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Transcript of Biogeography
the study of distribution patterns paper/crust basketball/Earth Magma core every year the tectonic plates move an average of four years since the Earth has been around for about 4.5 billion years
thats a lot of moving since formation there have been 3 major continental formations at around 1.5 billion years there was Cratons, Er, Atlantica, and Artica then came Pangea, a super continent
when all the continents collided and then, 220 mya, Pangea split to create our current formation this wasn't quick as Pangea split and the continents spread, land bridges remained, three of which were major contributers to biogeography the Bering Straigt(from Asia to the Americas) the Straight of Gibraltor(from North Africa to Europe) and the connection between South-East Asia and Australia many species, like the marsupials, attempted to travel into Europe via the Gibraltor bridge but failed due to cold environment and competition! the land bridges are now gone, which separated those who had crossed the bridges from those who stayed put, and the newly split species adapted to their environments differently which leads us into discontinuous distribution! this is when descendants of common ancestor inhabit separate environs and show variation in traits once they adapt enough they may form their own species like big cats vs. Continuous distribution means the species would show little variation, but the species still communicates or is capable of traversing physical boundries, thus keeping the gene pool mixed like fish and birds! Under Discontinuous Distribution there are two variations Disjunctive distribution Endemic Distribution this is a species that is very closely related but separate geographically an example is the Eurasian Pygmy Shrew, found in Andorra, Spain and Southern Ireland, brought to Ireland on Spanish boats endemic distribution represents a species that occurs naturally in only one region an example being the Takahe bird of New Zealand, which is endangered. some Endemic populations can be climatised to new regions, as with the Takahe bird, which is being raised on several islands surrounding New Zealand instead of just in the mountains, which is bringing the flightless bird's population up Another term for continuous Distribution is Cosmopolitan Distribution this describes a species that can be found anywhere on Earth, with little to no variation. the best example is humans, who spread from Africa after the split of Pangaea over the many land bridges, and settled in almost every environment, adapting as necessary(melanin, stature, hair), but remaining genetically the same and Gloger's Allen's Allen's rule states that animals from colder areas will have shorter limbs than those from warmer regions
like the Arctic Hare vs. the Desert Hare long legs and arms
huge ears short ears
lots of fur protecting small limbs
Bergmann's Bergmann's rule states that animals living in colder regions will develop larger bodies while those living in warmer regions will become smaller example being the bears of Canada, namely the huge and Arctic dwelling Polar Bear vs. the smaller southern Canadian Black Bear adult males between 125- 550 lbs adult males between 770–1500 lbs average length of 7.9–9.8 ft average length of 4–6 ft Gloger states that dark pigments increase in animals living in warm and humid climates an example is humans, with the exception of the Inuit, as their light skin is due to lots of fish consumption The Mayans of Mexico lived in humid and sunny conditions, and developed darker pigmentation while northern Europeans, who lived in relativly cold regions, developed a paler pigmentation Now you've got three rules for radiation
and then a general idea concerning radiation, called Adaptive Radiation In evolutionary biology, an adaptive radiation is the evolution of ecological and phenotypic diversity within a rapidly multiplying lineage. When a single form of life successfully expands into many environments, the process is termed "adaptive radiation." again, we can use as an example
any beneficial traits will be passed on and available to the whole species, though not all members will show it, as with skin pigmentation (the Mayans could mate with the northern Europeans) Every island has a limit of the number of species it can sustain. This mostly depends on:
* Immigration &
* Emigration other theories that take into accountfactors like animal size and weight, and human interference humans interference can be beneficial, like creating a conservation site which boosts population, or detrimental, like using land for developments or clear cutting. other factors are
* Degree of isolation
* Length of isolation
* Size of island
* The habitat suitability which includes:
o Initial plant and animal composition
o The current species composition &
* Location relative to ocean currents Island Biogeography
Marsupial and Placental Mammals Marsupials live in
Oceania and South America Placentals live in almost every habitable region on Earth, including oceans, air, and land. The marsupials who once inhabited North America and Eurasia(while still attached), the Laurasian Marsupials, died off, possibly due to placental competition for their habitats.
By this point, South America and Oceania were no longer attached to Pangaea, and the marsupials became a strong presence, with few predators to contend with. Why?
Activity! You are all Rabbits. Your friends, or warren, all live in the same land mass, happily enjoying your large and varied gene pool, which includes dominant and recessive traits, also, carrots and lettace. On your cards you have traits, like warren digging, ear size, furriness, speed, etc. and beside each trait is a rating. You also have a few loose cards that say things like white fur, grey fur, black fur, etc. Your trait cards, or abilities, you keep, but amongs your warren buddies you should trade your fur cards. Now stop where you are, no more mating! Any one with a 1 on the back of your card, you have wanderlust, so go to the door and stand there. Anyone with a 2, you're good, you can stay put and anyone with a three, you went for a walk because you felt like it, and then got captured by some humans, who brought you over to the human anatomy model. Now there are individual instructions for a few minutes.... This is an example of Discontinuous Distribution. The ones who went away and are now a new species, you are Endemic, and the ones who were captured are now disjunctive with their past warren buddies who stayed at home that day.