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Chapter 3
ch 4 in book!
Ecosystems: What Are
They and How Do They
Work?
Chapter Overview Questions
 What
is ecology?
 What basic processes keep us and other
organisms alive?
 What are the major components of an
ecosystem?
 What happens to energy in an ecosystem?
 What are soils and how are they formed?
 What happens to matter in an ecosystem?
 How do scientists study ecosystems?
Core Case Study:
Have You Thanked the Insects
Today?
 Many
plant species depend on insects for
pollination.
 Insect can control other pest insects by
eating them
Figure 3-1
Core Case Study:
Have You Thanked the Insects
Today?
 …if
all insects disappeared, humanity
probably could not last more than a few
months [E.O. Wilson, Biodiversity expert].

Insect’s role in nature is part of the larger
biological community in which they live.
THE NATURE OF ECOLOGY
 Ecology

is a study of connections in nature.
How organisms interact with one another and
with their nonliving environment.
Figure 3-2
Other animals
281,000
Known species
1,412,000
Insects
751,000
Fungi
69,000
Prokaryotes
4,800
Plants
248,400
Protists
57,700
Fig. 3-3, p. 52
Case Study:
Which Species Run the World?
 Multitudes
of tiny microbes such as bacteria,
protozoa, fungi, and yeast help keep us alive.






Harmful microbes are the minority.
Soil bacteria convert nitrogen gas to a usable
form for plants.
They help produce foods (bread, cheese, yogurt,
beer, wine).
90% of all living mass.
Helps purify water, provide oxygen, breakdown
waste.
Lives beneficially in your body (intestines, nose).
Universe
Galaxies
Solar systems
Biosphere
Planets
Earth
Biosphere
Ecosystems
Ecosystems
Communities
Populations
Realm of ecology
Organisms
Organ systems
Communities
Organs
Tissues
Cells
Populations
Protoplasm
Molecules
Atoms
Organisms
Subatomic Particles
Fig. 3-2, p. 51
Populations, Communities, and
Ecosystems
 Members
of a species interact in groups
called populations.
 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.
Populations
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.
Figure 3-4
Populations
 Genetic

diversity
In most natural
populations
individuals vary
slightly in their
genetic makeup.
Figure 3-5
THE EARTH’S LIFE SUPPORT
SYSTEMS
 The
biosphere consists of several
physical layers that contain:






Air
Water
Soil
Minerals
Life
“Bio” means life, so the biosphere is
anywhere on this planet we find life.
Figure 3-6
Oceanic
Crust
Atmosphere
Vegetation
Biosphere
and animals
Soil
Crust
Rock
Continental
Crust
Lithosphere
Upper mantle
Asthenosphere
Lower mantle
Core
Mantle
Crust (soil
and rock)
Biosphere
Hydrosphere (living and dead
(water)
organisms)
Lithosphere
Atmosphere
(crust, top of upper mantle)
(air)
Fig. 3-6, p. 54
Biosphere
 Atmosphere
•
•
– Membrane of air around the
planet.
several layers that vary in temperature and
composition78% nitrogen, 21% oxygen
Stratosphere is one layer: lower portion contains ozone to
filter out most of the sun’s harmful UV radiation.
– All the earth’s water: liquid,
ice, water vapor
 Hydrosphere
•
includes aquifers, groundwater, glaciers, etc.
 Lithosphere

The earth’s crust and upper mantle.
What Sustains Life on Earth?
 Solar
energy, the cycling of matter, and gravity
sustain all Earth’s life.
Biosphere
Carbon
cycle
Phosphorus
cycle
Nitrogen
cycle
Water
cycle
Oxygen
cycle
Heat in the environment
Heat
Heat
Heat
Fig. 3-7, p. 55
What Happens to Solar Energy
Reaching the Earth?
 Solar
energy flowing through the biosphere
warms the atmosphere, evaporates and
recycles water, generates winds and supports
plant growth.
Figure 3-8
Solar
radiation
Energy in = Energy out
Reflected by
atmosphere (34% )
UV radiation
Absorbed
by ozone
Visible
Light
Absorbed
by the
earth
Radiated by
atmosphere
as heat (66%)
Lower Stratosphere
(ozone layer)
Troposphere Greenhouse
effect
Heat
Heat radiated
by the earth
Fig. 3-8, p. 55
ECOSYSTEM COMPONENTS
 Life
exists on land systems called biomes
and in freshwater and ocean aquatic life
zones.
Average annual precipitation
100–125 cm (40–50 in.)
75–100 cm (30–40 in.)
50–75 cm (20–30 in.)
25–50 cm (10–20 in.)
below 25 cm (0–10 in.)
4,600 m (15,000 ft.)
3,000 m (10,000 ft.)
1,500 m (5,000 ft.)
Coastal
mountain
ranges
Sierra
Nevada
Mountains
Great
American
Desert
Coastal chaparral Coniferous
and scrub
forest
Rocky
Mountains
Desert
Great
Plains
Coniferous
forest
Mississippi
River Valley
Prairie
grassland
Appalachian
Mountains
Deciduous
forest
Fig. 3-9, p. 56
Nonliving and Living Components of
Ecosystems
 Ecosystems
consist of nonliving (abiotic) and
living (biotic) components.
Figure 3-10
Factors That Limit Population Growth
 Availability
of matter and energy resources
can limit the number of organisms in a
population.
Figure 3-11
Factors That Limit Population Growth
 The
physical
conditions of the
environment can
limit the
distribution of a
species.
Figure 3-12
Producers: Basic Source of All Food
 Most
producers capture sunlight to produce
carbohydrates by photosynthesis:
Photosynthesis:
A Closer Look
 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.
Figure 3-A
Producers: Basic Source of All Food
 Chemosynthesis:

