Characteristic Features of the Phylum
Chordata - Image
Single,
hollow dorsal nerve cord
Flexible
dorsal notochord
Pharyngeal
slits or pouches
Muscular
postanal tail
Tunicates - Image
Lancelets - Image - Image Fig 25.37
Characteristics of the vertebrates
A vertebral
column (Snake skeleton)
replaces the notochord
Possess
a distinct skull
(cranium) enclosing the brain
(cephalization)
Endoskeleton
with axial and appendicular portions, which grows with organism
Hollow
dorsal nerve cord (spinal
cord) enclosed in a groove in vertebral
column
Possess
characteristic liver, kidneys, endocrine glands
Circulatory
system with a heart and closed blood vessels
Endothermy versus ectothermy - Image
- Ectothermy = cold-blooded: Image
- Endothermy
= warm-blooded
Trends in circulatory systems - Image
Trends in respiratory systems - gills to lungs
Gills - Fig 30.2
Single-loop
blood circulation - 2-chambered heart
"Class"
Agnatha: Jawless
fishes: Hagfishes (Craniata) (Image) and
Lampreys (Image)
Evolution of jaws - (Fig 26.10)
occurred 410 million years
ago.
Radiation of jawed
fishes. - all ectothermic
Class
Chondrichthyes: Sharks, skates and rays - Image Manta
ray - the
movie!
Class Osteichthyes: Bony fishes
and Image
and
Most
fish are ray-finned fishes.
Lobe-finned
fishes (coelocanth - Image)
Lungfishes
A
Devonian tetrapod fish -
Image
Paired
fins consist of fleshy, muscular lobe supported by bone core
The path to
land.
Class Amphibia - Image - Image Table 26.3
-
Legs
-
Lungs
-
Partially divided heart - 3 chambers
-
Ectothermic
-
Water-bound reproduction
- Image
Different views of
the taxonomic classes of the amniotes - Image
Class Reptilia - Image Table 26.4
-
Amniotic egg
- Fig 26.17
-
Hatching reptile
- Image
-
Scales made of keratin
-
Most with 3-chambered heart
-
Ectothermic
-
Septum totally divides ventricle in crocodiles and birds (and likely
dinosaurs); makes 4 chambers
Class Aves - Birds -
Image Table 26.5
- Archaeopteryx - Image
- Feathers
of keratin - Image
-
Lungs and air sacs near and in bones of back - Image
-
Wall dividing ventricle is complete, two circulations do not mix
-
Endothermic
-
Amniotic egg with calcium carbonate for hardness
Class Mammalia -
Mammals - Image Table 26.6
- Hair
- Mammary
glands
-
Endothermic
-
Four-chambered heart
- Keratin is structural material for claws, fingernails,
hooves, horns, hair
- Differentiation
of teeth (Fig.
26.23) and refinement of ear bones - Image
The Groups of Mammals
Monotremes: egg-laying
mammals
-
Includes duck-billed
platypus and two species of spiny anteater - Image
-
Lay shelled eggs
Marsupials: pouched-mammals (Image)
- Early embryo
nourished by abundant yolk within shell-less egg and primitive placenta
-
Born at early stage of development and most enter marsupium
-
kangaroos, opossum, koalas, wallabies
-
Most live in Australia where have evolved to fill niches filled by placentals
in rest of world through convergent evolution. - Image
Eutherian (placental) mammals
-
Produce true placenta that nourishes embryos Fig. 26.22
-
Placenta (Image) is
first organ to form during course of development
-
Held in uterus of mother,
contains abundant fetal and maternal blood vessels
-
Fetus enclosed in amnion
