31.3 vertebrates
DESCRIPTION
31.3 Vertebrates. Vertebrate Intro. Have all 4 chordate characteristics at some point of development Embryonic notochord generally replaced by vertebral column Generally a high level of cephalization (brain and nervous system) with complex sense organs Closed circulatory system. - PowerPoint PPT PresentationTRANSCRIPT
31.3 Vertebrates
Vertebrate IntroHave all 4 chordate
characteristics at some point of development
Embryonic notochord generally replaced by vertebral column
Generally a high level of cephalization (brain and nervous system) with complex sense organs
Closed circulatory system
Vertebrate Intro (cont’d)Jaw evolution allowed for easier
predationStrong endoskeleton allows for
large terrestrial organismsComplete digestive tractGenerally, sexes are separate
(not hermaphrodites)Sexual reproduction typical
Vertebrate Intro (cont’d)Evolution of amnion
(extraembryonic membrane that encloses a fluid filled sac)
Some lay shelled eggsOthers are placental (e.g.
mammals) and development of offspring occurs in female uterus
FishesEvolutionary development:
(from least to most evolved)1. Jawless fishes (superclass Agnatha)
a) About 63 speciesb) Cylindricalc) Up to 1 meter longd) Include hagfish and lampreyse) Some are parasitic
Fishes (cont’d)2. Cartilaginous fishes (class
Chondrichthyes)a) About 850 speciesb) Include rays, sharks and skatesc) Have jaws (adapted gill arches – structure
that supports gills)d) Skeletons made of cartilage (not bone)e) Well-developed senses make good
predators:a) Ability to sense electric currents in waterb) Have lateral line system that allows them to sense
pressure changes in water from movement nearbyc) Keen sense of smell
Fishes (cont’d)3. Bony fishes (class Osteichthyes)
a) About 20 000 speciesb) Most diverse class of all vertebratesc) Types of bony fishes:
I. Ray-finned fishesi. Include fish we commonly eat: trout, cod, salmonii. Have a pair of fins with thin bodiesiii. Often have a swim-bladder, which regulates
buoyancyiv. Water passes into mouth and out through gill slits:
oxygen is absorbs and carbon dioxide given offv. Heart is simple pump with two chambers (one
atrium and one ventricle)
Fishes (cont’d)II. Lobe-finned fishes
i. Evolved into amphibiansii. Had fleshy appendages that were adapted
to limbs for terrestrial lifeiii. Had a lung used for respirationiv. E.g. coelacanth, though extinct 20 000
years ago was discovered off the coasts of Eastern Africa