SCI207 Week1 Sustaining Biodiversity and Ecosystems Prior to beginning work on this assignment, read Chapters 1 and 4 in the Turk and Bensel’s Contemporary

SCI207 Week1 Sustaining Biodiversity and Ecosystems Prior to beginning work on this assignment, read Chapters 1 and 4 in the Turk and Bensel’s Contemporary Environmental Issues textbook (2014).

The purpose of this assignment is twofold: first, to enable you to explore a term (concept, technique, place, etc.) related to this week’s theme of sustaining Earth’s biodiversity and ecosystems; second, to provide your first contribution to a collective project, the Class Sustainable Living Guide. Your work this week, and in the weeks that follow, will be gathered (along with that of your peers) into a master document you will receive a few days after the end of the course. The document will provide everyone with a variety of ideas for how we can all live more sustainably in our homes and communities.

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SCI207 Week1 Sustaining Biodiversity and Ecosystems Prior to beginning work on this assignment, read Chapters 1 and 4 in the Turk and Bensel’s Contemporary
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To complete this assignment, you will

Select a term from the list of choices in the Week 1 – Term Selection. Reply to the forum with the term that you would like to research. Do not select a term that a classmate has already chosen. No two students will be researching the same topic.
Download the Week 1 Assignment Template and replace the guiding text with your own words based upon your online research. Please do not include a cover page. All references, however, should be cited in your work and listed at the end, following APA format expectations.

In the template, you will

Define the term thoroughly.
Clearly relate the term to the week’s theme.
Explain how the term affects living things and the physical world.
Relate the term to the challenge of achieving environmental sustainability.
Justify if the term represents an obstacle to that goal, or perhaps a technique or technology that might promote it.
Suggest two specific actions we can take to promote sustainability in relationship to this term.
Provide detailed examples to support your ideas.

Please do not include a cover page, or even place your name directly on the work. In addition to submitting this assignment to Waypoint, you will also be submitting it for anonymous peer review by classmates in Week 2.

The Sustaining Biodiversity and Ecosystems assignment

Must be a minimum of three paragraphs in length (not including title, any quoted text, or references) and formatted according to APA style as outlined in the Ashford Writing Center’s APA Style (Links to an external site.)Links to an external site. resource.
Must utilize academic voice. See the Academic Voice (Links to an external site.)Links to an external site. resource for additional guidance.
Must use at least two credible and/or scholarly sources in addition to the course text. To receive optimal credit, use at least one scholarly source from a peer-reviewed academic journal. To aid you in your research, and particularly in locating scholarly sources via the Ashford Library or using Google Scholar, please review the following Ashford videos and tutorials:
Scholarly and Popular Resources (Links to an external site.)Links to an external site.
Database Search Tips (Links to an external site.)Links to an external site.
Research, Keywords, and Databases: An Overview (Links to an external site.)Links to an external site.
Accessing Full Text and Citation in Google Scholar (Links to an external site.)Links to an external site.
The Scholarly, Peer Reviewed, and Other Credible Sources (Links to an external site.)Links to an external site. table offers additional guidance on appropriate source types. If you have questions about whether a specific source is appropriate for this assignment, please contact your instructor. Your instructor has the final say about the appropriateness of a specific source for a particular assignment.
Must document any information used from sources in APA style as outlined in the Ashford Writing Center’s Citing Within Your Paper guide. (Links to an external site.)Links to an external site.
Must include a separate references list that is formatted according to APA style as outlined in the Ashford Writing Center. See the Formatting Your References List (Links to an external site.)Links to an external site. resource in the Ashford Writing Center for specifications. Ecosystems
Learning Objectives
After studying this chapter, you should be able to:

Identify the different terrestrial and aquatic biome types that cover the planet and explain why they
might differ in terms of biodiversity and species richness.

Explain how nutrients, such as nitrogen and phosphorous, cycle within ecosystems and how human
activities are altering the flow and location of these nutrients, often with unintended consequences.

