Biology 214 Lecture 3


Terms in this set (...)

Oldest most recent common ancestor
predates to 2 billion years ago (cyanobacteria fossil)
What is a fossil?
any trace left by an organism that lived in the past
Compression fossils
found in sedimentary rocks that have been compressed, soft bodied animals or plants, because anything that has a rigid structure could be deformed or fragmented
Casts and molds
fossils coming from streams of hot structures that move into sedimentary rock
Per mineralized fossils
example tree minerals into the cells with out distorting them, petrified wood
Unaltered remains
undergone little or no change in compositions usually fossils found in amber or frozen
Geography bias
depositional areas (lowlands, marine)
Taxonomic bias
bones and shells amenable to fossilization. *Best fossil records have been left by marine invertebrates with hard skeletons
Temporal bias
Earth's crust is recycled so older rocks are rarer
Paleontologists apply this term to temporally distinct parts of a single evolutionary lineage, which contains successive, phenotypically different forms. These different forms are called Chronospecies
change in a lineage
Pseudoextinction or Taxonomic Extinction
occurs when a lineage changes so much that its original name disappears.
Real Extinction
a lineage fails to leave any descendants
contrast this use of species with the usual use of the term speciation to describe the splitting of a lineage
Proterozoic Era
2.5 BYA - 543 MYA
most of this era was characterized by prokaryotes and eukaryotic algae. Oldest fossils of multi-cellular animals are 640 million years old. First evidence of animal life appeared less than 1 BYA.
Trace fossils
(tracks, burrows, feces)
Best Known Precambrian animals
Ediacaran Fauna (565-544 mya)
Soft bodied, lacking skeletons
Crept or stood upon the sea floor
Most don't fit into modern phyla
Relationships to life in Cambrian difficult to interpret
Ediacaran Period
(635-543 MYA)
Simple Morphology
Radial symmetry, maybe bilateral
Mainly sponges, Jellyfishes
Ediacaran Fossils
radial symmetry (sponges, jellyfish). There is a large diversity of forms with unknown affinities to more recent fossil groups. Fossil sponges with larvae similar to forms found in living sponges.
Paleozoic Era
Cambrian Period (541 to 485 MYA)
Almost all of the modern phyla and classes of skeletonize marine animals suddenly appear in the fossil record
This explosion may have occurred in 30 million years or maybe as little as 5-10 million years
The most amazing record of this period appears in the Burgess Shale, which is near Banff, BC, Canada
Almost all of the fundamentally different animal body plans were present by the end of the Cambrian
Cambrian Assemblege
Large animals
Complex Morphology
developed segmentation
Bilaterally Symmetric
Chordates present in the Cambrian
First vertebrates (jawless vertebrates - lamprey)
What precipitated the Cambrian Explosion?
Diversification may have been promoted by increasing oxygen levels in the atmosphere..
Vacant ecological habitats may have fostered diversification.
Key innovation related to multicellularity and the organization of developmental processes may have evolved
Paleozoic Era: Ordovician (485-443 MYA)
Lot of diversification with new classes and orders; first land plants and jawed fish; ended with one of the five largest mass extinctions of all time
Paleozoic Era Silurian (443-419) and Devonian (419-359)
Origin and diversification of bony fishes. Plants diversify on land. Trees present by the late Devonian. First terrestrial animals were arthropods, early Devonian. Terrestrial vertebrates (tetrapods) arose in late Devonian. Mass extinction at end of Devonian.
Paleozoic Era: Carboniferous (359-299) and Permian (299-252)
Widespread tropical swamp forests, gigantic dragonflies, reptiles, mammal like reptiles, worst extinction ever at end of Permian.
Mesozoic Era (252-66 MYA)
Triassic, Jurassic and Cretaceous Periods. Nass extinction at the end. Dinosaurs, mammals and birds appeared.
Ceozoic ERA: Paleocene epoch (66-56 MYA)
Mammalian radiation after the extinction of the dinosaurs
Pleistocene Epoch (1.8 MYA to 10,000 ya)
Repeated glaciations. Origin and extinction of large mammals. Origin of modern humans. Extinction of many taxa.
Holocene Epoch: The last 10,000 years
Agriculture, domesticated animals, digital watches, etc. Also in the midst of what might be the worst mass extinction ever.
the failure of a lineage to leave any descendants
Normal Extinction Rate
Within any group the chance of extinction is constant but rates may vary among taxa. The smaller the geographic range the greater the rate of extinction because they can't adapt to the changes in the environment.
What has caused mass extinctions?
Likely multiple reasons associated with rapid changes in climate, followed by a cascade effect caused by the breakup of complex biotic interactions, possible cause of KT )or K-Pg) extinction maybe an steroid impact around present day Chicxulub, Mexico.