Why is the transfer of energy in an ecosystem referred to as energy flow, not energy cycling?
energy passes through an ecosystem, entering as sunlight and leaving as heat. It is not recylcled
how does the second law of thermodynamics explain why ecosystem’s energy supply must be continually replenished?
-the second law states that in any energy tranfer or transformation, some of the energy is dissipated to the surroundings as heat.
-this “escape” of energy from an ecosystem is offset by the continuous influx of solar radiation
Why is only a small portion of the solar energy that strikes the earths atmosphere stored by primary producers?
only a fraction of radiation strikes plants or algae and only a portion of that fraction is of wavelengths suitable for photosynthesis and much energy is lost as a result of reflection or heating of plant tissue
Explain how nitrogen and phosphorus, the nutrients that most often limit primary production, are necessary for the calvin cycle to function?
-the enzyme rubisco, which catalyzes the first step in the calvin cycle, is the most abundant protein on earth
-photosynthetic organisms require considerable nitrogen to produce rubisco
-phosphorus is also needed as a component of several metabolites in the calvin cycle and as a component of both ATP and NADPH
Why does deforestation of a watershed increase the concentration of nitrates in streams draining the watershed?
-removal of the trees stops nitrogen uptake from the soil, allowing nitrate to accumulate there
-nitrates are then washed away by precipitation and enter the streams
Explain why it is too narrow to define the biodiversity crisis as simply a loss of species
in addition to species loss, the biodiversity crisis includes loss of genetic diversity within populations and species and the degradation of entire ecosystems
How can the addition of excess mineral nutrients to a lake threaten its fish populations?
-adding nutrients causes population explosions of algae and the organisms that feed on them
-increased respiration by algae and consumers, including detritivores, depletes the lakes oxygen, which the fish require
How does reduced ozone concentration in the atmosphere increase the likelihood of mutations in various organisms?
-reduced concentrations of ozone in the atmosphere increase the amount of UV radiation that reaches earths surface and organisms living there
-UV radiation can cause mutations by producing disruptive thymine dimers in DNA
In an ecosystem, phytoplankton are
An earthworm that feeds on the remains of plants and animals is acting as a
When a human eats a steak, the human is acting as a
secondary consumer
A cow eating grass is an example of a
primary consumer
A human who just ate a hamburger is eaten by a shark while swimming. The shark is acting as a
tertiary consumer
In a tide pool, 15 species of invertebrates were reduced to eight after one species was removed. The species removed was likely a(n)
keystone species.
Which of the following members of a marine food chain occupies a similar tropic level to a grasshopper in a terrestrial food chain?
Approximately how many kg of carnivore production can be supported by a field plot containing 2000 kg of plant material?
Which of the following are responsible for the conversion of most organic material into CO2, which can be utilized in primary production?
What is the most important role of photosynthetic organisms in an ecosystem?
converting inorganic compounds into organic compounds
Which of the following is true of detrivores?
They convert organic materials from all trophic levels to inorganic compounds usable by primary producers.
Which animal product is least efficient at converting feed consumed into the final product?
Roughly how many kilograms of pork do you expect to get for every 100 kilograms of feed consumed?
Assume you are raising beef and that feed is costing you $1.00 per kilogram. Roughly how much money are you spending on feed for each kilogram of beef produced?
Surprisingly, milk has a conversion efficiency greater than 100%. What is the best explanation for this?
Most of milk’s mass comes from water consumption, not feed consumption.
For a country with abundant land and water resources but limited financial resources, which animal product would most likely be favored by agricultural policy?
For a country where chicken raising and eating is a cultural taboo but water resources are scarce, which animal product would most likely be favored by agricultural policy?
Despite its high resource usage, beef is a major commodity due to the high value per kilogram of the final product. Which of the following changes would cause a reduction in beef production?
-a dramatic rise in the cost of feed, land, and water to the beef producer
-an agricultural program that subsidized pork production so that the profit per kilogram of pork was comparable to that for beef
-a recipitous fall in the price per kilogram of beef
In general, the total biomass in a terrestrial ecosystem will be greatest for which trophic level?
Which statement best describes what ultimately happens to the chemical energy that is not converted to new biomass in the process of energy transfer between trophic levels in an ecosystem?
It is dissipated into space as heat in accordance with the second law of thermodynamics.
True or false? Local biogeochemical cycles are isolated within their particular ecosystem and all ions and molecules remain in that ecosystem permanently.
Which area is not one of the three major reservoirs of the global carbon cycle?
Sedimentary rock.
True or false? In the global carbon cycle, rivers link the terrestrial and marine reservoirs of carbon, whereas carbon exchange between the atmosphere and the ocean is achieved by active transport.
How does carbon move from the biota to the atmosphere?
