Post on 18-Dec-2015
Introduction to Chordates
BIO 122: ZoologyNewberry College
Phylum Chordata
Most complex of all phyla All have a notochord
rod-like semirigid body of cellsusually extends length of bodyventral to nervous system’s spine
Purposes:1) support & stiffen body2) provide skeletal support for muscles
Phylum Chordata
Five important features of chordates:1. Notochord2. Dorsal tubular nerve cord3. Pharyngeal pouches and gill slits4. Endostyle5. Postanal tail
Chordate characteristics
1) Notochord - a flexible, rod-like structure* beginning of the internal skeleton* axis for muscle attachment, flexible w/o shortening* in vertebrates the notochord becomes segmented as vertebrae
Chordate characteristics
2) Dorsal Tubular Nerve Cord - produced by infolding of ectoderm during early development* in many invertebrates the nerve cord is ventral and solid* in many anterior end becomes swollen = brain
Chordate characteristics
3) Pharyngeal Pouches and Gill Slits - perforated openings* lead from pharyngeal cavity to outside body* in simplest aquatic chordates it allows for suspension feeding* in terrestrial organisms is only developmental
Chordate characteristics
4) Endostyle - or its derivative, the thyroid gland* in the simplest chordates the endostyle secretes mucus that traps small food particles
Chordate characteristics
5) Postanal Tail - extension of body beyond anus* enhances ability for movement (aquatic) & balance (terrestrial)
Additional Chordate Features
Development pattern as in Echinoderms: radial, indeterminate cleavage deuterostome enterocoelous
Segmented muscles in an unsegmented body
Complete digestive system Closed circulatory system Endoskeleton made of cartilage and/or
bone
Classification of Chordates
Three distinct Subphyla:Urochordata – tunicatesCephalochordata – lanceletsVertebrata - vertebrates
Subphyla of Chordates
SUBPHYLUM UROCHORDATA - tunicates Only larval form moves, adults are sessile
larvae with all chordate characteristics Adults relatively small, up to a few cm long
* produce a leathery outer surface (= tunic)* loss of notochord & tail, nerve cord greatly reduced* become filter feeders with siphons* gills slits become net-like to trap food
Individuals are hermaphroditic* reproductive cells into water, external fertilization
Diagramatic tunicate
Subphyla of Chordates
SUBPHYLUM CEPHALOCHORDATA - lancelets Slender, lancet-shaped, 5-7 cm long
* sandy bottoms of shallow marine environments Adults clearly with all the chordate
characteristics* suspension feeders, trap food in gills slits* circulatory system closed, but no distinct heart* no obvious brain
Separate males and females* fertilization external
Diagramatic lanceletDiagramatic lancelet
Subphyla of Chordates
SUBPHYLUM VERTEBRATA - vertebrates
Very large and diverse groupwell known due to large size
Not all chordatefeatures in adults
Characteristics of Vertebrates
1. Expanded endoskeleton - living endoskeleton* internal skeleton, grows with the organism* commonly is hollow, provides support* distinctive covering around brain = cranium
Characteristics of Vertebrates
2. Gills in pharynx - better respiration
* other subphyla use slits for filter feeding* more active aquatic vertebrates developed gills with muscles* heart developed to enhance circulation
Characteristics of Vertebrates
3. Enhanced Nervous System – * with anterior swelling* more complex behaviors of swimmers & predators* has tripartite brain (fore-, mid- and hind-brain)* development of enhanced senses
Characteristics of Vertebrates
4. Development of neural crest & ectodermal placode – enhances complexity* neural crest enhances development of skeleton, tooth dentine & endocrine glands* ectodermal placodes enhance sensory development (olfactory, eye, ear)
CLASSIFICATION OF VERTEBRATES
Several important characteristics to separate:1) skeleton & jaw composition: cartilage or bony2) number & structure of paired appendages3) dermal covering over body4) relative number of gill slits of an adult5) type of covering over egg
CLASSIFICATION OF VERTEBRATES
SUPERCLASS AGNATHA lampreys & hagfishcartilaginous skeleton and no jawno paired appendagesskin smooth (slimy)about 7 gill slits per sideeggs with gelatinous covering (aquatic)heart 2-chambered (1 atrium + 1 ventricle)
SUPERCLASS AGNATHA
Lamprey (note gill slits)
CLASSIFICATION OF VERTEBRATES
SUPERCLASS GNATHOSTOMATA All other vertebrates with jaws & paired appendages
CLASSIFICATION OF VERTEBRATES
Class Chondrichthyes (sharks & rays) cartilaginous skeleton and jaw present 2 pair fins placoid scales
(tooth like with root) 5-7 pair gill slits eggs with gelatinous
covering (aquatic)
CLASSIFICATION OF VERTEBRATES
Class Actinopterygii (bony ray-finned fish)
bony skeleton, jaw present 2 paired appendages; fins overlapping dermal scales
(typically thin & flexible) gill slits with covering
operculum egg covering gelatinous
CLASSIFICATION OF VERTEBRATES
Class Amphibia (amphibians) bony skeleton, jaw present 2 paired appendages, legs smooth skin gills only in juvenile forms eggs with gelatinous covering
(aquatic)
CLASSIFICATION OF VERTEBRATES
Class Reptilia (reptiles) bony skeleton, jaw present 2 paired appendages, legs hard scales (snakes) or plates
(turtles) gills embryonic only eggs with leathery
covering (terrestrial))
CLASSIFICATION OF VERTEBRATES
Class Aves (birds) bony skeleton, jaw present 2 paired appendages;
legs + wings feathers + scales on legs gills embryonic only eggs with calcified shell
(terrestrial)
CLASSIFICATION OF VERTEBRATES
Class Mammalia (mammals) bony skeleton, jaw present 2 paired appendages; legs (+ arms) fur and/or hair gills embryonic only viviparous (few with calcified shells)