Major Questions in Biology - Essay Example

? Biology Materials Science Some structural materials produced by animals include biological polymers and polymer composites. Ligaments are one example of these materials. The function of a ligament is to connect one bone to another. A ligament is made up of collagen fibers. Naturally, ligaments possess high ductility, are able to handle maximum stress, and have a strength which is independent of the strain rate (Meyers et al.). Silk is another form of structural material derived from animals. It is made up of two proteins named fibroin and sericin. There are various mechanical properties of silk depending on the animal that produces it. Spiders, for example, produce dragline silk that has a high tensile strength and a strain that fails at 6%. Other forms of silk produced by spiders, especially the orb-web-spinning spiders, are superior to almost all natural structural materials produced by man and other animals. Another type of spider silk, the viscid silk, possesses remarkable extensibility and maximum strength of over 1 GPa (Meyers et al.). Other structural materials derived from animals include exoskeleton of arthropods, as well as keratin-based hooves and horns (Meyers et al.). Synthetic fibers rayon and nylon are also actually organic in origin. Rayon comes from cellulose, which is the solid part of the plant cell wall. On the other hand, nylon is the first type of fiber that is considered truly synthetic. It is made up of linear superpolymers (“Miracle Fibers”). 2. Terrestrial Locomotion Typically, tetrapods have the upper arm and upper leg extended in such a way as it is almost at a straight horizontal line with respect to its body. Moreover, the forearm and the leg form a nearly right angle relative to the body. The body weight of the tetrapod is actually concentrated into the torso or the upper segment with only a small portion of the weight on the upper part of the lower limbs or the area of the thighs. The main task of the limbs is to lift the body off the ground in order to walk. Moreover, the legs of tetrapods have internal bones within them and with muscles that are externally attached in order to facilitate movement. Furthermore, the basic form of the leg of a tetrapod is that it has three key points or joints: the shoulder joint, the knee joint and the ankle joint. The sequence and the arrangement of these joints facilitate movement and make it possible and smooth (Polly). One principle of tetrapod locomotion includes the fact that locomotion must be a compromise or a balancing force between movement and gravity. This means that the animal must always remain in a state of balance whether it is at rest or it is in motion, except when it is falling over. Secondly, the force for locomotion is derived from muscles and gravity. Thirdly, bones and muscles must be regarded as lever systems in order to produce locomotion. Bones and the joints that they form are usually involved in one or more lever systems while muscles are confined to only one lever system. It is the action of these lever systems that produce a forward motion in tetrapods. There are several lever systems suited for each task in the body. However, those lever systems that work the hardest include those that support weight, close jaws or produce forward motion. The heavy muscles, in particular, which are located toward the center of the body and the proximal ends of bones, are actually a major source of movement for the tetrapod body (Polly). Unlike in bipedal and flying animals whose balance in locomotion centers on the hindlimbs, tetrapods have their balance concentrated over their forelimbs. Moreover, the propulsion for locomotion comes from their hindlimbs, and their head serves to counterbalance the body (Polly). Cats usually have a longer swing duration of the hind limbs, a shorter stance duration, and the same step durations of fore and hind limbs. However, as the cat moves faster, its step duration becomes shorter. These specifics may become slightly different in the case of a trotting or galloping cat (Afelt & Kasicki). The horse, on the other hand, has movement that is coming from the muscles of the torso and not the legs. Nevertheless, the force of the movement is coming from the hindquarters of the horse, or the rear part of its body. This movement is generated from the rear end of the horse and it is transferred to the front. Its front legs are the ones that determine direction while its hind legs are the ones responsible for momentum. The horse has a rather more complicated series of movements just to make one step. The reason is that the horse needs four basic movements in order to complete one step. These four basic movements include the impact, stance, thrust and flight. The impact happens when the leg touches the ground and absorbs both forward and downward forces on a horse’s body. The stance refers to the movement when ay of the horse’s limbs is steady on the ground while bearing its weight. The thrust is when the limb tries to stop backward movement but it still supports the animal’s weight. The flight happens when the horse moves forward into the air as when it jumps over obstacles in the equestrian games. Moreover, the horse has a variety of other special movements: walk, trot, canter, gallop, back, pace, rack, slow gait, running walk, fox trot, and paso fino. During these times, the smoothness, rhythm and speed of the horse’s walk vary (“Locomotion”). The camel’s locomotion is made possible by a digitigrade stance with large feet for supporting the animal in sand and flexible pads on the soles to be able to step readily wherever necessary. The