Bio Review Notes #60
BIOGEOGRAPHY
Performance Objectives:
Animal and plant distributions follow many global patterns.
Ecologically similar species form similar communities (biomes) in different places.
Also, many families and other taxa are confined to certain land masses, forming regions separated by barriers to dispersal. Animal and plant distributions thus reflect both adaptations and dispersal capabilities.

 Animal and plant distributions: All the animals of a habitat or region
are its fauna; all the plants are its flora.

Biomes: Ecologically similar conditions sustain communities with ecologically similar species showing convergent adaptations. These include:
  • Tundra: treeless and cold
  • Taiga: northern conifer forests
  • Temperate deciduous forests, with trees that shed leaves annually
  • Temperate grasslands: grain-rich prairies
  • Mediterranean or chaparral: mild, rainy winters; trees generally small
  • Desert: very dry habitat
  • Tropical rainforest: many tall trees; great species abundance
  • Tropical deciduous forest
  • Tropical scrub forest: scant rainfall, many thorny bushes
  • Tropical grassland (savanna)
  • Freshwater streams and lakes
  • Marine habitats, arranged by depth
Regions: Continental areas inhabited by related species, belonging to the same family, although ecological adaptations may differ.
The six zoogeographic regions are:
  • Nearctic: Alaska to central Mexico
  • Neotropical: the Americas from Mexico to Cape Horn
  • Palaearctic: North Africa and most of Eurasia
  • Oriental: tropical Asia
  • Ethiopian: Africa south of the Sahara
  • Australian: Australia, New Zealand, and the Pacific islands
Dispersal and colonization: Most species can disperse freely across continents, limited only by the need to adapt to new environments.
Land bridges, like Panama, allow dispersal in both directions.
Sweepstakes dispersal (e.g., to distant islands) is the occasional crossing of barriers by high-risk means, usually in one direction only by only a few species.

Island biogeography: Many forces that control animal and plant distributions are easier to study on islands. Islands receive most of their species from the nearest continent. Larger islands are more frequently colonized by new species, but they also suffer more competition and thus more local extinctions. A frequent pattern, the species-area curve, S = c Az, relates species diversity to island size.

Index             Syllabus
Prev rev. Aug. 2011 Next