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.
Similar species can co-exist more readily if they utilize different portions of shared niche axes – have different niches (determined by traits)
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
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”
Around my barn - Dillon Bustin
When the hound begins to howlAnd I’ve not heard a hooting owlWhen the chickens begin to squawkThat’s the time I’ll take a walk
Refrain: around my barn, around my barnyard
Could be the wind in the treesCould be a rabbit or a groundhog sneezeEating the peppers in my garden spotHe’d better hope that I am not
Around my barn, around my barnyard
Could be a cloud across the moonCould be a fox or a sly raccoonComing down to make a mealHe don’t know the way I feel
About my barn, about my barnyard
You ask me what’s dirty trickSkinny old weasel in among the chicksAnd when he’s done gnawing their legsAn old skunk come and he’ll suck the eggs
That are left in my barn, left in my barnyard
Down in the cornfield see the deerEach one chewing on a yellow earAnd every squirrel that’s ever been bornWants 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 snakeYou may not believe what I say is trueBut he ain’t eating mice I’m telling you
Out in my barn, out in my barnyard
Lindy tells me treat them like brothersI told her let them eat each otherIt’s what they done before I comeWhat they’ll do before I’m done
With my barn, done with my barnyard
Well I never expected life to beSimple or easy or completely freeBut I did not think that I’d have to fightTo get one drink or a single bite
Of food from my barn, food from my barnyard
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 otherParasitism (+/-) one eats (partially) the otherMutualism (+/+) each benefits from the otherCommensalism (+/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”
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 eatingCarnivory – meat eatingOmnivory – mixed dietsDetritivory – eating dead stuffPhotosynthesis – “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, drivingMaterial 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
EnergyMaterials
Both energy and materials are transferred together…
…except here
Heat
Heat
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 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?
ChlorophyllWhat controls nutrients?
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
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
DecomposersOM
Consumers
Reservoir
Ecosystems – nutrient cycling
Nitrogen Cycle
Reservoir – N2 gas in atmosphere – 79%
Nitrogen fixation (certain bacteria) – converts N2 to organic formenergetically 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 NProducers
Nutrients
DecomposersOM
Consumers
Reservoir
Some bacteria use NO3 for energy, releasing N2 gas – Denitrification. This is the cause of our N2 atmosphere
Percent Composition of the Atmosphere
CO2 O2 N2
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
Ecosystems – nutrient cycling
Producers
Nutrients
DecomposersOM
Consumers
Reservoir
2-21/2-27
Ecosystems – nitrogen cycling
Producers
Nutrients
DecomposersOM
Consumers
Reservoir
These nutrient cycles can be added to the water and carbon/oxygen cycles covered earlier.
2-19/2-25
2-20/2-26
Together they describe the global fluxes of major materials regulating ecosystem production
photosynthesis
CH2O
respiration
O2CO2, H2O
Ecosystems – nutrient cycling
Producers
Nutrients
DecomposersOM
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
Heat
Heat
Ecosystems - energy2-17/2-19The 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
EcosystemsPrimary 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 ecosystem’s capacity to support life (producers, consumers, decomposers)
Units: kcal/m2/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, CO2 and many nutrients.
Why is water so important?
Biomes
Result: Water is both a resource and a controller of CO2 and nutrients. More rain has several benefits.
How plants work:
Leaf – light, CO2
Root – water, nutrients
air
soil
But – water is lost in taking up CO2 more water = more CO2
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
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
Biomes
3-6/3-7
“niche diagram”
Ecology summary
1. The biosphere consists of diverse linked ecosystems2. 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
End Ecology
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