Chapter 7: Energy and Nutrient Relations

herbivores -main challenge (2)

1) Herbivores must compensate for large differences between the nutrient content of their food and their own requirements for growth and metabolism 2) Herbivores must also overcome the physical and chemical defenses of plants. (ex: *physical*: abrasive silica in grasses or toughened tissues or leaves due large quantities of cellulose and lignin >>>has led to evolutionary adaptation in some animals for teeth that are able to grind it)

The sulfur-oxidizing bacteria that exploit this resource around the vents are of two types:

1) free-living forms 2) and those that live within the tissues of a variety of invertebrate animals, including the giant tube worms (fig. 7.7). Other communities dependent on sulfur-oxidizing bacteria have been discovered in thermal vents in deep freshwater lakes, in surface hot springs, and in caves.

problems with C3 ( 2 main ones)

1) to fix carbon, plants must open their stomata, usually located on the underside of leaves, to let CO2 in. However, as CO2 enters, diffusing down its concentration gradient from the surrounding air to the leaf interior, water exits. Water vapor flows out faster than CO2 flows in. The movement of water is more rapid because the gradient in water concentration from the leaf to the atmosphere is generally much steeper than the gradient in CO2 concentration from the atmosphere to the leaf, particularly in arid climates. *summary: water loss* = problem for plants in hot 2) Rubisco has affinity for O2 (when it binds > photorespiration, which consumes energy). even though affinity for CO2 is higher, rubisco's affinity for O2 increases as temps rise; photorespiration makes carbon fixation in C3 plants rather inefficient, especially when CO2 concentrations are reduced, due to the need for plants to close their stomata; as O2 builds up in the leaf with less Co2 coming in (due to closed stomata) more photorespiration occurs and not a lot of photosynthesis occurs

Arnold Bloom (1985) studying how plants invest their energy -what did they predict plants would do in environments with ---abundant nutrients but little light ---rich in light but poor in nutrients

Arnold Bloom and his colleagues (1985) suggested that plants adjust their allocation of energy to growth in such a way that all resources are equally limited. They predicted that plants in environments with abundant nutrients but little light, would invest more energy in the growth of stems and leaves and less in roots to match their supply of energy to the supply of nutrients. They predicted that in environments rich in light but poor in nutrients, plants would invest more in roots. it appears that plants allocate energy for growth to those structures that gather the resources that most limit growth in a particular environment.

graph description of photosynthesis rate vs photon flux density in -low light -intermediate light -higher light (but below sunlight)

At low light intensities, photosynthesis increases linearly with photon flux density. At intermediate light levels, photosynthetic rate rises more slowly. Finally, at higher light levels, but well below that of full sunlight, photosynthesis levels off. PmaxOrganisms that show this type of photosynthetic response curve include terrestrial plants, lichens, planktonic algae, and benthic algae.

size-selective predation

Because predators must catch and subdue their prey, they often select prey by size, a behavior that ecologists call size-selective predation. Because of this behavior, prey size is often significantly correlated with predator size, especially among solitary predators. Augustin Iriarte and his colleagues (1990) found that as pumas increase in size, the average size of their prey also increases (

PAR (photosynthetically active radiation) -nm range -what is it used for

Between these extremes is the light we can see, so-called visible light, which is also called photosynthetically active radiation, or PAR. PAR, with wavelengths between about 400 and 700 nm, carries sufficient energy to drive the light-dependent reactions of photosynthesis but not so much as to destroy organic molecules.

bluegill sunfish study Werner an Mittelbach

Bluegills feed mainly on benthic and planktonic crustaceans and aquatic insects, prey that differ in size and habitat and in ease of capture and handling. Bluegills often choose prey by size, feeding on organisms of certain sizes and ignoring others. Werner and Mittelbach used published studies to estimate the amount of energy expended by bluegills while they search for (Cs) and handle prey. They used laboratory experiments to estimate handling times (H) and encounter rates (Ne) for various prey. The energy content of prey was calculated by measuring the lengths of prey available in lakes and ponds; prey length was converted to mass, and then mass was converted to energy content using published value The upper graph in figure 7.25 shows the size distribution of potential prey for bluegills in vegetation in Lawrence Lake, Michigan. The middle graph shows the composition of the optimal diet as predicted by the optimal foraging model just presented. Finally, the bottom graph shows the actual composition of bluegill diets in Lawrence Lake. Bluegills feeding in vegetation selected prey that were uncommon and larger than average. The optimal diet matches well with the actual diets of bluegills in Lawrence Lake. A similar match was obtained for bluegills feeding on zooplankton in open water.

alternative photosynthetic pathways (name the main ones)

C3, C4, an CAM pathways

where do C4 plants do better than C3 plants?

