Introduction: The Web of Life

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Introduction The Web of Life
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1 Introduction The Web of Life

• Connections in Nature
• Ecology

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Case Study Deformity and Decline in Amphibian
Populations

• High incidence of deformities in amphibians
• Declining populations of amphibians worldwide

Figure 1.1 Deformed Leopard Frogs
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Figure 1.2 Amphibians in Decline
Chytrid fungus
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Case Study Deformity and Decline in Amphibian
Populations

• Amphibian population declines
• 1. recent.
• 2. world-wide even in places far removed from
  human activity.
• Implications amphibians are biological
  indicators of environmental problems.

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Introduction

• Ecology The scientific study of how organisms
  affectand are affected byother organisms and
  their environment.
• Because human culture can have enormous impacts
  on the biosphere
• its important to understand how natural systems
  work.

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Ecology

• Levels of ecological organization.
• Individuals, populations, communities, ecosystems.

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Ecology

• A population A group of individuals of a single
  species that live and interact in a particular
  area.
• A community An assemblage of populations living
  in the same area.

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Figure 1.9 A Few of Earths Many Communities
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Ecology

• An ecosystem An ecological community plus its
  energy and nutrient relationships.
• Energy moves through ecosystems in a single
  direction onlyit cannot be recycled.
• Nutrients are continuously recycled from the
  physical environment to organisms and back again.
• The biosphere All the worlds ecosystems

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Ecology

• All living systems change over time.
• Evolution
• 1. A change in the genetic characteristics of a
  population.leading to
• 2. A change in phenotypic characteristics of a
  population. Keeps pace with environmental change.

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Ecology

• Natural selection Individuals with particular
  adaptations tend to survive and reproduce at a
  higher rate than other individuals.
• If the adaptation is heritable, the offspring
  will tend to have the same characteristics that
  gave their parents an advantage.
• As a result, the frequency of those
  characteristics may increase in a population over
  time.

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Figure 1.10 Natural Selection in Action
Note mutations here Prior to contact with
antibiotic Mutation did not take place
because of need.
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Answering Ecological Questions

• Scientists learn about the natural world by a
  series of steps called the scientific method
• 1. Make observations and ask questions.
• 2. Use previous knowledge or intuition to develop
  possible answers (hypotheses).
• 3. Evaluate hypotheses by observation or
  experiment.
• 4. Use the results to modify the hypotheses, to
  pose new questions, or to draw conclusions about
  the natural world.
• The process is iterative and self-correcting.

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The Physical Environment
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2 The Physical Environment

• Climate
• Atmospheric and Oceanic Circulation
• Global Climatic Patterns
• Regional Climatic Influences

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Climate
Concept 2.1 Climate is the most fundamental
characteristic of the physical environment.

• Weather Current conditionstemperature,
  precipitation, humidity, cloud cover.
• Climate Long-term description of weather, based
  on averages and variation measured over decades.

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Climate

• Climate determines the geographic distribution of
  organisms.
• Climate is characterized by average conditions,
  but extreme conditions are also important to
  organisms as they contribute to mortality.

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Figure 2.3 Widespread Mortality in Piñon Pines
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Climate

• The sun is the ultimate source of energy that
  drives global climate.
• Energy gains from solar radiation must be offset
  by energy losses if Earths temperature is to
  remain the same.

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Climate

• Most of the solar radiation absorbed by Earths
  surface is returned to the atmosphere as infrared
  radiation. Two routes
• 1. Latent heat flux loss of heat energy in the
  evaporation of surface water.
• 2. Sensible heat flux transfer of heat from warm
  air immediately above the surface to the cooler
  atmosphere by convection and conduction.
• Conduction Kinetic energy of molecules is
  transferred between contacting surfaces.
• Convection Energy transfer by movements of air
  and water currents..

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Climate

• Atmosphere contains greenhouse gases that absorb
  and reradiate the infrared radiation emitted by
  Earth.
• These gases include water vapor (H2O), carbon
  dioxide (CO2), methane (CH4), and nitrous oxide
  (N2O).
• Without greenhouse gases, Earths climate would
  be about 33C cooler.
• Anthropogenic increases in greenhouse gases
  appear to be altering Earths energy balance,
• Climate system is changing, and global warming
  is occurring.

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Atmospheric and Oceanic Circulation
Concept 2.2 Winds and ocean currents result from
differences in solar radiation across the surface
of Earth.

• Near the equator, the suns rays strike Earths
  surface perpendicularly.
• Toward the poles, the suns rays are spread over
  a larger area and take a longer path through the
  atmosphere.

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Figure 2.5 Latitudinal Differences in Solar
Radiation at Earths Surface
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Atmospheric and Oceanic Circulation

• When solar radiation heats Earths surface, the
  surface warms and emits infrared radiation to the
  atmosphere, warming the air above it.
• Warm air is less dense than cool air, and it
  risesuplift.
• Air pressure decreases with altitude, so the
  rising air expands, and cools.

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Figure 2.6 Surface Heating and Uplift of Air
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Atmospheric and Oceanic Circulation

• Cool air holds less water vapor than warm air.
• The rising air expands and cools, and water vapor
  condenses to form clouds.
• The condensation is a warming process, which may
  act to keep the pocket of air warmer than the
  surrounding atmosphere and enhance its uplift.

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Atmospheric and Oceanic Circulation

• Tropical regions receive the most solar
  radiation, and thus have the most precipitation.
• Uplift of air in the tropics results in a low
  atmospheric pressure zone.
• When air masses reach the boundary between the
  troposphere and stratosphere, air flows towards
  the poles.

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Figure 2.7 Equatorial Heating and Atmospheric
Circulation Cells
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Atmospheric and Oceanic Circulation

• The air descends when it cools and forms a high
  pressure zone at about 30 N and S.
• Major deserts of the world are at these latitudes.

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Atmospheric and Oceanic Circulation

• Cells of atmospheric circulation
• 1. Hadley cells low pressure zone with
  equatorial uplift
• 2. Polar cells high pressure zones with little
  precipitationpolar deserts.
• 3. Ferrell cells exist at mid-latitudes.
• The three cells result in the three major
  climatic zones in each hemisphere tropical,
  temperate, and polar zones.

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Figure 2.8 Global Atmospheric Circulation Cells
and Climatic Zones