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Introduction to Ecology
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What is ecology
• Oikos = house
• Logos = to study
• Study of how organisms interact w/
environment
• Central goals of ecology
– Understand distribution and abundance of
organisms
– Recognize/explain patterns in nature
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More on the environment
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Can be divided into two parts
Biotic = living
Abiotic = non-living
Biotic interactions = between organisms
Abiotic interactions = between organism
and non-living environment
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Scales of Ecological Study
• Organismal Ecology
– Focus: interaction between individual and
environment (morphology, physiology, behavior)
• Population Ecology
– Focus mechanisms regulating population growth
• Community Ecology
– Focus: Interspecific interactions, Community
structure/dynamics
• Ecosystem Ecology
– Focus: both biotic and abiotic interactions. Food
webs/energy flow, Biogeochemical cycles
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Climate
• Climate = prevailing long term weather
conditions
• Weather = short term atmospheric/aquatic
conditions
– Temp, precipitation, wind, sunlight
• Climate influences ecosystem structure
• Historically describes terrestrial systems
• Aquatic systems also have distinct climate
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Climate is what you expect,
weather is what you get
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More on weather/climate
• Can directly & indirectly affect
organisms
• Eg:
– Temp – metabolism
– Wind – moisture loss
– Sunlight – photosynthesis
• Terrestrial plants especially responsive to
temperature and moisture
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Global Variation in Climate
• Temperature – driven largely by solar
radiation
• At equator hits at 90o = warm temps
• Angle becomes increasingly shallower
towards poles = cooler temps
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Precipitation
• Influenced by temperature and air
circulation
• Hadley cell
– Formed by warming and cooling of air
– Creates a cyclical cell of circulation N and S
of equator
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More on Hadley Cell
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Air heats at equator
Warm air holds more moisture
Rising air expands & cools, causes rain
Cool air flows north and south
Cool air sinks
Warms as it descends, picks up moisture
from land
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Other cells
• Similar process causes Ferrell cells (N &
S of Hadley cells)
• Also forms polar cells at either extreme
of globe
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Polar
Ferrell
Hadley
Hadley
Ferrell
Polar
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Seasonality
• Caused by
– 23o tilt of earths axis
– Revolution of the earth around sun
• Results
– Boreal & austral summers/winters
– Transitional spring/fall
– More pronounced with latitude
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Regional Variation in Climate
• Caused by topographic features
• Mountains
– Cause air to rise cool and release moisture
– Slopes facing water (oceans, large lakes) = wet side
– Opposite slopes drier = rain shadow
• Oceans
– Modify temp due to high specific heat of water
– Result, cooler summers, warmer winters
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Biomes
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Key Abiotic Factors Regulating
Ecosystems
• Terrestrial ecosystems
– Temperature
– Precipitation
• Aquatic Ecosystems
– Sunlight
– nutrients
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Terrestrial Ecosystems
• Soil retains nutrients
– nutrients don’t become limited as easily
• Large regions characterized by distinct
vegetation types
– = biomes
• Each has distinctive temperature &
precipitation regime
– Annual average temp & precipitation
– Annual variation in temp & precipitation
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There are as many as 14 (or more) distinct
terrestrial biomes that have been described
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We will focus on the 6 most common
Tundra
Taiga
(Boreal Forest)
Temperate
deciduous
forest
Temperate
grassland
Subtropical
(hot) desert
Wet tropical
Evergreen
forest
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Tundra
• Temperature
– Average annual temp = very low
– Annual variation in temp = high
• Precipitation
– Average annual precip = low
– Annual variation in precip = low
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Boreal Forest (Taiga)
• Temperature
– Average annual temp = low
– Annual variation in temp = high
• Precipitation
– Average annual precip = low
– Annual variation in precip = low
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Temperate Deciduous Forest
• Temperature
– Average annual temp = moderate
– Annual variation in temp = high
• Precipitation
– Average annual precip = moderate
– Annual variation in precip = moderate
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Temperate Grasslands
• Temperature
– Average annual temp = moderate
– Annual variation in temp = high
• Precipitation
– Average annual precip = low
– Annual variation in precip = low
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Subtropical Deserts
• Temperature
– Average annual temp = high
– Annual variation in temp = moderate
• Precipitation
– Average annual precip = very low
– Annual variation in precip = low
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Tropical Wet Forests
• Temperature
– Average annual temp = high
– Annual variation in temp = low
• Precipitation
– Average annual precip = very high
– Annual variation in precip = high
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Aquatic systems
• nutrients easily lost
– Advection, sinking
• Productivity limited to regions of
adequate light
– Function of depth & water clarity
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Freshwater Ecosystems
• Lentic systems
– Still or slowly flowing water
– Lakes and ponds
– Swamps, marshes, bogs
• Lotic systems
– Rapidly flowing water
– Streams
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Lakes and ponds
• Horizontal structure
– Littoral zone = shallow enough for rooted vegetation
– Limnetic zone = too deep for rooted vegetation
• Vertical structure
– Photic zone = enough light for photosynthesis
– Aphotic zone = not enough light for photosynthesis
• Benthic zone = bottom of lake or pond
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Limnetic zone
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Marshes, swamps & bogs
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Marshes lack woody plants
Swamps have trees
Both have slow flowing water
Both typically connected to lakes or
streams
• Bogs = stagnant & highly acidic due to
decomposition
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Lotic Systems
• Rapid, unidirectional water flow
• Streams = rivers and creeks
– River = big stream
– Creek = little stream
• Linear progression
– Early = low temp low nutrients, high oxygen
– Mid = warmer temp, higher nutrients, lower oxygen
– Late – warmest temp, highest nutrients, lowest
oxygen
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Estuaries
• Formed where rivers meet ocean
• Mixture of fresh and salt water
– Include both salt marshes and mangroves
• Very productive
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Marine Ecosystems
• Like lakes & ponds, zones determined by depth
• Horizontal
– Intertidal – covered and uncovered by tides
– Coastal (Neritic) – portion of ocean over continental
shelf
– Pelagic (Oceanic) – portion off continental shelf
• Vertical
– Photic
– aphotic
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Intertidal zone
Coastal zone
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Coastal Zone (Neritic) Habitats
Kelp forest
Coral reef
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Pelagic Zone (Oceanic)
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