Ecology Final Exam

Water delivered to the Gulf of Mexico by the Mississippi River is warm and fresh, compared to the cool saline water already in the gulf. What can you say about how these differences contribute to the formation of the dead zone?

- Warm water is less dense than cold water and thus tends to float atop it

- Once layered, the Gulf's surface layer prevents the movement of gases to the layer beneath it

Which of the following statements offers the best description of how nutrients dumped into the Gulf by the Mississippi River contribute to the formation of the dead zone?

Nutrients stimulate algal growth. Bacteria then consumes O2 as they decompose dead algae, creating the dead zone

Which of the 4 macromolecules are built solely from carbon, hydrogen, and oxygen?

Carbohydrates

If adding nitrogen stimulates growth, its addition most likely allows algae to build more of which kind of macromolecule?

Nucleic acids and proteins

If adding phosphorus stimulates growth, its addition most likely allows algae to build more of which kind of macromolecule?

Nucleic acids and lipids

Which micronutrient is important both for the normal functioning of many enzymes, and for playing a role in hemoglobin formation?

Copper

Which micronutrient is essential for proper nerve signaling and muscle action in animals?

Potassium

What is most likely the reason that iron (Fe) fertilization stimulates algal growth?

Iron acids in synthesis of clorophyll, a photosynthesis pigment

What was limiting algal growth in the Gulf of Mexico in August 2012?

Nitrogen

What was limiting algal growth in Lake Erie in July 2003?

Phosphorous

In the phosphorus cycle, which biologically mediated transformation is driven by soil organisms' need to acquire phosphorus for the synthesis of key biomolecules?

Immobilization

When during a single tree's life should the phosphorus uptake rate be greater than the litterfall rate?

As a sapling

When during a single tree's life should the phosphorous uptake rate be equal to the litterfall rate?

As a mature tree

When should the average uptake rate for an entire forest be about equal to its average litterfall rate?

When the forest is healthy and mature, many decades after a fire

In an ecosystem where phosphorus cycles openly, imagine a phosphorus atom is exported to a recipient ecosystem. What do you think actually happens to this phosphorus atom?

It becomes an input for the recipient system, and becomes part of that system's phosphorous cycle

Consider the amino acid glycine, C2H5NO2. Glycine can be described by its various stoichiometric ratios. For example, it has carbon-to-nitrogen ratio (C:N) of 2:1, indicating that there are 2 carbon atoms per nitrogen atom. Now consider lysine, C6H14N2O2. What is lysine's C:N ratio?

3:1

Just as chemicals have their own stoichiometry, so too do individuals. Caterpillars, for example, tend to have C:N ratios of about 5:1, while the leaves it consumes can have C:N ratios closer to 30:1. The caterpillar has a lower C:N ratio because it contains more proteins than the leaves it eats. For every atom of nitrogen consumed, it gets 25 carbon atoms it does not need. How might the caterpillar deal with this excess of carbon?

- It could excrete carbon as waste before it is incorporated into it's biomass

- It could respire carbon, releasing carbon dioxide into the environment

How does the mass of an atom of carbon change as it's cycles between CO2 in the atmosphere and organic carbon in plants?

The mass of carbon doesn't change

Why do ecosystems require a constant supply of energy to power the carbon cycle?

- Energy is continuously lost as heat- this energy must be replaced for carbon to keep cycling

- The carbon cycle includes growth and reproduction, for which energy is needed

What are needed as elements to build biomolecules of life?

Nutrients

What are the 6 macronutrients that most biomolecules are built from?

Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorous, and Sulfur

How do humans affect Nitrogen and Phosphorous?

They are altering their availability

When does eutrophication occur?

When excess nutrients drive aquatic algal blooms that fuel excessive decomposition and hypoxia

What does nutrient addition bioassays do?

Can help identify the nutrients limiting plant and algal growth

What does a nutrient cycle describe?

The fluxes of an element through various organic and inorganic pools

What happens as nutrients cycle?

They are often transformed from one chemical compound to another, but they are neither created nor destroyed

Cycles can be...

Open or closed

What are changes in the size of a pool calculated as?

Storage rate = Total flux in - total flux out

Residence time is calculated as:

Residence time = Pool size/ total flux out

What are the 2 key ecosystem scale terrestrial nutrient cycles?

Carbon and Phosphorous cycles

Which biomolecules always require nitrogen?

Nucleic acids and proteins

Which of the following statements about algal blooms and eutrophication is true?

When algae in an algal bloom die, decomposition reduces oxygen levels, which can kill fish

Based on the figure to the right, which component of the global ecological footprint is most responsible for it's increase over the past 50 years?

Carbon footprint

The U.S.A. has the 7th largest total footprint per capita. This is largely because it has the 7th largest carbon footprint, suggesting that, on average, its citizens directly and indirectly use a lot of fossil fuels. The USA also ranks in the top 10 for its use of which of the following resources?

