Biogeography: 

• Biosphere is the whole are of earth’s surface
• The biosphere is made up of the atmosphere (air), lithosphere (land), hydrosphere (water)
• The process of drifting apart is known as continental drift; major factor in determining the current distribution of species
• Biosphere can be divided into a number of biogeographical regions – continents and islands; inhabited by distinctive species of animals and plants –
• Organisms can move freely from place to place within each region but not from one region to another
• Terrestrial biogeographical regions include the Nearctic (North America); Eurasia (Palaearctic); South America (Neotropic); Africa (Afrotropic); Australian; Indomalayan; Oceanic and Antarctica
• Biogeographical regions are related to land masses and not to climate

Diversity within each biogeographical region or continent: 

• Each region has a large diversity of its own

Diversity between different biogeographical regions: 

• Diversity between the land masses/ biogeographical regions more striking than the diversity of each region
• Each region has a group of organisms that are more closely related to each other than to organisms in other biogeographical regions – because of local diversification by speciation/ the dispersal of species within a biogeographical region
• Organisms in a region are descendants from the ancestors that were previously there

What is biogeography?

• The study of the past/present distribution of the worlds many species
• Biogeographers combine information from a very broad range of fields – ecology, evolution, palaeontology, climatology
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 Biogeographers attempt to answer various questions:

• Which species occur
• Where do they occur
• Why did the species get to where they are
• How have they adapted
• Why and how are distributions changing
• Why is a species not there

Alfred Russel Wallace; 19^th century British naturalist, explorer, geographer, anthropologist, biologist – helped found modern science of biogeography

What areas are studied in biogeographical? 

• Dispersal: Movement of populations away from their point of origin
• Evolution: Change in genetic composition of a population
• Extinction: Disappearance of a species

Biogeographical – Plate tectonics/continental drift: 

• Biogeographical has been one of the central fields of study of evolutionary biology

Biogeographical distributions of species: 

• Explorers were aware of broad global patterns of animal/plant distributions – they discovered new lands; found previously unknown varieties of plants/animals

Darwin’s explanation of biogeographical distribution of species: 

• Beagle Darwin made a careful study of the biogeographical patterns of the existing species by collecting first-hand evidence
• From these studies he developed his biogeographic ideas about which he wrote his book
• Darwin felt he had to reject the orthodox story firmly embraced by European science – time of the Beagle Voyage
• Theory proposed that all species remain unchanged – discontinues in the distribution patterns of species were due to separate multiple creations

Darwin’s explanation of how species came to be distributions: 

• Distribution patterns of a species could be explained by each species having its origin in a single centre of origin
• Species then dispersed, passively or actively – centre of origin
• Ancestors of each species became extinct in the ‘single centre of origin’
• Populations became isolated from their ancestors – result of being dispersed
• Separate populations colonised new areas the species adapted to conditions – became different, forming new species
• Darwin observed that some species in adjacent geographical areas tended to have more features in common than those living further apart
• Darwin observed that individual islands have species of the same genus that are slightly different

Worldwide distributions of large flightless birds: 

• Lost the ability of flight as they adapted to a new environmental circumstances
• Most flightless birds below to the order Struthioniformes – commonly known as ratites

What are ratites?

• A family of flightless birds
• One of the largest birds of all time, the extinct moa/ extant ratites such as the ostrich, emu and rhea
• They resemble each other, similar modes of life in each landmass

Extant: Living

Where are ratites? 

Found on the continents that were all part of what was Gondwanaland

• Ostrich: Northern, Eastern, Southern Africa
• Rheas: South America
• Emus: Australia
• Moas: New Zealand  

What are the physical characteristics of ratites? 

• Flat sternum (breastbone)
• Small wings
• Large bodies
• Heavy leg bone
• Thick, strong feet
• Specialized toe structure/ no opposable first toe