C4 plants do better than C3 plants under conditions of high temperature, high light intensity, low CO2, and limited water.

CAM photosynthesis -found mostly in what kind of plants in what kind of environments?

CAM (crassulacean acid metabolism) photosynthesis is largely found in succulent plants in arid and semiarid environments and among epiphytes growing in the canopies of tropical forests, where they are subjected to intense sunlight and drying winds.

carnivores

Carnivores consume animal prey, to which they are stoichiometrically similar; that is, both predators and prey have low C:N and C:P ratios. However, carnivores cannot go out into their environment and choose their nutritionally rich prey at will.

chemosynthetic autotrophs

Chemosynthetic autotrophs synthesize organic molecules using CO2 as a carbon source and inorganic chemicals, such as hydrogen sulfide (H2S), as their source of energy.

Chemosynthetic autotrophs -most common ones and their energy source

Chemosynthetic autotrophs synthesize organic molecules using CO2 as a carbon source and inorganic molecules as an energy source. The autotrophs on which these submarine oases depend are chemosynthetic bacteria. Some of the most common are sulfur oxidizers, bacteria that use CO2 as a source of carbon and get their energy by oxidizing elemental sulfur, hydrogen sulfide, or thiosulfite. The submarine volcanic vents with which these organisms are associated discharge large quantities of sulfide-rich warm water.

how can photosynthetic response curved be used to group plants into two categories and what does this suggest?

Differences in photosynthetic response curves have been used to divide plants into "sun" and "shade" species. The response curves of plants from shady habitats suggest selection for efficiency at low light levels, that is, low irradiance. The photosynthetic rate of shade plants levels off at lower irradiance, and they are often damaged by high irradiance. However, at very low light levels, shade plants usually have higher photosynthetic rates than sun plants.

If carbon, oxygen, hydrogen, nitrogen, and phosphorus make up 93% to 97% of living biomass, then what accounts for the remainder?

Essential plant nutrients include potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), chlorine (Cl), iron (Fe), manganese (Mn), boron (B), zinc (Zn), copper (Cu), and molybdenum (Mo). Most of these nutrients are also essential for other organisms. Some organisms require additional nutrients. For instance, animals also require sodium (Na) and iodine (I).

Herbs and short-lived perennial shrubs that have evolved in sunny environments show ______ Pmax rates, at ________ Isat.

Herbs and short-lived perennial shrubs that have evolved in sunny environments show high maximum rates of photosynthesis, Pmax, at relatively high irradiance, Isat.

heterotrophic organisms + 3 major categories

Heterotrophic organisms use organic molecules both as a source of carbon and as an energy source. They depend, ultimately, on the carbon and energy fixed by autotrophs. 3 major categories: herbivores (organisms that eat plants), carnivores (organisms that mainly eat animals), detritivores (organisms that feed on nonliving organic matter, usually the remains of plants)

heterotrophs

Heterotrophs ("other-feeders") are consumers that use organic molecules as a source of both carbon and energy.

functional response

If you gradually increase the amount of food available to a hungry animal, its rate of feeding increases and then levels off. This relationship is called the functional response.

photon flux density relation to photosynthesis production

If you gradually increase the quantity of light shining on plants growing under these conditions—that is, if you increase the photon flux density—the plants' rates of photosynthesis gradually increase and then level off.

3 types of functional response : Type 2

In a type 2 functional response, feeding rate at first rises linearly at low food density, rises more slowly at intermediate food density, and then levels off at high densities. At low food densities, feeding rate appears limited by how long it takes the animal to find food. At intermediate food densities, the animal's feeding rate is partly limited by the time spent searching for food and partly by the time spent handling food. At high food densities, an animal does not have to search for food at all and feeding rate is determined almost entirely by how fast the animal can handle its food. At these very high densities, the animal, in effect, has "all the food it can handle." MOST COMMON

However, remember that this process ultimately leads to the production of NO−3. Does adding sucrose to eliminate CN− lead to the buildup of NO−3, trading one pollution problem for another?