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Describe how energy produced through photosynthesis forms the basis for most life on the planet and
how this energy flows through different trophic levels in an ecosystem.
Understand the difference in life history strategy between different organisms, including those between
r-selected and K-selected species.
Explain the concepts of niche, limiting factor, keystone species, and trophic cascades and how these
relate to the functioning of ecosystems and the species within them.
Discuss how interactions between different species in an ecosystem (such as predators and their prey)
result in evolutionary changes in these organisms and how ecosystem change and succession over time
alters the balance of species present in a given location.
Describe how toxic substances like mercury can find their way into natural environments far from any
source and impact wildlife populations in that area.
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1. Which biome would be expected to have the warmest and wettest conditions?
a. Coniferous forest
b. Desert
c. Tropical forest
d. Temperate grassland
2. The major sources of human emissions of the pollutant mercury are
a. disposal of thermometers and hospital waste.
b. car and truck exhaust.
c coal burning and gold mining.
d. agriculture and cattle ranching.
3. Which of the following is NOT an example of an important biogeochemical cycle?
a. The water cycle
b. The phosphorous cycle
c. The solar cycle
d. The carbon cycle
4. The population biology concept that refers to the maximum number of organisms that a
given environment can support is
a. survival rate.
b. reproductive rate.
c. K-selection.
d. carrying capacity.
5. When a top predator is removed from an ecosystem it can have dramatic impacts on the
entire food web. These impacts are referred to as
a. biomagnification.
b. bioaccumulation.
c. trophic cascades.
d. photosynthesis.
6. Which of the following is NOT an example of an avoidance/escape feature used to deter
predators from attacking prey?
a. A panda feeding only on bamboo
b. Fish swimming in a school
c. Wildebeests moving in a herd
d. A moth with false eye spots on its hind wings
7. Because mercury tends to accumulate in an animal’s tissue, we would expect what kinds
of organisms to carry the highest amounts of this toxin?
a. Long-lived predators
b. Primary producers
c. Short-lived predators
d. Detritivores
ben85927_01_c01.indd 24
tropical forest. The answer can be found in section 1.1.
coal burning and gold mining. The answer can be found in section 1.2.
the solar cycle. The answer can be found in section 1.3.
carrying capacity. The answer can be found in section 1.4.
trophic cascades. The answer can be found in section 1.5.
a panda bear feeding only on bamboo. The answer can be found in section 1.6.
long-lived predators. The answer can be found in section 1.7.
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Anyone who has spent time outdoors in a favorite patch of forest or other natural setting
might gain an appreciation for the complexity of life present in these ecosystems. Though
silent and invisible to us, trees and other plants are busy converting sunlight into stored
energy through photosynthesis. Birds, insects, and other creatures are on the move searching
for food or themselves ending up as food for other organisms. Some of these ecosystems seem
little changed over time while others might undergo rapid and dramatic transformation over
the course of only a few years. For example, mature forests might change little from year to
year, while shallow lakes gradually fill with sediment and slowly morph into swamps. Such
changes to ecosystems move ecologists to investigate the mechanisms that maintain stability
in some systems like the forest, yet promote change in others like the lake. Indeed, ecology is
the study of all natural systems, including the forest and the lake.
Ecologists study the relationships between living organisms and the physical environment.
For example, in an ecosystem, plants compete with one another for sunlight, and some animals eat plants, while others eat plant eaters. Ecologists studying such an ecosystem might
ask questions, such as: What mineral qualities of the soil nourish this particular community
of plants? And, how does competition and predation among all the billions of soil microorganisms affect the nutrient qualities of the soil? Such queries help guide researchers as they
examine the interactions that occur within a particular ecosystem. Furthermore, the knowledge gained from such research helps environmental scientists study the impacts of human
actions on the environment, such as the damage done to a salt marsh by an oil spill or the
impact of air pollution on trees and plants.
This chapter will explore ecology as the study of change and stasis, balance and imbalance, life
and death in all natural systems—rainforests, tundra, grasslands, deserts, rivers, and oceans
that constitute our world. It begins with a review of the concept of biomes, major ecological
communities like forests, deserts, tundra, and oceans. While biomes differ dramatically in
terms of climate and the variety of life present, they all are generally powered by solar energy.
The second section examines how energy enters and flows through different trophic levels in
an ecosystem. The third section considers how nutrients, such as nitrogen and phosphorous,
are cycled within ecosystems. This is followed by an overview of population biology, the study
of how different organisms grow and reproduce in different ways. The fifth section introduces the concepts of niche, limiting factor, keystone species, and trophic cascades, and how
they impact the functioning of various ecosystems. Section 1.6 reviews evolution and natural
selection and how these processes alter the species composition of ecosystems over time. All
of these topics will provide you with a basic foundation in ecology and environmental science
needed to understand the subjects presented in later chapters. To illustrate how the topics
covered in this chapter connect, the final section presents a case history of how mercury contamination is affecting wildlife and ecosystems the world over.
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Earth’s Biomes
Earth’s Biomes
