Lecture 19 Origin of Animals Flashcards
what are 5 agreements between the old tree and new tree of animals?
- All animals share a common ancestor – metazoa (multicellular animals)
- Sponges (Porifera) are basal animals
- Eumetazoa is a clade of animals with true tissues
- Most animal phyla belong to clade Bilatera which is monophyletic
- Chordates belong to clade Deuterstomia
what are 3 disagreements between the old tree and new tree of animals?
- Which clade is sister to Bilatera?
- Morphology (old) based tree divides bilaterans in two clades: deutersomes and protostomes
- Recent molecular studies indicate tree bilaterian clades: Deuterstomia, Ecdysozoa, Lophotrochozoa
what are 3 pieces of morphological/developmental characters that support molecular evidence?
- ecdozoans undergo ecdysis
- some lophotrocozoans have a feeding structure called a lophophore
- other lophotrocozoans have a distinct developmental stage called trochophore larva
what is a key feature of ecdozoans?
give examples of ecdozoans
- shed their exoskeletons in a process called ecdysis
- anthropoda: insects, arachnids, milipedes, centipedes, crustaceans
what is a lophophore?
- a circular or horseshoe-shaped organ about the mouth especially of a brachiopod or bryozoan that bears tentacles and functions especially in food-getting
give examples of lophotrochozoans that have a stage called trochophore larva
- molloscs
- annelids
what are animals generally considered to have evolved from?
- flagellated eukaryote
what is the closest living relative of the ancestor of animals
- choanoflagellates (opisthokonts protists)
what are the three divisions of the geologic record?
- Archean
- Proterozoic
- Phanerozoic
what is the precambrian?
Archaen + Proterozoic
what does the phanerozoic encompass?
multicellular eukaryotic life
what are the three eras the Phanerozoic is divided into?
Paleozoic
Mesozoic
Cenozoic
what are the 3 evidence that choanoflagellates are closely related to animals?
- cell morphology (similarities)
- cell morphology unique to animals
- DNA sequence homology
what is the structure of heterotrophic protists?
- single flagellum surrounded by collar of microvilli
what are microvilli?
finger-like projections of cell membrane
what kind of colonies did heterotrophic protists display?
- some solitary others colonial
- stalked/ball like colonies
what is the hypothesis regarding the ball shaped colony?
ball shaped colony = blastula which evolved into simple animals with endo and ectoderm (NO FOSSIL EVIDENCE)
what did the evolution of eukaryotic cells allow for?
greater range of unicellular forms
when did the second wave of diversification arise?
- when multicellularity evolved and gave rise to algae, plants, fungi, animals
what happened in the Neoproterozoic Era?
- Ediacaran biota
- diverse tubular and frond shaped, mostly non-motile (sessile) soft bodied organisms
- larger ones disappered before cambrian
what happened in the Paleozoic Era?
- CAMBRIAN EXPLOSION - marks earliest fossil appearance of many major groups of living animals
- suddenly complex life - including many forms with skeletons
- most major phyla appeared (except cnidarian, porifera, molluscs which came prior)
what are hypotheses for the cambrian explosion?
- evolution of the hox gene complex
- new predator-prey relationships
- a rise in atmospheric O2
what happened in the Mesozoic Era?
- flowering plants and insects diversified
- coral reef emerged
- dinos were dominant
- first mammals emerged
what happened in the Cenozoic Era?
- mass extinctions of both terrestrial and marine animals (nonflying dinos and marine reptiles)
- mammals increased in SIZE and exploited vacated ecological niches
- climate cooled globally
what are most animals?
INVERTEBRATES - informal classification based on anatomy
