AP ENVIRONMENTAL SCIENCE: CHAPTER 5 ECOSYSTEMS: ENERGY, PATTERNS,
AND DISTURBANCE
NAME: _________________
I. Characteristics of Ecosystems
A. Trophic Levels, Food Chains, and Food Webs
B. Trophic Categories
1. Producers
2. Consumers
3. Decomposers
4. Limits on Trophic Levels
II. The Flow of Energy in Ecosystems
A. The Fate of Food
B. Energy Flow and Efficiency
C. Aquatic Systems
III. From Ecosystems to Global Biomes
A. The Role of Climate
1. Biome Examples
2. Examples of Aquatic Systems
B. Microclimate and Other Abiotic Factors
1. Biome Productivity
IV. Ecosystem Responses to Disturbance
A. Ecological Succession
1. Primary Succession
2. Secondary Succession
3. Aquatic Succession
B. Disturbance and Resilience
1. Fire and Succession
2. Long-Term Ecosystem Studies
3. Resilience
V. Human Values and Ecosystem Sustainability
A. Appropriation of Energy Flow
B. Involvement in Nutrient Cycling
C. Value of Ecosystem Capital
1. Using Ecosystem Value in Decision Making
2. A New Look
D. Can Ecosystems Be Restored?
E. The Future
F. Managing Ecosystems
Learning Objectives:
1. Characteristics of Ecosystems: Describe how matter and energy flow through ecosystems
by moving from one trophic level to another.
2. The Flow of Energy Through the Food Web: Explain three main ideas relating trophic
pyramids with the relative numbers and biomasses of different levels in a food chain.
3. From Ecosystems to Global Biomes: Define and recognize characteristics of major
aquatic regions called biomes, major aquatic regions, and factors that determine their
placement on the globe.
4. Ecosystem Responses to Disturbance: Explain the effects of ecological disturbances, such
as a fire or volcanic eruption, which are normal in ecosystems and can even be beneficial.
5. Human Values and Ecosystem Sustainability: Describe ways that humans alter ecosystem
services both positively and negatively, and explain why we need to manage ecosystems
to protect their components from overuse.
Instructional Goals:
1. All ecosystems contain communities that include a variety of species interacting with
each other and with the abiotic factors in the ecosystem.
2. Energy flows from the source (typically the sun) through producers and eventually to
higher and higher levels of consumers in each ecosystem. Producers always have the
greatest biomass in the environment while each additional feeding level must occupy less
biomass.
3. There are patterns in ecosystems throughout global regions. These patterns, based on
climate, determine which types of organisms will not only survive but also thrive in each
region.
4. Although ecosystems depend on balance, they are also usually able to adjust to
disturbances and return to their normal state through the process of succession.
5. Because of the unique place that humans occupy in the ecosystem, our evaluation of the
Earth’s natural services and our use and/or abuse of the Earth’s resources is necessary for
sustainable living.
Concepts and Connections:
Processes such as photosynthesis and respiration in organisms lead to the complex
interplay between members of an ecosystem, particularly related to feeding. Ecosystems can
change over time in response to selective pressures but also in response to natural disturbances
and disturbances caused by humans. An ecosystem will be at different stages of succession,
usually caused by a disturbance, at any given point in time. The result of different successional
stages within an ecosystem is that the ecosystem will be more diverse than an ecosystem in a
single stage of succession. Current succession theory does not describe any ecosystem in a single
stage of succession. Undisturbed areas, agricultural lands, parks, abandoned fields, golf courses,
and landscaped areas around homes or businesses can be compared to provide students with an
understanding of the impact of ecosystem simplification.
