global spike in iridium concentration that indicated massive asteroid impact @ KT boundary
1908 asteroid explosion over Siberia, heard around the world, just huge.
the death of a species - continuos ongoing consequence of env. change and nat. selection
Red Queen hypothesis
Species have a large amount of variation - but their genetic resources are finite
Environment never stops changing
Eventually even the most varied gene pool will be exhausted, species goes extinct [all species doomed]
With 50/50 odds, sometimes you win, sometimes you lose, but you WILL eventually bust.
random steps, never know where you'll be at any given point.
minimum viable population
the number of individuals below which a population cannot sustain itself.
shows that larger areas can sustain larger populations...loss of habitat=extinction
field of bullets
darwinian, survival of the fittest
extensive extinction, not tied to adaptation (mass ext.)
the regular extinction that constantly occurs bc of env. change and natural selection. 180-300 species every 1million yrs.
mass death of many species, abrupt change in earth's fossil record. eologically normal causes
regression (sea level)
fall of global sea levels (evident during great dying and KT boundary) effects reef environments.
plots the probability of percentage of species killed in a mass extinction event over time
use a "kill curve" to predict:
1) Likelihood of major extinction events
2) Average waiting time between mass extinctions
big five extinctions
Probability of 5% or less on kill curve:
caused by impact event, shocked into distinctive, disorganized mineral array.
octahedral shocked quartz, indication of impact shock
small glassy beads of liquified thrown off by massive impact event.
impact event likely caused extinction 65 million years ago, death of the dinosaurs. Also deccan traps messed stuff up w/ lava. Age of reptiles ends, age of mammals begin.
are large cosmic snowballs, made up of frozen gases and dust
Solar wind blows a steady stream of gas and dust from the surface, creating a long tail
solid balls of rocks, high metal content
Orbits take them throughout the solar system
Most are located in the asteroid belt, between Mars and Jupiter. May be the remains of a planet that did not coalesce when the solar system formed
Asteroids are 30 feet or larger (10 m),
smaller objects are called meteoroids, asteroids smaller than 10m.
meteoroids that survive earth's atmosphere.
every 26 million years, impacts have high periodicity attributable to four causes:
1) Planet X
3) Vertical oscillations of solar system through the plane of the Milky Way
4) Passing through the spiral arms of the galaxy as the solar system orbits galactic core. All either unlikely or not compatable with data.
Cloud of comets far out beyond the orbit of Pluto, at the outer edge of the solar system. Debris left over from the formation of Neptune and Uranus formed Kuiper Belt of comets, not sure if it exists.
mysterious tenth planet, out beyond Pluto
Orbit so eccentric (highly elliptical) that it only swings in through the comet cloud every 26 million years.
sun has a distant solar companion. , has a very eccentric orbit
Swings back every 26 million years, disturbing the Oort Cloud
The Great Dying
Permian extinction event
Devastation was truly profound
Estimated 52% of all families, 90-95% of all species on Earth went extinct in a relatively short period of time
Extinctions affected big and small, aquatic or terrestrial
Massive volcanic eruptions that could have cause, or contributed too, the Permian extinction (Great Dying). Led to global nuclear winter, and possibly tons of acid rain.
theory that continents drift around earth along lithosphere. Caused by convection currents in mantle.
formed by modern Africa, South America, Australia, and India. 200mya
formedby europe, asia, and north america. 200mya
Human caused extinction during the Pleistocene, ~10,000-15,000 years ago
72% of the Earth's large mammals disappeared
Common features of a mass extinction event:
Many species go extinct in a short period of time (30% or more)
Vanished species span all habitat types, sizes - marine and terrestrial, large and microscopic
eologically normal causes
Sea level change (regression)
Predation, diseases, parasites
Cosmic collision, rays
Characteristics that help survival
1) Being very widespread - greater chance that someone will be spared
2)High population densities - more numerous you are, higher chance some will make it through
3) Being lucky
Some species are much more vulnerable than others
1) Small population
2) Restricted range, habitat
3) Specialized niche
four ways in which smaller populations are vulnerable (simberoff)
Demographic randomness - random accidents can have a much greater effect on small popn.
Genetic deterioration - less variability, highly inbred, can't always adjust to rapid environmental change
evidence for large impacts
1) Big craters (duh)
2) Anomalous levels of iridium and other elements
3) Shocked quartz or other minerals
4) Mikrotektites in sediment
5) Soot particles
Possible causes of great dying
1) Possible asteroid/comet impact
2) Widespread volcanism
3) Global warming (methane release?)
4) Anaerobic conditions due to overturning of ocean sediments (releasing CO2)
5) Sea level changes (ice age?)
6) Breakup of Pangea (leading to global climate change)