Download 31.3 Vertebrates - Westgate Mennonite Collegiate

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

Vertebrate Intro (cont’d)
Jaw evolution allowed for easier predation
 Strong endoskeleton allows for large
terrestrial organisms
 Complete digestive tract
 Generally, 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 eggs
 Others are placental (e.g. mammals) and
development of offspring occurs in female
uterus

Fishes

Evolutionary development:
(from least to most evolved)
1. Jawless fishes (superclass Agnatha)
a)
b)
c)
d)
e)
About 63 species
Cylindrical
Up to 1 meter long
Include hagfish and lampreys
Some are parasitic
Fishes (cont’d)
2. Cartilaginous fishes (class Chondrichthyes)
a) About 850 species
b) Include rays, sharks and skates
c) Have jaws (adapted gill arches – structure that
supports gills)
d) Skeletons made of cartilage (not bone)
e) Well-developed senses make good predators:
a)
b)
c)
Ability to sense electric currents in water
Have lateral line system that allows them to sense
pressure changes in water from movement nearby
Keen sense of smell
Fishes (cont’d)
3. Bony fishes (class Osteichthyes)
a) About 20 000 species
b) Most diverse class of all vertebrates
c) Types of bony fishes:
I.
Ray-finned fishes
i.
Include fish we commonly eat: trout, cod, salmon
ii. Have a pair of fins with thin bodies
iii. Often have a swim-bladder, which regulates buoyancy
iv. Water passes into mouth and out through gill slits:
oxygen is absorbs and carbon dioxide given off
v. Heart is simple pump with two chambers (one
atrium and one ventricle)
Fishes (cont’d)
II.
Lobe-finned fishes
i.
Evolved into amphibians
ii. Had fleshy appendages that were adapted to limbs
for terrestrial life
iii. Had a lung used for respiration
iv. E.g. coelacanth, though extinct 20 000 years ago was
discovered off the coasts of Eastern Africa