Key Terms and Vocabulary:
biomes, trophic levels, productivity, consumption, food chains, food web, autotrophs,
heterotrophs, decomposers, chlorophyll, chemosynthesis, primary production, primary
consumers, herbivores, secondary consumers, carnivores, omnivores, detritus, fermentation,
anaerobic, biomass, biomass pyramid, cellulose, bioaccumulate, biome, temperate deciduous
forest, grassland, prairie, desert biome, tropical rain forest, coniferous forest biome, permafrost,
tundra biome, microclimate, disturbance, ecological succession, facilitation, climax ecosystem,
primary succession, secondary succession, aquatic succession, fire climax ecosystems, resilience
mechanisms, feedback loops, incremental value, ecosystem management
Discussion, Activities, and Labs:
1. To discuss how ecological succession can be extended to include human created
environments, divide the class into groups of three to four students. Have the students apply
ecological succession to the succession process observed in your home city. Examples of
succession in cities would include the changes that occur over time including how
neighborhoods change, industrial areas changing from manufacturing to providing services,
revitalization of downtown areas, open space becoming malls and housing, and so forth. Is
the succession observed in cities sustainable? How could you make a city sustainable? What
would be an ideal climax urban ecosystem? (Describe the components of a “perfect” city.)
2. Secondary succession can be easily demonstrated if you are willing to begin the process
during one class session and check the site periodically over the next month. (This activity
needs to be done during a portion of the term when the weather is favorable for plant
growth.) Find a location where plants are currently growing. Have each student stake a small
area and scrape all the plants from the area. The bare soil should be surrounded by plants that
have not been removed. Every few days the area should be watered (if needed) and the
students should periodically (at least once per week) record any changes to their area. Within
a short period of time plants should return to the bare area, demonstrating the first sequence
in secondary succession.
Introduction:
http://www.youtube.com/watch?v=Lf1PWap_GTw Mt Pinatuba eruption 1991
http://www.youtube.com/watch?v=f1ztg0wUqKY Live footage Icelad volcano 2010
How did volcanoes in Iceland and the Philippines change the environment to lesser or
greater extents?
The volcanic eruption in Iceland had less impact on humans and the environment
compared to that in the Philippines because it did not have large lava flows and mudslides
associated with it. However, the eruption in Iceland did cause the skies in the vicinity to be
filled with ash (disrupting air traffic) and ash covered the ground, affecting grazing animals.
The eruption in the Philippines, thankfully, was predicted and an evacuation of humans
took place. It did, however, have destructive and had long-term effects beyond those seen in
Iceland because of the accompanying mudslides that it produced.
Can you identify any eruptions in North America in the last 40 years?
Mt St Helens
I. Characteristics of Ecosystems
Name and describe the attributes of the two categories into which all organisms can
be divided based on how they obtain nutrition.
The two categories that organisms can be divided into (based on nutrition source) are
autotrophs and heterotrophs. Autotrophs “produce the organic compounds they need to
survive and grow. Green plants, photosynthetic single-celled organisms, and chemosynthetic
bacteria are autotrophs.”
Heterotrophs, on the other hand, include all other organisms that “feed on organic matter
as their source of energy.”
All ecosystems contain communities that include a variety of species interacting with
each other and with the abiotic factors in the ecosystem. “Ecosystems that have a
similar type of vegetation and similar climactic conditions are grouped into broader
areas called biomes.”
A. Trophic Levels, Food Chains, and Food Webs—All members of an ecosystem are
dependent upon those organisms that have the ability to undergo photosynthesis
or chemosynthesis. Food produced by those who do such processes provides food
energy for all the consumers in various tropic (eating) levels.
B. Trophic Categories— Name and describe the roles of the three main trophic
categories that make up the biotic structure of every ecosystem. Give examples of
organisms from each category.
See Table 5-3.
1. Producers—are organisms capable of converting radiant energy or chemical
energy into carbohydrates. This group of producers includes green plants and
algae, both of which can carry out photosynthesis.
http://www.youtube.com/watch?v=D69hGvCsWgA Hydrothermal vents to
4.20
A few autotrophs make food from inorganic chemicals in anaerobic
environments (without oxygen), through the process of chemosynthesis. This
is only carried out by a few simple bacteria, chemotrophs, some of which are
found in hydrothermal vents deep in the ocean. The unbalanced reaction is
with the use of chemicals such as sulphur to release chemical potential energy
and heat energy.
