history of life on earth pt 2 (plate tectonics -> exaptations)

plate tectonics

earth’s crust floating on the mantle

→ plates will collide, separate, or slide past each other and these interactions between plates cause the formation of mountains + islands + earthquakes

how did continental drift affect the formation of pangaea?

A) deepening of ocean basins

B) reduction in shallow water habitat

C) colder + drier climate inland

→ life on land has VERY different climatic effects today than it did earlier

allopatric specitation

as continents separate, species begin to evolve with different features that make them more specified to a particular area

→ i.e. australia moved so far away from the rest of the land masses on earth that it has VERY specific species that live only there

what causes mass extinction?

disruptive global environmental changes

what are the 2 major mass extinctions?

1) permian extinction (between paleozoic + mesozoic)

→ the oceans became anoxic

2) cretaceous extinction (between mesozoic + cenozoic) 

→ iridium found in an asteroid created a dust plume large enough to block out sun which made the dinosaurs die out

what caused the permian extinction?

volcanic activity caused increase of CO2 + global warming

this reduced the temperature gradient from equator to the poles

the oceans became anoxic, meaning they stopped circulating and mixing

what caused the creataceous extinction?

an huge asteroid hit the earth and sent a dust cloud of iridium big enough to block sunlight into the atmosphere

it was so big and so dark that it caused an ice age

this made the dinosaurs go extinct

what are the consequences of mass extinctions?

pave the way for adaptive radiations

→ extinct animals let new animals take up those empty spaces

→ promotes biodiveristy

adaptive radiation

evolution of diversely adapted species of a common ancestor

what causes adaptive radiation?

A) mass extinction

B) evolution or novel characteristics

C) colonization of new regions

what are examples of adaptive radiation?

dinosaurs went extinct → mammals took their place and diversified themselves

exaptations

structures that evolve in one context but are used for a different function

→ many novel biological structures evolve in many stage from previously existing structures

what are examples of exaptations?

swim bladder was ORIGINALLY a lung, but EVOLVED little by little to become a buoyancy device in fish

feathers were ORIGINALLY used for insulation, but EVOLVED little by little for flight in birds