Ecology lecture Part 2 spring 2010 BIO 102-001

1. Ecology lecture Part 2 spring 2010 BIO 102-001 These are the slides, without blanks, that go with the missed class ecology lecture. There is an mp3 you can listen to for the words, and the slides + words version is also available.

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 abiotic environment (another definition of ecology). Most common interaction? Eating. In economics – “follow the money”, in ecology, “follow the food”

4. Around my barn - Dillon Bustin Down in the cornfield see the deer Each one chewing on a yellow ear And every squirrel that’s ever been born Wants to make a living off the little corn That I get to my barn, get to my barnyard When the hound begins to howl And I’ve not heard a hooting owl When the chickens begin to squawk That’s the time I’ll take a walk Refrain: around my barn, around 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 ain’t eating mice I’m telling you Out in my barn, out in my barnyard Could be the wind in the trees Could be a rabbit or a groundhog sneeze Eating the peppers in my garden spot He’d 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 don’t know the way I feel About my barn, about my barnyard Lindy tells me treat them like brothers I told her let them eat each other It’s what they done before I come What they’ll do before I’m done With my barn, done with my barnyard You ask me what’s dirty trick Skinny old weasel in among the chicks And when he’s done gnawing their legs An old skunk come and he’ll suck the eggs That are left in my barn, left in my barnyard Well I never expected life to be Simple or easy or completely free But I did not think that I’d have to fight To get one drink or a single bite Of food from my barn, food from my barnyard

5. Communities Community – the array of interacting populations in a place. Major insight – to a large extent, the question is - who eats who? Communities are analyzed by the network of eating interactions, ultimately the overall food web or trophic structure. 2-16/2-18 A marine food web

6. 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.

7. 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 4-4/4-2

8. 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.

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

10. 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 are “assembled” by the component species Note potential for “re-assembly”

11. 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 foundation The rest of the food web depends on the photosynthesizers This led to the concept of ecosystem

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

13. 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?

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

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

16. Ecosystems This is a dynamic equilibrium (outputs ≈ inputs) Components may stay fairly stable, but… Energy flows through the ecosystem, driving Material cycleswithin Resource use by individuals (eating) drives these dynamics

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

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

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

20. Ecosystems – nutrient cycling What are nutrients? In addition to CO2, 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?

21. Consumers Decomposers OM Producers Nutrients Reservoir Ecosystems –nutrient cycling Nutrient Cycling Reservoirs. 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

22. Consumers Decomposers OM Producers Nutrients 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

23. Consumers Decomposers OM Producers Nutrients Reservoir Ecosystems – nutrient cycling Nitrogen Cycle Reservoir – N2 gas in atmosphere – 79% Nitrogen fixation (certain bacteria) – converts N2 to organic form energetically expensive Decomposition releases nitrogen to available forms (ammonium (NH4) and nitrate (NO3)) Producers take up available N so convert it back to organic Nitrogen – completing the short cycle N2 => OrgN => Available N

24. Consumers Decomposers OM Producers Nutrients Reservoir Ecosystems – nutrient cycling Some bacteria use NO3 for energy, releasing N2 gas – Denitrification. This is the cause of our N2 atmosphere Percent Composition of the Atmosphere CO2 O2N2 Venus 96.5 trace 3.5 Mars 95 0.13 2.7 Earth 98 0.0 1.9 (w/o life) Earth 0.03 21 79 (w/ life) This creates the longer cycle N2 => OrgN => Available N => N2

25. Consumers Decomposers OM Producers Nutrients Reservoir Ecosystems – nitrogen cycling 2-21/2-27

26. Consumers Decomposers OM photosynthesis Producers CH2O CO2, H2O O2 respiration Nutrients Reservoir Ecosystems – nutrient cycling These nutrient cycles can be added to the water and carbon/oxygen cycles covered earlier. 2-20/2-26 2-19/2-25 Together they describe the global fluxes of major materials regulating ecosystem production

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

28. 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

30. 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

31. 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/m2/year energy/area/time

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

33. Biomes Globally, there is a strong correlation between NPP, total plant biomass, and precipitation. We know that NPP is dependent on temperature, water, light, CO2 and many nutrients. Why is water so important?

34. Biomes How plants work: Leaf – light, CO2 Root – water, nutrients But – water is lost in taking up CO2 more water = more CO2 air soil And – water increases decomposition rate in soil more water = more nutrients Result: Water is both a resource and a controller of CO2 and nutrients. More rain has several benefits. Temperature? higher temp = more water lost per C lower temp = shorter growing season (less liquid water)

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

36. Biomes

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

38. Biomes Climate controls NPP Distribution of chlorophyll

39. Biomes “niche diagram” 3-6/3-7

40. Ecology summary • The biosphere consists of diverse linked ecosystems • 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. • Ecosystems consist of 4 main components: producers, consumers, decomposers, nutrients. Fit of kingdoms to these compartments suggests a deep connection of evolution and ecology. • 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.

41. End Ecology End Ecology