Comparative Vertebrate Anatomy Quiz

Study Notes

Comparative vertebrate anatomy studies the structure, function of structures, and variation in those structures and functions among vertebrates.
Vertebrates fall under the Kingdom Animalia and Phylum Chordata.
Vertebrates are a subphylum within Chordata.

A rod of living cells that lies ventral to the central nervous system and dorsal to the alimentary canal.
In the head region, it is incorporated into the floor of the skull.
In the trunk and tail, it is surrounded by cartilage or bone (except in Agnathans).
In adults:
- Fishes and amphibians: notochord persists along the length of the trunk and tail, but is constricted within the centrum of each vertebra.
- Reptiles, birds and mammals: notochord almost disappears during development (e.g., remains as a pulpy nucleus in the vertebrae of mammals).
- Protochordates: notochord remains as the chief axial skeleton.
- Agnathans: lateral neural cartilages are located on the notochord lateral to the spinal cord.

The section of the alimentary canal that exhibits pharyngeal pouches in the embryo.
Pouches may open to the exterior as slits.
Permanent slits: adults that live in water and breathe via gills.
Temporary slits: adults who live on land.

Oldest known vertebrates include ostracoderms.
Ostracoderms are jawless vertebrates also called armored fishes.
The oldest vertebrates are Myllokunmingia fengjiaoa and Haikouichthys ercaicunensis. They were primitive fish and lived approximately 530 million years ago.

Cathaymyrus diadexus is an example of a potential ancestor of modern lancelets (amphioxus), a non-vertebrate chordate.

Established in 1874.
Includes organisms with:
- Notochord
- Pharyngeal pouches or slits
- Dorsal, hollow nervous system
- Cells that produce the hormone thyroxine

Chordate ‘ancestor’ of vertebrates.
Sessile (like adult tunicates).
Tail evolved as an adaptation in larvae to increase mobility.
‘Higher forms’ emerged through the retention of the tail (neoteny).
Tunicate larva: also called ‘sea squirt’.
- Notochord is confined to the tail.
- Notochord is lost during metamorphosis into a sessile adult.
- Possess pharyngeal slits.

A 530 million-year-old creature, Cheungkongella ancestralis, probably a tunicate, found in the Chengjiang fauna in China might be the earliest known fossil evidence of primitive chordates.

Vertebrate features:
- Notochord
- Dorsal, hollow nervous system
- Pharyngeal gill slits
- ‘Circulatory’ system: vertebrate pattern with ‘pumping vessels’ (but no heart).

Bateson added acorn worms to the Chordata phylum in 1884 because they have:
- A dorsal, hollow nervous system
- Gill slits
- A short diverticulum of the gut called the stomochord.
The current consensus is that the stomochord is not homologous with the notochord and hemichordates belong in a separate phylum.

Annelid Worms:
- Evidence for:
  - Bilateral symmetry
  - Segmented
  - Central nervous system with brain and longitudinal nerve cord
- Evidence against:
  - Nerve cord is solid
  - Nerve cord is ventral
Echinodermata:
- Chordate characteristics include:
  - Radial cleavage
  - Anus forms near or at the blastopore (deuterostomous).