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Lecture Ecology
Chapter 54 ~
Ecosystems and the
Biosphere
 Chapter 55 ~ Ecology
and the Geography of
Life
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Relationships, I
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Trophic structure / levels~ feeding
relationships in an ecosystem
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Primary producers~ the trophic level
that supports all others; autotrophs
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Primary consumers~ herbivores
Secondary and tertiary consumers~
carnivores
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Detrivores/detritus~ special consumers
that derive nutrition from non-living organic
matter
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Food chain~ trophic level food pathway
Relationships, II
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Food webs~ interconnected
feeding relationship in an
ecosystem
Energy Flow, I
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Primary productivity (amount of light energy converted to chemical energy by autotrophs)
•Gross (GPP): total energy
•Net (NPP): represents the storage of energy available to consumers
•Rs: respiration
NPP = GPP - Rs
Biomass: primary productivity reflected as dry weight of organic material
Secondary productivity: the rate at which an ecosystem's consumers convert chemical
energy of the food they eat into their own new biomass
Energy Flow, II
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Ecological efficiency: % of E
transferred from one trophic level to the
next (5-20%)
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Pyramid of productivity:
multiplicative loss of energy in trophic
levels
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Biomass pyramid: trophic
representation of biomass in ecosystems
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Pyramid of numbers: trophic
representation of the number of
organisms in an ecosystem
Chemical Cycling
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Biogeochemical cycles: the various nutrient circuits, which involve both abiotic and
biotic components of an ecosystem
Water – Water moves among ocean, land and atmosphere in the hydrologic cycle
Carbon – Carbon dioxide is the pivotal molecule in this cycle
Nitrogen – Bacteria are essential to this cycle
Phosphorus – This cycle lacks a gaseous component
Human Impact

Biological magnification: trophic process
in which retained substances become more
concentrated at higher levels

Greenhouse effect: warming of planet due to
atmospheric accumulation of carbon dioxide and
other gases

Ozone depletion: effect of
chlorofluorocarbons (CFC’s) released into the
atmosphere
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Rainforest destruction
Cause: Overpopulation?
Abiotic factors

Biosphere~the sum of all the
planet’s ecosystems

Biome~ areas of predominant
flora and fauna
Temperature
 Water
 Sunlight
 Wind
 Rocks & Soil
 Periodic disturbances
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Ecotone: biome grading areas
Global climate
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Seasons
• Precipitation & Winds
Aquatic biomes
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Vertical stratification:
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•photic zone~ photosynthetic light
•aphotic zone~ little light
•thermocline~ narrow stratum of
rapid temperature change
•benthic zone~ bottom substrate
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Organisms
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– Phytoplankton ~ community of
small free-floating producers
– Zooplankton~ community of
small free-floating consumers
– Nekton ~ community of larger freefloating consumers
– Benthos~ community of
bottom-
dwelling organisms

Detritus~ dead organic matter; food
for benthic organisms
Freshwater biomes

Littoral zone~ shallow, well-lit
waters close to shore
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Limnetic zone~ well-lit, open
water farther from shore
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Profundal zone~ deep,
aphotic waters
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Lake classification:
•oligotrophic~ deep, nutrient poor
•eutrophic~ shallow, high nutrient
content
•mesotrophic~ moderate
productivity
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Wetland~ area covered with
water
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Estuary~ area where freshwater
merges with ocean
Lake stratification & turnover
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Thermal stratification~ vertical temperature layering
Biannual mixing~ spring and summer
Turnover~ changing water temperature profiles; brings oxygenated water
from the surface to the bottom and nutrient rich water form the bottom to the
surface
Marine biomes
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Intertidal zone~ area where
land meets water
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Neritic zone~ shallow
regions over continental shelves
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Oceanic zone~ very deep
water past the continental shelves
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Pelagic zone~ open water of
any depth
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Benthic zone~ seafloor
bottom
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Abyssal zone~ benthic
region in deep oceans
Terrestrial biomes
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Tropical forests~ equator; most complex; constant temperature and rainfall; canopy; dry and wet
Savanna~ tropical grassland with scattered trees; occasional fire and drought; large herbivores
Desert~ sparse rainfall (arid) (<30cm/yr)
Chaparral~ spiny evergreens at midlatitudes along coasts
Temperate grassland~ all grasses; seasonal drought, occasional fires; large mammals
Temperate deciduous forest~ midlatitude regions; broad-leaf deciduous trees
Coniferous forest~ cone-bearing trees
Tundra~ permafrost; very little precipitation