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Chapter 16 Modern Human Biology: Patterns of Adaptation.

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Chapter 16 Modern Human Biology: Patterns of Adaptation
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Page 1: Chapter 16 Modern Human Biology: Patterns of Adaptation.

Chapter 16

Modern Human Biology:

Patterns of Adaptation

Page 2: Chapter 16 Modern Human Biology: Patterns of Adaptation.

Adaptive Significance of Human Variation• Human variation is the result of

adaptations to the environment• Physiological response to the

environment operates at two levels:

1. Long-term evolutionary changes2. Short-term, temporary changes

• Terms– Homeostasis– Acclimatization

Page 3: Chapter 16 Modern Human Biology: Patterns of Adaptation.

Geographical Distribution of Skin Color in Indigenous Populations

Page 4: Chapter 16 Modern Human Biology: Patterns of Adaptation.

Ultraviolet Light and Skin Cells

Page 5: Chapter 16 Modern Human Biology: Patterns of Adaptation.

Three Points: Skin Color and Evolution1. Early hominids lived in the tropics,

where solar radiation is more intense than in temperate areas to the north and south.

2. Unlike modern city dwellers, early hominids spent their days outdoors.

3. Early hominids didn’t wear clothing that would have protected them from the sun.

Page 6: Chapter 16 Modern Human Biology: Patterns of Adaptation.

Thermal Environment

• Humans are found in a wide variety of thermal environments, ranging from 120° F to -60° F.

Page 7: Chapter 16 Modern Human Biology: Patterns of Adaptation.

Human Response to Heat

• Long-term adaptations to heat evolved in our ancestors:– Sweat Glands– Vasodilation

• Bergmann's rule - body size tends to be greater in populations that live in cold environments.

Page 8: Chapter 16 Modern Human Biology: Patterns of Adaptation.

Bergmann’s Rule

Page 9: Chapter 16 Modern Human Biology: Patterns of Adaptation.

Allen’s Rule

Page 10: Chapter 16 Modern Human Biology: Patterns of Adaptation.

Examples of Bergmann’s andAllen’s Rules

• (a) This African woman has the linear proportions characteristic of many inhabitants of sub-Saharan Africa.

• (b) By comparison, the Inuit woman is short and stocky.

Page 11: Chapter 16 Modern Human Biology: Patterns of Adaptation.

Human Response to Cold

• Short-term responses to cold: – Metabolic rate and shivering– Narrowing of blood vessels to reduce

blood flow from the skin, vasoconstriction.

– Increases in metabolic rate to release energy in the form of heat.

Page 12: Chapter 16 Modern Human Biology: Patterns of Adaptation.

High Altitude

• Multiple factors produce stress on the human body at higher altitudes:– Hypoxia (reduced available oxygen)– Intense solar radiation– Cold– Low humidity– Wind (which amplifies cold stress)

Page 13: Chapter 16 Modern Human Biology: Patterns of Adaptation.

Infectious Disease

Page 14: Chapter 16 Modern Human Biology: Patterns of Adaptation.

Environment


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