ECOLOGY – part 2

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? _________

Communities

In economics – “follow the money”, in ecology, “follow the food”

2-18 A marine food web

Communities are analyzed by the network of eating interactions, ultimately the overall food web or ___________ structure.

Communities

Community – the array of interacting populations in a place.

Major insight – to a large extent, the question is - _______________?

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.

4-2

Even _________ often about eating (or not being eaten) – usually involves a ______ (food, defense)

Plants – major mutualisms - nutrition – myccorhizae (________), nitrogen fixers (________), trade nutrient and carbohydrate

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.

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

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

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 ________________

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 ___________, herbivores & carnivores called _________

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 _______(since this is mostly food for the producers)

Note the difference in emphasis compared to the food web

Energy ______ through the ecosystem drivingMaterial ______ within

Resource use by individuals (eating) drives these dynamics

Ecosystems

This is a ________________ (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 ________ and ________

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 cyclingNutrient 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

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

DecomposersOM

Consumers

Reservoir

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.)

2-22/2-28

Producers

Nutrients

DecomposersOM

Consumers

Reservoir

Ecosystems – nutrient cycling

Nitrogen CycleReservoir – N2 gas in atmosphere – 79%

Nitrogen _______ (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 N

Some bacteria use NO3 for energy, releasing N2 gas – ____________. 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

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

respirationO2

CO2, H2O

Ecosystems – nutrient cycling

Producers

Nutrients

DecomposersOM

Consumers

Reservoir

Ecosystems

Trophic Structure – The energy pyramid

Energy flows through the ecosystem – from sun to _________

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 ______, 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 __________ about 10% (2-40%)

This limits trophic levels to 4 or 5

EcosystemsPrimary Productivity

Ecosystems depend on producers for energyPrimary 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 _____________

We know that NPP is dependent on temperature, water, light, CO2 and many nutrients.

Why is water so important?

Biomes & Productivity

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

airsoil

But – _______ is lost in taking up CO2 more water = more ______

And – water increases ___________ rate in soil more water = more ___________

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 summary1. 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