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Introduction to Ecology


Chapter 18 Introduction to Ecology – PowerPoint PPT presentation

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Title: Introduction to Ecology

Chapter 18
  • Introduction to Ecology

What Is Ecology?
  • Ecology The scientific study of interactions
    between organisms and their environment.
  • It is a relatively new branch of science, with
    roots in Darwins The Origin of Species.
  • Ernst Haeckel coined the name ecology, from the
    Greek root oikos, meaning house.

What Is Ecology?
  • Ecology is not equivalent to environmentalism.
  • Ecology is a science that generates knowledge
    about interactions in the natural world.
  • Environmentalism is the use of this knowledge
    (with economics, ethics, etc.), to inform
    personal decisions and public policy relating to
    stewardship of natural resources and ecosystems.

What Is Ecology?
  • Ecology encompasses both the living (biotic)
    components and the abiotic, or physical and
    chemical, components of the environment.
  • New tools such as mathematical models, molecular
    techniques, and satellite imaging, and new
    connections to other fields have dramatically
    changed ecological research.

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Interdependence- A key theme
Organisms and Their Environments Species interact
with both other species and their nonliving
environment. Interdependence is a theme in
ecologyone change can affect all species in an
Hierarchy System of Organization
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Biotic and Abiotic Factors
  • Both biotic, or living, factors and abiotic, or
    nonliving, factors influence organisms.
  • Examples of abiotic factors are climate,
    sunlight, and pH.

Organisms in a changing environment
  • Acclimation
  • Some organisms can adjust their tolerance to
    abiotic factors through the process of
  • Control of Internal Conditions
  • Conformers are organisms that do not regulate
    their internal conditions they change as their
    external environment changes.
  • Regulators use energy to control some of their
    internal conditions.
  • Escape from Unsuitable Conditions
  • Some species survive unfavorable environmental
    conditions by becoming dormant or by migrating.

  • An organisms role in the ecosystem
  • Explains why plants and animals are able to share
    the same habitats
  • Generalists (opossum) vs specialists (koala)

Energy Transfer
  • Sunlight is the ultimate source of energy for
    most of Earths communities.
  • Photosynthesis makes energy available to other
    organisms in an edible form.
  • Photosynthetic autotrophs get their energy
    directly from sunlight along with a few
    chemoautotrophs (energy from inorganic molecules)
    are known as primary producers.

Energy Flow through Trophic Levels
Energy Transfer
  • Gross primary productivity (GPP) is the rate at
    which primary producers in a community turn solar
    energy into stored chemical energy via
  • The energy that is accumulated is called gross
    primary production.

Energy Transfer
  • Primary producers use some of the GPP for
    respiration and metabolism.
  • Net primary productivity (NPP) is the rate at
    which energy is incorporated into primary
    producers bodies through growth and
  • Heterotrophs consume, either directly or
    indirectly, the energy-rich organic molecules
    produced by the photosynthetic organisms.

Energy Transfer
  • Net primary production is the amount of primary
    producer biomass (weight of organic matter)
    available for consumption by heterotrophs.
  • This can be described as

Energy Transfer
  • Communities can be organized by trophic levels,
    based on the source of energy for the organisms.
  • Primary producers start the chain.
  • Herbivores eat plants, and constitute the primary
    consumer level.

Energy Transfer
  • Organisms that eat herbivores are secondary
  • Organisms that eat secondary consumers are
    tertiary consumers.
  • Detritivores or decomposers consume dead bodies
    and waste products.

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Energy Transfer
  • Omnivores get their food from more than one
    trophic level.
  • Many species are omnivores, and trophic levels
    are not clearly distinct, but the concept is a
    useful way of thinking about energy flow in a

Energy Transfer
  • A food chain depicts the linear sequence of who
    eats whom in a community.
  • Food chains are interconnected to make food webs.

Food Webs Show Trophic Interactions in a Community
Energy Transfer
  • Communities can be characterized by the
    distribution of energy and biomass within them.
  • Energy flow is governed by the first and second
    laws of thermodynamics.
  • At each trophic level energy is lost to
    metabolism and respiration.

Energy Transfer
  • Only 10 percent of energy of one trophic level is
    transferred to the next level
  • Heat lossenergy used for respiration and
    metabolism dissipated as heat and lost to the
  • Biomass availabilitynot all biomass can be
  • Indigestibility

Food Chain vs. Food Web
  • Artic Food Chain
  • Artic Food Web

Energy Transfer through trophic levels
Primary productivity by ecosystem vs of surface
  • of Surface Area
  • Primary Productivity

Biogeochemical Cycles
  • The movements of elements through organisms to
    the physical environment and back again are
    called biogeochemical cycles.
  • Properties of biogeochemical cycles for each
    element depend on the physical and chemical
    nature of the element and how it is used by

58.3 How Do Materials Cycle Through the Global
  • Water and fire have important roles and affect
    rates at which elements cycle through ecosystems.
  • Movement of water transfers many elements. Fire
    speeds the cycling of many elements.