2. Consumers—“All organisms in the ecosystem other than the producers feed
on organic matter as their source of energy.” Consumers can be divided into
primary consumers (herbivores), omnivores, secondary consumers, higher
order consumers, and parasites. Examples of consumers include all animals,
fungi, and most bacteria, even parasitic plants.
3. Decomposers—Decomposers include scavengers, detritus feeders, and
chemical decomposers. They “use organic matter as a source of both energy
and nutrients” by “breaking down detritus into carbon dioxide, water, and
mineral nutrients.” Examples of decomposers include scavengers, like
vultures, and other detritus feeders like earthworms, some species of fungi and
also some bacteria and other microbes.
Describe different members of the decomposition food web.
Members of the decomposition food web include scavengers, detritus feeders, and
chemical decomposers.
“Scavengers eat larger dead things” and “may also eat living (things) some of the time.”
Detritus feeders are “organisms that feed directly on detritus,”
and chemical decomposers can include “fungi and bacteria that cause rotting.”
An interesting example is Trichonympha in the gut of termites.
https://www.youtube.com/watch?v=NOzwGSAPpmo
Give four categories of consumers in an ecosystem and the role that each plays.
Consumers can be divided into primary consumers (herbivores), omnivores,
secondary consumers (carnivores), higher orders of consumers, and parasites.
Primary consumers “feed directly on producers.”
“Animals that feed on primary consumers are called secondary consumers.” Each level of
consumer feeds on the level before.
Higher level consumers (like humans) may be found in several levels at the same time.
Parasites may become “associated with another plant or animal and feed on it over and
extended period of time.”
Each organism has a place in the food web and such predator-prey relationships help to
keep the ecosystem in balance.
Differentiate among the concepts of food chain, food web, and trophic levels.
Food chains “describe where the energy and nutrients go as they move from one
organism to another.
The food web is “all food chains” that are “interconnected and form a complex web of
feeding relationships.”
Trophic levels are feeding levels in an ecosystem.
Examine and understand the 2 below and then create your own complex food webs
for a different terrestrial and aquatic food web. This is to be handed in for grading. It
may be electronic or on paper.
4. Limits on Trophic Levels—There is a limit to the number of trophic levels
possible in an ecosystem. Each higher level comprises approximately 10% of
the biomass of the previous level, making it difficult to have more than three
to four levels in a biomass pyramid. See Figure 5-7.
II. The Flow of Energy in Ecosystems
Energy flows from the source (typically the sun) through producers and eventually to
higher and higher levels of consumers in each ecosystem. Producers always have the
greatest biomass in the environment while each additional feeding level must occupy
less biomass.
A. The Fate of Food—As food moves through an organism it is used by that
organism either for energy or for the building of muscles and tissue. Any material
that cannot be used by the consumer is excreted as waste and cycled back into the
environment.
B. Energy Flow and Efficiency—“When energy flows from one trophic level to the
next, only a small fraction is actually passed on.” This phenomenon can be
explained by three things: “1) much of the preceding trophic level is biomass that
is not consumed by herbivores, 2) much of what is consumed is used as energy to
fuel the heterotroph’s cells and tissues and, 3) some of what is consumed is
undigested and passes through the organism as waste.”
C. Aquatic Systems—Producers and consumers can also be found in aquatic
ecosystems; however, the “transfer of energy is often more efficient in aquatic
ecosystems” and “aquatic ecosystems do not result in the same kind of biomass
pyramid as the terrestrial ecosystems.” Aquatic ecosystems typically have a
“reverse pyramid” compared to terrestrial ecosystems.
Explain Figure 5-8
III. From Ecosystems to Global Biomes and Aquatic life zones.
Because different areas on earth differ so much in their abiotic and biotic
components, we can easily place them in broad categories. Ecosystems on land are
called biomes and aqueous environments are known as aquatic life zones.
Describe how differences in climate cause Earth to be partitioned into major biomes.
