ppt ch37 C&C Communities and Ecosystems.pdf

© 2015 Pearson Education, Inc.
PowerPoint Lectures
Campbell Biology: Concepts & Connections, Eighth Edition
REECE • TAYLOR • SIMON • DICKEY • HOGAN
Chapter 37
Lecture by Edward J. Zalisko
Communities and Ecosystems

Introduction
• Many drugs are derived from plants. For example,
• morphine, a powerful pain reliever, comes from
opium poppies,
• a chemical found in certain Ephedra species
relieves the symptoms of asthma, and
• a drug from foxglove is used to treat congestive
heart failure.
• Common plant stimulants include
• caffeine, found in coffee berries, tea leaves, and
kola nuts, and
• nicotine in tobacco leaves.

Introduction
• Researchers are eagerly testing newly discovered
compounds that show pharmaceutical promise
• against cancer and infectious diseases such as
malaria and HIV,
• as pain relievers and sedatives,
• to promote weight loss, and
• for many other uses.

Introduction
• But why do plants make these substances?
• What is the adaptive value?
• In a community, populations of many different
species interact with each other, and some of these
relationships are potentially harmful.

Figure 37.0-1

Figure 37.0-2
Chapter 37: Big Ideas
Community Structure
and Dynamics
Ecosystem Structure
and Dynamics

COMMUNITY STRUCTURE AND DYNAMICS

37.1 A community includes all the organisms
inhabiting a particular area
• In the hierarchy of life, a population is a group of
interacting individuals of a particular species.
• The next step up is a biological community, an
assemblage of all the populations of organisms
living close enough together for potential
interaction.
• Ecologists define the boundaries of the community
according to the research questions they want to
investigate.

• A community can be described by its species
composition.
• Community ecologists
• seek to understand how abiotic factors and
interactions between populations affect the
composition and distribution of communities and
• investigate community dynamics, the variability or
stability in the species composition of a community
caused by biotic and abiotic factors.

• Community ecology
• is necessary for the conservation of endangered
species and the management of wildlife, game, and
fisheries,
• is vital for controlling diseases, such as malaria,
bird flu, and Lyme disease, that are carried by
animals, and
• has applications in agriculture, where people
attempt to control the species composition of
communities they have established.

37.2 Interspecific interactions are
fundamental to community structure
• Interspecific interactions
• are relationships with individuals of other species in
the community and
• greatly affect population structure and dynamics.
• In Table 37.2, interspecific interactions are
classified according to the effect on the populations
concerned.

Table 37.2

37.2 Interspecific interactions are
fundamental to community structure
• Interspecific competition occurs when
populations of two different species compete for
the same limited resource.
• In mutualism, both populations benefit.
• In predation, one species (the predator) kills and
eats another (the prey).
• In herbivory, an animal consumes plant parts or
algae.
• In parasitism, the host plants or animals are
victimized by parasites or pathogens.

37.3 Competition may occur when a shared
resource is limited
• An ecological niche is the sum of an organism’s
use of the biotic and abiotic resources in its
environment.
• Interspecific competition occurs when
• the niches of two populations overlap and
• both populations need a resource that is in short
supply.
• In general, competition lowers the carrying capacity
of competing populations because the resources
used by one population are not available to the
other population.

Figure 37.3a

Figure 37.3b

37.4 Mutualism benefits both partners
• Reef-building corals and photosynthetic
dinoflagellates provide a good example of how
mutualists benefit from their relationship.
• Photosynthetic dinoflagellates
• gain a secure shelter that provides access to light,
• produce sugars by photosynthesis that provide at
least half of the energy used by the coral animals,
and
• use the coral’s waste products, including carbon
dioxide (CO2) and ammonia (NH3), a valuable
source of nitrogen for making proteins.

