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