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Stars as a Guiding Force

Submitted by drosen on Wed, 02/28/2018 - 19:18

In 1958 nocturnal migratory species were observed to naturally turn and yearn to fly in their respective north-south directions relative to the time of year.  While in captivity, this behavior was replicated using a synthetic night sky inside a planetarium. However, when this was removed, the subjects were disoriented and lacked proper positioning. In addition, when the planetarium was reversed, the birds too reversed the direction of their desired movement. This concept was then elaborated on in 1967 by determining which starts or constellations were used by these subjects.  It was presumed that the north star, a large and fixed beacon, would be used, however it was determined that constellations near the north star, such as the big and little dipper, were used instead.  The subjects also showed flexibility and were able to utilize several constellations for travel when other were removed.

Navigation- Routes

Submitted by drosen on Wed, 02/28/2018 - 18:56

NA species migrate on a north-south axis due to the fact that their wintering ranges lie south of their breeding ranges as well as the fact that the major mountain ranges in this region also follow this direction, such as the Appalachian or Rocky Mountains, preventing lateral travel. Species in EU and Asia migrate in a East to West direction due to the presence of major mountain ranges and deserts that spread on this axis such as the Alps and the Greater deserts of the middle east. These routes are sometimes fixed, ie species that have colonized a new land will occasionally return to their ancestral territory before embarking or they will eventually realign with the traditional route.  

The evolution of terrestrial birds

Submitted by drosen on Fri, 02/23/2018 - 07:07

Flight, the defining characteristic of birds, is typically only seen as an advantageous strength and I suspect this is related to human bias given it took our race thousands of years to achieve this feat through technology. However,  there are several species of birds that have appeared to sacrifice their ability to fly, yet they have retained similar vestiges in the from of their underdeveloped wings. This is suggestive that these birds did not struggle to every evolve flight, but instead, evolved flightlessness. Again, human bias may lead one to ask why this would ever occur as flying appears to be such a strong advantage. While true, flight is also associated with several costs including the high relegation of energy during wing development, the morphological trade offs necessary to have a body that can efficiently flight and the increased metabolic needs to sustain flight. In other words, for flight to be an advantage, the species in question must be able to achieve a net positive after factoring the massive expenses that are necessary.  This most often occurs on island settings with either low levels of predation or competition as well as in environments with open apex predatory niches. These roles require different developmental priorities to fully exploit resources they allow one to access.

Parietal-Premotor Cortex Relationship

Submitted by drosen on Thu, 02/22/2018 - 20:54

The human brain is composed of several segmented compartments that are responsible for a wide variety of functions. While individualized,  complex behavior, such as movement was theorized to be multifactorial, involving communication between several areas to coordinate actions. In the paper discussed, the connection between intent, movement and the predicted response to this action were all observed and analyzed via electrical stimulation during brain surgery. In summary, stimulation of the parietal lobe induced an intent and increased stimuli lead to a pseudo movement, where the patient believed they had moved and even interpreted sensation as if they had, however, no movement occured. In contrast, stimulation of the premotor cortex elicited movement, however the patient’s were completely unaware of these actions and they did not express any desire to move. The author infers that movement is an efferent response or plan created by the parietal region of the brain that is then communicated to the premotor cortex, which carries out this action independently of predicted consequences.  

Lift in relation to drag.

Submitted by drosen on Thu, 02/22/2018 - 20:08

In order to achieve elevation and forward motion, or flight, birds are able to manipulate air pressure to utilize a force known as lift while mitigating the opposing force to lift, known as drag. Lift is generated by the redirection of air to the ventral side of the wing. This occurs due to the streamlined and asymmetric structure of the wing. The accumulation of this pressure creates a natural gradient, which then pushes against the wing in an effort to restore equilibrium. This movement of fluid generates lift and the amount of lift generated is secondary to the SA of the wing as well as the speed of the air passing through the feather. In addition, lift can be artificially enhanced in slower wind speeds by increasing the angle of attack or the angle of the wing. By doing this, the SA of the wing is increased, which directly increases lift, however, this also increases drag and after a certain angle the drag will overwhelm the total lift, causing the bird to stall. This phenomenon is also utilized and is commonly used for precision landing that does not require a gradual decline in speed.

Loss of flight, an evolutionary perspective.

