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Chapter 18: Introduction to Ecology


Chapter 18: Introduction to Ecology Cycles in Nature Many of the abiotic factors in an ecosystem pass through cycles that allow the substances to be used and reused. – PowerPoint PPT presentation

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Title: Chapter 18: Introduction to Ecology

Chapter 18 Introduction to Ecology
Section 1 Vocabulary Pretest
  1. Thin zone of Earth that supports life
  2. All organisms living in a certain area
  3. All the members of one species in one area
  4. Study of the relationship of organisms and their
  5. All living things depend on other living things
  6. All living and nonliving parts of an environment
  7. Used to study the complexity of ecosystems
  1. Ecology
  2. Interdependence
  3. Ecological Model
  4. Biosphere
  5. Ecosystem
  6. Community
  7. Population

Answer Key
  • Ecology D
  • Interdependence E
  • Ecological Model G
  • Biosphere A
  • Ecosystem F
  • Community B
  • Population C

Ecology and Interdependence
  • Ecology is the study of the interactions between
    organisms and the living and nonliving components
    of their environment.
  • Interdependence is a key theme found throughout
  • Living things depend on each other in complex
    ways for survival.
  • Ecological models can be
  • used to study this complexity.

Levels of Organization
  • The hierarchy of environmental organization from
    largest to smallest is Biosphere, Ecosystems,
    Communities, Populations, and Organisms.
  • Biosphere thin zone of the Earth that supports
  • 20 km thick from the bottom of the ocean to the
    lowest atmosphere.
  • Three parts
  • lithosphereland on the surface
  • hydrospherewater on the Earth
  • atmosphereair that surrounds Earth

  • Biosphere is made of many smaller parts called
  • Ecosystemall living and nonliving parts of an
    environment. Every ecosystem is able to support
    itself and has both biotic and abiotic factors
  • Biotic factorsliving organisms
  • Abiotic factorsnonliving parts air, water,
    sunlight, soil, temperature, pH, humidity,
    salinity, oxygen concentration, availability of
    nitrogen, etc. They are not constantvary from
    place to place and over time.
  • Examples pond, garden, riverbank, puddle of

Communities and Populations
  • Each ecosystem is made up of one or more
  • Communityall the organisms living in a certain
  • Example pond community
  • Each community is made up of populations.
  • Populationall the organisms of the same species
    living in the same area.
  • Example pickerel frogs in a pond

Section 2 Vocabulary Pretest
  1. Habitat
  2. Biotic factor
  3. Abiotic factor
  4. Tolerance curve
  5. Acclimation
  6. Conformer
  7. Regulator
  8. Dormancy
  9. Migration
  10. Niche
  11. Generalist
  12. Specialist
  1. Nonliving things
  2. Living things
  3. Place where an organism lives
  4. Adjusting tolerance to abiotic factors
  5. Cannot regulate internal conditions
  6. Range of conditions that can be stood
  7. Temporarily moving away
  8. Temporarily not growing
  9. Organisms job or role
  10. Organism with narrow niche
  11. Organism with broad niche
  12. Can regulate internal conditions

Answer Key
  • Habitat C
  • Biotic factor B
  • Abiotic factor A
  • Tolerance curve F
  • Acclimation D
  • Conformer E
  • Regulator L
  • Dormancy H
  • Migration G
  • Niche I
  • Generalist K
  • Specialist J

Surviving in an Ecosystem
  • Each organism has a limited range of
    environmental conditions in which they can
  • The range for a particular factor can be measured
    using a tolerance curve
  • Some organisms can adjust their tolerance to
    abiotic factors through the process of
  • Happens within an organisms lifetime (not like

Strategies for Tolerance
  • Two strategies exist to deal with fluctuations in
  • Conformersorganisms who do not regulate their
    internal conditions they change with the
    environment. Ex ectothermic animals
  • Regulatorsorganisms that use energy to control
    some of their internal conditions.
  • Ex endothermic animals

Escaping Unfavorable Conditions
  • Sometimes, adjusting isnt possible and organisms
    must temporarily escape.
  • Ex Lizard hiding in the shade
  • Seed dormancy or animal hibernation
  • Migration

Habitats and Niches
  • Habitatplace where an organism lives. It
    provides food, water, shelter, and a place to
    reproduce. Example a woodpeckers habitat is
    the trees in a forest.
  • Nicheeverything an organism does and everything
    it needs in its habitat. It is often defined as
    an organisms job or role in its community.
    Example a woodpeckers niche is catching and
    eating insects.

