G2: Ecosystems & Biomes

(4 hours)

G.2.1 Define

• gross production• Total amount of energy trapped in organic

matter produced by plants per area per time (kJ)

• net production • Gross production – energy lost through

respiration• Biomass• Dry weight of an organism (g m-2 yr -1)

G.2.2 Calculate values for gross production and net production using the equation:

• gross production – respiration = net production• GP – R = NP • Sample question!!• Calculate % of energy moving up to herbivores

G.2.3 Discuss the difficulties of classifying organisms into trophic levels.

• Food webs give more realistic image of ecosystem

• Omnivores especially difficult--– Depending on what eating,

can be 1/2/3 consumer at different times

G.2.4 Explain the small biomass and low numbers of organisms in higher trophic levels.

• Top predators must be large enough to overwhelm their prey, so can only be relatively few of them

• Higher trophic levels: low total biomass per unit area of ecosystem

• Biomass lost during respiration @ each TLevel– Cell respiration: biomass of glucose is lost,

CO2, Water excreted– Each successive level loses more and more

biomass

G.2.5 Construct a pyramid of energy, given appropriate information. (Xref- pyramid of energy- 5.1.12)

• Trophic Level Energy Flow (kJ m–2 yr–1)

producers 20,810

primary consumers 3,368

secondary cons. 383

tertiary consumers 21

G.2.6 Distinguish between primary & secondary succession, using an example of each.• CHANGE in abiotic and biotic factors in ecosystem over

time...some species gradually replace others in a particular area

• Primary:– Previously barren, lifeless area– Newly created volcanic island– Pioneer species usually lichens—tolerant to extreme

temp changes and little/no soil; they decompose rock...soil forms

– moss can survive seeds germinate coconuts wash ashore, germinate; animals may swim/fly/carried on floats from other islands

• Secondary: follows natural or artificial “upheaval” of the primary succession

• MUCH faster b/c soil already present, may be existing seeds & roots

• Ex. Forest fire

Primary SecondaryBegins with no life Follows a disturbance of primary

succession

No soil Soil present

New area (volcanic island) Old area (following forest fire)

Lichen & mosses pioneers Seeds & roots already present

Biomass low Biomass higher

Production low (few plants) Production higher

G.2.7 Outline the changes in species diversity and production during primary succession.

• OVERALL TRENDS:– Few species to many– Pioneer species to those that compete with

others for nutrients– Little to high diversity (mature forest is home to

100s species)– Simple relationships to more complex

(mutualism, competition, predation)– More & more biomass at each stage of succ.

G.2.7 Outline the changes in species diversity and production during primary succession.

• Foredune: no soil, only sand, p.succ. Starts here—lyme

grass very salt tolerant, fastgrowing, roots stabilize dune;

marram grass too, wide roots.LITTLE PLANT

DIVERSITY• Yellow dune: developing thin layer of soil b/c yrs of

m.grass; more plants invade (sedge, etc); rabbits here, nutrients from poop ; summer dandelions/thistle. Humus builds as pioneers decay. MORE COMPLICATED, MORE SPECIES, SOIL BEING FORMED

G.2.7 Outline the changes in species diversity and production during primary succession.

• Grey dune: yrs of plants dying/decomposing, so layer of humus; it holds water; dune farther inland, less salt; thick shrubs eventually grow here

• Mature dune: final stage of succession.– Can support a forest– Wild flowers, trees, mosses/ferns in shade– Thick humus b/c 200 yrs of plants; high

moisture content– Many insects, birds, mammals– Cooler temp than foredune; less wind/blowing

sand

G.2.8 Explain the effects of living organisms on the abiotic environment with reference to the changes occurring during primary succession.

• soil development– Death/decay of plants/animals humus

• Quickly absorbs and releases water, good for plants – Leaf litter creates more org matter, mixes with sand,

creates deep, well-draining soil; can support tall trees• accumulation of minerals

– Sand doesn’t hold moisture but humus & soil do, takes time to get structure to hold moisture and minerals to allow aeration of roots (structure IMPROVES)

– Bacteria, fungus (decomposers) active in recycling nutrients in soil w/humus (recycling INCREASES)

• reduced erosion– Roots stabilize dune/soil, reduces erosion

G.2.9 Distinguish between biome & biosphere.

• Biosphere: living part of earth (where organisms live)– Crust, atmosphere

• Biomes: divisions of biosphere– Each is part of biosphere– Defined by community structure and vegetation

G.2.10 Explain how rainfall and temperature affect the distribution of biomes.

• A climograph showing the biomes in G.2.11 can be used to illustrate the interaction between these two factors.– PLOTS temp and rainfall in a region

• Tundra: organisms adapted to cold, dry• Conif forest: plants conserve water when ground frozen,

animals heavy coats in winter (summer-shed)• Temp forest: wide range of conditions (many deciduous to

reduce water loss in winter)• Desert: specific adaptations for extreme heat and dryness

(kangaroo rat’s specialized kidney; cacti’s spines)• Trop forest: high temp, high rainfall

G.2.11 Outline the characteristics of six major biomes.

Biome Temp Moisture Vegetation Desert Mostly very hot.

Soil temps >60C (140F) daytime

Low precip, <30cm/yr

Cacti, shrubs w/water storage tissues, thick cuticles & other water-loss adaptations

Grassland Cold winter temps;

hot summers

Seasonal drought; occasional fires; medium moisture

Prairie grasses hold soil w/long roots; occasional fires prevent trees/shrubs from invading...and don’t forget the dead zebras.

Shrubland Mild winter temps;

Long, hot summers

Rainy winters, dry summers

Dry woody shrubs killed by periodic fires; shrubs store food in fire-resistant roots; regrow quickly, produce seed that germinates only after fire!

G.2.11 Outline the characteristics of six major biomes.

Biome Temp Moisture Vegetation

Temp Decid Forest

Very hot summer, very cold winter

High rainfall evenly throughout yr. Winter: water may freeze for short time

Deciduous trees (oak, hickory, maple) dominate. Warmer seasons—wide range of herbaceous plants on forest floor

Tropical rainforest

Very warm Very high precip (>250cm/yr)

Plant diversity very high. Canopy of trees @ top layer, next layer is shrubs; ground layer is herb.plants and ferns. Vines, orchids, bromeliads on trees.

Tundra Very cold;

Summer-upper layer of soil thaws, but lower frozen (permafrost)

Little precipitation

Low-growing plants (lichen, mosses) and few grasses, shrubs. Permafrost prevents roots from growing deeply. Continuous daylight in summer allows plant growth & reproduction.