Animal Origins Flashcards
What is an animal?
Multicellular heterotrophs without a cell wall. They’re mobile, at least in part of the life cycle.
What are bacteria?
Unicellular prokaryotes with fatty ester lipids.
What are Archaea?
Unicellular prokaryotes with isoprenoid ether lipids.
What are Plantae?
Multicellular autotrophs with chloroplasts and a cellulose cell wall.
What are fungi?
Multi/ unicellular heterotrophs with chitin cell walls.
When did complex life evolve?
The Phanerozoic period (540Ma-Today)
What Ediacaran animal clade had of a ‘leafy’ like branching structure with similar morphologies (fronds) and fractal growth?
Rangeomorphs
What does the high surface area to volume ratio of many Ediacaran animals suggest?
Osmotrophic feeding
What is Kimberella and why is it important?
Kimberella is an extinct genus of bilaterian from the Ediacaran period. The slug like organism fed by scratching the microbial surface on which it dwelt. It is important because it is potentially the first ‘animal’ to exhibit movement.
Why did the Ediacaran evolutionary event occur?
Deglaciation (end of Gaskier’s glaciation), an increase in oxygen allowing for larger more complex life and and the Shuram carbon isotope excursion caused be meteor bombardment resulting in an increase in ocean nutrients.
What is a Phylum?
A taxonomic group with a unique body plan
What characteristics define the Arthropoda phylum?
Bilateria with jointed appendages.
What characteristics define the Chordata phylum?
Bilateria with a notochord and dorsal nerve chord.
What is a phylogeny?
An evolutionary tree based on either molecular similarity (genetics) or morphology (physical traits).
Why are fossils in the Burgess shale so well preserved?
A sea cliff collapsed so the whole ecosystem was rapidly buried leading to anaerobic diagenesis (resulting in soft tissue preservation).
What is the Burgess shale?
A very well preserved Cambrian fossil deposit in Canada.
What are Trilobites?
Fossil arthropods that became dominant and abundant during the Cambrian.
What is a crown group?
All living members of a clade including common ancestors and descendants.
What is a stem group?
The extinct organisms outside of a group that are part of a phylogeny.
What was the Cambrian explosion?
A sudden period of evolution and biological diversification of phyla after a long period of stasis.
What are the possible biotic and abiotic causes of the Cambrian explosion?
- Biological arms race-predator prey competition accelerated evolution.
- Rodinia broke apart leading to an abundance of shallow waters conducive to life at the time.
- Earlier in life’s history there were less constraints on life resulting in more experimentation.
- More exposed rock increasing carbonate input which increase alkalinity and nutrient levels.
