AD Vertebrate beginnings Flashcards
Describe chordate characteristics
Notochord
tubular dorsal nerve tube
Pharyngeal slits
Endostyle or thyroid glands
Postanal tail
Describe a notochord
Rod-like, flexible structure dorsal along longitudinal axis of the body
Located between the digestive tube and the nerve cord
It is composed of a core of large, fluid-filled cells encased in fairly stiff, fibrous connective tissue sheath
Hydrostatic organ, provides support, but is flexible, and allows swimming motion through lateral pressure against the surrounding substrate
In vertebrates the notochord is only a remnant – and skeletal support is provided by a complex, jointed skeleton
Describe a Dorsal tubular nerve cord
In Chordates, the nerve cord develops from dorsal ectodermal cells that form an invagination and sink inward
A fluid-filled tube of nerve tissue that runs the length of the animal, dorsal to the notochord
The nerve cord of the chordate embryo develops into the central nervous system: the brain and spinal cord.
Present in chordates throughout embryonic and adult life.
Describe Pharyngeal slits
Pharynx is part of the digestive system and has a series of longitudinal slits at some stage of the development
Water → mouth → pharynx → pharyngeal slits (filter food)
Humans: pharyngeal slits are only present in embryos
Describe a postanal tail
Chordates have a muscular tail extending posterior to the anus.
Although in many species it is lost during embryonic development
Blocks of Muscle (Myotomes) surround the notochord and nerve cord
Describe an Endostyle or thyroid gland
The endostyle or its derivate occurs in all chordates but in no other animals
Endostyle – a groove in the pharyngeal floor of protochordates
It’s a mucus-secreting gland that traps small food
Homologous with thyroid gland
Tunicates are marine invertebrate animals
True or false?
Tunicates most resemble chordates during their larval stage
Which may be as brief as a few minutes
True
Describe a tunicate metamorphosis
They are motile during larval stages, but sessile as adults
After settling head first on hard substrates the adults’ tail, notochord, muscle segments, and nerve cord disappear
a tunicate/sea squirt draws in water through an incurrent siphon, filtering food particles. Plankton is trapped in a sheet of mucus, and cilia later direct the food-laden mucus to the stomach
Describe Lancelets
Invertebrate chordate
Are named for their bladelike shape. They are marine suspension (filter) feeders
All chordate characteristics are present throughout their life history, even into adulthood
Craniates are an animal that possesses a skull.
A hagfish is an example
Describe a hagfish
cavengers that burrow into the flesh of dead or dying fishes.
The mouth, contains a rasping tongue, is surrounded by short tentacles
Has a notochord
Knots ‘travel’ from front to back
to free the hagfish from predators, or from its own slime
Vertebrates are craniates that have a backbone. They evolved during the Cambrian period
How are they characterised?
(a) neural crest
(b) pronounced cephalization
(c) a vertebral column
(d) a closed circulatory system
What is a lamprey?
extant jawless fish, have vertebra
filter-feeders as young but ectoparasitic blood-suckers as adults; the mouth consists of a circular adhesive disk and a rasping tongue-like structure by which the fish attaches to other fishes and sucks their blood.
They lack gill arches
