Biogeography is the study of the spatial patterns of biodiversity and the distributions of organisms over Earth. It seeks to understand why species are confined to certain ranges and how physical and biological factors influence distributions. While history plays a role in explaining some patterns, such as related species found on fragmented lands like Gondwanaland, processes like convergent evolution also shape distributions in similar environments. Biogeographers investigate relationships between patterns and the processes that create them, assuming through uniformitarianism that basic physical and biological laws have remained constant over time.

1. THE SCIENCE OFTHE SCIENCE OF
BIOGEOGRAPHYBIOGEOGRAPHY
 What is Biogeography?What is Biogeography?
 BiogeographyBiogeography - the science of documenting- the science of documenting
and understanding spatial patterns ofand understanding spatial patterns of
biodiversity. Includes the the study of thebiodiversity. Includes the the study of the
distributions of organisms (both past anddistributions of organisms (both past and
present) and of related patterns of variation overpresent) and of related patterns of variation over
the earth in the numbers and kinds of livingthe earth in the numbers and kinds of living
things.things.

2. QUESTIONSQUESTIONS
 Types of questions asked:Types of questions asked:
 1. Why is a species or higher taxonomic group1. Why is a species or higher taxonomic group
(genus, family, order, etc.) confined to its(genus, family, order, etc.) confined to its
present range?present range?

3. QUESTIONSQUESTIONS
 2. What enables a species to live where it does?2. What enables a species to live where it does?
What prevents its dispersal?What prevents its dispersal?

4. QUESTIONSQUESTIONS
 3. What roles do climate, topography, and3. What roles do climate, topography, and
interactions with other organisms play in limitinginteractions with other organisms play in limiting
the distribution of a species?the distribution of a species?

5. QUESTIONSQUESTIONS
 4. Why are the animals and4. Why are the animals and
plants of large, isolatedplants of large, isolated
regions, such as Australia,regions, such as Australia,
New Caledonia, andNew Caledonia, and
Madagascar, so distinctive?Madagascar, so distinctive?

6. QUESTIONSQUESTIONS
 5. Why are some groups of closely related5. Why are some groups of closely related
species confined to the same region, and othersspecies confined to the same region, and others
found on opposite sides of the world?found on opposite sides of the world?

7. QUESTIONSQUESTIONS
 6. Why are there so many more species in the6. Why are there so many more species in the
tropics than at temperate or arctic latitudes?tropics than at temperate or arctic latitudes?
How are isolated oceanic islands colonized, andHow are isolated oceanic islands colonized, and
why are there nearly always fewer species onwhy are there nearly always fewer species on
islands than in the same kinds of habitats onislands than in the same kinds of habitats on
continents?continents?

8. SPECIALIZATIONSPECIALIZATION
 Biogeography is a large field and specialization isBiogeography is a large field and specialization is
common:common:
 PhytogeographerPhytogeographer - study plants- study plants
 ZoogeographersZoogeographers - study animals- study animals

9. SPECIALIZATIONSPECIALIZATION
 Historical biogeographersHistorical biogeographers - reconstruct the origin,- reconstruct the origin,
dispersal and extinction of taxa and biotas.dispersal and extinction of taxa and biotas.
 Ecological biogeographersEcological biogeographers - account for present- account for present
distributions in terms of interactions betweendistributions in terms of interactions between
organisms and their physical and biotic environments.organisms and their physical and biotic environments.
 PaleoecologyPaleoecology - bridges the gap between historical and- bridges the gap between historical and
ecological biogeographers, investigates the relationshipecological biogeographers, investigates the relationship
between organisms and past environments.between organisms and past environments.

10. SPECIALIZATIONSPECIALIZATION
 Relationship to other sciences:Relationship to other sciences:
 Basic knowledge of Geography is important.Basic knowledge of Geography is important.

11. GondwanalandGondwanaland
 Example 1: We see related species on distinctExample 1: We see related species on distinct
land masses such as South America, Africa andland masses such as South America, Africa and
Australia (Living fishes, insects, birds,Australia (Living fishes, insects, birds,
earthworms and extinct reptiles). Until 135earthworms and extinct reptiles). Until 135
million years ago, South America, Africa andmillion years ago, South America, Africa and
Australia were part of a single giant land massAustralia were part of a single giant land mass
existed called Gondwanaland.existed called Gondwanaland.

14. LANDMASS FORMATIONLANDMASS FORMATION
 Example 2: As North America shifted awayExample 2: As North America shifted away
from Europe forming the North Atlantic, Northfrom Europe forming the North Atlantic, North
America moved closer to South America and theAmerica moved closer to South America and the
Isthmus of Panama formed about 3.5 millionIsthmus of Panama formed about 3.5 million
years ago.years ago.
 => Resulted in a terrestrial connection between=> Resulted in a terrestrial connection between
NA and SA.NA and SA.
 => Also resulted in the separation of the=> Also resulted in the separation of the
tropical Atlantic and Pacific oceans.tropical Atlantic and Pacific oceans.

