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Therefore, workers must wear a special costume to fool the chick into thinking it is associating with an adult whooping crane. Therefore, workers must wear a special costume to fool the chick into thinking it is associating with an adult whooping crane to avoid creating the expectation it will mate with a human. Therefore, workers must wear a special costume to fool the chick into thinking it is associating with an adult whooping crane to avoid creating the expectation that it will mate with a human. Whooping crane undergoes habituation in which the chicks only make a bond with the first object they see. Thus workers must wear a special costume to fool the chick into thinking it is associating with an adult whooping crane. During operant conditioning, the behavioral response is modified by its consequences, with regards to its form, strength, or frequency. The response to the original, unconditioned stimulus is called the unconditioned response. The conditioning stimulus that researchers associated with the unconditioned response was the ringing of a bell. This was 1646 Chapter 36 Population and Community Ecology repeated during several trials. After the conditioning period was finished, the dog would respond by salivating when the bell was rung, even when the unconditioned stimulus, the food, was absent. Thus, the ringing of the bell became the conditioned stimulus and the salivation became the conditioned response. Although it is thought by some scientists that the unconditioned and conditioned responses are identical, even Pavlov discovered that the saliva in the conditioned dogs had characteristic differences when compared to the unconditioned dog. It had been thought by some scientists that this type of conditioning required multiple exposures to the paired stimulus and response, but it is now known that this is not necessary in all cases, and that some conditioning can be learned in a single pairing experiment. Classical conditioning is a major tenet of behaviorism, a branch of psychological philosophy that proposes that all actions, thoughts, and emotions of living things are behaviors that can be treated by behavior modification and changes in the environment. Operant Conditioning In operant conditioning, the conditioned behavior is gradually modified by its consequences as the animal responds to the stimulus. Skinner put rats in his boxes that contained a lever that would dispense food to the rat when depressed. In this way, the animal is conditioned to associate a type of behavior with the punishment or reward, and, over time, can be induced to perform behaviors that they would not have done in the wild, such as the "tricks" dolphins perform at marine amusement park shows (Figure 36. Some primates, including humans, are able to learn by imitating the behavior of others and by taking instructions. The development of complex language by humans has made cognitive learning, the manipulation of information using the mind, the most prominent method of human learning. In addition to visual processing, cognitive learning is also enhanced by remembering past experiences, touching physical objects, hearing sounds, tasting food, and a variety of other sensory-based inputs. This implies that they could visualize the result of stacking the boxes even before they had performed the action. The motivation for the animals to work their way through the maze was a piece of food at its end. In these studies, the animals in Group I were run in one trial per day and had food available to them each day on completion of the run (Figure 36. It may not be immediately obvious that this type of learning is different than conditioning. This science is controversial; noted scientists such as the late Stephen Jay Gould criticized the approach for ignoring the environmental effects on behavior. Sociobiology also links genes with behaviors and has been associated with "biological determinism," the belief that all behaviors are hardwired into our genes. No one disputes that certain behaviors can be inherited and that natural selection plays a role retaining them. This inquirybased investigation provides an opportunity for you to design and implement a series of experiments using choice chambers to investigate behaviors that underlie directed movement (taxis) towards or away from environmental stimuli, including chemical signals, light, and temperature, in a small population of Drosophila. Activity Animal Behavior Field Study Animal behavior can be studied in nearly every environment. Visit a local park, zoo, athletic field, or even a location on your school campus and observe the behaviors and interactions among different animals and with their environment.