In another experiment, White and Markwiese showed that adding sucrose also stimulates uptake of NO−3 by heterotrophic bacteria and fungi. These organisms use organic molecules, in this case sucrose, as a source of energy and carbon and NO−3 as a source of nitrogen. The nitrogen taken up by bacteria and fungi becomes incorporated in biomass as complex organic molecules. Nitrogen in this form is recycled within the microbial community and is not a source of environmental pollution.

summary of predation

In summary, predators consume nutritionally rich but elusive and often well-defended prey. As a consequence, predators and their prey appear engaged in a coevolutionary race. In this race, predators eliminate poorly defended individuals in the population and average prey defenses improve. As average prey defenses improve, the poorer hunters go hungry and leave fewer offspring. Consequently, improved hunting skills evolve in the predator population, which exerts further selection on the prey population. Such selection was central to chapter 4, which focused on population genetics and natural selection.

C3 pathway

In the photosynthetic pathway used by most plants and all algae, the CO2 first combines with a five-carbon compound called ribulose bisphosphate, or RuBP. The product of this initial reaction, which is catalyzed by the enzyme RuBP carboxylase/oxygenase, or rubisco, is phosphoglyceric acid, or PGA, a three-carbon acid. Therefore, this photosynthetic pathway is called span photosynthesis and the plants that employ it, including crop plants such as rice, wheat, and soybeans, are called C3 plants *my summary: 5 carbon compund RuBP captures Co2 to form 6 carbon compound > two 3-carbon compounds

Optimal foraging theory predicts that predators will include a second prey species in their diet when: -what is this called?

In this case, feeding on two prey species gives the predator a higher rate of energy intake than if it feeds on one. The general prediction is that predators will continue to add different types of prey to their diet until the rate of energy intake reaches a maximum. This is called optimization

CAM -how does carbon fixation occur? -where do the reactions occur?

In this pathway, carbon fixation takes place at night, when lower temperatures reduce the rate of water loss during CO2 uptake. CAM plants fix carbon by combining CO2 with PEP to form four-carbon acids. As in C4 plants, this reaction is catalyzed by PEP carboxylase. These acids are stored until daylight, when they are broken down into pyruvate and CO2, which then combines with RuBP to form PGA (fig. 7.6). In CAM plants, all these reactions take place in the same cells.

infrared light impact on organisms and impact on photosynthesis

Infrared light, as we saw in chapter 5 (see Section 5.4), is very important for temperature regulation by organisms. This is because its main effect on matter is to increase the motion of whole molecules, which we measure as increased temperature. However, infrared light does not carry enough energy to drive photosynthesis.

How ubiquitous is the nutrient imbalance between herbivores and their food? James Elser and colleagues (2000)

James Elser and colleagues (2000) sought to answer this question and compiled a large data set for C:N and C:P ratios of plants and herbivorous insects. They found that herbivorous insects must overcome an average five- to tenfold difference in the ratio of carbon to nutrients they require (fig. 7.9). To compensate for these differences in elemental ratios, insects must consume large amounts of high C:N and C:P plant tissue to meet their requirements for nitrogen and phosphorus.

5 major elements that make up the majority of the chemical composition of organisms - what group of organisms has the most variable nutrient content?

Just five elements (carbon [C], oxygen [O], hydrogen [H], nitrogen [N], and phosphorus [P]) make up 93% to 97% of the biomass of plants, animals, fungi, and bacteria. But organisms allocate elements in different ways. Of these four groups, plants have the most variable nutrient content. *hint: PONCH pneumatic device*

mullerian mimicry vs batesian mimicry

Many noxious organisms, such as stinging bees and wasps, poisonous snakes, and butterflies, seem to mimic each other. This form of comimicry among several species of noxious organisms is called Müllerian mimicry. In addition, many harmless species appear to mimic noxious ones. For instance, king snakes mimic coral snakes, and syrphid flies mimic bees and wasps. This form of mimicry is called Batesian mimicry. In Batesian mimicry, the noxious species serves as the model (fig. 7.15a) and the harmless species is the mimic.

