IB BIO II
Van Roekel
Ecosystems and Biomes
G.2.1 Define Gross production, net production, and biomass & G.2.2 Calculate values for gross
production and net production using the equation gross production – respiration = net production
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Pyramid of energy shows how fast energy flows from one trophic level to the next in a community
(measured in [(kj/m2)/year] or kj*m-2*yr-1
Each level is always smaller than the one before because of the loss of energy.
Gross Production – total amount of energy trapped in organic matter produced by plants per area
per time in kilojoules
Net Production – the gross production minus the energy lost through respiration
Biomass – the dry weight of an organism measured in g*m-2*yer-1
Gross production – respiration = net production
G.2.3 Discuss the difficulties of classifying organisms into trophic levels & G.2.5 Construct a
pyramid of energy giving appropriate information
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Some organisms occupy more than one trophic level
o Eagle can be tertiary or secondary
o Mouse can be primary consumer or secondary consumer
o Grizzly bear can be omnivores, or top predators depending on season, temperature, and
ability to forage for food
Many ecosystems are not fully understood
Food webs do not show change over time as populations change
G.2.4 Explain the small biomass and low numbers of organisms in higher trophic levels
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Biomass - biological material derived from living, or recently living organisms
Similar to pyramid of energy,
Highest biomass at producers b/c the most energy is available
Decreases with each trophic level because of loss of energy
G.2.6 Distinguish between primary and secondary succession, using an example of each
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Ecological succession is the change in abiotic and biotic factors in an ecosystem over time
Primary Succession – begins when plants begin growing on previously barren and lifeless areas
(colonization of new volcanic island). Usually begins with lichen, which decompose thin layers of rock.
Lichens die and turn to soil, allowing other organisms to grow and survive
Secondary Succession – new group of organisms take over following a natural or artificial upheaval of
primary succession (recolonization after a forest fire). Much faster than primary succession
Primary
Begins w/ no life
No soil
New area such as volcanic island
Lichen and mosses are first plants
Biomass Low
Low production (increase in biomass/energy
Secondary
Follows disturbance of primary succession
Soil present
Old area such as following a forest fire
Seeds and roods already present
Biomass high
High production of biomass and energy
G.2.7 Outline the changes in species diversity and production during primary succession
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Sand dunes are excellent examples of primary succession
IB BIO II
Van Roekel
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Foredune: primary succession starts, no soil, only sand. Marram grass and Lyme grass grow
and help stabilize dune
o Yellow Dune: dune develops a thin layer of soil from dead and decaying Marram grass. Other
plants start to grow, rabbits live here and their feces add nutrients to soil. Humus (part of
soil composed of organic matter) builds
o Grey Dune: developed layer of humus, which holds water, no sand and thick shrubs grow
here.
o Mature Dune: can support a forest, including wide variety of plants (wild flowers, mosses,
ferns, trees). Thick layer of humus. High moisture content in soil. Large variety of animals as
well
Development of Primary Succession
o Few species  Many species
o Pioneer species  species that compete with others for nutrients
o Little diversity  high diversity
o Simple relationship  complex relationships (mutualism, competition, predation)
o More and more biomass at each stage of succession
G.2.8 Explain the effects of living organisms on the abiotic environment with reference to the
changes occurring during primary succession
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Living organisms change the abiotic factors in an ecosystem
o Death and decay of plants and animals increases the organic matter or humus in soil
(excellent medium for plant growth)
o Leaf litter and decayed plants creates deep, well-draining soil to support tall trees
o Plant roots stabilize sand and soil to reduce soil erosion
o Soil structure improves as humus is formed, holds more moisture, nutrients, and allows
aeration of plant roots
o Bacteria and fungus actively recycle nutrients in soil, increasing fertility of soil
G.2.9 Explain how rainfall and temperature affect the distribution of biomes
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Living part of Earth that contains all the parts where organisms live is called the Biosphere
Biomes are divisions of biosphere, defined by vegetation and community structure.
Biomes occur because of global weather patterns and topography. Temperature and rainfall
contribute to the climate of different areas which determines the different biomes
G.2.10 Outline the characteristics of the major biomes
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Desert Biome
o Mojave Desert
o Low elevation
o Mostly very hot soil temps (above 60⁰C /140⁰F) during the day
o Low precipitation (less than 30 cm per year)
o Cacti and shrubs with water storage tissues, thick cuticles, and other adaptations to reduce
water loss
Grassland Biome
o Tropical Grasslands & Temperate Grasslands
o Savanna (Africa) & Prairies (North America)
o Cold temperatures in winter, hot in summer
o Seasonal drought is common, w/ occasional fires, medium amount of moisture
IB BIO II
Van Roekel
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Prairie grasses hold soil with long roots, occasional fire prevents trees and shrubs from
invading grasslands
Shrubland Biome
o West Coast of USA, Cape Town, South Africa
o Mild temperatures in winter and long, hot summers
o Rainy winters and dry summers
o Dry woody shrubs are killed periodically by fires. Shrubs store food in fire resistant roots.
They regrow quickly and produce see, which germinates only after a fire.
Temperate Deciduous Forest
o Eastern North America, Mid Europe
o Lower elevations
o Very hot in summer, very cold in winters
o High rainfall spread evenly over the year. In winter water may freeze for short times
o Deciduous trees like oak, hickory, and maple dominate forest. Warmer seasons see a wide
variety of herbaceous plants grow and flower on forest floor
Tropical Rainforest
o Central & South America (Amazon river), Parts of Africa, Southeast Asia
o Low elevations
o Very warm temperatures
o Very high precipitation (more than 250 cm per year)
o High plant diversity. Canopy of trees, layer of shrubs, ground layer of herbaceous plants and
ferns. Large trees have vines, trees have orchids and bromeliads tucked into branches
Tundra
o Arctic Tundra (Alaska, Northern Canada, Northern Russia)
o High elevations
o Very cold, in summer upper layer of soil thaws, but lower layers remain frozen, known as
permafrost
o Little precipiation
o Low growing plants (lichen and mosses), few grasses and shrubs. Permafrost prevents roots
from growing deeply. Continuous daylight in summer allows plant growth and reproduction
Coniferous Forest (Taiga)
o North America, Eurasia
o High elevations
o Slightly warmer than tundra
o Small amounts of precipitation, but wet due to lack of evaporation
o Cone-bearing trees such as pine, spruce, fir, and hemlock.