A biome is “a large geographic biotic community usually named after the dominant
type of vegetation.” Climatic factors such as temperature and precipitation
determine which types of organisms are capable of surviving in a given area and also
carve out the Earth’s ecosystems into what are called biomes
A. The Role of Climate—The average temperature and amount of precipitation that
falls each year determine the biome of an ecosystem. Climate determines in large
part what the dominant species of an area will be.
Complete the table below to make your own summary of the main facts that you
should be familiar with in a biome
Biome
Annual
Soil type
Major
World location
rainfall
vegetation
Deciduous
forest
(temperate and
tropical)
Tropical
rainforest
Grasslands
Coniferous
forest (Taiga)
Tundra
Chaparral
(scrub forest)
Deserts (cold
and hot)
50 – 75cm
mostly in
winter
Soil is
shallow an
infertile
Small trees
with large
hard leaves,
spiny shrubs
Western North
America and
Mediterranean
region.
Examples of Aquatic Systems—Although aquatic ecosystems are not considered biomes, they
are important ecosystems and are classified according to Table 5-2.
1. Microclimate and Other Abiotic Factors. See Figure 5-12.
What are three situations that might cause microclimates to develop within an ecosystem?
A microclimate describes “the conditions found in a specific localized area...that result in
variations of ecosystems within a biome.” Three situations that might cause a microclimate
include: changes in elevation, soil type, and topography. Elevation effects the temperature of
the microclimate whereas soil type and topography “contribute to the availability of
moisture” in the microclimate. Since biomes are delineated by temperature and precipitation,
these factors can exceptions to the typical biome properties within a particular area.
2. Biome Productivity—Some biomes are more productive than others. See Figure 5-13.
Record one interesting piece of information that you find upon examining these graphs.
a)
b)
c)
Aquatic ecosystems
These are categorized mainly by salinity of their water. Fresh water and salt water falling into
separate categories.
Complete the table to compare major aquatic systems.
Aquatic
Environmental
Dominant
system/life zone parameters
vegetation
Dominant animal
life
Distribution
In reality biomes blend into each other; they do not have distinct boundaries.
What are ecotones? Transitional areas where ecosystems meet.
What are ecozones? Also called ecorerions! Smaller regions within ecosystems that share similar
physical characteristics.
http://canadianbiodiversity.mcgill.ca/english/ecozones/index.htm Canada’s ecozones.
What ecozone do we live in?
What ecozone is Ottawa in?
What are the following 2 laws and how do they relate to the study of ecosystems?
The Law of Tolerance – describes the degree to which organisms are capable of tolerating
changes in their environment. This concept is one of the bases for natural selection.
The Law of Minimum states that living organisms will continue to live, consuming available
materials until the supply of these materials is exhausted.
IV. Ecosystem Responses to Disturbance
Although ecosystems depend on balance, they are also usually able to adjust to
disturbances and return to their normal state through the process of succession.
How do disturbances allow for ecological succession?
Disturbances (e.g., fire, tornadoes, and hurricanes) can remove plants and animals from
an area, returning the area to an earlier stage of succession. Fire can increase the quantity of
light reaching the forest floor by reducing the density of the canopy. Fire can also be
necessary the reproduction of some trees. For example, the fire pines do not release their
seeds without fire, and the seeds need to germinate on bare soil. Patchiness results from
having different areas of an ecosystem in different successional stages. Because each
successional stage has a different array of species, a mosaic of successional stages creates an
ecosystem with more species present; biodiversity is enhanced by a mosaic ecosystem
structure.
Explain Ecological Succession. Include the terms; primary succession, secondary
succession, pioneer species, climax community, facilitation, aquatic succession.
Ecological succession is the transition from one biotic community to another. Because
niches and habitats form during the transition from one biotic community to another,
circumstances are favorable for the existence of a large number of species. See
1. Primary Succession—If an area has not been occupied by organisms
previously, the initial invasion and progression from one biotic community to
the next is called primary succession. Soil and soil organisms do not exist
prior to the beginning of the succession process. See Figure 5-14.