rhodopsin -what is it -how it varies in different environments

Oded Béjà and Edward Delong and their research team from the Monterey Bay Aquarium Research Institute in California and the University of Texas Medical School discovered that energy production from light involving bacterial rhodopsin is widely distributed in the oceans (Béjà et al. 2000, 2001). Rhodopsins are light-absorbing pigments found in animal eyes and in the bacteria and archaea. The rhodopsin in bacteria and archaea performs a variety of functions, including that of a proton pump involved in ATP synthesis—that is, in the production of energy-rich molecules. A particularly intriguing discovery is that the light sensitivity of bacterial rhodopsin appears adapted to local variations in light quality. For instance, bacterial rhodopsin from deep, clear waters absorbs light most strongly within the blue range of the visible spectrum, whereas that from shallow coastal waters absorbs most strongly in the green range.

nitrifying bacteria importance

Of these, the nitrifying bacteria, which oxidize ammonium to nitrite and nitrite to nitrate, are undoubtedly among the most ecologically important organisms in the biosphere. Figure 7.8 summarizes one of the energy-yielding reactions exploited by nitrifying bacteria. The importance of these bacteria is due to their role in cycling nitrogen. As we will see in Section 7.3, nitrogen is a key element in the chemical makeup of individual organisms.

what does optimal foraging theory attempt to predict?

Optimal foraging theory attempts to predict what consumers will eat, and when and where they will feed.

optimal foraging theory

Optimal foraging theory models feeding behavior as an optimizing process. Evolutionary ecologists predict that if organisms have limited access to energy, natural selection is likely to *favor individuals within a population that are more effective at acquiring energy*. This prediction spawned an area of ecological inquiry called optimal foraging theory. Optimal foraging theory *assumes that if energy supplies are limited, organisms cannot simultaneously maximize all of life's functions*; for example, allocation of energy to one function, such as growth or reproduction, reduces the amount of energy available to other functions, such as defense. As a consequence, there must be compromises between competing demands. This seemingly inevitable conflict between energy allocations is called the *principle of allocation* Optimal foraging theory attempts to model how organisms feed as an optimizing process, a process that maximizes or minimizes some quantity. (IE: the environment may favor individuals that assimilate energy or nutrients at a high rate (e.g., some filter-feeding zooplankton and short-lived weedy annual plants growing in disturbed habitats). In other situations, selection for minimum water loss appears much stronger (e.g., cactus and scorpions in the desert)

autotrophs

Organisms that use inorganic sources of both carbon and energy are called autotrophs ("self-feeders").

Other chemosynthetic bacteria oxidize (5)

Other chemosynthetic bacteria oxidize ammonium (NH+4), nitrite (NO−2), iron (Fe2+), hydrogen (H2), or carbon monoxide (CO).

-amount of PAR in solar spectrum (%) -vs energy actually available for photosynthesis (why is it this value?) -amount of infrared and UV light in solar spectrum

PAR makes up about 42% of the total energy content of the solar spectrum at sea level. Because the pigments involved in photosynthesis absorb unevenly across the PAR wavelengths, however, the energy actually available for photosynthesis amounts to about 26% of the total (Agrawal 2010). Meanwhile, infrared light accounts for about 46% and ultraviolet light for most of the remainder (~12%).

Park Nobel (1977) -study on photosyntetic response curves in plants living in low light levels and their characteristics

Park Nobel (1977) determined the photosynthetic response curve for the maidenhair fern, Adiantum decorum. This plant generally grows at low light levels in forests. In one of Nobel's trials, the maximum rate of net photosynthesis by A. decorum, Pmax, was approximately 9 μmol CO2 m−2s−1. Net photosynthesis can be measured as total, or gross, CO2 uptake during photosynthesis minus the CO2 produced by the plant's own respiration. The amount of light required to achieve this maximum rate of photosynthesis, Isat, was a PAR photon flux density of about 300 μmol per square meter per second (fig. 7.21). The values of Pmax and Isat shown by A. decorum are much lower than those observed in plants that have evolved in sunny environments.

photon flux density

Photon flux density is the number of photons striking a square meter surface each second. The number of photons is expressed as micromoles (µmol), where 1 mole is Avogadro's number of photons, 6.023 × 1023. To give you a point of reference, a photon flux density of about 4.6 μmol photons m−2s−1 (µmol per square meter per second) equals about 1 watt per square meter. Measuring light as photosynthetic photon flux density makes sense ecologically because chlorophyll absorbs light as photons.