Carbon dioxide is released during cellular respiration.
How have humans altered the global carbon cycle?
Carbon inputs into the atmosphere have risen.
How do greenhouse gases contribute to global warming?
They prevent infrared light from leaving Earth’s atmosphere.
Which of the following describes carbon dioxide, methane, and water vapor re-reflecting infrared radiation back toward Earth?
greenhouse effect
Which of the following statements best describes why biologists are currently concerned with global warming and the thawing of permafrost in many areas of the tundra biome?
The bacterial decomposition of the thawed organic materials on the widespread areas of the tundra will produce large quantities of CO2, which will add to greenhouse gases and exacerbate global warming.
Which of these are the two major sources of nitrate pollution in rivers?
Animal wastes and fertilizers
Aquatic nitrate pollution can result in?
an algal bloom that, when the algae die and are decomposed by bacteria, leads to hypoxia and the death of fish
True or false- Nitrates in drinking water have been found to have no negative effect on human health
A 1996 EPA study of nitrate pollution found that nearly _____ of lakes and rivers tested were unsafe for fishing and swimming.
What can you as an individual do to reduce nitrate pollution?
-Choose to eat organic foods which are grown without the use of chemical fertilizers.
-Test your soil for nitrogen.
-Mulch the grass clippings from your lawn.
-Use slow-release fertilizer on your lawn.
Explain how the sun’s unequal heating of earth’s surface leads to the development of deserts around 30 degrees north and south of the equator
In the tropics, high temps evaporate water and cause warm, moist air to rise. The rising, air cools and releases much of its water as rain over the tropics. The remaining dry air ascends approx 30 degrees north and south, causing deserts to occur in those regions
what are some of the differences in microclimate between an unplanted agriculture field and a nearby stream corridor with trees
the microclimate around the stream will be cooler, moister and shadier than that around the unplanted agricultural field
Changes in earths climate at the end of the last ice age happened gradually, taking centuries to thousands of years. If the current global warming happens very quickly, as predicted, how may this rapid climate change affect the ability of long-lived trees to evolve. compared with annual plants, which have much shorter generation times?
trees that require a long time to reach reproductive age are likely to evolve more slowly than annual plants in response to climate change, constraining the potential ability of such trees to respond to rapid climate change
If global warming increases average temps on earth by 4 degrees in this century, predict which biome is most likely to replace tundra in some location as a result
northern coniferous forest is likely to replace tundra along the boundary between these biomes
-currently northern coniferous forests are adjacent to tundras around the world
-temp range for forests is just above tundra
Why are phytoplankton, and not benthic algae or rooted aquatic plants, the dominant photosynthetic organism of the oceanic pelagic zone?
in the oceanic pelagic zone, the ocean bottom lies below the photic zone, so there is too little light to support benthic algae or rooted plants
many organism living in estuaries experience freshwater and saltwater conditions each day with the rising and falling tides. Explain how these changing conditions challenge the survival of these organisms
aquatic organisms either gain or lose water by osmosis if the osmolarity of their environment differs from their internal osmolarity
-water gain can cause cells to swell and water loss can cause cells to shrink
-To avoid excessive changes in cell volume, organisms that live in estuaries must be able to compensate for both water gain (under freshwater conditions) and water loss (under saltwater conditions)
What are the two major factors determining the distribution of terrestrial biomes?
temp and rainfall
What is the largest terrestrial biome on Earth?
Coniferous forests are the largest terrestrial biome on Earth. However, as a result of logging, they are disappearing at a very rapid rate.
Which biome is characterized by an extensive canopy that allows little light to penetrate to the ground and by the presence of epiphytes?
tropical rainforest
-Two of the characteristics of a tropical rain forest are the presence of epiphytes and an extensive canopy that allows little light to penetrate to the ground.
Which biome is characterized by the presence of permafrost?
-Permafrost: permanently frozen subsoil
True or false? Weather is defined as the prevailing long-term atmospheric conditions in a particular region.
-Climate is defined as the prevailing long-term weather conditions in a particular region
-weather is defined as the short-term atmospheric conditions of temperature, sunlight, moisture, and wind.
Which of the following statements about Hadley cells is true?
As warm air rises, air at the top of the atmosphere is pushed poleward and cools–> This cool air causes the cooler climates away from the equator.
Which location on Earth receives the most solar radiation per unit area?
What are rain shadows?
Rain shadows are dry regions on the leeward side of mountain ranges that result when an air mass releases its moisture on the windward side of the range and then is carried by winds to the leeward side.
Which desert is caused by a Hadley cell?
The Sahara Desert is caused by a Hadley cell; it is not the result of topography, since there are no extensive North-South mountain ranges in Africa.

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