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Unit 28


Unit Overview

This unit examines the spatial distribution of fauna on Earth. The main sections are as follows:

  • Processes of evolution
  • Emergence of zoogeography
  • The Earth's zoogeographic realms
  • Further studies in zoogeography
  • Zoogeography and conservation

A species's habitat is the environment it normally occupies within its geographic range. Species evolve to adapt optimally to the habitat, and as habitats change, species must change, move, or die. Species change through the process of evolution, which involves the mutation of genes. Therefore, the location of habitats and the characteristics of species within them are always changing.

One can generalize the distribution of fauna on the Earth's surface by considering zoogeographic realms. These realms contain different habitats, which, in turn, contain multiple ecological niches. Because humans can alter a habitat, we are capable of dramatic effects on the increases and decreases of animals in a specific habitat.

Unit Objectives

  • To briefly outline the theory of evolution and related principles such as natural selection, which led to the present-day spatial distribution of animals
  • To give a brief history of zoogeography
  • To relate zoogeography to the larger context of environmental conservation

Glossary of Key Terms

Animal ranges The area of natural occurrence of a given animal species; often changes over time, and in some cases even seasonally.
Convergent evolution Theory that holds that organisms in widely separated biogeographic realms, although descended from diverse ancestors, develop similar adaptations to measurably similar habitats.
Ecological niche The way a group of organisms makes its living in nature, or the environmental space within which an organism operates most efficiently.
Ecological zoogeography The study of animals as they relate to their total environment.
Habitat The environment a species normally occupies within its geographical range.
Mutation Variation in reproduction in which the message of heredity (DNA) contained in the genes is imperfectly passed on and from which new species may originate.
Wallace's Line Zoogeographer Alfred Russel Wallace's controversial boundary line that purportedly separates the unique faunal assemblage of Australia from the very different animal assemblage of neighboring Southeast Asia; Wallace's famous line, introduced over a century ago, is still the subject of debate today.

Unit Outline

  • Processes of evolution
    • Natural selection
      • genetic combination
      • mutations
    • Ecological niche
      • environmental spaces in which a species operates most efficiently
      • habitats: larger, more complex ecological niches
      • animal adaptations to their habitats
        • changing natural environments
        • Serengeti Plains example of complex adaptations
  • Emergence of zoogeography
    • von Humboldt's path-breaking studies
    • Darwin and the theory of evolution
    • Wallace's pioneering work on faunal assemblages in Southeast Asia
      • Wallace's Line
      • Weber's Line
      • the continuing debate about zoogeographical boundaries
  • The Earth's zoogeographic realms
    • Paleotropic (Ethiopian) realm
    • Indomalayan (Oriental) realm
    • Madagascan realm
    • Australian realm
    • New Zealand realm
    • Neotropic realm
    • Nearctic realm
    • Palearctic realm
    • Pacific realm
    • Antarctic realm
  • Further studies in zoogeography
    • Darlington's updating of Wallace's approach
    • Emergence of ecological zoogeography
      • Simpson's incorporation of evolution
      • Maurer's work on biodiversity
      • Jarvis's emphasis on plant and animal introductions
    • Island zoogeography
      • pioneering work of MacArthur and Wilson
      • subsequent studies
  • Zoogeography and conservation
    • Animal ranges
    • Human impacts on animal habitats
    • Preservation efforts

Review Questions

  1. Discuss the concept of faunal niches and link it to the notion of animal ranges.
  2. Describe the global distribution of zoogeographic realms and list the main features of the realms that span the Americas, Eurasia, and Africa.
  3. What was the significance of Wallace's Line? Trace the evolution of this controversy since that boundary was first drawn.