exam 4 ch 18.3 Flashcards
6 Periods: of the Phanerozoic
Cambrian
Ordovician
Silurian
Devonian
Carboniferous
Permian
Expansion and diversification of multicellular life and
the first representatives of all modern animal groups appear
The Cambrian Period:
The super-ocean surrounding the Cambrian landmass
Panthalassic Ocean:
Possible Supercontinent spanning across the south pole that broke up during the early Cambrian
Pannotia:
Main Cambrian continent containing portions of modern South America, Africa, Antarctica, & Australia
Gondwanaland:
The North American Craton present during the Cambrian.
Laurentia:
Carbon Dioxide levels reach their highest of the Phanerozoic
Cambrian Atmosphere:
Oxygen levels reached 14%
Cambrian Atmosphere:
No ice at the poles, with surface temp’s reaching 100 degrees F at the equator
Ocean Surface Temperatures:
Averaged 73–77 °F
Land surface temperatures:
The rapid adaptive radiation of species within clades expanding to
encompass the major groups of life seen today
Cambrian Explosion:
The process where a species or group of species rapidly diversifies into many new species
Adaptive radiation:
A group of conserved transcription factors which regulate expression of genes related to body plan in the embryos of animals
Hox (Homeobox) genes:
what caused the Cambrian Explosion?
- Predators put selective pressure on mutations that provided protection.
- Oxygen levels reached levels that made aerobic respiration more efficient, allowing for larger body sizes.
- Worldwide spread of photosynthetic eukaryotic Algae increased food supply.
- Evolution in Developmental Gene Regulatory Networks that control the construction of body plans
Generation of different protein molecules from the same pre-mRNA by incorporation of a
different set and order of exons into the mRNA product.
Alternative splicing:
became far more prominent.
Distal enhancers
Sequences in the DNA far from the gene where transcription factor complexes bind and
can increase gene expression several-fold to over 100-fold.
Enhancers:
provided a new level of transcriptional control.
CTCF sequences and TADs
Architectural protein that organizes the genome structure in ways
that alter topological domain interactions and ultimately regulate gene expression.
CCCTC-binding factor (CTCF):
DNA sequences organized into distinct regulatory territories
in the nucleus
topologically associating domain (TAD):
Worms that burrowed and ate other animals
Archaeopriapulida:
Different groups of fossils of likely ancestors of molluscs, brachiopods,
starfish, arthropods, Cephalopods (nautiloids)
Small shelly fossils (SSF):
Bivalves with shells usually composed of the mineral calcite (calcium carbonate
Brachiopods:
Filter feeders that dominated Cambrian oceans “sea lilies”.
Eocrinoids:
Group of extinct marine arthropods
Trilobites:
Any organism preserved in the rock record that is characteristic of a particular span of geologic time or environment
Index fossils:
An extinct genus of an order that diverged from arthropods.
anomalocaris:
An extinct group of sponges were the dominant reef builders in the
Cambrian
Cambrian archeocyathid reefs:
Chordate that had tubes that were the precursors to
the heart and vertebrae.
Fossils of Pikaia (& Myllokunmingia):
Haikouichthys: One of the first vertebrate fossils that also had a skull.
Haikouichthys:
The Cambrian saw a diversification of photosynthetic eukaryotic Algae.
Cambrian plants:
Pulses of anoxia in Cambrian oceans.
Cambrian–Ordovician extinction events:
