Ch 18 Flashcards
most of the animal phyla
living today appeared for the first time _____ yrs ago during the _____.
543 yrs ago, Cambrian Period
Cambrian to Present =
Phanerozoic
Any trace left by an organism that lived in the past.
Fossil
4 Types of Fossils
Unaltered remains (amber and freezing), premineralized remaines, casts and molds, and trace fossils
Unaltered remains examples
2,ooo yr old cadavers in peat bog, wooly mammoths in permafrost
Permineralized fossils are made how?
and examples
When structures are buried in sediments and dissolved minerals precipitate in the cells. Can preserve details of internal structure.
Fossilized dinosaurs and petrified wood
How are casts and molds made?
When remains decay after being buried in sediment. Casts form when
new materials infiltrate the resulting open space and harden into rock.
Molds consist of unfilled spaces.
Trace fossils are useful because?
Trace fossils
How Organic Remains Fossilize
Record behavior instead of form.
Dinosaur trackways can tell us about an animal’s
stride length and thus yield an estimate of
maximum speed.
Coprolites, or fossilized feces, represent another
type of trace fossil.
The fossil record consists primarily of hard structures left
in depositional environments such as
river deltas, beaches, floodplains,
marshes, lakeshores, and seafloors.
What 3 factors slow decomposition making preservation more likely?
Durability
Burial (usually in a water-saturated sediment)
Lack of oxygen
study of fossilization process
taphonomy
Taxon
any named group of organisms
The divergence of a clade into populations adapted to many ecological niches
adaptive radiation
Tiny glass particles created when minerals are melted by heat generated by a meteor or asteroid impact
microtektites
Compared to animals present earlier in the fossil record, the hallmarks of
the Cambrian fauna are
a dramatic increase in body size, the origin of
hard exoskeletons and complex body parts like limbs, and a
diversification in basic body shapes and organization.
The Burgess Shale and Chengjiang faunas are dominated by
large, bilaterally
symmetric animals with well-developed segmentation, heads, and appendages
The Fish–Tetrapod Transition
Late Devonian vertebrates that span the fish-to- tetrapod transition—characterized by a single proximal bone in the fin/limb recognized as the humerus (forelimb) or femur (hindlimb)
Dino- bird transition
Evolution of theropod feathers. A collection of transitional fossils documents
evolution of feathers in theropod dinosaurs.
Derived traits of synapsids
Dimetrodon was the top carnivore of the Early Permian.
It had most features we associate with reptiles today.
• Sprawling posture
• Simple teeth
• Ectothermic physiology
• Multiple bones forming its
lower jaw.
Where did the two extra bones in ear come from?
An extraordinary series of fossils show that the two bones that form the jaw hinge in non mammalian cynodonts were reduced in size and eventually incorporated into the middle ear (Luo 2011).
background extinctions
(occurred at
normal rates).
Mass extinctions occur as a
consequence of short-term,
catastrophic episodes of environmental change.
Today climet is changing and ______________________________ is preventing ____________
Dramatic loss of habitat not allowing gentic diversity and stability
Cretaceous–Paleogene Extinction
The K–Pg extinction, which included the demise of the non-avian dinosaurs, is
the most recent and best understood of the Big Five.
The K-Pg extinction was caused by…
an asteroid ~10 km wide.
More recent estimates suggest ~15 km wide.
Evedence for the Cretaceous-paleogene extinction
Anomalous concentrations of iridium (rare in the earths crust, but common
in meteorites) worldwide at this time, laid down at the K-Pg boundary
• Shocked quartz particles
• Microtektites
• Crater 180km in diameter near Chicxulub, Mexico (Yucatan)
Possible mass extinction killing mechanisms
• Intense acid rain • Global cooling • Widespread wildfires • Massive earthquakes • Volcanoes • Massive tsunami Long-term disruption of ecological processes, biogeochemical cycles of nutrients, and interactions among species.
Biologists have employed three types of approaches to predict how
continued habitat destruction will affect extinction rates
- Multiply the number of species found per hectare in different
environments by rates of habitat loss measured from satellite photos. - Quantify the rate that well-known species are moving from
threatened to endangered to extinct status in the lists maintained by
conservation groups. - Estimate the probability that all species currently listed as threatened
or endangered will actually go extinct over the next 100 or 200 years.
extinctions are now occurring at ______________ the normal, or background, rate of extinction
100 to
1,000 times
Lack of appreciable morphological change or
speciation over long periods of time.
Evolutionary stasis -
punctuated equilibrium
punctuated equilibrium, all morphological variation occurs at the time of a speciation (branching) event; otherwise, there is stasis.
phyletic gradualism,
morphological change occurs
gradually and is unrelated to
speciation events.
Although it might appear static, morphology in a lineage may actually
fluctuate over time around a long-term average.
This phenomenon has been called
habitat tracking or dynamic stasis.
What are some other species or clade-level characteristics upon which
selection could act?
- Abundance
- Reproductive mode
- Generation time
- Geographic range
- Aspects of life history (such as feeding ecology)
Occur when a single or small group of ancestral
species diversifies into a large number of descendant species that
occupy a wide variety of ecological niches
adaptive radeation
What factors trigger adaptive radiations?
Ecological Opportunity
A lineage can diversify into many different species with divergent ways
of life in response to the availability of new habitats and resources!
(by dispersal to a new habitat, creation of a new habitat, extinction of
competitors)
Morphological Innovation
! or in response to a newly evolved morphological trait that allows
individuals to exploit resources in a new way, e.g., arthropods and
modification and elaboration of their jointed limbs.
