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Which of the following statements about the concept of race as applied to humans is true? It
is a discredited concept in biology.
This chapter's "Appreciating Diversity" segment describes some of the identity issues that African Americans face in Ghana, where often—no matter how dark their skin color may be—they are equated with white foreign tourists. This situation shows how
racial and ethnic classification can depend on sociocultural factors such as class and nationality as well as on biological factors like skin color.
Which of the following statements about attempts to assign humans to discrete racial categories purportedly based on common ancestry is true? They are
culturally arbitrary, even though most people assume they are based in biology.
What is the term for a gradual shift in gene frequencies between neighboring populations?
Recall the mechanisms of genetic evolution discussed in the previous chapter. What is the relationship between gene flow and the existence of clines between human populations?
Gene flow, the exchange of genetic material across populations, results in clines, which are gradual, rather than abrupt, shifts in gene frequencies between neighboring groups.
In theory, a biological race is a geographically isolated subdivision of a species. Humanity (Homo sapiens) lacks such races because
human populations have not been isolated enough from one another to develop such discrete groups.
What term refers to an organism's evident traits, its "manifest biology?"
A. Manifest destiny
C. Biological circumscription
E. Hereditary inequality
In understanding the problems with attempts at human racial classification, why is it important to understand the difference between genotype and phenotype?
Attempts at human racial classification have typically used phenotypic traits like skin color as markers of common ancestry, but many such traits do not reflect shared genetic material. Instead, they are often the result of different populations biologically adapting to similar environmental stressors in similar ways.
An examination of racial taxonomies from around the world would indicate that
the classification of racial types is an arbitrary and culturally specific process.
In the early 20th century, anthropologist Franz Boas described changes in skull form among the children of Europeans who had migrated to North America. He found that the reason for these changes could not be explained by genetics. His findings underscore the fact that
phenotypic similarities and differences don't necessarily have a genetic basis.
Traditional racial classification assumed that biological characteristics such as skin color were determined by heredity and remained stable over many generations. We now know that
a biological similarity such as skin color is also the result of natural selection working among different populations that face similar environmental challenges.
Which of the following is the best plan of action for a light-skinned woman of childbearing age living in the tropics and concerned about giving birth to a child with neural tube defects (NTDs)?
Taking folic acid/folate supplements and protecting herself against the sun with sunscreen, clothing, and shelter
East Asians who have migrated recently from India and Pakistan to northern areas of the United Kingdom have a higher incidence of rickets and osteoporosis than the general British population. This illustrates that
natural selection continues today.
Which of the following statements about human skin color is not true?
The amount of melanin in the skin affects the body's ability to process lactose.
The explanations given in this chapter for the differences and distribution of skin color in populations around the world are examples of
explanatory approaches to human biological diversity.
Which of the following is the best example of how diseases have been powerful selective agents for humans, particularly before the arrival of modern medicine?
Smallpox, which appeared after people and animals started living together, has worked as a selective agent for people with blood types B and O who have an ability to produce antibodies against smallpox.
What does the relationship between genetic traits and the prevalence of diseases such as malaria and smallpox illustrate?
the ways in which human biological diversity reflects adaptation to such environmental stresses as disease, diet, and climate
What does Bergmann's rule state? Average body size tends to
increase in cold climates and decrease in hot ones.
What does Allen's rule state? The relative size of protruding body parts
A. decreases with temperature.
B. increases with altitude.
C. decreases with altitude.
D. increases with temperature.
E. increases with humidity.
What is a phenotypic adaptation, and what makes it possible?
It happens when adaptive changes occur during an individual's lifetime. It is made possible by human biological plasticity, our ability to change in response to the environments we encounter as we grow.
Genes and phenotypic adaptation work together to produce a biochemical difference between human groups in an ability to digest large amounts of milk. When is this an adaptive advantage? When
other foods are scarce and milk is available, as it is in herding societies
Indigenous highlanders living in the Andean altiplano in South America, in the Tibetan plateau in Asia, and at the highest elevations of the Ethiopian highlands in East Africa have all adapted to living in an environment of oxygen-thin air. Researchers have found that
each population has evolved its own distinctly different biological adaptation to this environment.
Human biological differences are evident only to individuals who wrongfully sustain the validity of human races.
Historically, scientists have approached the study of human biological diversity in two main ways: racial classification (now largely abandoned) versus the current explanatory approach, which focuses on understanding specific differences.
Biological races have been scientifically discredited not just among humans but also among all living species.
Humanity (Homo sapiens) lacks distinct races because human populations have not been isolated enough from one another to develop into discrete groups.
Biologists have rejected the idea of three great races (white, black, and yellow) largely because it fails to account for Native Americans.
The only chance for human racial classification schemes to work is to shift from using phenotypic to genotypic characteristics of human populations.
Physical features cluster into discrete genetic units.
Phenotypic similarities and differences always have a genetic basis.
There is much greater variation within each of the traditional so-called races than between them.
The role of natural selection in producing variation in human skin color illustrates the explanatory approach to explaining human biological diversity.
Higher amounts of melanin in the skin inhibit the body's ability to manufacture vitamin D. This confers an adaptive advantage in environments with excessive sun exposure.
Rickets is caused by an overabundance of vitamin D in the body.
The indigenous communities in the tropical regions of the Americas are not as dark skinned as populations living in other tropical regions, because the dense vegetation in this continent blocks out much of the sunlight.
Light-skinned individuals living in tropical climates are high-risk candidates for hypervitaminosis D
Skin color is a simple biological trait that is influenced by one gene and environmental exposure to sunlight.
One of the selective advantages of dark skin color in the tropics is that it reduces the susceptibility to folate destruction and therefore diminishes the likelihood of neural tube defects among human embryos. Folate is also necessary in men in order to maintain normal sperm production.
In the case of skin color, natural selection is no longer active today, thanks to human cultural adaptations that confer an advantage no matter the skin color or environment one lives in.
Thanks to medical advances, genetic resistance to diseases no longer confers any selective advantage.
According to Thomson's nose rule, longer noses are more adaptive to colder climates than shorter ones.
Allen's rule states that protruding body parts grow shorter as temperature increases.
This chapter's discussion of lactose tolerance highlights that genes and phenotypic adaptation can work together to produce human biological diversity.
Populations living at high altitudes have all developed similar biological and cultural adaptations to hypoxic conditions.
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