Ecology exam 3

nutrient sink

is a part of the biosphere where a particular nutrient is absorbed faster than it is released.

nutrient source

is a portion of the biosphere where a particular nutrient is released faster than it is absorbed.

trophic level

is a position in a food web and is determined by the number of transfers of energy from primary producers to that level.

nutrient pool

is the amount of a particular nutrient stored in a portion, or compartment, of an eco- system.

primary production

is the production of new organic matter, or biomass, by autotrophs in an ecosystem during some period of time

gross primary production

is the total amount of biomass produced by all the autotrophs in the ecosystem

Actual Evapotranspiration (AET)

is the total amount of water that evaporates and transpires off a landscape during the course of a year and is measured in millimeters of water per year

aquatic primary production is generally limited by ------

nutrient availability

ecosystems with greater primary production generally support higher levels of ------- -------

secondary production

terrestrial primary production is generally limited by ------, ------- and ------

temperature, moisture and nutrients

trophic dynamics

the transfer of energy from one part of an ecosystem to another.

consumers can influence rates of primary production in aquatic and terrestrial ecosystems through ------- -------

trophic cascades

decomposition

which is the breakdown of organic matter accompanied by the release of carbon dioxide.

net primary production (NPP)

- is the amount of biomass left over after autotrophs have met their own energetic needs. -NPP is gross primary production minus respiration by primary producers -is it the amount of energy in the form of biomass available to the consumers in an ecosystem

Secondary Production

-is the production of biomass by heterotrophic consumer organisms feeding on plants, animals, microbes, fungi or detritus during some period of time. -Secondary production, which is analogous to net primary production, includes consumer growth, reproduction, and, at the population level, mortality. Ecologists have measured primary production in a variety of ways but mainly as the rate of carbon uptake by primary pro- ducers or by the amount of biomass or oxygen produced.

Whole lake experiments

-know the lake experiment done is canada -manipulated nutrient availability. used a vinyl curtain to cut lake in half. on half added a mixture of carbon and nitrates and the other half added a mixture of carbon, nitrates and phosphate

18.1 3. How would actual evapotranspiration and net primary production in the desert dune ecosystem, which is a hot desert, and the arctic and alpine tundra ecosystems likely respond to a significant increase in precipitation?

Actual evapotranspiration would increase substantially in the desert dune ecosystem, since it is a hot desert. However, AET might not increase a great deal in the arctic and alpine tundra ecosystems, since they are both cold, which limits evaporation.

Decomposers release some energy that is cycled back to plants.

Answer: False

Plants can use the molecule CO2 as an energy source

Answer: False

Of the total amount of energy striking a forest though solar radiation, what percent is captured and held in the bonds through the process of photosynthesis

Answer: Less than 3% Most of the solar energy hits something besides plants, and photosynthesis itself is only 33% efficient,

The reason decomposers break down dead organic matter is because:

Answer: They use the dead material as an energy resource. The matter cycles from the dead material to CO2 in the air and the energy flows from within the bonds held by the dead material to energy for the microbe and heat loss "Everything we've learned is photosynthesis and cellular respiration."

18.4 2.Since increased phytoplankton biomass decreases water clarity in lakes, how should increased fishing pressure on the bass population in a lake ecosystem, such as that pictured in figure 18.12, affect lake clarity

Assuming that increased fishing pressure reduces the large-mouth bass population significantly, water clarity should decrease as fishing pressure on the largemouth bass population increases.

chapter 19 review 1. Of all the naturally occurring elements in the biosphere, why have the cycles of carbon, nitrogen, and phosphorus been so intensively studied by ecologists? (Hint: Think about the kinds of organic molecules of which these elements are constituents. Also think back to our discussions, in chapter 18, of the influences of nitrogen and phosphorus on rates of primary production.)

Carbon is the element common to all organic molecules, and energy enters ecosystems through the process of carbon fixation. Nitrogen and phosphorus are also key constituents of biomolecules, such as DNA and amino acids, and they often occur in relatively short supply.

third trophic level

Carnivores feeding on herbivores and detritivores are called secondary consumers and occupy the third trophic level.

bottom- up controls

Ecologists refer to the influences of physical and chemical factors on ecosystems, such as temperature and nutrients, as bottom-up controls.

nutrient cycling

Ecologists refer to the use, transformation, movement, and reuse of nutrients in ecosystems as nutrient cycling.

ch 19.2 1.During the past 30 years, thousands of papers have been published on decomposition within ecosystems. Why have ecologists spent so much time studying decomposition?

Ecologists study decomposition because it is a key ecosystem process that is integral to nutrient cycling. Understanding controls on rates of decomposition is fundamental to understanding how ecosystems work and is intimately related to ecosystem and community properties ranging from rates of primary production to species diversity.

While most of the CO2 enters through the stomata, a small but biologically significant portion comes in through the roots.

FALSE!

18.5 3.Would secondary production in a stream ecosystem dependent on inputs of detritus from a surround forest change, if detrital inputs to the stream, for example leaves falling from nearby trees, were reduced? How so?

Figure 18.22 shows how availability of leaf litter in a detritus-based stream ecosystem influenced secondary production (Wallace et al. 1999). As on African savannas, secondary production by primary consum- ers, in this case, production of detritivores, rose with increased availability of food. In addition, there was a positive correla- tion between primary consumer production and predator pro- duction in this stream ecosystem. yes, it would change due to the primary producers receiving less food and its biomass lowering. that would also lower secondary production because secondary production is dependent upon primary production

second trophic level

Herbivores and detriti- vores are often called primary consumers and occupy the second trophic level.

ch 19 review 6. Likens and Bormann (1995) found that vegetation substantially influences the rate of nutrient loss from small stream catchments in the northern hardwood forest ecosystem. How do vegetative biomass and rates of primary production in these forests affect their capacity to regulate nutrient loss? How much do you think vegetation affects nutrient movements in desert ecosystems?