Biogeochemical Cycles
  • The hydrologic cycle is the cycling of water
    through the four compartments.
  • The sun powers the hydrologic cycle by causing
    evaporation from the ocean surfaces.
  • More water is evaporated from the oceans than is
    returned by precipitation. The excess falls as
    precipitation on land.

Figure 58.8 The Global Hydrologic Cycle
Biogeochemical Cycles
  • Water returns to the ocean via streams, surface
    runoff, and groundwater.
  • Residence time of water in freshwaters and living
    organisms is very short in the oceans it is very
    long?3,000 years.
  • Large amounts of groundwater are stored in pools
    called aquifers. The residence time is long, and
    it plays a small role in the hydrologic cycle.

Biogeochemical Cycles
  • However, in some areas groundwater is being
    depleted as humans use it faster than it can be
    replaced, mostly for irrigation.
  • In the Northern Hemisphere, most groundwater was
    deposited during the most recent ice age, when
    regional precipitation was much greater than now.

Biogeochemical Cycles
  • Effects of groundwater depletion include the
    necessity of drilling deeper wells, and many
    people without safe drinking water.
  • In the United States and Europe, water
    consumption has decreased with more efficient
    appliances, increased cost of water, and
    regulations restricting water use.

Biogeochemical Cycles
  • Carbon cycle
  • All organisms contain carbon and their energy
    comes from carbon compounds.
  • Carbon is removed from the atmosphere as CO2 and
    incorporated into organic molecules by
  • Carbon is returned to the atmosphere by the
    metabolism of organisms.

Figure 58.9 The Global Carbon Cycle
Biogeochemical Cycles
  • Most carbon is stored in soils and rocks, marine
    sediments, and dissolved in ocean water.
  • CO2 moves into the ocean by simple diffusion it
    is stored in seawater as carbonate (CO32) or
    bicarbonate (HCO3).

Biogeochemical Cycles
  • Oceans absorb 2025 million tons of CO2 every
    day more than at any time during the past 20
    million years.
  • As a result, surface waters are becoming more
  • Decreasing pH and increasing temperature cause
    bleaching (loss of symbiotic algae) and death of
    corals, leading to collapse of coral reef systems.

Biogeochemical Cycles
  • Fossil fuels resulted from the burial of animals
    in anaerobic environmentsorganic molecules were
    not broken down by detritivores, but accumulated.
  • Fossil fuel burning has increased dramatically.
    CO2 is being released into the atmosphere faster
    than it can be dissolved in oceans and taken up
    by organisms.

Atmospheric CO2 Concentrations Are Increasing
Biogeochemical cycles
  • Not all the CO2 released by human activities
    remains in the atmosphere.
  • Some is dissolved in the oceans and taken up by
    organisms in photosynthesis and shell production.
  • Shells (CaCO3) sink to the ocean floor, removing
    carbon from surface waters.

Biogeochemical cycles
  • Some carbon is stored by terrestrial vegetation.
    Currently, photosynthetic consumption of CO2
    exceeds release by metabolism.
  • Experimental results suggest that young forests
    may store more carbon in a carbon-enriched world,
    but vegetation in general may actually lose

Biogeochemical cycles
  • Climate warming also increases rates of
    metabolismfor plants and for soil organisms,
    whose respiration returns a great deal of CO2 to
    the atmosphere.

Biogeochemical cycles
  • The buildup of atmospheric CO2 is warming Earth.
  • Analysis of air bubbles trapped in Greenland and
    Antarctic ice sheets shows that CO2
    concentrations were much lower during continental
    glaciations, but high during intervening warm

Figure 58.11 Higher Atmospheric CO2
Concentrations Correlate with Warmer Temperatures
Biogeochemical Cycles
  • Computer models are used to predict consequences
    of a doubling in atmospheric CO2 concentration
  • Increase in mean annual temperatures changes in
    precipitation patterns melting ice caps and
    glaciers sea level rise increased number and
    intensity of tropical storms.
  • Arctic sea ice is already shrinking.

Figure 58.12 The Ice Caps Are Melting
Biogeochemical cycles
  • Global warming is also affecting distribution of
  • Example Increased outbreaks of pests such as
    pine bark beetles, due to milder winters that
    dont kill off the beetles.

Biogeochemical cycles
  • Diseases may also proliferate. Winter cold
    typically kills many pathogens.
  • Warming may allow some diseases to spread to
    temperate regions.
  • Dengue fever and its mosquito vector are now
    spreading to higher latitudes.

Biogeochemical cycles
  • The Intergovernmental Panel on Climate Change
    (IPCC) issued an assessment report in 2007
  • Humans are exposed to climate change both
    directly and indirectly through changes in water,
    air, food quality and quantity, ecosystems,
    agriculture, and economy. Effects are projected
    to increase progressively in all countries and