most general concept of ecosystem includes decomposers as main component Also chemicals, or (since this is mostly food for the producers) Note the difference in emphasis compared to the food web 2-14/2-15

15 Ecosystems This is a (outputs inputs) Components may stay fairly stable, but Energy through the ecosystem driving Material within Resource use by individuals (eating) drives these dynamics

16 This is a basic picture of an ecosystem Heat Consumers Decomposers Energy Materials Both energy and materials are transferred together Heat Heat Producers except here Nutrients Sun

17 To a decent first approximation, you can stick our kingdoms into this basic picture of ecosystems Animals Bacteria & Fungi Animals & Protists Bacteria & Fungi Plants Algae & Cyanobacteria Nutrients Nutrients Sun Sun Terrestrial (land-based) Aquatic (water-based) This suggests a deep connection between and

18 Ecosystems nutrient cycling Decomposers are a complex of many species in an OM matrix 7-A/2-22 Terrestrial ecosystems - soil Rock particles & organic matter Aquatic systems Dissolved organic matter (DOM) & Sediments Soils & sediments can take 100s of years to develop

19 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? What controls nutrients? Chlorophyll

20 Ecosystems nutrient cycling Nutrient Cycling. Most elements originally come from rock the earth s 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 Short term (fast) community to dead organic matter (detritus; OM) via decomposition to the nutrient pool back to community Long term (slow) from system to reservoir, back to system Consumers Producers Reservoir Decomposers OM Nutrients

21 Ecosystems nutrient cycling In addition to water and carbon cycles, life creates cycles within ecosystems of essential nutrients for producers cycle is typical of most elements rock reservoir, organic matter derived available pool (also K, Ca, Mg, etc.) Consumers Producers Reservoir Decomposers OM Nutrients 2-22/2-28

22 Ecosystems nutrient cycling Nitrogen Cycle Reservoir N 2 gas in atmosphere 79% Nitrogen (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

23 Ecosystems nutrient cycling Some bacteria use NO 3 for energy, releasing N 2 gas. This is the cause of our N 2 atmosphere Percent Composition of the Atmosphere CO 2 O 2 N 2 Venus 96.5 trace 3.5 Mars Earth (w/o life) Earth (w/ life) This creates the longer cycle N 2 => OrgN => Available N => N 2

24 Ecosystems nitrogen cycling Consumers Producers Decomposers OM Nutrients Reservoir 2-21/2-27

25 Ecosystems nutrient cycling These nutrient cycles can be added to the water and carbon/oxygen cycles covered earlier. Consumers Producers Decomposers OM Nutrients 2-20/2-26 Reservoir O 2 photosynthesis CH 2 O respiration CO 2, H 2 O Together they describe the global fluxes of major materials regulating ecosystem production 2-19/2-25

26 Ecosystems TrophicStructure The energy pyramid Energy flows through the ecosystem from sun to Heat Consumers Energy is transformed by photosynthesis from light to chemicals (e.g., sugar) Heat Producers Energy of chemicals is transformed from producers to consumers and to decomposers Sun Decomposers Nutrients Heat Energy is lost in all transformations as, generating EM waves -Respiration (can be >90% of energy taken in) -The energy transformations are not 100% efficient

27 Ecosystems -energy The flow of energy up is a diminishing one 2-17/2-19 Only a portion of energy flowing into a trophic level is transferred to the next higher level. Ecological about 10% (2-40%) This limits trophiclevels to 4 or 5

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29 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

30 Ecosystems -productivity Net Primary Productivity (NPP) = Gross Primary Productivity (GPP) Respiration (R) NPP measures the ecosystem s capacity to support life (producers, consumers, decomposers) Units: kcal/m 2 /year energy/area/time

31 Ecosystems -productivity 2-18/2-21 Ecosystems differ in NPP area of systems not shown (e.g., ocean) Why?

32 Biomes & Productivity Globally, there is a strong correlation between NPP, total plant biomass, and We know that NPP is dependent on temperature, water, light, CO 2 and many nutrients. Why is water so important?

33 Biomes How plants work: Leaf light, CO 2 Root water, nutrients But is lost in taking up CO 2 more water = more air soil And water increases rate in soil more water = more Result: Water is both a resource and a controller of CO 2 and nutrients. More rain has several benefits. Temperature? higher temp = more water lost per C lower temp = shorter growing season (less liquid water)

34 Biomes In general: NPP controlled by light and water. Light is relatively un-varying; water is variable Variation in NPP primarily due to water

35 Biomes

36 Biomes So precipitation and temperature are the master controllers of plant production (NPP) Distribution of climates. Precipitation and temperature = climate

37 Biomes Climate controls NPP Distribution of chlorophyll

38 Biomes niche diagram 3-6/3-7

39 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.

40 End Ecology End Ecology