Lecture 3 Exam 1 Flashcards
When did O2 enter the atmosphere and how did this change life on earth?
- appeared 2.5 billion years ago
- O2 supports multicellular life
What is a fossil?
Any trace left by an organism that lived in the past
What is a trace fossil?
- footprints, burrows, feces, anything left behind by an organism
What is a compression fossil?
- a fossil that has undergone compression in a sedimentary rock (mostly plants)
What is a cast and mold fossil?
cast: fossilized imprint made in rock that are filled with minerals
mold: fossilized imprint made in rock.
- mostly organisms with exoskeleton: shell, rigid structures
What is a permineralized fossils
- deposit of minerals within cells (crystallized fossils)
What are unaltered remains?
- also known as frozen remains: mostly found in permafrost
What are the biases of the fossil record
- Geography: depositional areas (lowlands, marine)
- Taxonomic bias: bones and shells amenable to fossilization. Best fossil records have been left by marine invertebrates with hard skeletons. Not all organisms make good fossils
- Temporal bias: earth’s crust is recycled so older rocks are rarer, so older fossils are harder to find
List reasons why origins of higher taxa have not been documented
- many organisms are completely consumed by other organisms
-sediments usually form only sporadically at a given location - there is little reason to assume that all evolutionary changes in which we are interested occurred at the few localities of a time interval that actually allowed fossilization
How do we know that the fossil record in incomplete?
- many periods are represented by few known sedimentary formations and strata are often separated by more than 10,000 years
- many lineages are represented by only at very widely separated time intervals
- many extinct species of large conspicuous organisms are known from only one or a few specimens
- new fossil taxa are discovered at a steady rate
What are the 2 difficulties in the interpretation of fossils?
- age can only imprecisely be estimated by their location in strata
- many fossils are crushed or fragmented
What are chronospecies
- successive phenotypically different forms of a single evolutionary lineage
What is speciation?
The splitting of a lineage (cladogenesis)
What is pseudoextinction or taxonomic extinction
when a lineage changes so much that its original name disappears. Also known as anagenesis
What are the different ages?
- proterozoic
- paleozoic
- mesozoic
- cenozoic
Describe the proterozoic era
- characterized by prokaryotes and eukaryotes
- Ediacaran fauna (635-543 mya): soft bodied, lacking skeletons, crept or stood upon the sea floor. Simple morphology, radial/bilateral symmetry, mainly sponges/jellyfish. Thought to may be a “failed” metazoan lineage
- in paleozoic era
Describe the cambrian period
- Cambrian explosion started (paleozoic era)
- almost all modern phyla and classes of skeletonized marine animals suddenly appear in the fossil record
- Burgess Shale has the best record of this period
- large animals, complex morphology (developed segmentation, head, appendages), and bilateral symmetric
- chordates (first vertebrates and jawless):
- the number of phyla existing in the cambrian is equivalent to the diversity observed today
What precipitated the cambrian explosion?
- diversification may have been promoted by increasing oxygen levels in the atmosphere and ocean
- vacant ecological habitats
- key innovations related to multicellularity and the organization of developmental processes may have evolved (collagen, gene action)
- maybe there was no such thing
Describe the Ordovician era
- in the paleozoic era
- first land plants and jawed fish
Describe the Silurian and Devonian era
- in the paleozoic era
- origin and diversification of bony fishes (silurian)
- first fungi, tetrapods and insects (devonian)
Describe the carboniferous and permian era
- in the paleozoic era
- widespread tropical swamp forests, gigantic dragonflies, reptiles, mammal like reptiles
- Appalachian mountains rise
What is the mesozoic era divided into?
- triassic
- jurassic
- cretaceous
What is the Pleistocene epoch
- pleistocene epoch
-repeated glaciations, origin of modern humans, repeated extinctions/glaciations
What is the triassic period?
- first dinosaurs and mammals
What is the jurassic period
-first eutherian mammals and first bird
What is the cretaceous period
- first flowering plants
- KT extinction
What is the pleistocene epoch
- repeated glaciations
- origin and extinction of large mammals
- origin of modern humans
- extinction of many taxa
what is pseudoextinction?
- when a lineage changes so much that the original name disappears
What is anagenesis
new species is transformed into a different species
What is the cenozoic era
- mammal radiation after extinction of dinosaurs
- pollinating insects
- first apes
- humans appear
what is the holocene epoch
agriculture, domesticated animals, digital watches
What is the Pleistocene epoch
- Pleistocene epoch
-repeated glaciations, origin of modern humans
What are the big 5 extinction events
- cretaceous-Paleocene boundary
- end Triassic
- end Permian
- late Devonian
- end Ordovician
What is background extinction?
- the normal extinction rate
- within any group the chance of extinction is constant but rates may vary among taxa
- rate of extinction and ability to survive the mass extinctions may be related to geographic range