camel’s stride is long and slow with the body supported by the two right or the two left legs. The difference in the matter of supporting legs in camels usually lies on whether the camel is young or old, or whether it is a slow-walking camel or a fast one. Nevertheless, the manner of locomotion of a camel does not differ whether it is loaded or unloaded. The camel never trots unlike a horse and it simply paces all the time, unless when it is pursued for that is the time that it gallops (Dagg). Human locomotion, on the other hand, is characterized by bipeda plantigrade progression as well as the coordination of the various muscles and bones as well as segments and lever systems of the body in order to control muscular activity and thus minimize the expenditure of energy during locomotion. The various basic movements involved in human locomotion include the horizontal rotation of the pelvis, the vertical displacement of the body, the flexion of the knee, the mediolateral pelvic tilt, the plantar flexion of the foot and ankle, the rotation that the shoulder girdle makes, and the lateral displacement of the torso (Ayyappa). The biggest difference between humans and other tetrapods when it comes to locomotion is that humans use bipedal locomotion and that they usually try to conserve as much energy as possible when walking. 3. Endothermic Homeotherms There is a controversy among evolutionary biologists regarding the theory whether dinosaurs were once warm-blooded because the birds that they descended from them are warm-blooded. One of the various pieces of evidence that somehow prove the warm-bloodedness of dinosaurs is bone histology, or the microscopic analysis of the structure of the bone cell and tissue. Bone reworking is generally a characteristic of tachymetabolic or warm-blooded animals. Based on current bone evidence, dinosaurs possessed a high degree of bone reworking even when they were young. On the other hand, cold-blooded or bradymetabolic animals do not possess such extensive reworking of the bones (“The Hot-Blooded Dinosaurs”). Another evidence of the warm-blooded nature of dinosaurs was the results of skeletochronology, which calculates the maximum levels of dinosaur growth. Based on evidence from skeletochronology, dinosaurs had a much higher rate of growth compared to the cold-blooded organisms of the same size. In fact, the growth rate of dinosaurs somehow parallels those of birds and humans, thus classifying them as warm-blooded in this respect (“The Hot-Blooded Dinosaurs”). Another evidence for the warm-bloodedness of dinosaurs is the texture of the bones, which are considered as indicative of the rate of growth. While the normal cold-blooded animals show a relatively slower growth rate, dinosaurs grew as fast as mammals do right now. This characteristic somehow classifies dinosaurs as warm-blooded (“The Hot-Blooded Dinosaurs”). A fourth piece of evidence is the metabolic rates of dinosaurs as shown by computer models. The rate of metabolism of dinosaurs even just for walking or slow running generally exceeded those of other ectotherms, which are characteristically less active than warm-blooded animals. Thus, the dinosaurs may have been warm-blooded. Moreover, small dinosaurs and dinosauromorphs had even had metabolic rates akin to warm-blooded animals (“The Hot-Blooded Dinosaurs”). One last piece of evidence for the warm-bloodedness of dinosaurs is the results of the examination of the nutrient foramina. This is related to the fast metabolic rate of these animals. Evidence from the nutrient foramina of dinosaurs states that the amount of blood that used to flow through the bodies of dinosaurs far exceeded that of other cold-blooded animals at present, and it even exceeded that of other mammals. Indeed, the huge amount of blood that travelled through the bodies of dinosaurs may have made them warm-blooded (“The Hot-Blooded Dinosaurs”). 4. Sea Otters and Kangaroo Rats In order to survive the frigid seawater environment, the sea otter has many distinguishing survival mechanisms and adaptations. First, the sea otter has its feet placed out of the water when it floats on its back. This way, its feet help to reduce heat loss when the temperature of the water is too cold. In order to lose heat, the sea otter extends its feet out underwater thus maximizing surface area. However, when preserving body heat, it tends to fold up its feet or spread them out (“Enhydra lutris”). The sea otter also has been known to naturally increase or decrease its buoyancy as the temperature of the water changes. Sea otters have the ability to control their lung capacity in order to decrease their buoyancy in high-temperature water while increasing their buoyancy in low-temperature water (“Enhydra lutris”). Moreover, sea otters have smaller tails and webbed feet. The relatively smaller tails help reduce the surface area, and the fact that it has a plump base and a flattened tip helps sea otters swim fast when they are underwater. Moreover, the webbed feet are also very helpful when it comes to picking up speed when the animal is in the water (“Enhydra lutris”). The sea otter also has a large amount of fur to insulate them or to keep them warm. There is an estimated 850,000 to 1,000,000 hairs on the sea otter per square inch of its body. The stout guard hairs type is waterproof and it is important in order to preserve body heat because the sea otter does not have a blubber (“Enhydra lutris”). On the other hand, kangaroo rats possess extremely sensitive hearing through their broad skulls and large bony structures around their inner ear. Moreover, they possess nasal passages that make them reabsorb moisture