BiogeographyBiogeography Biogeography: is the study of where organisms live and how their populations spread into different parts of the world

On a Global Scale: One important factor affecting how species are distributed is Continental Drift. The slow movement of the continents over the ages separated populations and allowed new species to develop in isolation.One important factor affecting how species are distributed is Continental Drift. The slow movement of the continents over the ages separated populations and allowed new species to develop in isolation. For example: >For example: > One important factor affecting how species are distributed is Continental Drift. The slow movement of the continents over the ages separated populations and allowed new species to develop in isolation.One important factor affecting how species are distributed is Continental Drift. The slow movement of the continents over the ages separated populations and allowed new species to develop in isolation. For example: >For example: >

AustraliaAustralia Millions of years ago, the Australian island split off the mainland, permitting the evolution of koalas and kangaroosMillions of years ago, the Australian island split off the mainland, permitting the evolution of koalas and kangaroos

Means of Dispersal On a smaller scale organisms are dispersed (the movement of populations) in several different ways.On a smaller scale organisms are dispersed (the movement of populations) in several different ways.

WindWind Many larger organisms can move into a new area by flying but many smaller organisms such as plants, or even spiders use wind to travel to new areas.Many larger organisms can move into a new area by flying but many smaller organisms such as plants, or even spiders use wind to travel to new areas.

Wind (cont.) Plants use the wind to carry their seeds to new places while spiders climb to a high spot and spin a thread of silk which the wind picks up (called parachuting) carrying the spider to somewhere else.Plants use the wind to carry their seeds to new places while spiders climb to a high spot and spin a thread of silk which the wind picks up (called parachuting) carrying the spider to somewhere else.

WaterWater Organisms may also move into new areas by swimming or getting washed into new areas during floodsOrganisms may also move into new areas by swimming or getting washed into new areas during floods

Or maybe…

Other Living Things Organisms may also be dispersed by other living things like birds eat fruits carrying seeds in one area and later deposit the seeds elsewhere in their wastes. Some plants have adaptations that help spread their seeds elsewhere.Organisms may also be dispersed by other living things like birds eat fruits carrying seeds in one area and later deposit the seeds elsewhere in their wastes. Some plants have adaptations that help spread their seeds elsewhere.

Other Living Things (cont.) Humans have been extremely important to the dispersal of other species, importing plants and animals all over the globe.Humans have been extremely important to the dispersal of other species, importing plants and animals all over the globe. Species that naturally evolved in an area are called native species.Species that naturally evolved in an area are called native species. Species carried into a new area by people are exotic speciesSpecies carried into a new area by people are exotic species Humans have been extremely important to the dispersal of other species, importing plants and animals all over the globe.Humans have been extremely important to the dispersal of other species, importing plants and animals all over the globe. Species that naturally evolved in an area are called native species.Species that naturally evolved in an area are called native species. Species carried into a new area by people are exotic speciesSpecies carried into a new area by people are exotic species

Limits of Dispersal  Fortunately, or we’d have the same critters all over the globe. There are several factors that limit the dispersal of species… remember to thank me. I do my best to hold them off!!! …

Physical Barriers Natural obstacles such as water, mountains, and deserts are hard to cross, tending to limit the spread of species.Natural obstacles such as water, mountains, and deserts are hard to cross, tending to limit the spread of species.

CompetitionCompetition When an organism enters a new area it must compete for resources with organisms that are already there, making it often difficult to establish new populationsWhen an organism enters a new area it must compete for resources with organisms that are already there, making it often difficult to establish new populations

ClimateClimate Differences in climate can also be limits to dispersal. For example, many organisms require specific temp. ranges. That’s why no polar bears in Maryland or piranhas in our ponds (although people keep trying).Differences in climate can also be limits to dispersal. For example, many organisms require specific temp. ranges. That’s why no polar bears in Maryland or piranhas in our ponds (although people keep trying).