Ana - Methods/session 5: 2nd synopsis
=COMPARATIVE CRITICISM: 2nd synopsis=
Gaia hypothesis formulated by the chemist James Lovelock and co-developed by the microbiologist Lynn Margulis in the 1970s proposes that the living organisms interacting with inorganic surroundings on the earth. This action forms synergistic and self-regulating complex system which helps to perpetuate and maintain the conditions for life on earth. The biosphere and the evolution of organisms should be able to affect the stability of global temperature, salinity, seawater, atmospheric oxygen levels, the maintenance of a hydrosphere of liquid water and other variables that affects life on earth.
Homeostasis a complex dynamic adaptation of an organism or a device to the environment. It’s a resistance and the ability to change in the optimal condition and equilibrium made by homeostatic mechanism and regulators. Homeostatic systems are ultra-stable and their whole organization contributes to the balance.
The mechanism of homeostasis consists of three parts: the receptor which recives the information of a change in the environment, the control center or integration center which receives and process the information and the effector that responds to the commands either opposing or enhancing the stimulus. The system mainly reacts to positive or negative feedback. The negative feedback tends to keep the homeostasis constant that means the system will reverse in such a way as to reverse the direction of a change. An example of negative feedback is the thermoregulation. When the temperature of the body rises receptors in the skin and hypothalamus sense the change triggering a command from the brain to decrease the body temperature. The positive feedback is not so common in living organisms. It has a destabilizing result so does not result in homeostasis. For example, in blood clotting platelets process mechanism to transform blood liquid to solidify.
One of the first devices capable of adapting itself to the environment was the homeostat made by the English psychiatrist and a pioneer in cybernetics William Ross Ashby in 1948. This adaptive ultra-stable system was able to learn and reinforce itself to maintain the homeostasis. In 1949 Time described it as ‘’the closest thing to a synthetic brain so far designed by man’’.
Multicellular organism is relying on a complex communication between cells. One of the most profound evolutionary events in the history of life on earth is the development of a multicellular organisms from unicellular ancestors. During this transitions the cells started to communicate with each other in many ways while playing specific roles in the development and later controlling the cellular function. This process is particularly delicate during the early embryonic development. In the developed organism intercellular communication coordinates activities between multiple cells and makes an organism-wide process like growth, immune response and homeostasis.
Cells use a molecular code to communicate with each other. This phenomenon was discovered by a team of Caltech scientists. They release molecules called ligands into the environment to send messages to their neighbors. Ligands bind to receptors on the surface of other cell which interpret the message and trigger a set of chemical reactions. They communicate by analyzing the relationships between ligands, which embody the messages between themselves and the receptors located on the cell surface when they get bound by the ligands.
All of the ligands interact promiscuously with all of the receptors. The cell decodes information from ligand combinations and not the individual ligands themselves, that means that a different combination of ligands encodes different instructions for the cell. But there is not only one information that is encoded in the group of ligands. The information from the same combination of ligands can be read differently from non-identical kinds of cells because each type of cells has a different combination of receptors. The scientists discovered that most cells create a highly connected signaling network expressing tens or even hundreds of ligands and receptors to communicate which each other through multiple ligand-receptor paths. They also discovered that receptors evolved earlier than ligands.
Cells communication with their environment is based on chemicals that they release or absorb., but they have also the ability to respond to the mechanical forces, such as flow or the distortion or deformation of the material they are interacting with. Cells tend to bind to the environment, they interact with it exerting forces and unravel its elastics properties by ‘measuring’ the deformations these forces induce. Their ‘elastics-matching’ tendency coordinates the cell type they want to differentiate into. If the environmental elasticity is similar to brain tissue it will differentiate into neuron. The scientists are rising the questions how the cells sense elasticity, how does the cell ‘know how much force to apply and what can be the evolutionary advantage of this mechanism.
Claude Bernard discovered that the extra-cellular fluid environment, more particularly the interstitial fluid has a physiological capacity to ensure protective stability for the tissues and organs of multicellular organism. He claimed that all of the vital mechanisms have always one goal, which is to maintain the uniformity of the conditions of life in the internal environment. The condition for the free and independent life is the stability of the internal environment. He named this phenomenon as Milieu intérieur.
Synergy is the creation of a whole that is greater than the simple sum of its parts. We can find synergistic phenomena in physics, chemistry, cooperative interactions among genes and genomes, the division of labor in bacterial colonies, the synergies of scale in multicellular organisms and one that are produced by socially-organized groups, from honeybee, colonies to wolf packs and human society. The result is the self-assembly of complex systems. Human tools which are spread in the natural world represent important sources of synergistic effects. In a technical context is a construct or collection of different elements that work together and produces results that can’t be obtainable by any of the elements alone. The elements can include people, softwares, machines, facilities, etc. The relationship between the parts creates the value of the system.