coming from their own breath thus conserving water. They also have very large eyes that facilitate their nocturnal activities by making them see in the dark (Albert). However, their more important adaptations are those when it comes to handling the heat in the desert. The fact that kangaroo rats have very oily coats makes them not sweat despite the heat of the desert. Moreover, the fact that kangaroo rats do not sweat makes them less able to retain the coolness of their bodies. This is why they dig burrows underground in order to make their bodies cool (Albert). Kangaroo rats also can survive without water because they obtain the moisture that they need from their seed diet (“Animal Fact Sheet”). Lastly, kangaroo rats have very efficient kidneys that have a lengthened loop of Henle for the production of urine which is five times as concentrated as concentrated human urine at the maximum level. Because of this ability, kangaroo rats never really have to take in water. Its cells produce water during the oxidation of food and it is sufficient for their body (Albert). 5. Osmoregulation and Excretion Diffusion is the intermingling of the solute molecules of a particular liquid or gaseous substance, and their natural movement from an area of greater concentration to that of lesser concentration. Osmosis, on the other hand, is the movement of water molecules from an area of lesser solute concentration to an area of greater solute concentration across a semi-permeable membrane like the cell membrane (“Diffusion”). In the animal body, diffusion is important in the cardiovascular system as the diffusion of oxygen into the blood across the capillary and alveolar cells. Similarly, carbon dioxide in the blood also diffuses into the alveoli as a form of waste product. There are also many other biological processes that are made possible by diffusion (Reasoner). Osmosis inside the animal body is useful in that cells with a relatively higher solute concentration than its surrounding fluid environment absorb water or other solvents fast, thus resulting to hypotonic solutions or cell bursting. Osmosis actually involves a constant movement of fluid in and out of the cell. In the case of the single-celled protest known as paramecium, there is a constant struggle to maintain equilibrium within the cell thus there is a need to remove water that flows into the cell all the time. In order to prevent the paramecium from a possible rupture in the case of a hypotonic state, it uses a contractile vacuole that constantly pumps water out of its body (Reasoner). In the case of planarians into whose bodies water enters through osmosis, they have a special excretory organ that is made up of interconnecting canals running through the entire length of the organism’s body. Moreover, the cilia in the planaria’s flame cells sweep the water towards the excretory pores. This is essential so that the planarian body is constantly emptied with water (“Anatomy of Animals”). Osmosis is related to the functioning of the kidneys. It is in the animal body’s best interest to recover as much water as it can from the blood filtrate, thus creating the most possible concentrated urine. In order to make the water from the filtrate move to the kidney, the area surrounding the nephron must be in a state of high salt concentration. Unless this is the case, there will be a problem with one’s excretion of urine (Reasoner). The idea behind kidney filtration and urine formation is causing the filtrate to move to the area surrounding the nephron. Filtrate then passes down the descending limb of the loop of Henle. Since this fluid is flowing in the opposite direction in the other limb, then the fluid moving down is getting increasingly concentrated, while the fluid moving up gets increasingly dilute. The countercurrent multiplier that reflects the opposing directions is the one factor that allows the production of concentrated urine (“Water Levels and the Kidney”). Top of Form Bottom of Form Works Cited Afelt, Zofia & Kasicki, Stefan. “Limb Coordinations during Locomotion in Cats and Dogs.” Acta Neurobiologiae Experimentalis 35 (1975): 369-376. Albert, Sarah. “Structural Adaptations of the Kangaroo Rat.” 2013. Pawnation. 17 July 2013. “Anatomy of Animals.” 2013. A Review of the Universe – Structures, Evolutions, Observations, and Theories. 17 July 2013. “Animal Fact Sheet: Merriam’s Kangaroo Rat.” 2008. Arizona-Sonora Desert Museum. 17 July 2013. Ayyappa, Ed. “Normal Human Locomotion, Part 1: Basic Concepts and Terminology.” Journal of Prosthetics and Orthotics 9.1 (1997): 10-17. Dagg, Anne Innis. “The Locomotion of the Camel (Camelus dromedarius).” [Abstract]. Journal of Zoology 174.1 (1974): 67-78. “Diffusion.” 2013. Georgia State University. 17 July 2013. < http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/diffus.html> “Enhydra lutris.” 2008. University of Wisconsin La Crosse. 16 July 2013. “Locomotion.” 2013. Iowa State University. 17 July 2013. Meyers, Marc Andre, Po-Yu Chen, Albert Yu-Min Lin & Yasuaka Seki. “Biological materials: Structure and mechanical properties.” Progress in Materials Science 53 (2008): 1-206. Print. “Miracle Fibers – Rayon and Nylon.” 2013. Fabrics.net. 17 July 2013. Polly, P. David. “Principles of locomotion: Functional Morphology and Artistic Reconstructions.” 2011. Indiana University. 16 July 2013. Reasoner, Amanda. “Teaching Osmosis and Diffusion through Kidney Dialysis.” 2007. Yale University. 17 July 2013. “The Hot-Blooded Dinosaurs: Reconstructing Dinosaur Physiology.” 2013. University of Maryland. 17 July 2013. “Water Levels and the Kidney.” 2013. S-Kool Youth Marketing Limited. 17 July 2013. Read More