Chapter 50 “An Introduction to Ecology and the Biosphere”
Ecology – the scientific study of the interactions between organisms and their environment; how they
affect the number of species living in an area (distribution), the cycling of nutrients, or the growth of
populations.
Ecology and evolution are closely related
Ecological time (minutes to years) vs. evolutionary time (decades to millennia)
Ex. Hawk feeding on field mice kill certain individuals (those without fur color that camouflages them)
Ecological time – feeding, reducing population
Evolutionary time – altering the gene pool, selecting for camouflage fur color
Environmental components:
Abiotic (nonliving) & Biotic (living) factors
Organismal ecology – behavioral, physiological, morphological ways individuals interact
Population ecology – factors that affect population size and composition
Community ecology – interactions between species, factors affecting structure/organization
Ecosystem ecology – energy flow, cycling chemicals among abiotic and biotic
Landscape ecology – exchanges between ecosystems
Global ecology – biosphere, sum of all the planet’s ecosystems
Ecology vs. environmentalism (advocacy)
1962 Rachel Carson, Silent Spring – warning of pesticides declining nontarget organisms
Acid precipitation, land misuse, toxic wastes, habitat destruction, endangered species
Precautionary principle (“an ounce of prevention is worth a pound of cure”)
Biogeography – study of past and present distributions of individual species in the context of
evolutionary theory; limits on distribution, dispersal,
Biotic affects: predation, parasitism, disease, competition
Abiotic affects: temperature, water, sunlight, wind, pH, soil composition, rates of evaporation
Climate – major components – temperature, water, sunlight, and wind
Major influence on distribution of organisms
Determines biomes (major types of ecosystems) specifically temperature and rainfall
Climate patterns determined by –
 sun’s warming effect on the atmosphere, land, water
 bodies of water and topographic features
 ocean currents – coast more moist than inland
 south facing slopes
 altitude – ambient temperature declines 6oC every 1,000-m increase
 leeward side of mountain – cool, dry air descends producing a rain shadow
 changing angle of sun over the course of a year
 past climate changes – N.A. continental glaciers 16,000 yrs. ago melted, tree distribution
expanded northward
Research – Is seed dispersal rapid enough to sustain the migration of the species as climate changes?
Ex. American beech – climate models predict – northern and southern range will move 700-900 km
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over the next century; will have to migrate 7-9 km/yr to maintain distribution; since the Ice Age its rate
of migration only 0.2 km/yr; extinction is imminent without human assistance.
Aquatic Biomes:
Freshwater vs marine – physical and chemical differences
Marine – 3% average salt concentration; freshwater - < 1%
Marine ecological importance: provides most of the planet’s rainfall, 75% earth’s surface, contribute
to climate and wind patterns, large amount of world’s O2 supply from algae and photosynthetic
bacteria, atmospheric carbon dioxide consumption by respiration
Stratified: photic zone – light for photosynthesis, aphotic zone, benthic (bottom) – benthos organisms
feeding on detritus; thermocline – narrow stratum of rapid temp change
Aquatic Community distribution determined by:
Depth of the water
Distance from shore
Open water versus bottom
Major aquatic biomes:
Lakes, wetlands, streams, rivers, estuaries, intertidal biomes, oceanic pelagic biomes, coral reefs,
marine benthic biomes
Freshwater lakes: oligotrophic (deep, nutrient poor, oxygen rich, little life); eutrophic (shallow,
nutrient rich, oxygen poor); littoral zone – shallow, close to shore; limnetic zone – open surface water.
Wetlands: supports aquatic plants, marshes, bogs, and swamps, most productive biomes on Earth, high
organic production and decomposition, high capacity to filter dissolved nutrients/chemical pollutants
Streams/rivers: moving continuously in one direction, headwaters – cold, clear, turbulent, swift; carry
little sediment, few minerals; accumulates O2 and nutrients along the way
Estuaries: transition between river and sea, salinity varies greatly, abundance of fish, invertebr4ate
species, and crucial feeding areas for waterfowl.
Intertidal zone: periodically submerged and exposed by tides; organismal distribution by stratum due
to oxygen and moisture requirements
Oceanic pelagic biome: open blue water, high oxygen levels, low nutrient levels, 70% Earth’s surface
Coral reefs: photic zone, tropic marine, high water clarity, formed by calcium carbonate skeletons of
coral animals, mutualistic dinoflagellate algae live within the tissues of the corals, home to assortment
of vertebrates and invertebrates.
Marine benthic zone: neritic zone – coastal; pelagic zone – offshore; abyssal zone – deep, 3oC,
extremely high pressure; deep-sea hydrothermal vents – chemoautotrophic prokaryotes oxidize H2S
from a reaction of volcanically heated water with dissolved sulfate (SO42-)
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