Flashcards
Lecture 3
Cards in this deck (15)
- 1Metazoa (Definition)The multicellular animals
- 2Why are most animals bilateral? (2)Bilaterial symmetry is a consequence of a mobile lifestyle dining two directions:
1) Direction of movement = posterior -> anterioor
2) direction of gravitational forces = dorsal -> ventral - 3Relevant direction for sessile animalsDirection of gravitational field.
- 4D-V Axis Inversion (When did this happen?)- The similarity in the d-v signaling and polarity suggests that in the evolution of chordates the d-v axis has been inverted.
- Most likely after the split between echinoderms and chordates. - 5Protostomia (mouth and anus theory)Blastoporus becomes the mouth, anus is secondary
- 6Deuterostomia (mouth and anus theory(Blastoporus becomes the anus, mouth is secondary.
- 7Echinoderms-Deuterostomes (highly derived)
- Sessile ancestor (radial body shape)
- Little affinity to vertebrates in body organzation (only in fossil form) - 8Hemichordates- Pharyngeal pores
- Terminal anus (like invertebrates) - 9What makes hemichordates interesting? (2)1) Gill slits (innovation for suspension feeding)
2) A Neural Tube (likely not homologous to chordate neural tube --> wrong side of body) - 10Two modes of nervous system development1) Epithelial mesenchymal interaction: most invertebrates and PNS
2) Neurolation: CNS forms from an epithelial tube (vertebrates, chordates and hemichordates) - 11Intra-epithelial nervous systemNervous system is within the skin
- 12Why have a neural tube?Chordate ancestor had intra-epithelial nervous system, too rushed to reorganize CNS into ganglia, so just rolled it up and sank it into body.
- 13Cephalochordates affinities to vertebrate body plan (5)1) notochord (goes all the way to anterior tip (no head), CNS is shorter than notochord (no forebrain))
2) hollow dorsal nerve cord (spinal chord)
3) Segmented musculature
4) Gill slits
5) tail - 141) What group is Amphioxus in? 2) What important gland does it introduce?1) Cephalochordates
2) Endostyl related to thyroid - 15Urochordates- Chordata
- Larvae of tunicates reflect relationship to other chordates (Gill slits, spinal cord, notchord, postanal tail)
- Tail with notochord is not obligatory.
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- Vertebrate Relations and Body Symmetry
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- Krisstel Gomez
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