Video: Clownfish and Anemone

Figure 37.4

37.5 EVOLUTION CONNECTION: Predation
leads to diverse adaptations in prey species
• Predation benefits the predator but kills the prey.
• Prey adapt using protective strategies that include
• camouflage,
• mechanical defenses, and
• chemical defenses.

Video: Seahorse Camouflage

Figure 37.5a

Figure 37.5b

37.6 EVOLUTION CONNECTION: Herbivory
leads to diverse adaptations in plants
• A plant whose body parts have been eaten by an
animal must expend energy to replace the loss.
• Thus, numerous defenses against herbivores have
evolved in plants.
• Plant defenses against herbivores include
• spines and thorns and
• chemical toxins, often the substances that we use
medicinally or for other purposes.

• Like the chemical defenses of animals, toxins in
plants tend to be distasteful, and herbivores learn to
avoid them.
• Some plants even produce chemicals that cause
abnormal development in insects that eat them.

• Herbivores and plants undergo coevolution, a
series of reciprocal evolutionary adaptations in two
species in which change in one species acts as a
new selective force on another species, and the
resulting adaptations of the second species in turn
affect the selection of individuals in the first
species.
• Figure 37.6 illustrates an example of coevolution
between an herbivorous insect (the caterpillar of
the butterfly Heliconius) and a plant.

Figure 37.6
Decoy
eggs
Heliconius
Eggs

37.7 Parasites and pathogens can affect
community composition
• A parasite lives on or in a host from which it obtains
nourishment.
• Internal parasites include nematodes and tapeworms.
• External parasites include mosquitoes, ticks, and aphids.
• Pathogens are disease-causing microscopic parasites
that include bacteria, viruses, fungi, or protists.
• Plants are also attacked by parasites, including
nematodes and aphids, that tap into the phloem and
suck plant sap.

Figure 37.7

37.7 Parasites and pathogens can affect
community composition
• Non-native pathogens can have rapid and dramatic
impacts.
• The American chestnut was devastated by the
chestnut blight protist.
• A fungus-like pathogen is currently causing sudden
oak death on the West Coast.

37.8 Trophic structure is a key factor in
community dynamics
• Every community has a trophic structure, a
pattern of feeding relationships consisting of
several different levels.
• The sequence of food transfer up the trophic levels
is known as a food chain.
• This transfer of food moves chemical nutrients and
energy from producers up through the trophic levels
in a community.

community dynamics
• Producers are autotrophs that support all other
trophic levels.
• Consumers are heterotrophs.
• Herbivores are primary consumers.
• Secondary consumers
• on land typically eat herbivores and
• in aquatic ecosystems typically eat zooplankton.
• Tertiary consumers typically eat secondary
consumers.
• Quaternary consumers typically eat tertiary
consumers.

Video: Shark Eating a Seal

Figure 37.8
Hawk
Snake
Mouse
Secondary
consumers
Tertiary
consumers
Quaternary
consumers
Grasshopper
Primary
consumers
Producers
Plant
A terrestrial food chain
Zooplankton
Herring
Phytoplankton
An aquatic food chain
Tuna
Killer whale

community dynamics
• Detritivores derive their energy from detritus, the
dead material produced at all the trophic levels.
• Decomposers
• are mainly prokaryotes and fungi and
• secrete enzymes that digest molecules in organic
materials and convert them into inorganic forms in
the process called decomposition.

37.9 VISUALIZING THE CONCEPT: Food
chains interconnect, forming food webs
• A more realistic view of the trophic structure of a
community is a food web, a network of
interconnecting food chains.
• A consumer may eat more than one type of
producer, and several species of primary
consumers may feed on the same species of
producer.
• Some animals weave into the food web at more
than one trophic level.