2. Secondary Succession—If an area has been occupied by organisms previously
and something has occurred to leave only the bare soil, then the invasion and
progression from one biotic community to the next is called secondary
succession. Soil and soil organisms exist prior to the beginning of this
succession process. See Figure 5-15.
3. Aquatic Succession—Succession can take place in lakes and ponds as well.
When soil particles “erode from the land and settle out” they can fill aquatic
ecosystems in over time, turning them into ecosystems that are partially
terrestrial. See Figure 5-16.
Create a flow diagram to show Ecological Succession from bare rock to a deciduous
forest. P. 73 PR
A. Disturbance and Resilience—Disturbances provide habitat for a wide array of
species. In any area, there are likely to be all stages of succession represented
because of large and small disturbances.
1. Fire and Succession— what role may fire play in ecological succession and
how may fire be used in the management of certain ecosystems?
https://www.youtube.com/watch?v=CQ2Xl6ZqzRI
Fire is a necessary factor for a diverse number of species. Certain species, for
example the fire pines, are dependent upon fire. Without fire their cones do
not open and the bare ground necessary for seed germination does not exist.
Other species are adapted to fire conditions. Fire helps to maintain a balance
between species or may release nutrients that have not decomposed because of
arid conditions. Fire creates pockets of secondary succession.
“Fire is being increasingly used as a tool in the management of” grasslands
and pine forests. “In pine forests, if ground fires occur every few years,
relatively little deadwood accumulates. With only small amounts of fuel, fires
usually just burn along the ground, harming neither pines nor wildlife
significantly.” In forests where fires have not occurred for many decades,
however, deadwood accumulates and if a fire does break out, it will almost
certainly become disastrous.
2. What is meant by ecosystem resilience? What can cause it to fail? How does
this relate to environmental tipping points? See Figure 5-19
“The ability of an ecosystem to return to normal functioning after a
disturbance is resilience.” Resilience mechanisms are “the processes of
replenishment of nutrients, dispersion by surrounding plants and animals,
rapid re-growth of plant cover and succession to a forest.” Resilience can fail
when soil is lost through deforestation, overgrazing, and other devastating
factors.
V. Human Values and Ecosystem Sustainability
Due to the unique place that humans occupy in the ecosystem, our evaluation of the
Earth’s natural services and our use and/or abuse of the Earth’s resources is necessary
for sustainable living.
A. Appropriations of Energy Flow—
How much of Earth’s primary productivity is used or pre-empted by humans?
Since humans are at the top of the biomass pyramid it can be expected that a very high
percentage of Earth’s primary productivity is used by humans and other top level organisms.
However, because of their place in the ecosystem and tendency to treat the ecosystem in an
un-sustainable fashion, humans use and preempt the Earth’s primary productivity at
unreasonably high rates—approximately 30% of the earth’s total production.
B. Involvement in Nutrient Cycling—Human intrusion into the natural cycle of
nutrients “is substantial” and “has long term consequences.”
C. Value of Ecosystem Capital—“Goods and services we derive from natural
systems are ecosystem capital.” The Earth provides very important services
naturally that would cost us a lot of money to replace. See Table 5-3.
1. Using Ecosystem Value in Decision Making—Once we know the value that
natural systems provide we can use that value to make smart decisions about
whether to disrupt an ecosystem to replace it with a different one for human
benefit. Unfortunately, when we disrupt natural systems we replace them with
less efficient and less economical systems.
2. A New Look—“In 2002, a new team looked at the 1997 team's calculation of
value and examined the benefit-cost consequences of converting ecosystems
to more-direct human uses.… In every case, the net balance of value was a
loss—that is, services lost outweighed services gained.”
D. Can Ecosystems Be Restored? Our ability as humans to “fix” mistakes we have
made in the ecosystem is determined by whether 1) abiotic factors in the
ecosystem are unaltered, 2) viable native species are still available and, 3) lack of
introduced species.
E. The Future—“To turn human efforts in a sustainable direction, we need to protect
or manage the natural environment in a way that maintains the goods and services
vital to the human way of life, and we need to manage ourselves.”