16. LANDBRIDGESLANDBRIDGES
 Example 3: Bering landbridge connected Alaska toExample 3: Bering landbridge connected Alaska to
Siberia in NE Asia up to approximately 10,000 yearsSiberia in NE Asia up to approximately 10,000 years
ago.ago.

17. GEOLOGIC TIME SCALEGEOLOGIC TIME SCALE
 Example 4: Great lakes of North America didExample 4: Great lakes of North America did
not exist 15,000 yrs ago.not exist 15,000 yrs ago.

19. Mediterranean ClimatesMediterranean Climates
 However, history can not explain all patterns -However, history can not explain all patterns - Mediterranean ClimatesMediterranean Climates forfor
example!example!
 - Distinctive vegetation occurs throughout the world in- Distinctive vegetation occurs throughout the world in
 isolated regions.isolated regions.
 - Rainfall is low and occurs in mild winter months- Rainfall is low and occurs in mild winter months
 - Summers dry and hot- Summers dry and hot
 - Distinctive semiarid plant communities- Distinctive semiarid plant communities
 - Plants appear superficially similar- Plants appear superficially similar
 - Plants in each region belong to different genera and even- Plants in each region belong to different genera and even
 familiesfamilies
 => Result of convergent evolution in response to similar=> Result of convergent evolution in response to similar
 environmentsenvironments

20. Mediterranean ClimatesMediterranean Climates

21. Philosophy and Basic Principles:Philosophy and Basic Principles:
 ““Philosophers and historians of science, viewing its progress with 20/20Philosophers and historians of science, viewing its progress with 20/20
hindsight, often suggest that it is possible to give a recipe for the mosthindsight, often suggest that it is possible to give a recipe for the most
effective way to conduct an investigation. Unfortunately, as most practicingeffective way to conduct an investigation. Unfortunately, as most practicing
scientists know, scientific inquiry is much more like working on a puzzle orscientists know, scientific inquiry is much more like working on a puzzle or
being lost in the woods than like baking cookies or following a road map.being lost in the woods than like baking cookies or following a road map.
There are numerous mistakes and frustrations. Luck, timing, and trial andThere are numerous mistakes and frustrations. Luck, timing, and trial and
error play crucial roles in even the most important scientific advances. Someerror play crucial roles in even the most important scientific advances. Some
important discoveries, such as Alfred Wegner’s evidence of continental drift,important discoveries, such as Alfred Wegner’s evidence of continental drift,
are long ignored or even totally rejected by other scientists. While theare long ignored or even totally rejected by other scientists. While the
progress of science owes much to such admirable human traits as intelligence,progress of science owes much to such admirable human traits as intelligence,
creativity, perseverance, and precision, it is also retarded by equally humancreativity, perseverance, and precision, it is also retarded by equally human
but less admirable characteristics such as prejudice, jealousy, shortsightedness,but less admirable characteristics such as prejudice, jealousy, shortsightedness,
and stupidity. ” Brown and Lomolino, 1998.and stupidity. ” Brown and Lomolino, 1998.

22. PATTERN AND PROCESSPATTERN AND PROCESS
 Scientists investigate the relationships betweenScientists investigate the relationships between
pattern and process:pattern and process:
 PatternPattern - is defined as nonrandom, repetitive- is defined as nonrandom, repetitive
organization.organization.
 ProcessProcess - or processes, lead to the occurrence- or processes, lead to the occurrence
of pattern in the natural world.of pattern in the natural world.

23. UniformitarianismUniformitarianism oror Actualism:Actualism:
 In dealing with historical aspects,In dealing with historical aspects,
biogeographers make one critical assumption -biogeographers make one critical assumption -
UniformitarianismUniformitarianism oror Actualism.Actualism.
 - The assumption that basic physical and- The assumption that basic physical and
biological processes now operating on the earthbiological processes now operating on the earth
have remained unchanged throughout timehave remained unchanged throughout time
because they are manifestations of universalbecause they are manifestations of universal
scientific laws.scientific laws.

24. UniformitarianismUniformitarianism oror Actualism:Actualism:
 -- ActualismActualism is the preferred term because someis the preferred term because some
scientists have implied thatscientists have implied that UniformitarianismUniformitarianism
also means that the average intensities ofalso means that the average intensities of
processes have remained approximately constantprocesses have remained approximately constant
over time and that both geological and biologicalover time and that both geological and biological
changes are always gradual.changes are always gradual.