photosynthetic autotrophs

Photosynthetic autotrophs use carbon dioxide (CO2) as a source of carbon and light as a source of energy to synthesize organic compounds, molecules that contain carbon, such as sugars, amino acids, and fats.

percentages of nitrogen and phosphorous in - plants -invertebrates, bac, and fungi -vertebrate animals

Plant tissues generally contain about 45% carbon and much lower concentrations of nitrogen and phosphorus. Plant leaves contain around 2% nitrogen and less than 0.3% phosphorus. In contrast, invertebrates, bacteria, and fungi average 5% to 10% nitrogen and about 1% phosphorus. Vertebrate animals have an even higher requirement for phosphorus to support the growth and maintenance of a mineral-rich internal skeleton. Fast-growing organisms require relatively more nutrient-rich resources to support their higher allocation to tissue building compared to those with slower growth rates. Thus, how an organism allocates elements has consequences for its elemental requirements.

prokaryotes -diversity -description -include what (2)

Prokaryotes, which include heterotrophic, photosynthetic, and chemosynthetic species, show more trophic diversity than do other groups of organisms (fig. 7.2). Prokaryotes, which have cells with no membrane-bound nucleus or organelles, include the bacteria and the archaea.

archaea

The archaea are prokaryotes distinguished from bacteria on the basis of structural, physiological, and other biological features -widely spread throughout biosphere

"warning" colors

The conspicuous, or aposematic, colors of many distasteful or toxic butterflies, snakes, and nudibranchs warn predators that "feeding on me may be hazardous to your health." Aposematic, or warning, coloration generally consists of sharply contrasting patches of orange or yellow and black.

temperate vs tropical seaweeds toxins

The generalization about higher levels of chemical defense among tropical plants also appears to apply to marine algae. Robin Bolser and Mark Hay (1996) tested the hypothesis that tropical seaweeds have more chemical defenses than temperate seaweeds. They gathered several species of seaweeds from the coast of temperate North Carolina and from the tropical Bahama Islands. On shore, the seaweeds were transferred to a colder freezer (−70°C) to minimize chemical changes. To remove the potential confounding effect of various physical factors, Bolser and Hay created artificial algae to test their hypothesis. The result was strips of artificial seaweed that could be cut up into equal-sized squares and presented to sea urchins in equal numbers. This method of presentation also provided an easy means of quantifying the actual amount of seaweed eaten. *results*: The results of this study showed a clear preference for temperate species of seaweed (fig. 7.13). When given a choice the urchins removed approximately twice as much of the available temperate seaweed. Bolser and Hay showed that the tropical seaweeds have more potent chemical defenses.

What accounts for these differences in photosynthetic response curves? (2)

The photosynthetic response curves of different plant species generally level off at different maximum rates of photosynthesis (Pmax) A second difference among photosynthetic response curves is the photon flux density, or *irradiance* (Isat) required to produce the maximum rate of photosynthesis.

3 types of functional response : Type 3

The type 3 functional response is S-shaped. At low food densities, type 3 functional response curves increase more slowly than during either type 1 or type 2 functional response. Food intake then rises steeply at intermediate food densities, eventually leveling off at higher densities.

Use of cellulose and lignin as a plant defense

The use of cellulose and lignin to strengthen tissues may also provide plants with a kind of chemical defense (even though its considered a *physical defense*). Increasing the cellulose and lignin content of tissues increases their C:N ratios. An increased C:N ratio decreases the nutritional value of plant tissues. (*recall that animals need to get their nitrogen*) additionally, most animals cannot digest either cellulose or lignin. Those that can, generally do so with the help of bacteria, fungi, or protists that live in their digestive tracts. This suggests that the cellulose and lignin in plants may be a first line of chemical defense against herbivores, a defense that most herbivores overcome with the help of other organisms.

problem faced by detritovores

These organisms consume food that is rich in carbon and energy but very poor in nitrogen. In fact, plant tissues, already relatively low in nitrogen when living (see figs. 7.9 and 7.11), are even lower in nitrogen content when cast off by plants as detritus. Keith Killingbeck and Walt Whitford (1996) averaged the nitrogen contents of living and dead leaves of many plant species of environments from tropical rain forests through deserts and temperate forests. Their results show that in all these environments, living leaves contain about twice the nitrogen as dead leaves