Depending on the subtype, they can be either O-glycosylated or non-glycosylated, and present over 70% amino acid homology with each other. Beyond being abundant in leucine and glutamate, they are characterized by conserved cysteines, usually at positions 1, 29, 99, and 139, which generally form two disulfide bonds. The molecule has a disulfide bond as well as an N-linked carbohydrate chain bound to asparagine 80. The level of glycosylation of these proteins determines the expression system in which they should be expressed. Its structure is characterized by the presence of two disulfide bonds and four Ж-helices. There are three forms of this protein, with molar masses varying from 45 to 90 kDa and the largest one having 522 amino acids (Walsh, 2003). It has a molar mass between 34 and 40 kDa, 40% of which is due to carbohydrate chains. The molecule has three N-glycosylation sites (asparagine residues 24, 38, and 83) and an O-glycosylation site (serine 126). The carbohydrate chains contribute to the solubility, in vivo metabolism, and cellular processing of the molecule. However, its complex glycosylated tetra-antennary structure and the high degree of sialylation enhance the importance of a careful control of operational conditions during the manufacturing process. This aims at minimizing the micro- and macroheterogeneity and, consequently, maximizing the yield in terms of isoforms with high biological activity (see Chapter 6). There are other non-renal applications, such as the minimization of blood transfusion after surgery, the prevention of anemia after bone marrow transplantation, and the treatment of anemia caused by the use of antiretroviral drugs, by chemotherapy, and by prematurity. There are two isoforms of this protein that are most commonly encountered in the human body: one with 110 amino acids and another with 125. Its therapeutic use is still under study and future medical applications for this protein are likely to be the treatment of dwarfism, diabetes type 2, and renal diseases, among others. The secondary structure is characterized by the presence of two anti-parallel в-sheets and three disulfide bonds, which confer stability to the molecule. The most well known therapeutic hormones are insulin, glucagon, growth hormones, and gonadotropins. Recombinant human insulin and recombinant human growth hormone, both produced by microbial cells, were the first biopharmaceuticals to obtain approval from the regulatory agencies. Insulin is widely used for diabetes treatment, whereas growth hormone is used in the treatment of short stature, obesity, and for stimulating ovulation. These three proteins are heterodimers that contain an identical polypeptide subunit (Ж) and another specific subunit (в), which confer the respective biological activity. Its function is to proteolytically convert the zymogen, plasminogen, into active plasmin, which in turn degrades fibrin strands, thus dissolving the clots (Walsh, 2003). Two variants of this protease have already been isolated: one of 54 kDa and another of 33 kDa, both displaying proteolytic activity over plasminogen. In this case the glucocerebroside, the lipid component of cell membranes, accumulates in the organism, leading to an exaggerated enlargement of the liver and other 1 organs. Another genetic metabolic disorder is Fabry disease, which is related to a deficiency in the enzyme Ж-galactosidase A. This enzyme is involved in the metabolism of lipids, and its deficiency leads to the accumulation of lipids in the eyes, kidneys, and nervous and cardiovascular systems. A hemophilic person is constantly at risk of undergoing a hemorrhage because of the incapacity to correctly carry out coagulation. Until the development of recombinant blood coagulation factors in the 1990s, hemophiliacs were treated by blood transfusion and with proteins obtained from the plasma of human donors. However, both solutions presented high risk of transmission of pathogenic agents, especially viruses. Since then, although an additional virus inactivation step has been added to the manufacturing of plasma-derived molecules to increase product safety, there is still the risk of transmitting unknown viruses and pathogens of other types. Apart from that, limitations related to the availability of raw material (plasma from donors) also pose problems for plasma-derived coagulation factors.

The taller the tree, the greater the tension forces needed to pull water, and the more cavitation events. In larger trees, the resulting embolisms can plug xylem vessels, making them non-functional. Evaporation from the mesophyll cells produces a negative water potential gradient that causes water to move upwards from the roots through the xylem. Negative water potential draws water into the root hairs, cohesion and adhesion draw water up the xylem, and transpiration draws water from the leaf. Negative water potential draws water into the root hairs, cohesion and adhesion draw water up the phloem, and transpiration draws water from the leaf. Regulation of transpiration, therefore, is achieved primarily through the opening and closing of stomata on the leaf surface. Stomata are surrounded by two specialized cells called guard cells, which open and close in response to environmental cues such as light intensity and quality, leaf water status, and carbon dioxide concentrations. When stomata are open, however, water vapor is lost to the external environment, increasing the rate of transpiration. Therefore, plants must maintain a balance between efficient photosynthesis and water loss. Plants have evolved over time to adapt to their local environment and reduce transpiration(Figure 23. Desert plants (xerophytes) and plants that grow on other plants (epiphytes) have limited access to water. Aquatic plants (hydrophytes) also have their own set of