Higher rates of primary production and plant biomass should increase the capacity of a forest ecosystem to regulate nutrient losses from stream catchments. Low vegetative biomass and low primary production likely reduces the influence of desert vegetation on nutrient losses from desert catchments.

ch 18 review 8. Most of the energy that flows through a forest ecosystem flows through detritus-based food chains, and the detritus consists mainly of dead plant tissues (e.g., leaves and wood). In contrast, most of the energy flowing through a pelagic marine or freshwater ecosystem flows through grazing food chains with phytoplankton constituting the major primary producers. Ecologists have determined that on average, a calorie or joule of energy takes only several days to pass through the pelagic ecosystem but a quarter of a century to pass through the forest ecosystem. Explain.

More of the energy within the forest is tied up in slowly-processed organic molecules, especially cellulose and lignin. The abundance of these molecules in terrestrial plant detritus slows the passage of energy through forest ecosystems.

It can take an average of 25 years for a calorie of energy to flow through a forested ecosystem, where is it all that time?

Most people put that it was found in the woody tissues of the tree, but the answer is both B and C (it is in the woody tissues of the tree AND it is also held as organic matter in the soil).

fourth trophic level

Predators that feed on carnivores occupy a fourth trophic level.

first trophic level

Primary producers occupy the first trophic level in eco- systems since they use inorganic forms of energy, principally light, to convert CO2 into biomass.

ch 19.1 3. What are two ways in which the cutting of tropical forests and replacing them with lower productivity cattle pastures affect the global carbon balance?

Replacing tropical forests with less productive cattle pastures adds CO2 to the atmosphere as the cut forest vegetation decomposes and/or burns and reduces the amount of tropical forest available to act as a carbon sink.

Give an example of an ecosystem restoration that is modeled after primary succession and one after secondary succession. Be sure to specifically state the goal of the restoration project in ecological terms that could be quantified.

Restoration after primary succession: Restoration after secondary succession:

trophic cascades

Since they visualized the effects of con- sumers coming from the top of food webs to the base, they called these effects on ecosystem properties trophic cascades.

18.1 2. How are the desert dune ecosystem and the arctic and alpine tundra ecosystems indicated in figure 18.2 the same?

The desert dune ecosystem and the arctic and alpine tundra ecosystems all show low actual evapotranspiration and low net primary production.

top-down controls

The influences of consumers on ecosystems are known as top-down controls.

18.2 1.Suppose that when you add nitrogen to one-half of a lake, you observe no change in phytoplankton biomass, but when you add phosphorus to the other half of the lake, phytoplankton biomass more than doubles. What is the most likely explanation of your results?

The most likely explanation is that nitrogen is not limiting phytoplankton biomass in the study lake, while phosphorus is highly limiting.

18.2 2.Suppose you fertilize a lake with nitrogen only, phosphorus only, and nitrogen plus phosphorus and observe no change in phytoplankton biomass. What is the most likely explanation of your results?

The most likely explanation is that phytoplankton biomass in the study lake is not controlled by nitrogen and phosphorus concentrations.

carbon cycle

The organic circulation of carbon from the atmosphere into organisms and back again

ecological efficiency

The percentage of biomass produced at a lower trophic level that is transferred to biomass produced at the next higher trophic level is called ecological efficiency,

nitrogen cycle

The transfer of nitrogen from the atmosphere to the soil, to living organisms, and back to the atmosphere

24. What's the best explanation for why the line for North Carolina (35º latitude) is higher than the line for New Hampshire (43º latitude)? Y axis is mass loss (decomposition).

This is because the temperature in New Hampshire is lower (decomposition rates are driven by temperature).

18.5 1. How can energy losses between trophic levels limit the number of trophic levels in an ecosystem?

This shape results from energy losses between trophic levels. Ecologists have proposed that these energy losses are also a major contributor to limiting the number of trophic levels in ecosystems. For instance, Lake Mendota supports four tro- phic levels, while Cedar Bog Lake includes only three. Following Lindeman's pioneering work, many other ecolo- gists have studied energy flow. Secondary production is key to understanding energy flow in ecosystems. !!Because energy and biomass is lost between each level of a food chain, the number of potential trophic levels are limited Higher trophic levels receive less energy / biomass from feeding and so need to eat larger quantities to obtain sufficient amounts Because higher trophic levels need to eat more, they expend more energy (and biomass) hunting for food If the energy required to hunt food exceeds the energy available from the food eaten, the trophic level becomes unviable

How NASA able to measure NPP from space?

We all answered:(not correct answer) They use satellite images to quantify how green the surface is and estimate photosynthetic rates. But it's a little more complicated than that: By monitoring different light wavelengths, they can detect the quantity removed through photosynthesis

biodiversity

We should note, however, that several other aspects of biological diversity, generally shortened to biodiversity, are of potential importance to ecological processes, including primary production.

ch 18 review 4. Field experiments demonstrate that variation in soil fertility influences terrestrial primary production. However, we can not say that nutrients exert primary control. That role is still attributed to temperature and moisture. Why do ecologists still attribute the main control of terrestrial primary production to temperature and moisture? Consider the difference in primary production between arctic tundra and tropical forest (see fig. 18.2) and the extent to which nutrient additions (Shaver and Chapin 1986) changed primary production in tundra.

While the experiments of Shaver and Chapin showed that nutrient additions can increase primary production in tundra, the production of fertilized plots is still nowhere near that of tropical rain forest.