The diversity of life on Earth is vast. Yet ecologists have found that areas on different continents
that share similar climate conditions tend to have similar ecosystem structures and functions.
As a result, ecologists use the concept of a biome to classify large areas of the planet into a small
number of similar units. Biomes include both terrestrial (land-based) and aquatic (in water)
communities. Biomes display huge differences in the number or diversity of species present and
how these species interact with one another. The following section, which has been excerpted
from Habitable Planet: A Systems Approach to Environmental Science by Annenberg Learner,
discusses the different types of biomes and how they are classified. It will help you gain an appreciation for the incredible variety of ecosystems and natural conditions on the planet, and how
conditions shape the diversity of life found in each area.
The reading points out that scientists have determined that a handful of factors—namely temperature, availability of moisture, abundance of light, and availability of nutrients—are the key
influences on the number and variety of organisms in a given ecosystem. Generally speaking,
tropical regions with their warm temperatures, abundance of moisture, and relatively constant
levels of daylight have the highest number and diversity of organisms. Indeed, tropical, moist forest ecosystems make up the terrestrial biome with the highest productivity and diversity of life.
In contrast, polar regions with their frigid temperatures, low moisture conditions, and months of
the year with little or no natural light tend to have the lowest levels of productivity and diversity.
Scientists study all types of biomes in order to learn about the life cycle and optimal conditions
within different types of climates.
By Annenberg Learner
Geography has a profound impact on ecosystems because global circulation patterns and climate zones set basic physical conditions for the organisms that inhabit a given area. The most
important factors are temperature ranges, moisture availability, light, and nutrient availability, which together determine what types of life are most likely to flourish in specific regions
and what environmental challenges they will face.
Earth is divided into distinct climate zones that are created by global circulation patterns. The
tropics are the warmest, wettest regions of the globe, while subtropical high-pressure zones
create dry zones at about 308 latitude north and south. Temperatures and precipitation are
lowest at the poles. These conditions create biomes—broad geographic zones whose plants
and animals are adapted to different climate patterns. Since temperature and precipitation
vary by latitude, Earth’s major terrestrial biomes are broad zones that stretch around the
globe. Each biome contains many ecosystems (smaller communities) made up of organisms
adapted for life in their specific settings.
Land biomes are typically named for their characteristic types of vegetation, which in turn
influence what kinds of animals will live there. Soil characteristics also vary from one biome
to another, depending on local climate and geology. [. . .]
ben85927_01_c01.indd 26
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Earth’s Biomes
Figure 1.1: Global biomes
Earth’s major biomes result primarily from differences in climate. Each biome contains many
ecosystems made up of species adapted for life in their specific biome.
30° N
of Cancer
Tropic of
30° S
Tropical forest
deciduous forest
Tundra (arctic
and alpine)
Polar and highmountain ice
Adapted from U.S. Department of Agriculture Natural Resources Conservation Service. Retrieved from
Aquatic biomes (marine and freshwater) cover three-quarters of the Earth’s surface and
include rivers, lakes, coral reefs, estuaries, and open ocean. Oceans account for almost all of
this area. Large bodies of water (oceans and lakes) are stratified into layers: surface waters
are warmest and contain most of the available light, but depend on mixing to bring up nutrients from deeper levels. The distribution of temperature, light, and nutrients set broad conditions for life in aquatic biomes in much the same way that climate and soils do for land biomes.
Marine and freshwater biomes change daily or seasonally. For example, in the intertidal zone
where the oceans and land meet, areas are submerged and exposed as the tide moves in and
out. During the winter months lakes and ponds can freeze over, and wetlands that are covered
with water in late winter and spring can dry out during the summer months.
There are important differences between marine and freshwater biomes. The oceans occupy
large continuous areas, while freshwater habitats vary in size from small ponds to lakes covering thousands of square kilometers. As a result, organisms that live in isolated and temporary freshwater environments must be adapted to a wide range of conditions and able to
disperse between habitats when their conditions change or disappear.
ben85927_01_c01.indd 27
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Earth’s Biomes
Biomes and Biodiversity
Since biomes represent consistent sets of conditions for life, they will support similar kinds of
organisms wherever they exist, although the species in the communities in different places may not
be taxonomically [the science of classifying animals]
related. For example, large areas of Africa, Australia, South America, and India are covered by savannas (grasslands with scattered trees). The various
grasses, shrubs, and trees that grow on savannas all
are generally adapted to hot climates with distinct
rainy and dry seasons and periodic fires, although
they may also have characteristics that make them
well-suited to specific conditions in the areas where
they appear.
Species are not uniformly spread among Earth’s
biomes. Tropical areas generally have more plant
and animal biodiversity [the diversity of animal and
plant life in a region] than high latitudes, measured
in species richness (the total number of species
present). This pattern, known as the latitudinal biodiversity gradient, exists in marine, freshwater, and
terrestrial ecosystems in both hemispheres. [. . .]
Why is biodiversity distributed in this way? Ecologists have proposed a number of explanations:

