Transcript Unit 3 – Environmental Biology

Unit 3 – Environmental Biology
Understanding the interactions between
organisms and their environment
ENERGY
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All organisms require energy
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Growth, reproduction, movement, heat etc.
Energy captured by autotrophs
AUTOTROPH – self feeder
Sources of energy
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e.g. LIGHT – photoautotroph –major importance
e.g. CHEMICAL energy in inorganic molecules
chemoautotroph
e.g. BLACK SMOKERS, GEYSERS, some SOIL BACTERIA
HETEROTROPHIC NUTRITION
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Heterotrophs
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Use organic molecules as a source of energy
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Herbivores
Carnivores
Omnivores
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Ultimately their energy source depends
on starch stored in green plants
PRIMARY PRODUCTIVITY
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Gross Primary Productivity =
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Plants use some of the energy (15-70%)
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amount of energy (light) captured by an ecosystem
and converted into stored chemical energy (plants)
Respiration, reproduction etc.
The remainder (held in the organism’s body) is
available for passage to the next trophic level in
the food chain
This is the Net Primary Productivity (NPP)
NPP =GPP- Energy used by organism
ESTIMATING NPP
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Harvest and dry crop over a given area
Express productivity as Kcal.m-2.yr-1 or as
grams of carbon incorporated into tissue
NPP varies widely from region to region,
Plant cover
Satellite image showing ocean chlorophyll levels (increasing purple to red). The land scale shows chlorophyll
at maximum (blue) to a minumum (yellow/orange)
Solar irradiation
Satellite image showing UV radiation exposure. This can be taken as an estimate of visible
light exposure.
Temperature
Satellite image showing mean global temperature. Hot (red) to cold (blue)
Rainfall
Satellite image of the precipitation across the globe. Purple relatively small, red relatively high (data for
Dec. 1987).
Satellite image showing UV radiation
exposure. This can be taken as an estimate of visible light exposure.
Satellite image showing ocean chlorophyll levels
(increasing purple to red). The land scale shows
chlorophyll at maximum (blue) to a minumum
(yellow/orange)
Satellite image of the precipitation across the
globe. Purple relatively small, red relatively
high (data for Dec. 1987).
Satellite image showing mean global temperature.
Hot (red) to cold (blue)
Ocean Productivity
PRODUCTIVITY
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Photosynthesis captures energy
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Rate of photosynthesis will determine
productivity of an ecosystem
Factors affecting rate
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SUNLIGHT
TEMPERATURE
RAINFALL
CARBON DIOXIDE concentration
NUTRIENT AVAILABILITY
Biodiversity
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Generally the greater the productivity of
an ecosystem, the higher the biodiversity
Primary Productivity in Major
Biomes - Forest
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Forest:
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Boreal forest (Taiga)
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Northern/ High altitude
Water limits (winter – frozen)
Coniferous trees
Nutrient rich soil (acid)
Temperate forest
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700-1200g/m2/yr
Lower altitude
Seasonal variation in rainfall/ temperature
Generally more water/ warmer
Broad leaved species
Nutrient rich soil
Tropical Rainforest
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800-1300g/m2/yr
1600-2200g/m2/yr
Equatorial
High temperature/ rainfall
Rapid nutrient recycling (soil poor – due to leaching)
High biodiversity
Primary Productivity in Major
Biomes – Grasslands
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Savannah (Tropical grasslands)
900g/m2/yr
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Seasonal rains
Moisture limits nutrient cycling
Temperate Grasslands (Steppe, Prairie,
Pampas)
600g/m2/yr
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Rich soil,
Moderately dry, (effect depends on soil moisture
retention)
Primary Productivity in Major
Biomes – Tundra & Desert
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Arctic Tundra (northern polar regions)
Alpine Tundra (above tree line)
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Cold, relatively dry regions (moisture usually
falls as snow)
Short summer allows plant growth
140 g/m2/yr
Desert
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Low rainfall, limits productivity
3-90 g/m2/yr
Primary Productivity in Major
Biomes – Aquatic Biomes
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Freshwater & Marine
Freshwater
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Lakes
Rivers
Swamps
Bogs
Marine –
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Intertidal zone
Coral reef
Salt marsh
Mudflats
Mangroves
Aquatic Ecosystem –
Stratification/ Productivity
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Zonation on temperature/ light penetration
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Factors which affect photosynthesis & hence
productivity
PHOTIC zone warm & light – productive
THERMOCLINE – separates photic zone from colder,
darker waters (APHOTIC ZONE)
Nutrient availability limits ocean productivity
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More productive coastal waters due to nutrients in
rivers running into seas
Mixing caused by storms/ upwellings recycle nutrients
in open oceans