BISC 102 Lecture 19: Adaptive Radiations & Extinction- Lecture Notes

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November 5th, 2015
What are we doing today?
what is macroevolution?
adaptive radiations
mass extinctions
evolution on a small scale
changes in allele frequency within a species
processes: natural selection, drift, mutation
focus on changes in living species
evolution on a large scale, as seen through the
history of life
patterns of stasis, change, origin of new
lineages, and extinction
often informed by the fossil record
Adaptive Radiation
one twig that splits into two (simple) speciation
adaptive radiation is a sudden and rapid
diversification of a phyletic line into several
Hallmarks of adaptive radiation
they are monophyletic groups
spectated rapidly
diversified ecology
occurs when a new set of niches opens up
evolution of a novel feature
this feature evolves and if it’s
good it spreads (not intentional)
opening up of a new habitat
new ecological opportunities
extinction of other species or clade
there is empty space that can be
used up
Galapagos finches are an example of adaptive
inspired Darwin
there are 13 species right now in the 20
the dier mostly in the size of beak
association between the shape of
the beak and the type of food that
the birds eat
new habitat
new food sources
speciation by island hopping
the ancestral finch lived on the South
American island and then when the
island split this one dispersed onto
most likely the closest island
it had a lot of ecological opportunities
founder eect - small population that
separated from the large population
the birds can disperse from island to
lots of recolonization and new
colonization with the exploitation of new
ecological opportunities
Adaptive Radiation - Bats
Order: Chiroptera
2nd most diverse order of mammals
very large order
radiated - 50mya
we know this from the fossil
extinction of pterosaurs
these were flying dinosaurs that
were obviously monopolizing the
a new niche has opened up
peak insect diversity
novel features
echolocation (allowed them to
exploit the air at night)
Tempo of Speciation
highly variable between taxa
a fact of life
99% of species that have existed are now
what we see today is a tiny fraction of
what has existed so far
typical ‘lifetime’ of a species = 1 million years
based on the fossil record
these are all marine taxas
each column represented the number of
species that have existed
you can track the diversity of these groups
lots of speciation events and lots of
extinction events
these patterns are dierent from group
to group
P= Palaeozoic M= Me...
diversity goes up over time
there is a lot of ups and downs
downs represent extinction events
Mass extinctions
1. Ordovician
2. Devonian
3. Permian
4. Triassic
5. Cretaceous
this is just marine animals
extinction rates are going down
on average we lose anywhere between 2 and
5 families of marine organisms per million
this is background extinction that
happens for whatever reason
the red dots are the 5 periods of mass
extinction *NEED TO KNOW THESE*
1. End of the Ordovician
2. End of the Devonion
3. End of the Permian
250 million years ago
“the great dying"
“the mother of mass extinctions"
90% of all species
4. End of the Triassic
5. End of the Cretaceous
a mass extinction ends a period
mammal-like reptiles disappeared in the
beginning of the age of dinosaurs
Permian Extinction ( 250 mya)
The “Great Dying"
90% + of all species died
96% of all marine species died out
(84% marine genera, 54% marine
70% of land species
(included plants, insects and
victims include...
Mammalian Reptiles
Possbile Causes? (There are lots of these)
siberian volcanoes
biggest volcanic event
huge amount of the earth covered
in volcanic matter
period of darkening
massive amounts of acid rain
Very rapid elevation of CO2
rapid increase in global temps (
went up 6 degrees)
formation of Pangea
Large land masses coming
changed ocean circulation
amount of coastal regions
drop in sea level
large parts of the ocean
became anoxic
reduced oxygen in oceans
climate change
Explanation must be a global
phenomenon that is able to explain why
some survived but others died out
have global consequences
This was the biggest extinction
Cretaceous-Tertiary (K/P) Extinction (65 mya)
60-80% of animal species extinct
dinosaurs were aected by this
terrestrial animals hardest hit
Many plants and invertebrates
mammals, crocodiles, non-north
american plants
these animals survived
more hit and miss than the Permian
possible causes?
climate change
sea level changes
increased volcanic activity
meteorite impact
what we have the most evidence
to support
evidence for meteorite hypothesis
global iridium layer at K/T boundary
180 k/m diameter crater from meteorite
impact 65 ma o Yucatan, Mexico
This layer was deposited when there
was a very large meteorite impact
the crater has been found for a meteor
that was big enough to cause this
global impact
Caused by a meteor that was 10km
meteorite impact likely caused:
tidal waves (as much as 4km high)
dust, darkness, cooling
water vaporized from ocean and acid
earthquakes and volcanoes
mass extinction
Are we in the middle of a sixth mass extinction?
Recent Megafauna Extinctions
large terrestrial animals (>44 kg)
began in the Late Pleistocene (100,000 to
10,000 years ago)
Victims - Australia
Victims - South America
Ground sloth
Victims - North America
Short-faced bear
Wooly Rhino, Saiga, Antelope, Saber toothed
Late Pleistocene Extinctions of Genera of
Causes of Megafauna Extinction?
Climate change?
Overexploitation by humans?
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