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Concept 17.1: Patterns of species diversity and distribution vary at global, regional, and local spatial scales.
global, regional, and local spatial scales.
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Concept 17.2:
Global patterns of species diversity and composition are controlled by geographic area and isolation, evolutionary history, and global climate.
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Concept 17.3:
Regional differences of species diversity are controlled by area and distance due to a balance between immigration and extinction rates.
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Biogeography is the study of
patterns of species composition and diversity across geographic locations.
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Richness vs composition
- Species richness is number of different species
- Composition-The actual species that are in an area
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Species richness and composition vary with
latitude.
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In general, the lower tropical latitudes have
many more, and different, species than the higher temperate and polar latitudes.
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The same community type or biome can vary in species richness and composition depending on
its location on Earth.
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Global scale—
the entire world.Species have been isolated from one another, on different continents or in different oceans, by long distances and over long periods.Rates of speciation, extinction, and migration help determine differences in species diversity and composition.
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Regional scale—
climate is roughly uniform and the species are bound by dispersal to that region.
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Regional species pool—
all the species contained within a region (gamma diversity).
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Local scale—
equivalent to a community.Species physiology and interactions with other species weigh heavily in the resulting species diversity (alpha diversity).
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Beta diversity—
change in species number and composition, or turnover of species, as one moves from one community type to another.Beta diversity represents the connection between local and regional scales of species diversity.
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The six biogeographic regions correspond
roughly to Earth’s six major tectonic plates.The plates are sections of Earth’s crust that move or drift (continental drift) through the action of currents generated deep within the molten rock mantle.
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Pangaea first split into two land masses
, Laurasia to the north and Gondwana to the south.
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Gondwana separated into
present-day South America, Africa, India, Antarctica, and Australia.
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Laurasia eventually split up into
North America, Europe, and Asia.Some continents were separated from one another; others came together (e.g., India collided with Asia, forming the Himalayas).
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While the number of families increased at ---------, -----also had an effect.
low latitudes, longitude also had an effect. So-called hot spots or areas of high species richness occur at particular longitudes, sometimes secondary to latitude.
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Some groups of organisms display the opposite pattern in latitudinal diversity.
- Seabirds have highest density at temperate and polar latitudes.This pattern correlates with marine productivity, which is substantially higher in temperate and polar oceans.
- The same pattern has been observed in marine benthic communities, which have much higher productivity at higher latitudes.Productivity differences are one possible explanation for latitudinal gradients in species diversity.
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What ultimately controls the rates of speciation and extinction?
- Temperature Hypothesis
- Evolutionary History Hypothesis
- Productivity Hypothesis
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1) Temperature Hypothesis:
Terrestrial species diversity is highest in the tropics because the tropics have more land area than other latitudes.This area is also the most thermally stable—temperatures remain uniform year-round.
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2) Evolutionary History Hypothesis:
Tropical regions have longer histories, they have been climatically stable and thus had a lot of time for evolution to occur.At higher latitudes, severe climatic conditions such as ice ages would increase extinction rates and hinder speciation.
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The tropics could be seen as a ---------- But they can also be a
a “cradle” of diversity. But they can also be a “museum”—species that diversify there tend to stay there.
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Species–area relationship—
species richness increases with increasing area sampled.
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The Species-Area Law
- Large areas harbor more species than small ones
- S=cAz
- S = number of species A = island area c = y-intercept (constant) z = line slope (constant)
- log S=(log c)+z(log A)
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Species–area curves plot
species richness (S) of a particular sample against the area (A) of that sample.The relationship between S and A is estimated by linear regression: S=zA=c z = slope, c = y-intercept
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equilibrium theory of island biogeography.
The number of species on an island depends on a balance between immigration rates and extinction rates.
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turnover,
or replacement of one species with another.
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The species-area curves on mainlands are
less steep than that of islands due to the increased resuce effect of populations, look into more I don't get it
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Look into forest case study results more
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Species that occur in one area, but nowhere else on Earth, are called _______ species.
endemic
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Which of the following is not a benefit provided by rainforests?
A rainforest provides all of the above.
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Regional species diversity is referred to as _______ diversity.
gamma
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Which of the following statements about Wilson and MacArthur's equilibrium theory of island biogeography
They postulated that species richness is a balance between immigration and extinction.
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Which of the following statements about regional scale is true?
The climate within a region is roughly uniform.
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Which of the following groups shows greater species richness in the temperate regions than in the tropics?
Seabirds
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The number of species on an island usually _______ with the size of the island and _______ the distance from the mainland to the island.
increases; decreases with
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Which of the following statements about global biogeographic patterns is true?
Most groups of organisms show increased diversity at the tropics than at higher latitudes.
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Which of the following results did Simberloff and Wilson observe in their tests of the equilibrium theory of island biogeography in islands of the Florida Keys?
The species diversity on islands most distant from the mainland did not return to pre-experimental levels after a year.
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Which of the following processes or events is most responsible for current species losses in the Amazon?
Deforestation
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Which of the following statements about plate tectonics is true?
Sections of Earth's crust, known as plates, drift across Earth's surface due to currents generated deep within Earth's mantle.
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Most of India is located in the _______ biogeographic region.
Oriental
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