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Title: Ecosystems: What Are They and How Do They Work?


1
Ecosystems What Are They and How Do They Work?
  • Chapter 3

2
3-1 What Is Ecology?
  • Concept 3-1 Ecology is the study of how
    organisms interact with one another and with
    their physical environment of matter and energy.

3
3-1 What Is Ecology?
  • Ecology is a study of connections in nature.
  • How organisms interact with one another and with
    their nonliving environment.

4
Species Make Up the Encyclopedia of Life
  • Organisms individual forms of life
  • Classified into species based on certain
    characteristics
  • Species a set of individuals that can mate and
    produce viable, fertile offspring
  • 1.75 Million species identified
  • Up to 1014 million species not yet identified??
  • Insects make up most of the known species

5
Science Focus Have You Thanked the Insects
Today?
  • Many times we classify insects as pests
  • Compete with us for food
  • Spread human diseases
  • Bite or sting us
  • Can be a nuisance
  • However, they are VERY beneficial
  • Pollinators
  • Eat other insects
  • Loosen and renew soil
  • Estimated 57 billion/yr in ecological services

6
Species Make Up the Encyclopedia of Life
  • A population is a group of interacting
    individuals of the same species occupying a
    specific area.
  • The space an individual or population normally
    occupies is its habitat.

7
Species Make Up the Encyclopedia of Life
  • Genetic diversity
  • In most natural populations individuals vary
    slightly in their genetic makeup.
  • These genetic diversity is crucial to the
    survival of the population.

8
Levels of Organization of Matter in Nature
  • Populations of different species living and
    interacting in an area form a community.
  • A community interacting with its physical
    environment of matter and energy is an ecosystem.
  • The biosphere is where all of the Earths life is
    found
  • A global ecosystem

9
3-2 What Keeps Us and Other Organisms Alive?
  • Concept 3-2 Life is sustained by the flow of
    energy from the sun through the biosphere, the
    cycling of nutrients within the biosphere, and
    gravity.

10
Natural Capital General Structure of the Earth
  • The biosphere consists of several physical layers
    that contain
  • Air
  • Water
  • Soil
  • Minerals
  • Life

11
The Earths Life-Support System Has Four Major
Components
  • Biosphere All of the life on the planet
  • Atmosphere Membrane of air around the planet.
  • Troposphere lowest layer - most gas of any
    layer
  • where weather occurs
  • Stratosphere contains ozone to filter out most
    of the suns harmful UV radiation.
  • Hydrosphere All the earths water liquid, ice,
    water vapor
  • Geosphere The earths crust and upper mantle
  • Lithosphere hard outer crust
  • Asthenosphere molten interior

12
Three Factors Sustain Life on Earth
  • One-way flow of energy beginning with the sun
  • Follows the laws of thermodynamics
  • Most is lost as heat
  • Cycling of matter or nutrients
  • Nutrients exist in a fixed amount
  • Follows the law of conservation of matter
  • Gravity

13
Flow of Energy to and from the Earth
  • Solar energy flowing through the biosphere warms
    the atmosphere, evaporates and recycles water,
    generates winds and supports plant growth.
  • Natural greenhouse effect natural process that
    keeps the Earth warmer than it would otherwise be

14
Life Exists on Land and in Water
  • Life exists on land systems called biomes and in
    freshwater and ocean aquatic life zones.

15
3-3 What Are the Major Components of an
Ecosystem?
  • Concept 3-3A Ecosystems contain living (biotic)
    and nonliving (abiotic) components.
  • Concept 3-3B Some organisms produce the
    nutrients they need, others get their nutrients
    by consuming other organisms, and some recycle
    nutrients back to producers by decomposing the
    wastes and remains of organisms.

16
Ecosystems Have Living and Nonliving Components
  • Ecosystems consist of living (biotic) and
    nonliving (abiotic) components.
  • Biotic or Abiotic?
  • Plants
  • Water
  • Animals
  • Temperature
  • Rocks/Minerals
  • Bacteria
  • Solar Energy
  • Landforms
  • Soil

17
Several Abiotic Factors Can Limit Population
Growth
  • Populations have a range of tolerance to
    variations in their physical and chemical
    environments.

18
Several Abiotic Factors Can Limit Population
Growth
  • Availability of matter and energy resources can
    limit the number of organisms in a population.
  • Limiting factor principle
  • Too much or too little of any abiotic factor can
    limit or prevent growth of a population, even if
    all other factors are at or near the optimal
    range of tolerance

19
Several Abiotic Factors Can Limit Population
Growth
  • The physical conditions of the environment can
    limit the distribution (range) of a species.

