Evolutionary, Adapation, Sensory Systems & Brain Receptors

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1. How adaptation is important from an evolutionary perspective.

Evolutionary theory is based on Charles Darwin's theory that humans are products of evolution, as are any other biological phenomena. Second, human nature is a biological phenomenon in that it adapts over time to the environment and culture (e.g. hunting and gathers began to walk straight up as they adapted to their new ways of gathering food for their families. Thus, the evolution process is also a socio-cultural phenomenon, and, since culture is a product of human nature, culture is also a biological phenomenon. These tenets have been accepted within Evolutionary Psychology (EP) (Cosmides & Tooby, 1987; Tooby, 1988, as cited in Kennair, 2002). Thus adaptation is essential to an evolutionary perspective because that is how they explain the evolutionary process, the organism adapting to the environment over time in order meet the biological needs of the organism. The theory depends on adaptation as a major tenet of the theory; indeed there would be not theory without the idea of adaptation (http://www.human-nature.com/nibbs/02/ep.html). In other words, adaptations are the evolved solutions to problems encountered consistently through periods of evolutionary history. These adaptations are designed through the natural selection of available genetic variation, which in the process, tend to be reduced. Thus human adaptations make up human nature, and are believed to be universal to almost all humans (Tooby & Cosmides, 1990a, as cited in Kennair, 2002); however, degenerative mutations or non-nurturing environments cause the variations (Kennair, 2002).

There are some formal properties of an adaptation proposed. Adaptation is:

1. A Cross-generationally recurring set of characteristic of the phenotype,
2. that is reliably manufactured over the developmental life history of the organism
3. according to instructions contained in its genetic specification,
4. in interaction with stable and recurring features of the environment (i.e., it reliably develops normally when exposed to normal ontogenetic environments),
5. whose genetic basis became established and organized in the species (or population) over evolutionary time, because
6. the set of characteristics systematically interacted with stable and recurring features of the environment (the "adaptive problem?,
7. in a way that systematically promoted the propagation of the genetic basis of the set of characteristics better than the alternative designs existing in the population during the period of selection. This promotion virtually always takes place through enhancing either the reproduction of the individual bearing the set of characteristics, or the reproduction of the relatives of that individual (Kennair, 2002).

Please see a broader discussion in the article attached (Kennair, 2002), which includes criticisms of the concept of adaptation and alternative explanations.

2. Describe in detail the theories surrounding one of the sensory systems in regards to how we smell, touch, taste, see, etc

Vision, hearing, taste, smell and touch are the five senses each with its own sensory systems and receptor cells. For example, touch perception includes skin receptors separate for warmth, cold and pain, travel from the skin cell receptors to the brain and spinal cord. Theoretically, each sensory system is a channel receiving information from the internal and external world, with sense receptors, which are nerve fibres leading from the receptor to the brain or spinal cord, which relay messages (it is hot) stations and processing areas within the brain. It is when the sensory channel is stimulated, that we have a sensation that is characteristic of that channel (feeling of cold or hot; hearing a loud of soft tone). So, as things change around us, there is activity in the nervous system, where physical energy is converted into chemical impulses (nervous system activity or receptor potential) referred to as process of transduction that occurs at the "specialized?receptor cells that converts physical energy into chemical voltage. Conversely, in some sensory systems, the receptor potential directly triggers the nerve impulses that then travel to receptors in the brain through the spinal cord.

In vision, for example, the light enter the eye through the pupil and travels through the cornea, the lens, and the eyeball interior to contact the rod and con cells of the retina at the back of the eyeball that contain photosensitive pigments-where transduction occurs (rods and cons), changing the physical energy into receptor potential. Rods - sensitive and responding to low light and cones - less sensitive and responding to bright light. There are three kinds of cones containing red-, green-, or blue sensitive pigment. Then, nerve impulses are generated in specific cells of the retina ?which travel to the brain along the optic nerve, with the pattern signalling the visual event from the environment.

The sense of smell involves olfactory receptor cells lie in the olfactory epithelium in upper part of nasal cavity. These cells have several long, non-motile cilia, which contain binding sites for olfactory stimuli. Each cell contains one type of receptor. Axons of olfactory receptor cells of same specificity synapse together. Information is passed into the olfactory cortex in the limbic system (http://www.biology-online.org/9/8_sensory_systems.htm).

In hearing, many signals and cues strike the receptor cells in the ear, such as the warning of a vehicle horn, the ticking of a clock or the ambulance siren. These are physical stimulus for hearing, for example, like when an object vibrates -the molecule of air around it are pushed together and thus are put under positive pressure. Then, they against the molecules close to them and these ...