F. Managing Ecosystems—“Good ecosystem management is based on
understanding how ecosystems function, how they respond to disturbances, and
what goods and services they can best provide to the human societies living in or
around them.”
Examine the key messages from the Millennium Ecosystem Assessment’s Governing Board,
and evaluate how these points affect you now and will impact you and your children in the
future.
“At the heart of this assessment is a stark warning. Human activity is putting such a strain
on the natural functions of Earth that the ability of the planet’s ecosystems to sustain future
generations can no longer be taken for granted.” “We are living off the future…. Human
well-being apparently now depends on drawing down the ecosystem capital that provides the
goods and services; agricultural soils erode, fish stocks decline, forests shrink, and pollution
of land, water, and air increases. This situation is unsustainable.”
It is very likely that the current generation of college students will see substantial changes
in how we live our lives. The changes will either be ones we choose or ones that are forced
upon us. If we choose to begin living in a more sustainable manner we and future generations
will have more pleasant lives. We need to eliminate our wasteful lifestyles. The structure of
our cities needs to change; transportation cannot be via the automobile, homes cannot be
large stand-alone structures that are distant from other dwellings, and food needs to be
locally grown. If we don’t change how we live, mass starvation and death are likely to occur.
Thinking Environmentally:
# 2. Look at the following description of a broad global region and describe what the biome
name and main biota would be and how you know; 40 centimeters (16 inches) of
precipitation a year, seasons, frozen much of the year, high winds.
This type of biome would be described as tundra. Because of the relatively low amount of
precipitation in the area and cold temperatures (causing freezing through most of the year),
the main producers that would be able to survive in this biome would be “low-growing
sedges, dwarf shrubs, lichens, mosses, and grasses.” Consumers would include “lemmings,
arctic hares, arctic foxes, lynx, caribou, insects, and migrant shorebirds.”
1. Consult the Web site www.ecotippingpoints.org , and read several of the success stories from
the site. Compare the tipping points as presented and explain the common properties of the
tipping points.
Put your answer on Turnitin
From the web site: “What is an Ecotipping Point? An ‘ecotipping point’ is a point in a
linked eco-social system where a small action can catalyze major changes in the system’s
health.”
“A tipping point is a lever that sets a system moving in a better direction or a worse one.
An invasive species like water hyacinth may degrade a lake, by choking out native plants.
But introducing a creature that feeds on the hyacinth may tip aquatic plants back into
balance.”
“Tipping points work by stimulating feedback loops. These are mutually reinforcing
cycles of cause and effect. Plants and animals contain hundreds of biological feedback loops,
keeping parameters like body temperature and blood sugar in healthy balance. Ecological
feedback loops regulate plant and animal populations in an ecosystem, so they can continue
working together as a whole.”
“Through history, many human societies have worked in harmony with feedback loops,
reaping nature’s bounty while respecting nature’s boundaries. But critical social changes—in
technology, values, organization and institutions—can disrupt the interplay of these forces.
Then, feedback loops may amplify the disruption, until an eco-social system slides from
healthy function into devastating decline.”
“Once tipped, a system can spiral downward with surprising speed. On the Great Plains
in the 1930s, interlocking feedback loops of overgrazing, declining crop yields, wind erosion,
and foreclosures of farmers' mortgages produced the eco-social collapse of the Dust Bowl.
The good news is that, once a system is tipped the right way, the multiplier effect of feedback
loops can speed its recovery. Nature does much of the work, instead of cumbersome
technological fixes. As recovery gains momentum, it can spin off further helpful feedbacks.”
“The ecotipping point’s paradigm is like a lens. It helps us focus on the systemic causes
behind environmental problems. It also helps focus on the core solutions behind
environmental success stories, so that we can apply them to other problems.”
Ecotipping points are not magic bullets to solve environmental problems overnight. What
they can do is set eco-social systems moving in the right directions, so that nature—and
human nature—can take over the work of healing themselves. Moreover, they’re not visions
of a utopian future. They’re at work, even now.