20
Producers and Consumers Are the Living Components
of Ecosystems
  • Producers, or autotrophs, make their own food
    from nutrients/energy obtained from the
    environment
  • Most producers capture sunlight to produce
    carbohydrates by photosynthesis

You must memorize this equation if you havent
already. It will come up throughout the year.
21
Photosynthesis
  • Chlorophyll molecules in the chloroplasts of
    plant cells absorb solar energy.
  • This initiates a complex series of chemical
    reactions in which carbon dioxide and water are
    converted to sugars and oxygen.

22
Producers and Consumers Are the Living Components
of Ecosystems
  • Some organisms can obtain energy from inorganic
    compounds in their environment WITHOUT sunlight
    through a process called chemosynthesis.
  • Deep ocean bacteria draw energy from hydrothermal
    vents and produce carbohydrates from hydrogen
    sulfide (H2S) gas.

23
Producers and Consumers Are the Living Components
of Ecosystems
  • Consumers, or heterotroph, cannot produce their
    own food and, therefore, must obtain their
    nutrients by feeding on other organisms.
  • Herbivores
  • Primary consumers that eat producers
  • Carnivores
  • Secondary consumers eat primary consumers
  • Third- and higher-level consumers carnivores
    that eat carnivores
  • Omnivores
  • Feed on both plant and animals

24
Producers and Consumers Are the Living Components
of Ecosystems
  • Detritivores Insects or other scavengers that
    feed on wastes or dead bodies (detritus)
    physically break down
  • Decomposers Bacteria and/or fungi that use
    enzymes to recycle nutrients in ecosystems
    chemically break down

25
Producers and Consumers Are the Living Components
of Ecosystems
  • Organisms break down carbohydrates and other
    organic compounds in their cells to obtain the
    energy they need.
  • This is usually done through
    aerobic respiration.
  • Aerobic means with oxygen

You must memorize this equation if you havent
already. It will come up throughout the year.
26
Producers and Consumers Are the Living Components
of Ecosystems
  • Some decomposers get energy by breaking down
    glucose (or other organic compounds) WITHOUT
    oxygen through a process called anaerobic
    respiration, or fermentation
  • Anaerobic means without oxygen
  • The end products vary based
    on the chemical reaction
  • Methane gas
  • Ethyl alcohol
  • Acetic acid
  • Hydrogen sulfide

27
Energy Flow and Nutrient Cycling Sustain
Ecosystems and the Biosphere
  • An ecosystem is sustained by a combination of a
    one-way flow of energy and the cycling of key
    nutrients.

28
Science Focus Many of the Worlds Most
Important Species Are Invisible to Us
  • Multitudes of tiny microbes such as bacteria,
    protozoa, fungi, and yeast help keep us alive.
  • Harmful microbes are the minority
  • Soil bacteria (nitrogen fixing bacteria) convert
    nitrogen gas to a usable form for plants
  • They help produce foods bread, cheese, yogurt,
    beer, wine
  • Make up 90 of all living mass on Earth
  • Help purify water, provide oxygen, breakdown
    waste
  • Live beneficially in your body (intestines, nose)

29
3-4 What Happens to Energy in an Ecosystem?
  • Concept 3-4A Energy flows through ecosystems in
    food chains and webs.
  • Concept 3-4B As energy flows through ecosystems
    in food chains and webs, the amount of chemical
    energy available to organisms at each succeeding
    feeding level decreases.

30
Energy Flows Through Ecosystems in Food Chains
and Food Webs
  • Food chains and webs show how eaters, the eaten,
    and the decomposed are connected to one another
    in an ecosystem.
  • The arrows point in the direction of the energy
    flow.

31
Energy Flows Through Ecosystems in Food Chains
and Food Webs
  • A food web shows the connections of all organisms
    within an ecosystem.

32
Usable Energy Decreases with Each Link in a Food
Chain or Web
  • Biomass the dry weight of all organic matter
    contained in an organism(s).
  • Chemical energy in biomass is transferred from
    one trophic level to another.

33
Pyramid of Energy Flow
  • Ecological efficiency percentage of useable
    energy transferred as biomass from one trophic
    level to the next.
  • Typically, only 10 efficient (90 lost as heat)

34
Usable Energy Decreases with Each Link in a Food
Chain or Web
  • Food chains rarely have more than 4 steps or 3
    trophic levels. Why?

