III. EcosystemDef. - the combination of biotic and abiotic

components through which energy flows and materials cycle (usually a self-contained unit, such as a pond, swamp, meadow, or woods)

A. Energy Flow1. Ultimate source - SUN

- 50% of suns energy reaches surface of earth

- 0.1 % of that ends up in living organisms

Primary ProductivitySynthesis of organic material from inorganic

substances.Primary productivity is measured in grams of

carbon bound into organic material per square meter of ocean surface per year, or, more simply: gC/m2/yr

2. Trophic levels (food chain or web)a. Producers - first trophic level , primarily

plants on the land and algae in the water(99% of all organic matter is at this level)

Gross primary productivity (light energy converted) - Cost of metabolic activity (cell respiration by plant)

Net primary productivity* (energy stored in chemical compounds)

*when positive, there is an increase in biomass (total dry weight of all organisms being measured)

b. Primary consumer (herbivores)c. Secondary consumer (carnivores), eat

herbivores [There a four levels of consumer in most food

chains]

d. Detritovores - live on the refuse of the ecosystem, i.e. dead leaves, branches, carcasses, feces, etc.

i. Scavengers - consumers of dead prey- vultures, jackals, crabs, earthworms

ii. Decomposers - specialized organisms that get at the trapped chemical energy

- fungi, bacteria

3. Efficiency of energy transfera. In Cayuga Lake in New York

1000 calories of light yields150 calories of algae, which yields30 calories of smelt, which yields6 calories of trout, which yields1.2 calories of human

b. Energy flow pyramid (“10% rule”)

GPP & NPPAn ecosystem's gross primary productivity (GPP) is the total

amount of organic matter that it produces through photosynthesis. Net primary productivity (NPP) describes the amount of energy that remains available for plant growth after subtracting the fraction that plants use for respiration. Productivity in land ecosystems generally rises with temperature up to about 30°C, after which it declines, and is positively correlated with moisture.

In the oceans, light and nutrients are important controlling factors for productivity. As noted in Unit 3, "Oceans," light penetrates only into the uppermost level of the oceans, so photosynthesis occurs in surface and near-surface waters. Marine primary productivity is high near coastlines and other areas where upwelling brings nutrients to the surface, promoting plankton blooms. Runoff from land is also a source of nutrients in estuaries and along the continental shelves. Among aquatic ecosystems, algal beds and coral reefs have the highest net primary production, while the lowest rates occur in the open due to a lack of nutrients in the illuminated surface layers

If tropical rainforests produce 200 times as much NPP than the open ocean, why do we get more than twice as much carbon from the open ocean each year?

B. Biological magnification - increase in the concentration of toxins as those

toxins move through the food chain (DDT, PCB’s)

C. Ecological succession- the succession of communities that follows the

disturbing of and area (plowing, landslide, volcano, fire)

Characteristics1. Increase in total biomass2. Gradual decrease in net productivity3. Mature systems have a greater

capacity to entrap and hold nutrients4. Number of species increase5. r-species early K-species late

[Climax community = final stable stage]

[Current thinking is that this model is simplistic and incomplete, that disturbances themselves drive succession throughout the process.]

1

2

5

10

20

D. Biogeochemical cycles - the cycling of chemicals through the biotic and abiotic portions of the ecosystem

1. Water cycle

2. Carbon cycle

3. Nitrogen cycle

4. Phosphorus cycle

IV. Terrestrial Biomes (life zones) A. Def. - geographical areas distinguished by

particular dominant plant typesB. Characteristics

1. Not a place, but a class of plants2. Determined by climate3. Boundaries are indistinct4. Convergent evolution common between

similar biomes

V. Aquatic Biomes (life zones)A. Primary ecological subdivisions of organisms

1. Plankton - at mercy of currents, weak or nonswimmers (small or microscopic)

a. Phytoplankton - primary producers, (cyanobacteria or diatoms)

b. Zooplankton - protists and small animals (larval stages)

2. Benthos - bottom dwellers (sessile, walking, or burrowing)

3. Nekton - larger, strong swimmers (top of the food chains)

B. Freshwater1. Zones

a. Littoral zone - near shoreline, richest in life

b. Limnetic zone - open water, sparse lifec. Profundal zone - deep. anaerobic, no

light, detritovores, mineral rich

2. Lake stratification and seasonal turnover

3. Types of lakesa. Oligotrophic - nutrient-poor, deep, sandy

or rocky bottom, clear b. Eutrophic - nutrient-rich, phytoplankton

very productive, shallow, murky

Oligotrophic lake Eutrophic lake

Eutrophication(lake aging)

C. Marine life zones1. Estuaries and salt marshes - where rivers

(freshwater) meets saltwater of ocean- most fertile water in the world, breeding

grounds for many fish, nutrients from rivers meets constant mixing of tides

(plants)

2.Intertidal zone - between high and low tides, rich in life forms (barnacles, clams, crabs), tidal pools

3.Subtidal zone - sea stars, sea urchins, worms, crabs, flounder

4.Neritic zone - over continental shelf (nekton and most benthic organisms are here (food is here)

[photosynthetic limit - 200 meters]5. Pelagic zone – includes neritic and open ocean6. Benthic zone - deep waters, mostly predators

(Neritic zone)

= Neritic zone

PelagicZone