Vertebrate Origins and Integumentary Systems Flashcards
(61 cards)
What are the important terms regarding function?
Function
Biological Role
Preadaptation
What are the important terms regarding trait evolution?
Homology
Analogy
Convergent evolution (homoplasy)
Synapomorphy
What are the important terms regarding phylogenetic trees?
Taxon
Clade (monophyletic group)
Ingroup
Outgroup
Topology
What are phylogenetic relationships?
Uncertain
Hypotheses
Gaps in animal diversity (i.e. many species are extinct)
Fossils are rare –> Gaps in the fossil record
What are Bilatera?
Bilaterally symmetrical
What are urochordates?
Easy to deal with, not very diverse.
Sit on sea bed
What are Cephalochordates?
Important
See them clearly
What are the Chordate features?
1) Pharyngeal slits
2) Notochord
3) Dorsal hollow nerve tube - very beginning of a nervous system
4) Endostyle (–> thyroid gland)
5) Post-anal tail
For chordates - tail as an appendage
What is a good example of Chordate features?
Amphioxus
Very remote from us
The poster child for learning about chordate features
What are cephalochordate features?
No brain
Filter animal
If you’re a food particle you get trapped between slits and then extra water leaves through the slits
What are the three sub-phyla of chordates?
Cephalochordates
Urochordates
Vertebrates (us!)
Describe the larval vs adult stage of urochordates:
Larval stage:
- Tadpole-like
Adult stage:
- Sponge like
- Sit on sea floor
What is a body plan?
Fundemental structural organisation - like a template
Applies to the entire phylum - all chordates express these features at some point in the life cycle
Some features of the body plan are unique to chordates, but others also exist in other phyla
Body plan DOES NOT equal phylum-specific traits
Body plan = body organisational scheme + phylum-specific traits
What is the organisational “scheme” of the chordate body plan?
I. Symmetry and Direction
II. Segmentation (repetition of elements)
III. Compartmentalisation
Are vertebrates a phylum?
NO!
They have no formal body plan (distinct from the chordate BP)
What is Symmetry and Direction?
Direction is the patterning along an axis –> One end is different from another.
Chordates have bilateral symmetry = mirrored about anterior-posterior axis
Chordate dorso-ventral axis arose through hypothetical dorso-ventral inversion via a flip in chordin-BMP gradients
What are the 3 Axes of the chordates?
Left/right - Symmetric
Dorso/Ventral - Nerve Chord dorsal, heart ventral
Anterior/Posterior - Central NS anterior, etc.
What are the three planes of the Chordates?
Frontal Plane
- Top view
- A/P axis + R/L axis
Sagittal Plane
- Side view
- A/P axis + D/V axis
Transverse Plane
- Front view
- D/V axis + R/L axis
What is segmentation?
Repetition of tissues/organs/features along an A-P axis
Most obvious in other phyla, less so in Chordates (muscles and bones show segmentation, but not coelom and organs)
What is compartmentalisation (vertebrates)?
In vertebrates, formation of a coelomic space
What do you recall about the early embryo?
Has ectoderm and endoderm
Then gastrulation occurs –> Formation of mesoderm
What is a coelomic space, or cavity?
A fluid filled compartment lined by mesodermal epithelium
It is closed and ‘empty’
Describe the process of the coelomic space formation, including uses in vertebrates:
Mesoderm makes coelomic space
Fluid filled
Allows space for gut or lungs to expand etc
For us it organises the organs, inside the space, inside little bags.
Many functions - earthworm has internal compartments so if they have a puncture they can still live.
What is it called when two walls of coelomic space meet in the middle?
Mesentery