See pic and describe what it means...do not look at definition

This expression says that the rate of energy intake is greater if the predator feeds only on prey 1. If the predator feeds on both prey species, the rate will be lower.

example of a species that uses C4 and how it helps

This pathway, which has evolved independently over 30 times, has been documented in approximately 8,000 to 10,000 plant species belonging to 18 plant families. Currently, about half the grass species employ C4 photosynthesis, which enables them to thrive in hot, semiarid environments. (this led to the evolution of a high diversity of grazing mammals and their predators)

what percentage to C4 plants contribute to global terrestrial primary production? how are they important economically?

Though the vast majority of plants employ C3 photosynthesis, C4 plants are estimated to contribute up to 20% of global terrestrial primary production. They are also of great economic significance, since many important crops, such as corn, and many noxious weeds are C4 plants. Because the C4 pathway is more efficient than the C3 pathway under conditions of low atmospheric CO2, ecologists have predicted that rising levels of atmospheric CO2 (see chapter 23, fig. 23.21) will favor C3 plants.

-toxins -digestion-reducing substances

Toxins are chemicals that kill, impair, or repel most would-be consumers. Digestion-reducing substances are generally phenolic compounds such as tannins that bind to plant proteins, inhibiting their breakdown by enzymes and further reducing the already low availability of nitrogen in plant tissues.

3 types of functional response : Type 1

Type 1 functional responses are those in which feeding rate increases linearly (as a straight line) as food density increases and then levels off abruptly at some maximum feeding rate. The only animals that have type 1 functional responses are consumers that require little or no time to process their food—for example, some filter-feeding aquatic animals that feed on small prey.

functional response curve similarity to photosynthetic response curve

Type 2 functional responses are remarkably similar to the photosynthetic response curves shown by plants (see fig. 7.21) and have the same implications. Even if you provide an animal with unlimited food, its energy intake eventually levels off at some maximum rate. This is the rate at which energy intake is limited by internal rather than external constraints.

Maribeth Watwood and Cliff Dahm (1992) and using bacteria for clean-up

Watwood and Dahm collected sediments from a shallow aquifer that contained approximately 8.5×108 bacterial cells per gram of wet sediment. Of these, 6.55×104 bacterial cells per milliliter were capable of living on benzene as their only source of carbon and energy. By exposing sediments from the aquifer to benzene for 6 months, the researchers increased the populations of benzene-degrading bacteria approximately 100 times. Watwood and Dahm found that with no prior exposure, bacterial populations could break down 90% of the benzene in their test flasks within 40 days (fig. 7.28). Exposing sediments to benzene prior to their tests increased the rate of breakdown. Briefly, this study demonstrated that naturally occurring populations of bacteria can rapidly break down benzene leaking from underground storage tanks. This study suggests that these bacteria will eventually clean up the organic contaminants from leaking gasoline storage tanks without manipulation of the environment.

Earl Werner and Gary Mittelbach (1981) equation to model rate of energy intake for a predator feeding on a single prey species

We can represent the rate of energy intake of a predator as E / T, where E is energy and T is time. Earl Werner and Gary Mittelbach (1981) modeled the rate of energy intake for a predator feeding on a single prey species as follows: (see pic) this equation expresses the net rate at which a predator takes in energy when it feeds on a particular prey species.

trophic biology (organization)

We generally group organisms on the basis of shared evolutionary histories, creating taxa such as vertebrate animals, insects, coniferous trees, and orchids. However, we can also classify them by their trophic (feeding) biology.

How do plants "forage"?

What animals do with behavior, plants do with growth. Plants forage by growing and orienting structures that capture either energy or nutrients. They grow leaves or other green surfaces to capture light and roots to capture nutrients. Terrestrial plants harvest energy from sunlight aboveground and nutrients and water from soil. Because of the structure of their environment and the distribution of their resources, plants forage in two directions at once. Like animals, however, plants face limited supplies of energy and nutrients and so face the prospect of compromises between competing demands for energy. Allocation of energy to leaves and stems reduces the amount of energy available for root growth. Increased allocation to root growth reduces energy available for leaves and stems.

factors that predators must consider (just name the 3 and their symbol)