Some organisms such as deep ocean bacteria
draw energy from hydrothermal vents and
produce carbohydrates from hydrogen sulfide
(H2S) gas .
Consumers: Eating and Recycling to
Survive
 Consumers
(heterotrophs) get their food by
eating or breaking down all or parts of other
organisms or their remains.

Herbivores
• Primary consumers that eat producers

Carnivores
• Primary consumers eat primary consumers
• Third and higher level consumers: carnivores that eat
carnivores.

Omnivores
• Feed on both plant and animals.
Decomposers and Detritivores


Decomposers: Recycle nutrients in ecosystems.
Detritivores: Insects or other scavengers that feed
on wastes or dead bodies.
Figure 3-13
Aerobic and Anaerobic Respiration:
Getting Energy for Survival
 Organisms
break down carbohydrates and
other organic compounds in their cells to
obtain the energy they need.
 This is usually done through aerobic
respiration.

The opposite of photosynthesis
Aerobic and Anaerobic Respiration:
Getting Energy for Survival
 Anaerobic


respiration or fermentation:
Some decomposers get energy by breaking
down glucose (or other organic compounds) in
the absence of oxygen.
The end products vary based on the chemical
reaction:
•
•
•
•
Methane gas
Ethyl alcohol
Acetic acid
Hydrogen sulfide
Two Secrets of Survival: Energy Flow
and Matter Recycle
 An
ecosystem
survives by a
combination of
energy flow and
matter recycling.
Figure 3-14
BIODIVERSITY
Figure 3-15
Biodiversity Loss and Species
Extinction: Remember HIPPO
H
for habitat destruction and degradation
 I for invasive species
 P for pollution
 P for human population growth
 O for overexploitation
Why Should We Care About
Biodiversity?
 Biodiversity



provides us with:
Natural Resources (food water, wood, energy,
and medicines)
Natural Services (air and water purification, soil
fertility, waste disposal, pest control)
Aesthetic pleasure
Solutions
 Goals,
strategies
and tactics for
protecting
biodiversity.
Figure 3-16
ENERGY FLOW IN ECOSYSTEMS
 Food
chains and webs show how eaters, the
eaten, and the decomposed are connected to
one another in an ecosystem.
Figure 3-17
Food Webs
 Trophic
levels are
interconnected
within a more
complicated food
web.
Figure 3-18
Energy Flow in an Ecosystem: Losing
Energy in Food Chains and Webs
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.
 In
Energy Flow in an Ecosystem: Losing
Energy in Food Chains and Webs
 Ecological
efficiency: percentage of
useable energy transferred as biomass
from one trophic level to the next.
Heat
Tertiary
consumers
(human)
Heat
Decomposers
Heat
10
Secondary
consumers
(perch)
Heat
100
1,000
Primary
consumers
(zooplankton)
Heat
10,000
Producers
Usable energy (phytoplankton)
Available at
Each tropic level
(in kilocalories)
Fig. 3-19, p. 66
Productivity of Producers:
The Rate Is Crucial
 Gross
primary
production
(GPP)

Rate at which an
ecosystem’s
producers
convert solar
energy into
chemical energy
as biomass.
Figure 3-20
Net Primary Production (NPP)
 NPP
= GPP – R
Rate at which
producers use
photosynthesis to
store energy minus
rate at which they
use some of this
energy through
respiration (R).
Figure 3-21
 What
are nature’s three most productive and
three least productive systems?
Figure 3-22