Cropland

Ecology students often venture out into local ecosystems to conduct experiments and learn about the natural world. What class of ecosystem service does education fall under?

Cultural services

Earth's mean temperature is increasing largely because the concentration of CO2 is increasing. Growing forests can mitigate some of the effects of fossil fuel combustion by removing CO2 from the atmosphere and storing carbon as wood. What class of ecosystem services does carbon sequestrion fall under?

Regulating services

Which of the supporting services discussed in this chapter are most important for the production of a feedstock for biofuels, a provisioning ecosystem service?

Primary production and Nutrient cycling

What does the fact that human consumption of NPP is often greater than 100% in urban areas suggest?

Cities are heterotrophic ecosystems

If you were to draw a flower diagram for the atlantic ocean, which petals do you think would be the longest and which would be the shortest?

Longest: Food, Climate Regulation, and Cultural Services

Shortest: Timber and Water Flow Regulation

How large is the ecological footprint today?

50% larger than Earth's biocapacity

Why is the ecological footprint so large today?

Humanity's carbon footprint

Which countries have a larger ecological footprint?

Oil-rich middle eastern countries and developed countries in North America and Western Europe

What are supporting services?

Compromise fundamental processes like primary production and are necessary for producing all other ecosystem services

What are provisioning services?

Include those ecosystem goods and services that are directly consumed by people

What are regulating services?

Include benefits that result from the regulation of ecosystem processes including earth's climate,water purification, and flood control

What are cultural services?

Include the various nonmaterial cultural and recreational benefit people gain from ecosystems

What is Net Primary Production?

The amount of organic matter (biomass) that remains after primary producers use some to carry out cellular respiration

Wetlands effectively remove nutrients like nitrogen and phosphorus from the water column, reducing the likelihood that the water discharged from the wetlands will stimulate excess primary production in downstream lakes or estuaries. In what class of ecosystem services is the removal of such pollutants?

Regulating

A drama of the commons results when individuals choose to use more than their "fair" share of a common-pool resource. Under what circumstances are these dramas more likely to occur?

When the benefit to the individual for using a bit more of the resource is more than their associated costs

The growth in the global Ecological Footprint since 1961 is largely a result of an increase in global carbon footprint. As fossil fuel combustion has increased, what subsequent change has resulted in the rise of our global carbon footprint?

The land required to assimilate CO2 emissions has increased

What is the approximate ratio of net primary productivity to secondary production on the farm?

51:1

Which of the following statements is best supported by your data?

Sheep grew better on clover because they had higher production efficiencies when feeding on clover

Which of the 3 herbivores had the highest rate of production?

Sheep

The fact that domesticated sheep have much higher ingestion efficiencies than the other 2 herbivore species is strong evidence that sheep are more efficient foragers than grasshoppers or mice.

False

The 3 herbivores differ markedly in their production efficiencies. Which of the following statements are supported by the data?

- Mice have the smallest production efficiency

- Grasshoppers have the largest production efficiency

Which of the following hypotheses is supported by the observation that many carnivores have higher production efficiencies than many herbivores?

Food quality drives production efficiency

Which group of animals had the lowest field metabolic rates for their size?

Reptiles

Based on the slope of the regression for mammals, which of the following statements has the most support?

Smaller animals will use energy less efficiently than larger animals

What 2 primary food chains do ecosystems contain?

The grazer food chain and the detrital food chain

Plants sit at the base of the ___ food chain and are fed on by ___, which in turn are fed on by carnivores.

Grazer, Herbivores

What sits at the base of the detrital food chain?

Detritus (dead organic matter)

Who feeds on Detritus?

Decomposers

What does secondary production describe?

The rate at which biomass collects in an ecosystem's heterotrophs

When does secondary production increase?

When the net primary production of an ecosystem increases

What happens to the trophic levels regarding energy transfers?

Energy transfers between trophic levels are inefficient and energy is lost as heat at each step

What do endothermic animals tend to have?

Higher metabolic costs and thus lower production efficiencies

Production efficiency is calculated as:

Secondary production/assimilation

In our simulation of herbivores feeding in a farm pasture, we treated each species as if it were foraging all by itself. Of course, in real ecosystems, there are many different herbivores, some of which compete with one another for food. If both sheep and grasshoppers were feeding in a pasture, how do you think the grasshoppers would affect sheep? Choose the best answer.

Sheep consumption efficiency would be reduced

Some migratory birds are heterothermic, meaning they sometimes maintain a constant body temperature and other times allow their body temperature to vary. For example, on cold nights, they sometimes reduce their metabolic rate and allow their body temperature to drop as the air temperature falls. Which of the following hypotheses about this unusual strategy is consistent with what you learned in this section?

Birds allow their temperature to drop in order to increase their assimilation efficiency

Which of the following statements about secondary production is false?

The production efficiency off ectothermic species tends to be lower than that of endotherms

If production efficiencies are partly determined by metabolic rate, which group do you expect to have the lowest mass-specific metabolic rate?