35
Usable Energy Decreases with Each Link in a Food
Chain or Web
  • In accordance with the 2nd law of thermodynamics,
    there is a decrease in the amount of energy
    available to each succeeding organism in a food
    chain or web.
  • Cellular respiration - the breakdown of glucose
    to release energy is only 38 efficient
  • Energy is lost as heat
  • Energy is also used for growth, reproduction,
    movement
  • Ultimately, only about 10 of the original energy
    is available for the next trophic level (90 lost
    as heat)

36
Some Ecosystems Produce Plant Matter Faster Than
Others Do
  • Gross primary production (GPP)
  • Rate at which an ecosystems producers convert
    solar energy into chemical energy
    (photosynthesis) as biomass.

37
Some Ecosystems Produce Plant Matter Faster Than
Others Do
  • Net Primary Production (NPP)
  • Rate at which producers use photosynthesis to
    store energy minus the rate at which they use
    some of this energy through respiration (R).
  • NPP GPP R

38
Estimated Annual Average NPP in Major Life Zones
and Ecosystems
  • What are natures most productive/least
    productive systems?

39
Info from notes handout
  • Sample food chain

40
Info from notes handout
  1. Pyramid of Numbers
  1. Pyramid of Biomass
  1. Pyramid of Energy

41
3-5 What Happens to Matter in an Ecosystem?
  • Concept 3-5 Matter, in the form of nutrients,
    cycles within and among ecosystems and the
    biosphere, and human activities are altering
    these chemical cycles.

42
Nutrients Cycle in the Biosphere
  • Biogeochemical Cycles recycle nutrients through
    the earths air, land, water, and living
    organisms.
  • Nutrients are the elements and compounds that
    organisms need to live, grow, and reproduce.
  • Biogeochemical cycles move these substances
    through air, water, soil, rock and living
    organisms.
  • Connect past, present , and future forms of life

43
The Water Cycle
44
The Water Cycle
45
Effects of Human Activities on Water Cycle
  • Humans alter the water cycle by
  • Withdrawal of large amounts of freshwater at
    rates faster than nature can replace it
  • Clearing vegetation and eroding soils.
  • Increased flooding when wetlands are drained
  • Polluting surface and underground water.
  • Contributing to climate change.
  • Increases melting, evaporation, precipitation,
    etc.

46
The Carbon Cycle
47
The Carbon Cycle
48
Effects of Human Activities on Carbon Cycle
  • Humans alter the carbon cycle by adding excess
    CO2 to the atmosphere through
  • Burning fossil fuels
  • Clearing/burning vegetation faster than it is
    replaced

49
The Nitrogen Cycle
50
The Nitrogen Cycle
51
Nitrogen Cycles through the Biosphere Bacteria
in Action
  • Nitrogen fixation converting atmospheric N2
    into ammonia (NH3) or ammonium (NH4) that can be
    used by plants
  • Lightning ammonia falls to the ground with the
    rain
  • Nitrogen-fixing bacteria
  • Nitrification Nitrifying bacteria convert
    ammonium (NH4) to nitrates (NO3) and/or nitrites
    (NO2)
  • Denitrification Denitrifying bacteria convert
    ammonia, nitrates, or nitrites back into
    atmospheric N2.
  • Ammonification Decomposers convert ditritus
    into ammonia or ammonium.

52
Nitrogen Fixation A Closer Look
53
Effects of Human Activities on the Nitrogen Cycle
  • Humans alter the nitrogen cycle by
  • Adding gases that contribute to acid rain
  • NO and N2O
  • Contaminating bodies of water with excess
    nitrates from inorganic fertilizers
  • Humans fix more nitrogen than all natural sources
    combined
  • Adding nitrogen to the troposphere through
    deforestation
  • Remove nitrogen from topsoil

54
The Phosphorous Cycle
55
The Phosphorous Cycle
56
Effects of Human Activities on the Phosphorous
Cycle
  • Cycles through water, the earths crust, and
    living organisms (NOT the atmosphere like the
    others)
  • May be limiting factor for plant growth
  • Humans alter the phosphorus cycle by
  • We remove large amounts of phosphate from the
    earth to make fertilizer.
  • We reduce phosphorous in tropical soils by
    clearing forests.
  • We add excess phosphates to aquatic systems from
    runoff of animal wastes and fertilizers.

57
The Sulfur Cycle
58
The Sulfur Cycle
59
Effects of Human Activities on the Sulfur Cycle
  • Sulfur found in organisms, ocean sediments, soil,
    rocks, and fossil fuels.
  • Sulfur dioxide (SO2) in the atmosphere
  • Humans alter the sulfur cycle by adding sulfur
    dioxide to the atmosphere through
  • Burning sulfur-containing coal and oil
  • Refining sulfur-containing petroleum
  • Smelting sulfur-containing metallic mineral ores
  • These can all lead to acid rain
  • Sulfuric acid (H2SO4) when SO4 mixes with H2O
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