Biogeography Flashcards
Define biogeography
Study of distribution of species
Why was Darwin interested in the Galapagos islands?
Lack of mammals & only 1 species of rodent
- when mammals have the potential to do well there
Who was the 1st to map out the distribution of species?
Alfred Russell Wallace
What controls animal distributions?
What does this suggest?
Physical barriers to movement
- e.g. oceans, mountains, deserts
Groups of animals & plants at 1 point had moved to occupy their present ranges until they couldn’t move any further
What are the 2 types of dispersal mechanisms?
Land bridges
Oceanic dispersal
What is the evidence for land bridges?
Bering Strait between Russia & Alaska = 50miles of water 100-160ft deep
Britain’s geology shows marine rocks on land
–> sea level could change or land could rise
How was biology used to infer the existence of land bridges?
Late Cretaceous = closely related dinosaurs in North America & Asia
How does climate act as a filter on land bridges?
Some species can only inhabit warm climates
–> can’t spread across high-latitude land bridges
When was climate no longer a filter on the land bridges?
What did this result in?
55mya when the climate suddenly became very warm & the poles became subtropical
Warm-loving species could move north
e.g. primates & horse-ancestors spread throughout the northern hemisphere
Why do some suggest N.America & S.America were once not connected?
Their flora & fauna are v different
BUT fish & marine life either side of the land bridge are v similar
How do birds colonise islands?
> Birds get blown out to sea by storms or get lost while migrating
Travel in flocks
Birds carry seeds in beaks/guts
Give an example of a plant species adapted to float long distances
Coconut
- husk is a buoyant float that can drift 100s of miles
How can plants be transported across water?
> plants dry out & float
icebergs trap rocks & soil could carry seeds
soil trapped in tree roots could carry seeds
How can animals be transported across water?
Give examples
Tortoises have lightweight shell = buoyant
& can survive months w/out food or water
Crocodiles can drink saltwater & are powerful swimmers
Lizards cling to trunks & branches
How are orgs that aren’t well adapted to dispersal found across multiple continents? (i.e. what are the theories?)
E.g. Worm lizards
Continental drift (theory by Wegener) Dispersal (floating islands?)