Figure 37.9-1
Producers provide the chemical
energy and nutrients used by all
other members of the food web.
Prickly pear
cactus
Saguaro
cactus
Mesquite
Producers (plants)

Figure 37.9-2
Prickly pear
cactus
Saguaro
cactus
Mesquite
Producers (plants)
Desert
kangaroo
rat
Harvester
ants
Grasshopper
Primary
consumer
Primary
consumer
Harris’s
antelope
squirrel
Grasshopper
mouse
Producers Primary consumers
To
From
Nutrient Transfer
Gila
woodpecker

Figure 37.9-3
Prickly pear
cactus
Saguaro
cactus
Mesquite
Producers (plants)
Desert
kangaroo
rat
Harvester
ants
Grasshopper
Primary
consumer
Primary
consumer
Harris’s
antelope
squirrel
Grasshopper
mouse
To
From
Nutrient Transfer
Gila
woodpecker
Primary consumers Secondary consumers
Collared lizard
Secondary
consumer
Elf owl
Praying
mantis
Western
diamondback
Primary
and
secondary
consumer
Red-tailed
hawk

Figure 37.9-4
Prickly pear
cactus
Saguaro
cactus
Mesquite
Producers (plants)
Primary consumers Secondary consumers
Collared lizard
Secondary
consumer
Elf owl
Praying
mantis
Western
diamondback
Primary
and
secondary
consumer
Red-tailed
hawk
Desert
kangaroo
rat
Harvester
ants
Grasshopper
Primary
consumer
Primary
consumer
Harris’s
antelope
squirrel
Grasshopper
mouse
Gila
woodpecker
To
From
Nutrient Transfer
Secondary consumers Tertiary consumers
Tertiary consumers Quaternary consumers
Secondary, tertiary,
and quaternary
consumer
Secondary and
tertiary consumer

37.10 Species diversity includes relative
abundance and species richness
• Species diversity is defined by two components:
1. species richness, the number of species in a
community, and
2. relative abundance, the proportional
representation of a species in a community.

Figure 37.10a

Figure 37.10b

Table 37.10

• Plant species diversity in a community often has
consequences for the species diversity of animals
in the community.
• Species diversity also impacts pathogens.
• Most pathogens infect a limited range of host
species or may even be restricted to a single host
species.
• When many potential hosts are living close
together, it is easy for a pathogen to spread from
one to another.

• Low species diversity is characteristic of most
modern agricultural ecosystems.
• To combat potential losses, many farmers and
forest managers rely heavily on chemical methods
of controlling pests.
• Modern crop scientists have bred varieties of plants
that are genetically resistant to common pathogens,
but these varieties can suddenly become
vulnerable, too.

37.11 SCIENTIFIC THINKING: Some species
have a disproportionate impact on diversity
• Ecologist Robert Paine hypothesized that the
species diversity of a community is directly related
to the ability of predators to prevent any one
species from monopolizing local resources.
• To test this hypothesis, Paine
• manually removed a predatory sea star known as
Pisaster from certain areas of the intertidal zone,
• left comparable areas intact as controls, and
• determined the species richness of these
experimental and control areas over the next
several years.

Figure 37.11a

Figure 37.11b
With Pisaster (control)
Without Pisaster (experimental)
’73
’72
’71
’70
’69
’68
’67
’66
’65
’64
1963
Year
0
5
10
15
20
Data from R.T. Paine, Food web complexity and species diversity,
American Naturalist 100:65–75 (1996).
Number
of
species
present

• In the absence of Pisaster, species richness
dropped from more than 15 species to fewer than 5.
• What accounted for the dramatic change?
• A mussel of the genus Mytilus proved to be a
superior competitor for the available space,
eliminating most other invertebrates and algae.
• In the control areas, population growth of Mytilus
was suppressed by Pisaster, a voracious predator
on the mussel.
• Thus, interspecific interactions can be an important
factor in the species diversity of a community.

Figure 37.11c

• Paine’s experiment and others like it gave rise to
the concept of a keystone species, defined as a
species
• whose impact on its community is larger than its
biomass or abundance indicates and
• that occupies a niche that holds the rest of its
community in place.
• Examples in marine ecosystems include
• Pisaster sea stars and
• long-spined sea urchins.

