Unit 3

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Unit 3 Environmental Biology

• Understanding the interactions between organisms
  and their environment

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ENERGY

• All organisms require energy
• Growth, reproduction, movement, heat etc.
• Energy captured by autotrophs
• AUTOTROPH self feeder
• Sources of energy
• e.g. LIGHT photoautotroph major importance
• e.g. CHEMICAL energy in inorganic molecules
• chemoautotroph-
• e.g. BLACK SMOKERS, GEYSERS, some SOIL BACTERIA

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HETEROTROPHIC NUTRITION

• Heterotrophs
• Use organic molecules as a source of energy
• Herbivores
• Carnivores
• Omnivores
• Ultimately their energy source depends on starch
  stored in green plants

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PRIMARY PRODUCTIVITY

• Gross Primary Productivity
• amount of energy (light) captured by an ecosystem
  and converted into stored chemical energy
  (plants)
• Plants use some of the energy (15-70)
• Respiration, reproduction etc.
• The remainder (held in the organisms 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

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ESTIMATING NPP

• 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,

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Plant cover
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Solar irradiation
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Temperature
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Rainfall
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Ocean Productivity
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PRODUCTIVITY

• Photosynthesis captures energy
• Rate of photosynthesis will determine
  productivity of an ecosystem
• Factors affecting rate
• SUNLIGHT
• TEMPERATURE
• RAINFALL
• CARBON DIOXIDE concentration
• NUTRIENT AVAILABILITY

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Biodiversity

• Generally the greater the productivity of an
  ecosystem, the higher the biodiversity

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Primary Productivity in Major Biomes - Forest

• Forest
• Boreal forest (Taiga) 800-1300g/m2/yr
• Northern/ High altitude
• Water limits (winter frozen)
• Coniferous trees
• Nutrient rich soil (acid)
• Temperate forest 700-1200g/m2/yr
• Lower altitude
• Seasonal variation in rainfall/ temperature
• Generally more water/ warmer
• Broad leaved species
• Nutrient rich soil
• Tropical Rainforest 1600-2200g/m2/yr
• Equatorial
• High temperature/ rainfall
• Rapid nutrient recycling (soil poor due to
  leaching)
• High biodiversity

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Primary Productivity in Major Biomes Grasslands

• Savannah (Tropical grasslands)
• 900g/m2/yr
• Seasonal rains
• Moisture limits nutrient cycling
• Temperate Grasslands (Steppe, Prairie, Pampas)
• 600g/m2/yr
• Rich soil,
• Moderately dry, (effect depends on soil moisture
  retention)

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Primary Productivity in Major Biomes Tundra
Desert

• Arctic Tundra (northern polar regions)
• Alpine Tundra (above tree line)
• Cold, relatively dry regions (moisture usually
  falls as snow)
• Short summer allows plant growth
• 140 g/m2/yr
• Desert
• Low rainfall, limits productivity
• 3-90 g/m2/yr

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Primary Productivity in Major Biomes Aquatic
Biomes

• Freshwater Marine
• Freshwater
• Lakes
• Rivers
• Swamps
• Bogs
• Marine
• Intertidal zone
• Coral reef
• Salt marsh
• Mudflats
• Mangroves

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Aquatic Ecosystem Stratification/ Productivity

• Zonation on temperature/ light penetration
• 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
• More productive coastal waters due to nutrients
  in rivers running into seas
• Mixing caused by storms/ upwellings recycle
  nutrients in open oceans