When ecologists consider potential prey for a consumer, they try to identify the prey attributes that may affect the rate of energy intake by the predator. 1) abundance (where Ne = the prey encountered by the predator per unit time) 2) energy cost of searching for the prey (Cs) 3) time spent processing prey (activities such as cracking shells, fighting, removing noxious scent glands, and so forth) Time spent in activities such as these are summarized as handling time, H.

role of abundance

When ecologists consider potential prey for a consumer, they try to identify the prey attributes that may affect the rate of energy intake by the predator. One of the most important factors is the abundance of a potential food item. All things being equal, a more abundant prey item yields a larger energy return than an uncommon prey. In optimal foraging studies, prey abundance is generally expressed as the number of the prey encountered by the predator per unit of time, Ne.

two main classes of chemical defenses that plants use (just name)

When ecologists talk about plant chemical defenses, however, they are generally referring to two other classes of chemicals: toxins and digestion-reducing substances.

which photosynthesis method is most efficient at reducing water loss?

While CAM plants do not normally show very high rates of photosynthesis, their water use efficiency, as estimated by the mass of CO2 fixed per kilogram of water used, is higher than that of either C3 or C4 plants. C3 plants lose from about 380 to 900 g of water for every gram (dry weight) of tissue produced. C4 plants lose from about 250 to 350 g of water per gram of tissue produced, while CAM plants lose approximately 50 g of water per gram of new tissue.

what was White and Markwiese's suggestion to add to the coal mines?

White and Markwiese recommended that sucrose be added to leached gold-mining ores to stimulate breakdown of CN− and uptake of NO−3 by bacteria. This environmental cleanup project was successful because the researchers were thoroughly familiar with the energy and nutrient relations of bacteria and fungi. Another key to the project's success was the great trophic diversity of bacteria. Bacteria will likely continue to play a great role as we address some of our most vexing environmental problems.

results of white an markwiese study

White and Markwiese tested their ideas in the laboratory. In one experiment, they added enough sucrose to produce a C:N ratio of 10:1 within leached ores. This experiment included two controls, both of which contained leached ores without sucrose. One of the controls was sterilized to kill any bacteria. The other control was left unsterilized. Bacteria in the treatments containing sucrose broke down all the CN− within the leached ore in 13 days. Meanwhile, only a small amount of CN− was broken down in the unsterilized control and no CN− was broken down in the sterilized control (fig. 7.29). Why did the researchers include a sterilized control? The sterilized control demonstrated that nonbiological processes were not responsible for the observed breakdown of CN−. summary: adding sucrose to the residual ore stimulates the breakdown of CN−.

what color do leaves mainly absorb?

Within the range of photosynthetically active radiation, leaves absorb mainly blue and red light and transmit mostly green light with a wavelength of about 550 nm.

toxins in temperate vs tropical plants - consumption of leaves rates in temperate vs tropical plants -what does this suggest?

a higher proportion of tropical plant species contain toxic alkaloids when compared to temperate species (fig. 7.12). In addition, on average, the alkaloids produced by tropical plants are more toxic than those produced by their temperate counterparts. Despite these higher levels of chemical defense, herbivores appear to remove approximately 11% to 48% of leaf biomass in tropical forests, while in temperate forests they remove about 7%. These higher levels of herbivore attack on tropical plants suggest that natural selection for chemical defense is more intense in tropical plant populations.

protists -are either what or what

are either photosynthetic or heterotrophic, while most plants are photosynthetic, and all fungi and animals are heterotrophic.

Some of the most thorough tests of optimal foraging theory have been conducted on the

bluegill sunfish

ecological stoichiometry -what is it -how can it be used to indicate what organisms eat and why?

concerns the balance of multiple chemical elements in ecological interactions, for example, the balance of multiple chemical elements between plants and the herbivores that consume them. In this instance, the ratio of carbon to nitrogen in plants is much higher than in the herbivores eating them. When such a large difference, or imbalance, in elemental composition exists, the consumer must eat more food to obtain the limiting nutrient, in this case nitrogen. Differences in elemental ratios among tissues or among organisms significantly influence what organisms eat, how rapidly consumers reproduce, and how rapidly organisms decompose