• The word “keystone” comes from the wedge-
shaped stone at the top of an arch that locks the
other pieces in place.
• If the keystone is removed, the arch collapses.
• A keystone species occupies a niche that holds the
rest of its community in place.

Figure 37.11d
Keystone
Keystone
absent

37.12 Disturbance is a prominent feature of
most communities
• Disturbances
• are events that damage biological communities and
• include storms, fires, floods, drought, and human
activity.
• The types of disturbances and their frequency and
severity vary from community to community.

most communities
• Small-scale disturbances often have positive
effects.
• However, communities change drastically following
a severe disturbance that strips away vegetation
and removes significant amounts of soil.

most communities
• The disturbed area may be colonized by a variety
of species, which are gradually replaced by a
succession of other species, in a process called
ecological succession.

most communities
• Primary succession begins in a virtually lifeless
area with no soil.
• Examples of such areas are the rubble left by a
retreating glacier or fresh volcanic lava flows.

Figure 37.12a

most communities
• Secondary succession occurs when a
disturbance destroys an existing community but
leaves the soil intact.
• Whenever human intervention stops, secondary
succession begins.
• Numerous studies have documented the stages by
which an abandoned farm field returns to forest.

Figure 37.12b
Annual
plants
Perennial
plants and
grasses
Time
Shrubs Softwood
trees
Hardwood
trees

37.13 CONNECTION: Invasive species can
devastate communities
• Invasive species
• are organisms that have been introduced into non-
native habitats by human actions and
• have established themselves at the expense of
native communities.
• The absence of natural enemies often allows rapid
population growth of invasive species.

37.13 CONNECTION: Invasive species can
devastate communities
• Examples of invasive species include the
deliberate introduction of
• rabbits into Australia and
• cane toads into Australia.

Figure 37.13a
Key
Frontier of rabbit spread
1860
1870
1
8
9
0
1880
1910
1900
1910
1910
600 km
1980

Figure 37.13b

Figure 37.13c

ECOSYSTEM STRUCTURE AND DYNAMICS

37.14 Ecosystem ecology emphasizes energy
flow and chemical cycling
• An ecosystem consists of
• all the organisms in a community and
• the abiotic environment with which the organisms
interact.
• In an ecosystem,
• energy flow moves through the components of an
ecosystem and
• chemical cycling is the transfer of materials within
the ecosystem.

37.14 Ecosystem ecology emphasizes energy
flow and chemical cycling
• A terrarium
• represents the components of an ecosystem and
• illustrates the fundamentals of energy flow.

Figure 37.14
Energy
flow
Light
energy
Chemical
energy
Chemical
elements
Heat
energy
Bacteria,
protists,
and fungi

37.15 Primary production sets the energy
budget for ecosystems
• The amount of solar energy converted to chemical
energy (in organic compounds) by an ecosystem’s
producers for a given area and during a given time
period is called primary production.
• Ecologists call the amount, or mass, of living
organic material in an ecosystem the biomass.
• Different ecosystems vary in their
• primary production and
• contribution to the total production of the biosphere.

Figure 37.15
Open ocean
Estuary
Algal beds and coral reefs
Desert and semidesert scrub
Tundra
Temperate grassland
Cultivated land
Boreal forest (taiga)
Savanna
Temperate deciduous forest
Tropical rain forest
0 500 1,000 1,500 2,000 2,500
Average net primary production (g/m2/yr)
Data from R.H. Whittaker, Communities and Ecosystems, second edition, New York: Macmillan (1975).

37.16 Energy supply limits the length of food
chains
• A caterpillar represents a primary consumer.
• Of the organic compounds a caterpillar ingests,
about
• 50% is eliminated in feces,
• 35% is used in cellular respiration, and
• 15% is converted to caterpillar biomass.

