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Study Guide Exam 1
1. What does the Greek word oikos mean? By the way, the word ecology is derived from
this Greek word.
2. Know the hierarchy of ecological systems, i.e. levels of biological organization.
3. Know definitions: population, community and ecosystem. For ‘ecosystem,’ know both
definitions.
4. Know about experimentation – replication, confounding variables (and how to control –
e.g. greenhouses, incubators, microcosms), control/treatment, microcosms, permanent
plots (and annual data collection to address variation over time), how to address spatial
variation.
5. What does the word phenology mean in “The National Phenology Network”
6. What is iNaturalist and how might data from it be used by ecologists?
7. Read the document (on D2L) related to sea otters and relate the text to figure showing
the interaction of species.
8. Know the sizes of soil particles and how size variation determines field capacity? What
is field capacity?
9. Know about photosynthesis – What organelle does it occur in? What are the reactants
and products?
10. What is photorespiration and what is rubisco’s role in photorespiration?
11. What is the most common form of photosynthesis? What forms of photosynthesis are
found in dry habitats? How does CAM operate daily? In what cells does the Calvin
cycle occur – it differs between C3/CAM and C4?
12. Name some adaptations that plants may have to deal with hot, dry conditions.
13. If a plant wanted to extract additional water from soil, would it increase/decrease solute
concentration in root cells?
14. From the reading on owls posted on D2L, know about the biology of skunk cabbage.
See page 8, Figure 4.8 on the “owl heat regulation text” document on D2L.
15. Name environmental events from smallest to largest spatial scale.
16. What is the relationship between duration and spatial scale of environmental events?
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17. Define phenotypic plasticity, phenotypic trade-off, acclimation, isozymes. What type of
traits respond most rapidly vs least rapidly to the environment?
18. How does root/shoot ratio change in relation to soil water availability?
19. Know about the patter of monarch butterfly migration and the purpose of torpor in
hummingsbirds.
20. What is the solar equator? Where’s the location?
21. Know about Earth’s rotation and how the sun shines on the Earth during the equinox.
22. How does a Hadley cell function? How does it determine wet vs dry habitats? Where
are the wet vs. dry habitats found in relation to the Hadley cell?
23. What is the intertropical convergence zone? How does it determine wet vs dry season
and the timing of these seasons north and south of the equator?
24. What are the major precipitation effects of El Niño–Southern Oscillation around the
globe?
25. Describe a rain shadow and how it influences the environment.
26. Be able to explain the diagram below.
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© 2014 W. H. Freeman and Company
Terrestrial Environments
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Physiological plasticity
Behavioral Plasticity
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Morphological plasticity
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The California sea otter. This once abundant marine mammal has experienced large
fluctuations in numbers as a result of human activities during the past three centuries.
In this first chapter, we have examined a wide range of topics, including the hierarchy of
perspectives in ecology, the biological and physical principles that govern natural systems, the
variety of roles that different species play, the multiple approaches to studying ecology, and the
influence of humans on ecological systems. To help you see how these topics interconnect, let’s
examine a case study of the sea otter (Enhydra lutris) off the Pacific coast. Humans have
affected sea otter populations for hundreds of years. Several scientific approaches have been
taken to understand these effects and to help reverse them.
The sea otter was once abundant, with a geographic range that extended around the northern
Pacific Rim, from Japan up to Alaska and down to Baja California. However, in the 1700s and
1800s, intense hunting for otter pelts reduced the population to near extinction, which caused the
fur industry to subsequently collapse. When a small population was discovered off the coast of
central California in the 1930s, the otters were placed under protection. As a result, the
population increased to several thousand individuals by the 1990s, though in more recent years,
the otter has again experienced population declines. These changes in the size of otter
populations presented an opportunity for scientists to examine a natural experiment in action.
Ecologists quickly realized that to understand the causes and consequences of the sea otter’s
fluctuations in abundance, they needed to use a range of ecological approaches, from the
individual to the ecosystem. Taking an individual approach, ecologists established that the sea
otter was a predator on a wide range of prey species, including abalone, spiny lobsters, small
fish, crabs, sea urchins, and small snails. Among these prey items, observations of otter feeding
behavior revealed that otters prefer certain prey such as abalone, a large species of sea snail.
They will only eat other small species of snails when their preferred prey becomes rare.
