Summary
Chordate/Vertebrate Diversity COMPLETE SUMMARY
- Institution
- University Of Cape Town (UCT)
Notes covering the chordate and vertebrate diversity module of the BIO1004S course.
[Show more]
Content preview
Module 4 — Chordate DiversityCHAPTER 34 — Vertebrates
COCNEPT 34.1 CHORDATES
• Vertebrates —> derive name from vertebrae (series of bones that make up the backbone/
vertebral column)
• Much less diverse than insects…
• Great disparity!! —> enormous variation in characteristics (eg. Body mass)
• Vertebrates = member of chordata
phylum
• Chordates =
• Bilaterian (bilaterally symmetrical)
• Belong to clade of deuterostomina
• Deuterostomes = second mouth
• After fertilisation, cell division
begins
• At 32C stage, embryo = hollow
ball of cells (gastrulation)
• Opening called blastopore
forms + extends throughout
development opening on the
other end to form the gut
• In protostomes - rst opening =
mouth
• In deuterostomes - rst
opening = anus
DERIVED CHARACTERISTICS OF CHORDATES —> all possess these structural trademarks at
some point during development
• Notochord
• Longitudinal, exible rod located between the digestive tube and the nerve cord
• Composed of large, uid- lled cells encased in sti brous tissue (made of collagen +
cartilage)
• Provides skeletal support throughout majority of chordate’s length + allows muscles to work
against it
• Fulcrum for locomotion
• In most vertebrates —> more complex joined skeleton develops around the ancestral
notochord —> adult only retains remnants of embryonic notochord (nucleus pulposus of
intervertebral disks)
• Persists in shes and amphibians
• Replaced by vertebral column in reptiles, birds, mammals
• In air (less dense than water), need a stronger more supportive structure
• In humans = reduced + forms part of gelatinous disks between vertebrae
• Dorsal hollow nerve cord
• Develops from a plate of ectoderm that rolls into a tube dorsal to the notochord
• Unique to chordates
• Develops into a central nervous system (brain + spinal cord)
• Unique origin = neurulation (process leading to formation of nerve chord)
• Notochord send biochemical signals upwards causing a thickening of ectoderm unto
neural plate —> invaginated and rolls up to form a hollow tube
• Then leads to cephalisation
fi fl fi fifl fi ff fi
, • Pharyngeal slits/clefts
• Digestive tube of chordates extends from mouth to anus
• Pharynx = posterior to mouthing chordate embryos —> series of arches separated by
grooves from along outer surface of pharynx = pharyngeal clefts
• Can develop into slits that open into pharynx
• Slits allow water entering mouth to exit body w/out passing through digestive tract
• In invertebrate chordates —> Function as suspension feeding devices (>50 in non
craniate chordates)
• Vertebrate chordates (without limbs) —> arches + slits modi ed into gills for gas
exchange
• Tetrapods —> pharyngeal arches develop into parts of ear, sinuses, tonsils + some
glands
• Post anal tail
• Greatly reduced in many species
• Non chordates have a digestive tract that extends almost full body length
• Chordate tail contains skeletal elements + muscles (propulsion in water)
• Balance, support + signalling
• Embryonic in humans + other great apes
• Muscle segments
• Work against notochord
• Muscle blocks with nerves (somites/myomeres) in cephalochordates + craniates
• V-shaped + simple in lancelets (early form)
• W shaped in vertebrate sh
• NOT homologous to invertebrate segmentation
• Did not develop from same germ layers or in same sequence of developmental events
(Non craniate chordates) = PROTOCHORDATES = Subphylum Urochordata (tunicates) +
Subhylum Cephalochordates
• SUBPHYLUM CEPHALOCHORDATA -
lancelets
• Notochord extends into head
• Tail with myomeres w/ segmented
nerves
• No larval stage —> free swimming
• Pharyngeal bars lack gills ( lter
feeders)
• Blade-like shape
• Burrowers —> trap particulate
matter in mucus nets secreted
across pharyngeal slits to lter feed
• Respire through external body
surface
• Closed circulatory system
• Have all chordate characteristics throughout lifetime
• Light receptive pigments (no eyes)
• Move via contraction of muscles against notochord (muscles arranged like chevrons <<<
and ex notochord to produce side to side undulations)
• Serial arrangement of muscles is evidence of segmentation
• Muscle segments develop from blocks of mesoderm —> somites (each side of the
notochord in all chordate embryos)
• External fertilisation
• Simple brain (swollen tip of dorsal nerve chord) but same genes as craniates in brain
development (HOX GENES!!)
fl fi fifi fi
, • SUBPHYLUM UROCHORDATA (tunicates eg. Ascidians)
• Tunciates = Urochordates
• More closely related to chordates than lancelets
• Ascidians, sales, larvaceans
• Most resemble chordates during larval stage
• Larvae use tail muscles + notochord to swim in order to nd suitable substrate (guided by
light-gravity sensitive cells)
• Attaches to substrate with sucker on the anterior
• Once settle on substrate = retrograde metamorphosis (many of its chordate
characteristics disappear) (advanced to simple body plan)
• Tail + notochord resorbed
• Nervous system degenerates
• Remaining organs undergo torsion by 90°
• As adult —> only remaining chordate characteristic = pharyngeal slits
• Draws water in via incurrent siphon, passes through pharyngeal slits to chamber
(atrium) and exists via excurrent siphon
• Food particles ltered by a mucus net and transported to oesophagus via cilia
• Anus empties into excurrent siphon
• Some can expel water via excurrent siphon when attacked (sea quirts)
• RESPIRATION + FEEDING VIA PHARYNX
• Loss of chordate characteristics in adult occurs after the tunicate lineage branched o from
other chordates
• Tunicates = 9 hox genes
• Other chordates = 13 hox genes
• Loss of four hox genes = chordate body plan of tunicate larva is built using a di erent set
of genetic controls than other chordates
• Reproduction —>
• Generally hermaphroditic
• External or internal fertilisation
CONCEPT 34.2
• SUBPHYLUM CRANIATA (main characteristic = cranium/brain case)
• Great disparity
• Diverse morphologies
• Colonised nearly all habitats
• Ecological impacts (eg. Elephants pushing over trees) + important to humans
DERIVED TRAITS OF CRANIATES
• Head with cranium, brain and sophisticated sensory organs
• Eyes —> evolved early in craniate evolution
• Inner/middle ears (hearing, balance + vestibular senses)
• Noses —> smell
• Allows for completely new way of feeding —> active predation
• Neural crest cells —> unique tissue type (42 di erent structures)
• Teeth, bones, skull bones/cartilages, jaws
• Rods supporting gill bars, pharyngeal muscles, ventilation of lungs, gill pouches —> improved
respiration and water ow (allows for more active lifestyle)
ORIGINS OF CRANIATES
• Yannanozoans
• All chordate characteristics and some derived craniate features
• Large brain
• Well de ned eyes
• Muscular pharynx + gill bars
• Derived from neural crest cells??
fi fi fl ff fi ff ff
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through EFT, credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying this summary from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller erinsnotes. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy this summary for R100,00. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
64438 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy summaries for 14 years now