Figure 37.16a
100 kilocalories (kcal)
Plant material
eaten by caterpillar
50 kcal
15 kcal
35 kcal
Growth
Feces
Cellular
respiration

chains
• A pyramid of production illustrates the cumulative
loss of energy with each transfer in a food chain.
• Only about 10% of the energy stored at each
trophic level is available to the next level. The
efficiencies of energy transfer usually range from 5
to 20%.

Figure 37.16b
Tertiary
consumers
Secondary
consumers
Primary
consumers
Producers
10 kcal
100 kcal
1,000 kcal
10,000 kcal
1,000,000 kcal of sunlight

chains
• An important implication of this stepwise decline of
energy in a trophic structure is that the amount of
energy available to top-level consumers is small
compared with that available to lower-level
consumers.
• Only a tiny fraction of the energy stored by
photosynthesis flows through a food chain all the
way to a tertiary consumer.
• This explains why top-level consumers such as
lions and hawks require so much geographic
territory.

37.17 CONNECTION: A pyramid of production
explains the ecological cost of meat
• As omnivores, people eat plant material and meat.
• When humans eat
• grain or fruit, we are primary consumers,
• beef or other meat from herbivores, we are
secondary consumers, and
• fish like trout or salmon, we are tertiary or
quaternary consumers.

37.17 CONNECTION: A pyramid of production
explains the ecological cost of meat
• Only about 10% of the chemical energy available
in a trophic level is passed to the next higher
trophic level.
• Therefore, the human population has about 10
times more energy available to it when people eat
plants than when they eat the meat of herbivores.
• Eating meat of any kind is expensive
• economically and
• environmentally.

Figure 37.17
Corn
Corn
Cattle
Meat-eaters
Vegetarians
Trophic
level
Secondary
consumers
Primary
consumers
Producers

37.18 Chemicals are cycled between organic
matter and abiotic reservoirs
• Ecosystems are supplied with a continual influx of
energy from the
• sun and
• Earth’s interior.
• Except for meteorites, there are no extraterrestrial
sources of chemical elements.
• Thus, life also depends on the recycling of
chemicals.

37.18 Chemicals are cycled between organic
matter and abiotic reservoirs
• Biogeochemical cycles include
• biotic components,
• abiotic components, and
• abiotic reservoirs, where chemicals accumulate or
are stockpiled outside of living organisms.
• Biogeochemical cycles can be
• local or
• global.

Figure 37.18
Decomposers
Producers
Consumers
Abiotic
reservoirs
Geologic processes
Nutrients
available
to producers
3
2
1
4

37.19 The carbon cycle depends on
photosynthesis and respiration
• Carbon is
• the major ingredient of all organic molecules and
• found
• in the atmosphere,
• in fossil fuels, and
• dissolved in carbon compounds in the ocean.
• The reciprocal metabolic processes of
photosynthesis and cellular respiration are mainly
responsible for the cycling of carbon between the
biotic and abiotic worlds.

Figure 37.19
Wastes; death
Plant litter;
death
Photosynthesis
Cellular respiration
Burning
Wood
and fossil
fuels
Decomposition
Decomposers
(soil microbes) Detritus
Higher-level
consumers
Plants, algae,
cyanobacteria
Primary
consumers
CO2 in atmosphere
5
3
1
2
4

37.19 The carbon cycle depends on
photosynthesis and respiration
• On a global scale, the return of CO2 to the
atmosphere by cellular respiration closely balances
its removal by photosynthesis, but the increased
burning of wood and fossil fuels (coal and
petroleum) is raising the level of CO2 in the
atmosphere.

37.20 The phosphorus cycle depends on the
weathering of rock
• Organisms require phosphorus, usually in the form
of the phosphate ion (PO4
3−), for nucleic acids,
phospholipids, ATP and as a mineral component of
bones and teeth.

weathering of rock
• In contrast to the carbon cycle and the other major
biogeochemical cycles, the phosphorus cycle does
not have an atmospheric component.
• Rocks are the only source of phosphorus for
terrestrial ecosystems.
• Plants absorb phosphate ions in the soil and build
them into organic compounds.
• Phosphates are returned to the soil by
decomposers.
• Phosphate levels in aquatic ecosystems are
typically low enough to be a limiting factor.