Reptiles

Based on the slope of the regression for mammals, which of the following statements has the most support?

Smaller animals will use energy less efficiently than larger animals

If we take a "ballpark estimate" of 10% for ecological efficiencies of herbivores and carnivores, what percentage of the energy content of net primary production (100%) would we expect to find in production at the THIRD (carnivore) trophic level?

1%

A drama/tragedy of the common results when individuals choose to use more than their fair share of a common-pool resource. Under what circumstances are these dramas more likely to occur?

When the benefit to the individual for using a bit more of the resource is greater than the associated cost

The cycles for which nutrients contain a prominent gaseous component?

Carbon and nitrogen only

Where do you think most of these nitrogen in the Gulf come from?

Indiana

Imagine you conducted a nutrient additional bioassay to determine whether the growth of a diatom in the ocean was limited by silicon or iron or both. You collected water samples with the diatom and established 4 bioassay treatments: Control, addition of silicon, addition of iron, and additions of both silicon and iron. You then let the diatoms grow for a while. At the end of your experiment you measured growth rate and plotted your results. What can you conclude from these results?

Growth is silicon limited

The pacific yew trees, from which the drug Taxol, (more than $1.5 billion in annual sales) derived, is an example of ___ services of ecosystems.

Provisioning

Humans rely on insect pollinators for ~1/3 of the food we eat. Insect pollination is an example of _____ services of ecosystems.

Regulating

The storage rate for soil inorganic P is _____ and the soil inorganic P pool size in year 1 will be _____.

-10, 340

The residence time of P in the plant P pool is ___ years.

6

In an agricultural landscape in the Midwest with remnant forest patches, a forested corridor connecting 2 forest patches could function:

- As a conduit to forest animals

- As a barrier to open-land animals

- As a barrier or filter to erosion flow

What is the matrix of a post oak savanna landscape (-10 km^2) that consists of grass area (60%), wooded areas (30%), crop fields (7%), and water (3%)?

Grass areas

A stream flowing through or under a glacier can leave deposits of soil and rock in its path. After the retreat of the glacier, these deposits appear as long, winding hills in the landscape, called esker. This is a case of ___ on landscape structure.

Legacy effects of natural processes.

Which of the following statement is true regarding landscape structure and landscape process?

Landscape structure affects landscape process, and vice versa

On small islands created by damming of a large river in Venezuela, predator abundance _____ and herbivore abundance ______, which led to an increase in tree mortality and ______ in tree recruitment.

Decreased, increased, a decrease

If we consider the areas within 100m of forest to cropland edge as the edge habitat, which of the following patch has the highest proportion of interior habitat?

A circular patch 100 ha in size

If patch A and patch B are of the same size but patch A has a greater patch shape index value than patch B, then

Patch A has a more complex shape than patch B

Of the three types of bees included in their study, Ingolf Steffan-Dewenter and colleagues found that wild bees, which fly relatively short distances when foraging, were influenced by the nature of the landscape mosaic at ___?

Small (250 m) scales

Phenomena of processes occur over small areas change ___, and those occur over large areas change ___.

Fast, Slow

How would you best describe the species-area curve from these islands?

Large islands tend to have more species

How did the equilibrium number of species, S*, change as the island's distance increased?

The equilibrium species richness decreased

How did the equilibrium number of species, S*, change as the island's size increased?

The equilibrium species richness increased

What other combination of size and distance describes an island that supports approximately 5 species at equilibrium?

Size = 50, Distance = 14

Assuming island size does NOT change, what can you say about the differences between near and far islands based on this model?

- S LN > SLF

- Near islands will have a higher immigration rate than far islands with the same value of S

Assuming island distance does not change, what can you say about the differences between small and large islands based on this model?

- SLF>SSF

- Large islands will have a lower extinction rate than small islands with the same value of S

You can predict which islands should have the highest turnover rates and which should have the lowest from the graphical model to the right. According to this model, which is the proper way to order turnover rates at equilibrium?

T SN> T SF = T LN> T LF

As a group, mammals are highly mobile species, but some species are better travelers than others. Some, like deer and wolves, easily travel long distances over varied terrain. Others, like many squirrels and mice, keep to very specific habitats and may never stray far from where they were born. Given this, how do you expect mammals to perceive a dispersal route over a high mountain pass?

As a filter

Most plants drop their seeds near where they grow. Some small seeds like dandelion seeds travel longer distances by catching a ride on the wind or floating on the water. Occasionally, some seeds can hitch a ride on or in animals. Given this, how do you expect large-seeded plants (think walnuts or peach pits) to perceive a dispersal route over a high mountain pass?

As a sweepstakes route

Fans of Shakespeare introduced about 100 European starlings (Sturnus vulgaris) in New York's Central Park late in 1890 and 1891. Over the next 100 years, its range expanded to encompass all of the continental U.S. and much of Canada with a population of more than 200 million birds. This example illustrates which migration types?

- Jump dispersal

- Diffusion