Submitted by drosen on Thu, 02/22/2018 - 19:47

Flight is typically regarded as an evolutionary marvel and a defining characteristic of birds, however, there have been dozens of species that have thrived by evolving a more terrestrial lifestyle. Flightlessness has typically evolved in environments where flight, and the various tradeoffs necessary to both achieve and sustain this, are a total net-negative in terms of fitness or survivability. Some of these consequences of flight include the the high cost during development, the morphological trade offs necessary to have a body that can efficiently flight and the increased metabolic needs to sustain flight. Environments where flight would not be beneficial are places with low rates of predation or low competition for resources. It could also evolve due to the lack of necessity, as there are terrestrial niches that would favor larger size and beaks (predatory role).  Dodo bird, Giant Moa and Phorusrhacos all lost flight  (lack of predation, increased E to size, predatory role) specifically.  These species seem to exhibit Neoteny or retention of juvenile characteristics as opposed to complete recession of wing development as they still have a not well ossified sternum and obtuse scapula-coracoid joint.  Also, developmental heterochrony, which shortens the embryonic process of wing development

Theropod Origin of Birds

Submitted by drosen on Thu, 02/22/2018 - 19:39

The discovery of archaeopteryx 2 years after Darwin published his theory of evolution initiated the argument that birds were of theropod descent. This creature, while reptilian in nature, had wings with asymmetrical pattern (flight) as well as a larger skull which presumably housed a larger brain.  The prevailing alternative hypothesis states that thecodonts are potential ancestors  due to their large, wing-like scales found on their dorsal aspects. Following this discovery, multiple fossils of feathered dinosaurs were uncovered including sinosauropteryx,  protarchaeopteryx, caudipteryx as well as several microraptor skeletons that all contributed their own unique clues which supported the theropod descent theory.

Observational differences between #25

Submitted by drosen on Fri, 02/16/2018 - 14:48

Observational Differences:

1. The bottom panel is more blurry than the top panel.

2. The pictures of pannel1&2A and 1&2B are not the same distance from the camera in the bottom panel.  This is due to the differnet bee sizes as well as the different leaf sizes. 

3. The Flowers in 1 and 2 B panels are not the same color.

4. There is no glass rim in 1A or 1B

5. There is no gray surface in 1A or 1B

6. The width and color of the bees do not appear to be consistent betwee the 2panels.

7. There appears to be a light source illuminuating 1A and 1B 

8. The leaves in panel A appear to be facing in different directions. 

9. The bee is resting in a flower in Panel 2B however it is residing on leaves in 1B


1. Different cameras were used given the degrees of clarity.

2. Different bees were used given the differences in size and color

3. The speciments used in the bottom photohraph are not the same as the top given the array of differences.

4. The photograph was taken at a later date due to the flowers having changed.

5. The photograph was taken in a different location or at a different time of day due to the degrees of lighting differences. 


Starting the observational paragraph:

Perfect replication of any experiment or action is an unfair expectation in experimental science. The complexity and wide array of variables that simply cannot be controlled will always contribute to indescrepancies between data.  However, these differences should be expected and properly acknowledged or explained. Here we see that even a brief comparison of the two figures allows one to find several discrepencies, including distance from the material, level of focus,  time of day and location of the photograph, that are likely secondary to variables not approrriately discussed in the methods section above.

For the capture of clear, useful information while photographing detailed objects, such as insects, the distance one captures the image and the level of focus used help one construct clear and informative images. Based on the dife









Inference vs. Observation.

Submitted by drosen on Fri, 02/16/2018 - 13:44

At the hospital; we typically see patient's that display a wide variety of observable symptoms that are then used to make inferences pertaining to their underlying cause. A classic example would be a rash. Typically, these are most offten treated as either a reaction to a fungal source or an allergic reaction to a new chemical.  The observable symptoms,  i.e the rash and any associated chatacteristics such as the type of nodules, scale, color etc all allow the provider to make an educated guess, or inference,  as to the method of treatment used (topical steroid if allergic or a topical antifungal if tinea based).

Perfect Paragraph - Stable isotope analysis.

Submitted by drosen on Fri, 02/16/2018 - 10:11

Stable isotope analysis is a revlutionary analytical process that has several implications on both the ornithological field and conservative movements worlwide. This technique allows for the analysis of isotope concentrations that collect in the tissues of species following meals and this information can be used to make inferences on location given the geographic predicatilbity of these isotopope concentrations. This is atypically powerful with avian species as their feathers are unique and metabollicaly inert once they reach maturity. Similar to fossills, this leaves a lasitng mark that can be analyzed months after the standard isotopes would have naturally been released in normal tissues. Conservatonalist advocates have used this evidence to support movements for the protection breeding and molting grounds that can be thousands of miles away from the speices that are affected by their destruction.


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