Figure 37.20
4
2
1
3
5
6
Weathering
of rock
Uplifting
of rock
Runoff
Phosphates
in rock
Phosphates
in soil
(inorganic)
Assimilation
Phosphates
in solution
Precipitated
(solid) phosphates
Decomposition
Rock
Plants
Animals
Detritus
Decomposers
in soil

weathering of rock
• Because phosphates are transferred from terrestrial
to aquatic ecosystems much more rapidly than they
are replaced, the amount in terrestrial ecosystems
gradually diminishes over time.
• Soil erosion from land cleared for agriculture or
development accelerates the loss of phosphates.
• Farmers and gardeners often use crushed
phosphate rock, bone meal (finely ground bones
from slaughtered livestock), or guano, the droppings
of seabirds and bats, to add phosphorus to the soil.

37.21 The nitrogen cycle depends on bacteria
• Nitrogen is
• an ingredient of proteins and nucleic acids,
• essential to the structure and functioning of all
organisms, and
• a crucial and often limiting plant nutrient.
• Nitrogen has two abiotic reservoirs:
1. the atmosphere, of which about 80% is nitrogen
gas, and
2. soil.

• Nitrogen fixation
• converts N2 to compounds of nitrogen that can be
used by plants and
• is carried out by some bacteria.
• Figure 37.21 illustrates the actions of two types of
nitrogen-fixing bacteria.

Figure 37.21
Plant Animal
Nitrogen (N2) in atmosphere
Organic
compounds
Organic
compounds
Assimilation
by plants
Death; wastes
Detritus
Decomposers
Decomposition
Nitrogen fixation
Nitrogen
fixation
Nitrogen-fixing
bacteria in
root nodules
Free-living
nitrogen-fixing
bacteria
Ammonium (NH4
+)
in soil
Nitrifying
bacteria
Denitrifiers
Nitrates
in soil
(NO3
−)
8
5
3
6
1
4 7
2

• Human activities are disrupting the nitrogen cycle by
adding more nitrogen to the biosphere each year than
natural processes.
• Combustion of fossil fuels in motor vehicles and
coal-fired power plants produces nitrogen oxides
(NO and NO2).
• Modern agricultural is another major source of nitrogen.
• Some nitrogen escapes to the atmosphere, where
it forms NO2 or nitrous oxide (N2O), an inert gas that
lingers in the atmosphere and contributes to global
warming.

37.22 CONNECTION: A rapid inflow of
nutrients degrades aquatic ecosystems
• In aquatic ecosystems, primary production is
limited by low nutrient levels of
• phosphorus and
• nitrogen.
• Over time, standing water ecosystems gradually
accumulate nutrients from the decomposition of
organic matter and fresh influx from the land, and
primary production increases in a process known
as eutrophication.

• Eutrophication of lakes, rivers, and coastal waters
• depletes oxygen levels and
• decreases species diversity.
• In many areas, phosphate pollution leading to
eutrophication comes from
• agricultural fertilizers,
• pesticides,
• sewage treatment facilities, and
• runoff of animal waste from feedlots.

Video: Cyanobacteria (Oscillatoria)

Figure 37.22a

• Nitrogen runoff from Midwestern farm fields has
been linked to a “dead zone” observed each
summer in the Gulf of Mexico.
• Vast algal blooms extend outward from where the
Mississippi River deposits its nutrient-laden waters.
• As the algae die, decomposition of the huge
quantities of biomass diminishes the supply of
dissolved oxygen over an area that ranges from
13,000 to 22,000 km2, or roughly 5,000 to 8,500
square miles.

