Marco Flores
Period 3
March 30, 2000
Physical Anthropology
Chapter 5 Worksheet
HUMAN VARIATION and ADAPTION
2. A polytipic species is one composed of local populations that differ with the regard to the expression of one or more traits. But within the local populations there is a great deal of phenotypic variation between individuals. Race is defined as being the various attributions to certain people. When there is a combination of things such as skin color, shape of face, hair color, and eye color. People that have these particular attributes have been placed together into categories; these categories are called races. 'Ethnicity' is the same thing as 'race', but in the 1950's the term ethnicity was used instead. Stereotypes enter the discussion because of the fact that they classify people through their outer features. They deal with implied actions of a group that help further separate them from other ethnicities.
3. The adaptive significance of human variation is the result of such evolutionary factors as genetic drift, founder effect, gene flow, and other adaptations to environmental conditions, both past and present. Acclimatization is the physiological response to environmental change, which occurs in all people. Tanning is a great example of acclimatization. The main difference between acclimatization and adaptation is that acclimatization is short term or temporary response to change, and adaptation refers to more long term evolutionary (genetic) changes that characterize all individuals within a population of a species.
5A. Human physiological response to the cold combine factors that increase heat retention with those that enhance heat production. Heat retention is more efficient because it requires less energy. Short-term responses to the cold include increased metabolic rate and shivering, both of which generate body heat. Vasoconstriction another short term response, restricts heat loss and conserves energy. Also humans posses a subcutaneous fat layer that provides an insulative layer throughout the body. Behavioral modification include increased activity, wear more clothes, increased food consumption.
5B. Human physiological response to the heat by having sweat glands distributed throughout the skin. This wide distribution of sweat glands makes possible the loss of heat at the body surface through evaporative cooling, a mechanism that has evolved to the greatest degree in humans. Another mechanism for radiating body heat is vasodilatation whereby capital eaves near the skin surface wider to permit increased blood flow to the skin. Body size is also important in regulating body temperatures. The best body shape in hot estimate is linear with long arms and legs.
7. At high altitudes, there are multiple factors that produce stress in the human body. These include hypoxia, more intense solar radiation, cold, low humidity, wind, and a reduced nutritional base. People who live at higher elevations display a number of manifestations of their hypoxic environment. Reproduction is affected through increased rates or infant mortality, miscarrying and prematurity. Low birth weight is also more common and is attributed to decreased fetal growth due to impared maternal fetal transport of oxygen compared to populations at lower elevations. Life long residents of high altitudes display slower growth and maturation. Other differences include a larger chest size due to a greater lung volume and larger hearts. Developmental acclimatization occurs in high altitude. These adaptations are required during growth and development. In addition to greater lung capacity, people born at high altitudes are more efficient than migrants at diffusing oxygen from blood to body tissue. They do not
rely as heavily on increased red blood cell formation as do newcomers.
8. HIV is transmitter from person to person through the exchange of bodily fluids, usually blood or semen. HIV must invade certain types of cells and alter their functions of those cells to produce more virus parties in a process that eventually leads to cell destruction. HIV targets T4 helper cells, which are a major event of the immune system. As HIV spreads T4 cells are destroyed and the immune system begins to fail. Then the person affected begins to exhibit symptoms caused by various pathogens that are commonly present but usually kept in check by a normal immune response. When an HIV infected person's T cell count drop to a level that indicates immune suppression, and when symptoms of "opportunistic" infections appears, the patient is said to have AIDS. Evolutionary speaking it is to the advantage of any pathogen not to be so deadly as to kill the host too quickly. If the host dies shortly after becoming infected the viral or bacterial agent may not have time to reproduce and infect other hosts. Through the adoption of various cultural practices humans have radically altered patterns of infectious disease. Here, then is another example of biocultural evolution in our species. The interaction of culture and biological factors has influenced microevolutionary change in humans to accommodate altered relationships with diseased organisms.
10. Other things that affect growth besides nutrition are genetic, hormones, and environmental factors.
Genetic Factors - No matter how much you eat in your lifetime or how excellent your health is you will not be able to exceed your genetic potential for stature and a number of physiological parameters. Genetic factors set the underlying limitations and potentialities for growth and development but the life experience and environment of the organism influence how much the body grows within these parameters.
Hormones - hormones are substances that are produced by cells within endocrine glands. The growth hormone is primarily responsible for the growth of bone and muscle. And the amount of GH produced during growth phases strongly influences how tall an individual will be.
Environmental Factors - environmental factors such as altitude and climate also effect growth. For example populations in cold climates tend to heavier and have longer trunks and shorter extremities than populations in tropical areas. Sunlight also appears to affect growth, most likely through vitamin D. This is due to vitamin D having a large effect on skeletal growth.