ben85927_01_c01.indd 28
. luoman/iStock/Thinkstock
Tropical rainforests produce their own
moisture. Scientists believe that as
these ecosystems are cleared through
deforestation—as shown here in the
Amazon—there is a threshold beyond
which they will no longer produce
enough moisture to sustain themselves.
The result could be conversion of
rainforests to drier savannas.
Higher productivity in the tropics allows
for more species;
The tropics were not severely affected by glaciation and thus have had more time for
species to develop and adapt;
Environments are more stable and predictable in the tropics, with fairly constant
temperatures and rainfall levels year-round;
More predators and pathogens limit competition in the tropics, which allows more
species to coexist; and
Disturbances occur in the tropics at frequencies that promote high successional
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Energy Flows Through Ecosystems
Of these hypotheses, evidence is strongest
for the proposition that a stable, predictable environment over time tends to produce larger numbers of species. For example, both tropical ecosystems on land and
deep sea marine ecosystems—which are
subject to much less physical fluctuation
than other marine ecosystems, such as
estuaries—have high species diversity.
Predators that seek out specific target
species may also play a role in maintaining species richness in the tropics.
Consider This
Recall that as part of the scientific method
scientists regularly formulate and test
hypotheses about how the world works.
Now, note the language used in the previous paragraph about how “evidence is
strongest . . . ” for one proposition over
the others. What does this tell you about
the scientific method and the kind of language and terminology used by scientists
to describe the natural world?
Excerpted from Weeks, S., Moorcoft, P.R. (2007). Unit 4: Ecosystems. The Habitable Planet: A Systems Approach to
Environmental Science. Retrieved from
=0. Used with permission of Annenberg Learner.
Energy Flows Through Ecosystems
Despite the incredible range of conditions that characterize the ecosystems found in different biomes, they all have something in common. With few exceptions, Earth’s ecosystems are
powered by solar energy. Primary producers such as plants and algae use sunlight in a process
known as photosynthesis to convert carbon dioxide and water into glucose (sugars). Glucose
represents a form of stored energy that is used by plants for their own growth and maintenance.
Other organisms can then consume this plant material and use it as a source of energy. Animals,
in turn, can eat the organisms that ate the plants in order to acquire energy. Ecologists use
the concept of trophic levels to study how energy moves through ecosystems. The following
selection adapted from Habitable Planet: A Systems Approach to Environmental Science, by
Annenberg Learner, explains how energy flows through ecosystems and discusses the impact on
the environment. It will introduce you to the critical concept of primary productivity, the basis
for almost all life on the planet.
Trophic levels can be best visualized as a series of steps, with the base made up of large amounts
of primary producers such as plants and algae. These primary producers have the unique ability to transform solar energy from the sun into stored energy in the form of sugars through the
process of photosynthesis. Animals that feed on primary producers are known as primary consumers. An example of a primary consumer is a rabbit that eats grass and then utilizes much of
the energy stored in the grass for its own growth and bodily functions. In order to sustain the
rabbit there must be a huge amount of available grass for it to eat. This is why the trophic level
comprised of primary producers is the largest. However, the animals that eat rabbits and other
primary consumers are fewer in number than rabbits, so their step is smaller than the one below
it that represents plants and algae.
ben85927_01_c01.indd 29
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Energy Flows Through Ecosystems
Ecologists study dynamics between and among trophic levels as well as the concept of primary
productivity to figure out how much energy is available to support the organisms within a particular ecosystem. For example, net primary productivity is the amount of energy available as
plant matter for primary consumers, or the amount left over after plants use some of the energy
from photosynthesis for themselves. The last section made clear that tropical, moist forests are
the most productive of terrestrial biomes. That’s the same as saying that tropical forests have
the highest net primary productivity (NPP). Since it is the NPP of an ecosystem that supports
all life at higher trophic levels, the high NPP in tropical forests helps explain the abundance and
diversity of life in these ecosystems.
One note of clarification regarding the following discussion on bioaccumulation. Bioaccumulation describes an increase, or an accumulation, of a specific pollutant or toxin in an organism
over time. Many toxic substances, such as mercury, are what are known as lipophilic, or having
the tendency to dissolve in fat. Human emissions of mercury from activities like coal burning and
gold mining tend to end up in water bodies. Fish in those water bodies might ingest small amounts
of that mercury, and over time this substance can build up or bioaccumulate in their tissue. When
another organism at a higher trophic level, such as a bear or a fish-eating bird, ingests large numbers of fish, the mercury contained in the fish is transferred higher up the food chain. This process
is known as biomagnification, an increase in the concentration of a pollutant as you move higher
up the food chain. The case history section at the end of this chapter discusses some of the unexpected and troubling ways in which mercury is bioaccumulating in individual organisms, biomagnifying in many food chains, and wreaking havoc on wildlife populations.
By Annenberg Learner
Ecosystems maintain themselves by cycling energy and nutrients obtained from external
sources. At the first trophic level, primary producers (plants, algae, and some bacteria) use
solar energy to produce organic plant material through photosynthesis. Herbivores—animals
that feed solely on plants—make up the second trophic level. Predators that eat herbivores
comprise the third trophic level; if larger…
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