Chapter 15 Flashcards
define extinction
all individuals in that species/genus/etc. have died out and left no descendants
dissolution
water dissolves fossil leaving behind a cast
carbonization
thin carbonized layer
What are the right conditions fossilization requires?
Geological and abiotic conditions.
Most often occurs in sedimentary rocks
What factors can disrupt the process of fossilization?
scavengers/predators
soft tissue preservation rare
abiotic factors break down organism
Lagerstatten (resting place)
Large number of fossils found together due to perfect geological and biotic conditions
Ediacaran fossils
Huge burst of new multicellular organisms
Where do you look for fossils?
Look for sites that are prone to have fossils based of ideal geological and abiotic conditions
Look near previously identified sites
phylogenetic/ biogeographical reconstructions
combinations of above
Law of superposition (relative aging)
Fossils found lower down in the sediment at a particular locality are older than those found closer to the surface
Radiocarbon dating (absolute aging)
Isotope carbon-14 decays into carbon-12 at a steady state, half-life 5730 years.
Potassium-14 to argon-40
(1.3 by half-life), volcanic in origin; date surrounding volcanic rocks around fossil
Paleomagnetic dating
Changes in the earth’s magnetic field which is preserved in metal grains in rocks.
Does a fossil represent the first or last appearance of the species?
NO
Signore-Lipps effect
Time lag between the last known fossil and extinction;
result= extinction date is estimated to be earlier that it actually is
“Forward smearing”
reworking of strata; mixing of layers
Mass extinctions
Spike in extinction rates; 40-50% of all species & 5-8 in earth’s history
Background extinction
extinction outside of mass extinction, 95% of all extinctions
How is background extinction caused?
Mainly caused by predation, competition, diseases, climate change.
endemic
native to only one area
What can happen if natural selection favors traits in predators that make them efficient at capturing prey?
Can cause prey to go extinct; also cause an evolutionary arms race
What can happen if new predators enter an area (natural or unnatural)?
Can extirpate native fauna
What are the 5 big mass extinctions?
Ordovician, Devonian, Permian, Triassic, Cretaceous (K-T)
How is extinction a double-edged sword?
Besides wiping out lineages and genetic variation, the evolutionary landscape changes opening up new opportunities for surviving lineages
What are the 4 causes of loss in mass extinctions?
taxonomic diversity, morphological diversity, behavioral diversity, number of different types of niches
Dead clade walking
Clade that survives a mass extinction event to only going extinct in the next geological time period
K-T Mass Extinction aka Cretaceous-Tertiary
Occurred over very short period of time; supernova/ asteroid collision theories (iridium deposits)
Permian Extinction
Greatest mass extinction, all walks of life hit hard, coral reefs depleted
What caused Permian extinction?
Siberian traps- huge volcanic eruptions &
massive “greenhouse” effect due to CO2 release, so surviving species adapted to hypoxia
How come species longevity has no effect on the probability of extinction
Extinction is a function of how well individuals in a species adapt to the current environment, not how well they adapted to past conditions
What is the advantage of having a broader geographic range?
The less likely a taxon will go extinct
Phyletic gradualism model
Adaptations that arise within a species are the result of slow gradual processes, where any variant that provides the slightest benefit slowly increases in frequency
ex. equine evolution
cladogenesis
a new form that appears in the fossil record arising through branching speciation events
anagenesis
a new form that appears in the fossil record arising through gradual modification WITHOUT branching speciation
Punctuated equilibrium
predicts that a lot of evolutionary change takes place in short periods of time tied to speciation events
ex. Cambrian explosion
Cambrian explosion (5 facts)?
-543-490 mya spike in number of species
-new body forms and shapes
most of the animal groups that have ever lived can be traced back to this time period
What is Punctuated equilibrium in bryozoans tied to?
tied to changes in oceanic boundaries
Cope’s rule
Species in mammalian clades tend to increase in body size over evolutionary time. (Doesn’t always hold up within mammals and across other groups)
general increase in organismal complexity
What is the difference between passive & active trends?
Passive: no directional tendency to change, but the precursor starts at a minimum size which evo can’t take new lineages
Active: each lineage tends to increase in body size
What two processes lead to active trends?
- trait values with each subclade shifting in parallel
- species selection
Species selection
speciation and extinction rates that vary according to the value of the trait in question
In what body size does speciation events take place more frequently?
Speciation events are more frequent among LARGER species
Tree branches are longer in larger species, what does this indicate?
Fewer extinctions
