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Ecosystems: What Are They
and How Do They Work?
Chapter 3
Key Concepts
•
• PART 1:
Ecology: Earth and ecosystems
Energy flows
• PART 2:
Matter cycles
Studying ecosystems and human impacts
PART
1
(Sections 1
through 3)
Section 3-1
WHAT KEEPS US AND OTHER
ORGANISMS ALIVE?
Ecology
•Ecology is the study of
connections in nature. ABC’s:
•A= Abiotic (Non-living)
•B= Biotic (Living)
•C= Cultural (Human Interactions)
Earth’s life-support system has
four major components
•The atmosphere is the thin membrane of air
around the planet.
- The troposphere is the air layer about 4–11
miles above sea level. It contains greenhouse
gases that absorb and release energy which
warms the inner layer of the atmosphere.
- The stratosphere lies above the troposphere
between 11–31 miles; it filters out the sun’s
harmful radiation.
•The hydrosphere consists of earth’s water,
found in liquid water, ice, and water vapor.
•The geosphere is the hot core, a thick mantle,
and thin crust (lithosphere).
•The biosphere includes parts of the
atmosphere, hydrosphere, and geosphere.
All parts are interconnected!
Flow of Solar Energy to and from
the Earth
• Greenhouse
gaseswater vapor, CO2,
N2O, CH4, O3
• Greenhouse effectHeat trapped in the troposphere
to warm planetwithout
natural greenhouse effect
life would not be possible.
http://www.cengage.com/earthscience/book_content/9781111988937_miller/animations/ch0
3/animation_media/sun_to_earth/sun_to_earth.html
Earth’s Life-Support Systems(3
interconnected factors)
• One way flow of highquality energy
• Cycling of matter
• Gravity- holds atmosphere,
enables movement of
chemicals thru various
spheres
“Energy flows, nutrients cycle, gravity holds it together.”
Section 3-2
WHAT ARE THE MAJOR
COMPONENTS OF AN ECOSYSTEM?
Levels of Organization in the
Biosphere
•
• Organisms
• Cells
• Species
• Microbes rule!Benefits Include:Decomposition,
nutrient cycling, foods, water purification, digestion,
antibiotics
Ecosystem structure
•Ecology focuses on how organisms interact with
each other and with their non-living environment:
•Population is a group of individuals of the same
species living in a particular place.
•Community is populations of different species living in
a particular place, and potentially interacting with each
other.
•Ecosystem is a community of different species
interacting with one another and with their nonliving
environment of matter and energy
Key Living and Nonliving
Components of an Ecosystem
Main Structural Components of
an Ecosystem
http://www.cen
gage.com/eart
hscience/book
_content/9781
111988937_mil
ler/animations/
ch03/animation
_media/matter
_energy/matter
_energy.html
Major Components of Freshwater Ecosystems
Sun
Producers (rooted plants)
Producers (phytoplankton)
Primary consumers (zooplankton)
Secondary consumers (fish)
Tertiary
consumers
(turtles)
Dissolved
chemicals
Sediment
Decomposers (bacteria and fungi)
Trophic levels
•Every organism belongs to a particular trophic
level depending on its source of nutrients.
•Producers, or autotrophs, use photosynthesis to
make nutrients from components in the
environment.
•Consumers, or heterotrophs, get their nutrients by
feeding on other organisms or their remains.
•Consumers can be herbivores (feed on plants),
carnivores (feed on animals) or omnivores (feed
on both plants and animals).
Producers
Consumers
Trophic levels, continued
•Consumers can be primary, secondary or tertiary
consumers, depending upon their trophic level.
•Decomposers (bacteria/fungi) break down organic
detritus into simpler inorganic compounds.
•Detritivores (detritus feeders) feed on waste or dead
bodies.
•Producers, consumers and decomposers utilize
chemical energy stored in organic molecules. In
most cells, this energy is released by aerobic
respiration:glucose + oxygen = carbon dioxide + water +
ENERGY
Detritivores
Section 3-3
WHAT HAPPENS TO ENERGY IN AN
ECOSYSTEM?
Energy flows through ecosystems
in food chains and food webs
A food chain is a sequence of organisms, each of which
serves as a source of nutrients and energy for the next
organisms. Organisms are assigned to trophic levels in a food
chain.
Energy flows through ecosystems
in food chains and food webs
•A food web is a series of
interconnected food chains.
Food webs occur in most
ecosystems. Organisms are
also assigned to trophic levels
in food webs.
•
•Producers are the first level.
•Primary consumers are the second.
•Secondary consumers belong to the
third.
•Tertiary consumers are the fourth
(top) level.
•Detritivores and decomposers
process detritus from all trophic
levels.
Energy Flow in an Ecosystem
There is less high-quality energy available to organisms
at each succeeding feeding level because about 90%
the energy is lost as heat
• Ecological efficiency= % of usable energy
•
transferred as biomass from one trophic level to the next (2% 40%)10% Rule-assumes 10% ecological efficiency
Ecological Pyramids- 3 Types
1. Pyramid of Numbers
2. Pyramid of Biomass
3. Pyramid of Energy Flow
Ecological Pyramids (3 Types)
Numbers and
Biomass
Energy
Heat
Heat
Tertiary
consumers
(human)
Decomposers
Heat
10
Secondary
consumers
(perch)
Heat
Usable energy
available at
each tropic level
(in kilocalories)
100
1,000
10,000
Primary
consumers
(zooplankton
)
Heat
Producers
(phytoplankton
)
Fig. 3-18, p. 49
Pyramid of Energy Flow
Biomass Productivity
•The rate of an ecosystem’s producers converting energy into
biomass is the gross primary productivity (GPP).
•Some of the biomass must be used for the producers’ own
respiration! Net primary productivity (NPP) = GPP – energy
used NPP measures how fast producers can provide biomass
and support consumers in an ecosystem.
The three most productive systems: swamps & marshes
(wetlands), tropical rain forests, estruaries
The three least productive:tundra, desert scrub, extreme
desert
Differences between GPP and NPP
Sun
Respiration
Gross
primary
production
Growth and reproduction
Energy lost and
unavailable to
consumers
Net
primary
production
(energy
available to
consumers)
Fig. 3-19, p. 49
NPP in Major Life Zones and
Ecosystems
Three Big Ideas
•PART 1: Life is sustained by the flow of energy
from the sun through the biosphere, the cycling of
nutrients within the biosphere, and gravity.
•PART 2: Some organisms produce the nutrients
they need, some survive by consuming other
organisms, and others recycle nutrients back to
producers.
•Human activities are altering the flow of energy
through food chains and webs, and the cycling of
nutrients within ecosystems and the biosphere.