John Gross (1993) studying type 2 functional response

conducted a well-controlled study of the functional responses of 13 mammalian herbivore species. The researchers manipulated food density by offering each herbivore various densities of alfalfa, Medicago sativa. The rate of food intake was measured as the difference between the amount of alfalfa offered to an animal at the beginning of a trial and how much was left over at the end. Every species of herbivore examined, from moose to lemmings to prairie dogs, showed a type 2 functional response. Figure 7.23 shows the type 2 functional response by moose, Alces alces. same data was shown when studying wolf functional response to increasing moose densities

bacteria to clean up cyanide -carleton white and james markwiese (1994): how did they go about finding the bacteria needed? -what was needed to add to the bacteria?

documented the presence of CN− degraders by looking for bacterial growth in a diagnostic medium. This medium contained CN− as the only source of carbon and nitrogen. Using this growth medium, White and Markwiese estimated that each gram of ore contained approximately 103 to 105 cells of organisms capable of growing on, and breaking down, CN−. White and Markwiese predicted that adding a source of carbon to the residual ores would increase the rate at which bacteria break down CN− and reduce the concentration of NO−3 in the environment. Why should adding organic molecules rich in carbon increase bacterial use of nitrogen in the environment? Bacteria have a carbon:nitrogen ratio of about 5:1. In other words, growth and reproduction by bacteria require about five carbon atoms for each nitrogen atom.

how is PAR quantified?

ecologists quantify PAR as photon flux density

Tilman and Cowan on species of grass root-shoot ratio in nitrogen-poor vs nitrogen-rich soil

exhibited similar results to Setala and Huhta: In general, the study species had lower root:shoot ratios when grown with more nitrogen.

energy limitation

if organisms are not limited by the availability of energy in the environment, their energy intake is limited by internal constraints. Limits on the potential rate of energy intake by animals have been demonstrated by studying how feeding rate increases as the availability of food increases. Limits on rates of energy intake by plants have been demonstrated by studying how photosynthetic rate responds to photon flux density.

use of cyanide in extracting gold -how? -what was the effect?

in the 1970s, techniques were developed to economically extract gold from low-grade ores. One of the main extraction techniques was to leach ore with cyanide (CN−). Dissolved CN− forms chemical complexes with gold and other metals. The solution containing gold-bearing CN− can be collected and the gold and CN− removed by filtering the solution with activated charcoal. solved a technical problem but contaminated soils and groundwater. Several kinds of bacteria can break down CN− and produce NH3. This NH3 can, in turn, be used by nitrifying bacteria as an energy source, producing NO−3 (see "The Nitrogen Cycle" in chapter 19, Section 19.1). Thus, leaching gold-bearing ores and subsequent microbial activity can contaminate soil and groundwater with CN−, a deadly poison, and with nitrate, another contaminant.

roots to biomass ratio for birch seedlings grown on infertile soil vs grown on fertile soil

plant species grown in nutrient-poor soils often develop a higher ratio of root biomass to shoot biomass, the so-called root:shoot ratio, than when grown on nutrient-rich soils. (Setala and Huhta)

C4 photosynthesis

separates carbon fixation and the light-dependent reactions of photosynthesis into separate cells (fig. 7.5) . C4 plants fix CO2 in mesophyll cells by combining it with phosphoenol pyruvate, or PEP, to produce a four-carbon acid, the source of the name "C4" photosynthesis. This initial reaction, which is catalyzed by PEP carboxylase, captures CO2 in the mesophyll cells with PEP to form a four-carbon acid, which then flows into bundle sheath cells that convert it to a 3 carbon sugar and Co2, which are then used in photosynthesis. The separate-cell methods allows high concentrations of Co to build up in the bundle sheath cells, increasing the affinity of RuBp (in the bundle sheath cells) for Co2, leading to the production of PGA . Because PEP carboxylase is specialized for fixing CO2, for which it has a high affinity, C4 plants can reduce their internal CO2 concentrations to very low levels. Low internal concentration of CO2 increases the gradient of CO2 from atmosphere to leaf, which in turn increases the rate of diffusion of CO2 inward. Consequently, compared to C3 plants, C4 plants need to open fewer stomata to deliver sufficient CO2 to photosynthesizing cells. By having fewer stomata open, C4 plants conserve water.

UV light impact on organisms and impact on photosynthesis

ultraviolet light carries so much energy that it breaks the covalent bonds of many organic molecules. Consequently, ultraviolet light can destroy the complex biochemical machinery of photosynthesis.