Once scientists understood the sea otter’s niche, they were better able to protect it. However, not
everyone was happy about the resurgence of sea otters after they became protected. California
anglers became upset; they argued that the growing otter population would cause a dramatic
change in the marine community, including a drastic reduction in the populations of
commercially valuable fish, clams, abalone, and spiny lobsters — all harvested for human
consumption. While otters do have negative effects on their prey — especially clams —
scientists who took a community approach to ecology found that an increasing otter population
was also having other dramatic effects on the marine community that were positive for many
species of commercially harvested fish and shellfish. For example, otters eat a lot of sea urchins,
which consume giant algae known as kelps. Kelps can grow up to 100 m long, and regions of the
ocean containing large amounts of kelps are called kelp forests. As the growing otter population
caused sea urchins to decrease, the reduction in sea urchins caused predation of kelp forests to
decrease, providing young fishes greater refuge from predators and providing them areas in
which they could feed. Kelps also can be harvested by humans to make fertilizer, food, and
pharmaceuticals, so the increase in otters also allowed an increase in the commercial harvesting
of kelps. Thus, the sea otter plays a key role in determining the community composition of
coastal marine ecosystems.
Sea otters and the species with which they interact. Once scientists determined the major
species in the ocean that affected the abundance of otter populations, they could better protect the
otter from extinction. Solid arrows indicate consumption of one species by another.
In the 1990s, the sea otter population mysteriously began to decline. To understand these
declines, scientists used individual, community, and ecosystem approaches. In 1998, researchers
showed that populations of otters in the vicinity of the Aleutian Islands, Alaska, had declined
precipitously during the 1990s. The reason was that killer whales, or orcas (Orcinus orca), which
previously had not preyed on otters, had begun to come close to shore where they consumed
large numbers of otters. Why did killer whales adopt this new behavior? The researchers pointed
out that populations of the principal prey of killer whales — seals and sea lions — collapsed
during the same period, perhaps causing the whales to hunt the otters as an alternative food
source. Why did the seals and sea lion populations decline? One can only speculate at this point,
but intense human fisheries have reduced fish stocks exploited by the seals and sea lions to levels
low enough to seriously threaten their populations.
There also were declines in otter populations along the California coast. Initially, declines in sea
otters were attributed to the use of gill nets along the coast to exploit a new fishery that
inadvertently killed otters in substantial numbers. Subsequent legislation moved the fishery
farther offshore to help protect the otters. In this same region, the otters were also dying from
infections by two protist parasites, Toxoplasma gondii and Sarcocystis neurona. These parasites
cause a lethal inflammation of the brain. In 2010, for example, 40 dead and dying sea otters were
found near Morro Bay, California, and 94 percent were infected with S. neurona. This was a
surprising observation because the only known hosts of these parasites are opossums (Didelphis
virginiana) and several species of cats. Given that these mammals live on land, how did sea
otters become infected?
Scientists hypothesized links between the terrestrial and marine ecosystems that allowed the
parasites to infect sea otters. To date, two potential links have been suggested. First, house cats
that spend time outside defecate on land and their feces contain the parasites. When it rains, the
parasites get washed into local streams and rivers and eventually end up in the ocean. Second,
when humans flush cat feces and kitty litter down the toilet and into the sewer system, the
wastewater eventually enters the ocean. Although manipulative experiments found that the
protists do not infect marine invertebrates and cause illness, the invertebrates can take the
parasites into their bodies inadvertently while feeding. When invertebrates infested with parasites
are consumed by otters, the otters get infected. New research indicates that abalone do not carry
the parasites, whereas small marine snails do. Thus, when otters have an abundance of their
preferred food, such as abalone, they have a low risk of being infected by the deadly parasite.
When abalone is scarce, however, the otters are forced to feed on small snails that carry the
parasite, which dramatically increases the risk of infection and death.
The story of the sea otter highlights the importance of understanding ecology from multiple
approaches using both manipulative and natural experiments. It also underscores the multiple
roles that species can play in communities and ecosystems and how humans can dramatically
influence these roles. This understanding can then be used to take action to reverse harmful
effects on the environment. In the case of the sea otter, education campaigns now encourage the
public to keep their cats inside more and to put used cat litter into the trash rather than flushing it
down the toilet.