anatomical and morphological leaf adaptations. The leaves of a prickly pear are modified into spines, which lowers the surface-to-volume ratio and reduces water loss. Shyamal/Wikimedia Commons; credit c: modification of work by Huw Williams; credit d: modification of work by Jason Hollinger) this OpenStax book is available for free at cnx. Trichomes are specialized hair-like epidermal cells that secrete oils and substances. Transportation of Photosynthates in the Phloem Plants need an energy source to grow. Once green shoots and leaves are growing, plants are able to produce their own food by photosynthesizing. Structures that produce photosynthates for the growing plant are referred to as sources. Sugars produced in sources, such as leaves, need to be delivered to growing parts of the plant via the phloem in a process called translocation. The points of sugar delivery, such as roots, young shoots, and developing seeds, are called sinks. The products from the source are usually translocated to the nearest sink through the phloem. For example, the highest leaves will send photosynthates upward to the growing shoot tip, whereas lower leaves will direct photosynthates downward to the roots. Translocation: Transport from Source to Sink Photosynthates, such as sucrose, are produced in the mesophyll cells of photosynthesizing leaves. Neighboring companion cells carry out metabolic functions for the sieve-tube elements and provide them with energy. The high percentage of sugar decreases s, which decreases the total water potential and causes water to move by osmosis from the adjacent xylem into the phloem tubes, thereby increasing pressure. This increase in total water potential causes the bulk flow of phloem from source to sink (Figure 23. Unloading at the sink end of the phloem tube occurs by either diffusion or active transport of sucrose molecules from an area of high concentration to one of low concentration. Water diffuses from the phloem by osmosis and is then transpired or recycled via the xylem back into the phloem sap.

On the contrary, concentration gradients are a form of potential energy, dissipated as the gradient is eliminated. This movement accounts for the diffusion of molecules through whatever medium in which they are localized. A substance will tend to move into any space available to it until it is evenly distributed throughout it. After a substance has diffused completely through a space, removing its concentration gradient, molecules will still move around in the space, but there will be no net movement of the number of molecules from one area to another. This lack of a concentration gradient in which there is no net movement of a substance is known as dynamic equilibrium. The closer the distribution of the material gets to equilibrium, the slower the rate of diffusion becomes. Lower temperatures decrease the energy of the molecules, thus decreasing the rate of diffusion. The molecules slow down because they have a more difficult time getting through the denser medium. A large, spherical cell will die because nutrients or waste cannot reach or leave the center of the cell, respectively. Therefore, cells must either be small in size, as in the case of many prokaryotes, or be flattened, as with many single-celled eukaryotes. A concentration gradient exists that would allow these materials to diffuse into the cell without expending cellular energy. However, these materials are ions are polar molecules that are repelled by the hydrophobic parts of the cell membrane. The material being transported is first attached to protein or glycoprotein receptors on the exterior surface of the plasma membrane. This allows the material that is needed by the cell to be removed from the extracellular fluid. Others are carrier proteins which bind with the substance and aid its diffusion through the membrane. Channels the integral proteins involved in facilitated transport are collectively referred to as transport proteins, and they function as either channels for the material or carriers. Passage through the channel allows polar compounds to avoid the nonpolar central layer of the plasma membrane that would otherwise slow or prevent their entry into the cell. Aquaporins are channel proteins that allow water to pass through the membrane at a very high rate. In some tissues, sodium and chloride ions pass freely through open channels, whereas in other tissues a gate must be opened to allow passage. Cells involved in the transmission of electrical impulses, such as nerve and muscle cells, have gated channels for sodium, potassium, and calcium in their membranes. Opening and closing of these channels changes the relative concentrations on opposing sides of the membrane of these ions, resulting in the facilitation of electrical transmission along membranes (in the case of nerve cells) or in muscle contraction (in the case of muscle cells). Proteins can change shape when their hydrogen bonds are affected, but this may not fully explain this mechanism. Each carrier protein is specific to one substance, and there are a finite number of these proteins in any membrane. This can cause problems in transporting enough of the material for the cell to function properly. When all of the proteins are bound to their ligands, they are saturated and the rate of transport is at its maximum. Glucose, water, salts, ions, and amino acids needed by the body are filtered in one part of the kidney. This filtrate, which includes glucose, is then reabsorbed in another part of the kidney. Because there are only a finite number of carrier proteins for glucose, if more glucose is present than the proteins can handle, the excess is not transported and it is excreted from the body in the urine. Water, like other substances, moves from an area of high concentration to one of low concentration.