Macroevolution Flashcards
What is adaptive radiation?
Event in which a lineage rapidly diversifies, with the newly formed lineages evolving different adaptations
Different factors may trigger adaptive radiations, but each is a response to opportunity
Describe Hyracotherium.
Earliest horse like form
Small brain case
Teeth: flattened, grinding molars and pre-molars so probably herbivore
Common in Northern Hemisphere in early Eocene
When Laurasia separated to 2 continents, what happened to the early horse lineage?
Took 2 different paths
In N. America led to horse genus Equus
In Eurasia, led to modern tapirs, rhinos and others
Describe Miohippus.
By late Oligocene in N. America, Hyracotherium evolved into Miohippus
Larger animal, still not quite a horse
Big brain case
Different forefeet: loss of little digit, lateral digits reduced
There were several branches of the lineage
Describe Merychippus.
True horse line: arose in Miocene Teeth like modern horses Changes in tooth structure coincided with extensive worldwide development of grasslands Grazer Deeper skull
How many separate lines developed from Merychippus?
At least 6, only 1 led to modern horses
Why are founding populations subject to different selection pressures compared to the parent/ mainland population?
No/ few competing, related species
No/ few predators
Larger islands and lakes, allopatric speciation more likely
We are currently in the 6th mass extinction, why?
Human activities
Over-hunting, deforestation, habitat fragmentation, introduction of alien species, pollution and climate change
Give some general observations on continental drift.
Land masses split and join up with others
Terrestrial flora and faunas become isolated/ fuse with others
Isolated seas join up with oceans
Fossil distribution reflects drift
What are the effects of ice ages on faunas?
Extinction of species
Formation of barriers to movement
Splitting of populations and subsequent speciation
What is Wallace’s line?
Imaginary line used by biogeographers to delineate faunas among islands: SE Asia and Melanesia
West of line, birds more like in mainland Asia
East of line, birds more like in Australia
Why do we get the distinctive distributions seen in Wallace’s line?
Australia and New Guinea were previously part of Gondwanaland
But Asia, Indonesia and Malaysia were part of Laurasia
During ice ages Australia and New Guinea became connected due to lower sea levels
What is symbiosis?
Physically close (long or short term) association between different species
Why do we expect a degree of coevolution in mutualism and parasitism?
Due to 2 way selection
Coadaptation in mutualism
Counteradaptation in parasitism
What is cospeciation?
As the host speciates, so does its associated specialist mutualist or parasite