Generalist vs. Specialist
  • Generalistspecies with broad niches
  • Ex opossum (eats almost anything)
  • Specialistspecies with narrow niches
  • Ex koala (eats eucalyptus leaves only)

Section 3 Vocabulary Pretest
  1. Producer
  2. Chemosynthesis
  3. Gross primary productivity
  4. Biomass
  5. Net primary productivity
  6. Consumer
  7. Herbivore
  1. An organism that eats food
  2. An organism that makes food
  3. An organism that eats plants only
  4. An organism that uses chemicals to generate
  5. Rate at which biomass accumulates
  6. Rate at which producers capture energy from
    sunlight by producing organic compounds
  7. All organic material produced in an ecosystem

  1. An organism that eats both producers and
  2. Model of the flow of energy through an ecosystem
  3. An organism that breaks down organic material by
    causing decay
  4. An organism that feeds on the wastes of an
  5. An organism that eats other consumers.
  6. Many food chains combined
  7. An organisms position in a sequence of energy
  1. Carnivore
  2. Omnivore
  3. Detritivore
  4. Decomposer
  5. Trophic level
  6. Food chain
  7. Food web

Answer Key
  • Producer B
  • Chemosynthesis D
  • Gross primary productivity F
  • Biomass G
  • Net primary productivity E
  • Consumer A
  • Herbivore C
  • Carnivore L
  • Omnivore H
  • Detritivore K
  • Decomposer J
  • Trophic level N
  • Food chain I
  • Food web M

Energy and the Environment
  • Sunlightmain source of energy in an ecosystem.
  • In photosynthesis, plants change light energy
    from the sun into chemical energy stored in food.
  • Some of the plants food energy is used for their
    own growth and reproduction. The rest is stored.
  • Animals eat the plants and use the stored food
    for energy for growth, reproduction and movement.

Ecological Classification of Organisms
  • Ecologists classify organisms into two major
    groups according to the way they get food
  • Producersmake food
  • Consumerseat food

  • Producersmake or produce their own food.

Some protists
All plants
Some bacteria
Types of Producers
  • Photoautotrophsuse solar energy (photosynthesis)
    to produce sugar
  • Chemoautotrophsuse energy stored in inorganic
    molecules (chemosynthesis) to produce

Measuring Productivity
  • Gross primary productivitythe rate at which
    producers capture energy from sunlight by
    producing organic compounds.
  • Measured in biomass organic material that has
    been produced in an ecosystem
  • Net primary productivity rate at which biomass
  • Expressed in kcal/m2/yr or g/m2/yr.
  • Calculated by Gross primary productivity minus
    the rate of respiration in producers.

The graph shows the net primary productivity
varies between biomes. The rainforest is 25 times
greater than the desert of the same
size. Variations in light, temperature and
precipitation account for the difference in
terrestrial biomes. Variations in light and
availability of nutrients accounts for
differences in aquatic biomes.
  • Consumersget food by eating other organisms or
    organic wastes. (Heterotrophs)
  • Four types

Herbivoreseat producers
Omnivoreseat producers and consumers
Carnivoreseat other consumers
  • Detritivores--feed on wastes (dead plants,
    animal wastes, and dead animal carcasses.)
  • A few are specifically classified as decomposers
    because they cause decay and return important
    nutrients to the soil.

Decomposing Detritivores
Energy Flow
  • Energy flow through an ecosystem can be
    illustrated using trophic levels (shows an
    organisms position in a sequence of energy
  • 1st level producers
  • 2nd level herbivores
  • 3rd and higher levels predators

  • Consumers are also grouped into feeding or
    trophic levels according to the foods they eat.
  • Many organisms feed at more than one level,
    especially omnivores.

C2second level consumers eat C1
C1first level consumers eat plants
C3third level consumers eat C2
Food Chains
  • Food chainmodel of the flow of energy through
    the organisms of an ecosystem
  • Source of energy is the sun.
  • Arrows always point in the direction of the flow
    of energy.
  • Energy that flows through a food chain is not
    recycled. Sunlight must continue to flow through
    the biosphere to power the food chain.