Figure 37.22b
Winter
Summer

37.23 CONNECTION: Ecosystem services are
essential to human well-being
• Humans rely upon natural ecosystems to
• supply fresh water and some foods,
• recycle nutrients,
• decompose wastes, and
• regulate climate and air quality.

• Wetlands
• buffer coastal populations against tidal waves and
hurricanes,
• reduce the impact of flooding rivers, and
• filter pollutants.
• Natural vegetation helps to
• retain fertile soil and
• prevent landslides and mudslides.

• Ecosystems that we create are also essential to
our well-being. Agricultural ecosystems
• supply most of our food and fibers,
• make use of ecosystem services, such as control of
agricultural pests by natural predators and
pollination of crops, and
• rely upon nutrient cycling to maintain soil fertility, the
foundation for crop growth.

• But agricultural methods introduced over the past
several decades have pushed croplands beyond their
natural capacity to produce food.
• Nutrient runoff affects freshwater and marine ecosystems
as fertilizer use increases.
• Pesticides may kill beneficial organisms as well as pests.
• Clearing and cultivation expose land to wind and water
that erode the rich topsoil. In China, for example,
overgrazing and other poor agricultural practices are
turning 900 square miles of land—an area the size of
Rhode Island—into desert each year.

Figure 37.23a

• Human activities also threaten many forest
ecosystems and the services they provide.
• Forests are also cut down to provide timber and fuel
wood.
• Many people in nonindustrialized countries use
wood for heating and cooking.

Figure 37.23b

• The growing demand of the human population for
food, fibers, and water has largely been satisfied at
the expense of other ecosystem services, but
these practices cannot continue indefinitely.
• Sustainability is the goal of developing,
managing, and conserving Earth’s resources in
ways that meet the needs of people today without
compromising the ability of future generations to
meet theirs.

You should now be able to
1. Define a biological community. Explain why the study of
community ecology is important.
2. Define interspecific competition, mutualism, predation,
herbivory, and parasitism and provide examples of
each.
3. Define an ecological niche. Explain how interspecific
competition can occur when the niches of two
populations overlap.
4. Describe the mutualistic relationship between corals
and dinoflagellates.
5. Define predation. Describe the protective strategies
potential prey employ to avoid predators.

6. Explain why many plants have chemical toxins, spines,
or thorns. Define coevolution and describe an example.
7. Explain how parasites and pathogens can affect
community composition.
8. Identify and compare the trophic levels of terrestrial and
aquatic food chains.
9. Explain how food chains interconnect to form food
webs.
10. Describe two components of species diversity.
11. Define a keystone species.

12. Explain how disturbances can benefit communities.
Distinguish between primary and secondary
succession.
13. Explain how invasive species can affect communities.
14. Compare the movement of energy and chemicals within
and through ecosystems.
15. Compare the primary production of tropical rain forests,
coral reefs, and open ocean. Explain why the
differences between them exist.
16. Describe the movement of energy through a food chain.

17. Explain how carbon, nitrogen, and phosphorus cycle
within ecosystems.
18. Explain how rapid eutrophication of aquatic ecosystems
affects species diversity and oxygen levels.
19. Explain how human activities are threatening natural
ecosystems.

Figure 37.UN01
Killer whale
Tuna
Herring
Zooplankton
Phytoplankton
An aquatic food chain
Quaternary
consumers
Tertiary
consumers
Secondary
consumers
Primary
consumers
Producers

Figure 37.UN02
Autotrophs Heterotrophs
Producer
Energy
Chemical
elements
Herbivore
(primary
consumer)
Carnivore
(secondary
consumer)
Light
Detritus
Decomposer
Inorganic compounds
(chemical elements)

Figure 37.UN03
Approximately 90%
loss of energy at
each trophic level
Energy

Figure 37.UN04

Figure 37.UN05

ppt ch37 C&C Communities and Ecosystems.pdf

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