A food chain from a typical meadow ecosystem.
Food Webs
  • Food web many food chains combine to form a food
    web. It is generally a better model because it
    gives more information.
  • The members of a food web can be identified by
    their trophic level.
  • Many organisms function on more than one trophic

Which is a producer? Which are C1
consumers? Which are C2 consumers? Which is a C3
consumer? Which is a C4 consumer?
A complex food web from an aquatic ecosystem
Energy Pyramid
  • An energy pyramid is a model that shows how the
    amount of energy decreases at each level of the
    food chain.
  • Some escape being eaten so their energy is never
    transferred to the next level.
  • Animals gain only a small amount of energy from
    the food they eat. Some parts of prey cannot be
    broken down for food (Ex antlers and hoofs)
  • Much of the energy is used up or is released as
    heat energy.
  • Therefore, fewer organisms can be supported at
    each level of the pyramid.

A kilocalorie is a measure of energy. The
energy transfer from one level to the next is
about 10 . For example if there are 1,000
kcal at one level, only 100 kcal are transferred
to the next. Thus each level can support
fewer and fewer organisms.
Types of Ecological Relationships
  • Competition occurs when populations require the
    same resource. The
  • Competitive Exclusion Principle states that
    overtime, only one population will be successful
    in acquiring the resource. The other will be
  • Predation occurs when one population captures
    and feeds on another.

  • Symbiosis occurs when individuals of two
    different species live in close association.
    Three types
  • Mutualism both benefit. Examples lichens
    (alga and fungus), micorhizzae (fungus and
    plants), clown fish and sea anemones.
  • Commensalism one benefits/ the other is
    unaffected. Example barnacles on a whale
  • Parasitism one benefits/ the other is harmed.
    Example fleas on a dog

Cycles in Nature
  • Many of the abiotic factors in an ecosystem pass
    through cycles that allow the substances to be
    used and reused.
  • Four important cycles of abiotic substances
  • Water cycle
  • Carbon cycle
  • Nitrogen cycle
  • Phosphorus cycle

Water Cycle
  • Water also passes through both living and
    nonliving parts of the environment. The water
    cycle is maintained by evaporation,
    transpiration, condensation and precipitation.

  • Evaporation adds water as vapor to the
    atmosphere. Water evaporates as water, soil, and
    living bodies heat up.
  • Transpiration evaporation of water from
    plantscauses them to take in more water.
  • Condensation change of water from a gas to a
    liquidcauses the formation of clouds in the
    water cycle.
  • Precipitation the return of water from the
    atmospherethe amount of water the atmosphere can
    hold depends on temperature and air pressurewhen
    clouds become saturated with water vapor,
    precipitation falls.
  • Types Rain, snow, sleet, hail and fog

Carbon Cycle
  • Photosynthesis and cellular respiration form the
    basis of the carbon cycle.
  • In the past 150 years, atmospheric carbon dioxide
    has risen more than 30..mostly due to the
    burning of fossil fuels

Nitrogen Cycle
  • Air is 78 nitrogen gas. Most organisms cannot
    use nitrogen in this form.
  • Nitrogen-fixing bacteria change nitrogen gas into
    nitrates which can be used by living things to
    make proteins and nucleic acids.
  • Live in the soil and on the roots of certain
    plants (beans, peas, clover and alfalfa).
  • Receive carbohydrates from plants and produce
    nitrogen for plants
  • Release extra nitrogen into the soil.
  • Decomposers--make the nitrogen from decaying
    organisms and wastes available in the soil by
    turning it to ammonia (NH3) which changes in the
    soil to ammonium (NH4) in a process called
  • Soil bacteria turns ammonium into nitrites (NO2-)
    and nitrates (NO3-) in a process called
    nitrification. Plants can use the nitrates and
    then animals can eat the plants.
  • Anaerobic bacteria return nitrogen to the air by
    breaking down soil nitrates in the process of

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Phosphorus Cycle
  • Phosphorus is necessary for healthy bones, teeth,
    and the formation of DNA and RNA.
  • The erosion of rocks is important in adding
    phosphorus to the soil and water.
  • Excreted wastes and decaying organisms also add
    phosphorus to soil and water.
  • Plants absorb phosphorus. Animals get phosphorus
    from plants.

Ecosystem Response to Change
  • Ecological Succession the orderly process by
    which an ecosystem changes over time.
  • Primary succession (no soil) occurs on surfaces
    that did not previously support plant life.
    Pioneer species such as mosses and lichens are
    the first organisms to colonize the area and
    create layers of soil for future inhabitants.
  • Secondary succession occurs in areas that
    previously supported life but have been
    disturbed. Example following a fire