Ch. 29 Vertebrates
Vertebrate Evolution and Diversity Phylum Chordata
Vertebrates have unique endoskeletons composed of
o Cranium
o Backbone made of a series of bones
Characteristics of Chordates
The last phylum in the animal kingdom is Chordata
Chordates all share four key features that appear in the embryo and sometimes the adult:
o A dorsal, hollow nerve cord
o A notochord
o Pharyngeal skills
o A post-anal tail
Another chordate characteristic is a body segmentation, apparent in the:
o Backbone of vertebrates
o Segmental muscles of all chordates
Trends in Vertebrate Evolution
Improvements in vertebral column- cartilage, bone
Gill slit supports- jaws, other head bones
Appendages- fins, legs, wings
Respiration- gills and lungs
Circulation- heart (4 chambered)
Reproduction- eggs, shells, “live” young
Phylum Chordata
Dorsal hollow nerve cord- brain and spinal cord develop from this
Notochord- beneath nerve cord, acts as an anchor for internal muscles, permitting rapid body
movement
Pharyngeal slits- slits behind the mouth into the pharynx. From this, ear bone, and the pharynx
or gills develop
Post anal tail- extends beyond the anus
Invertebrate Chordates: Fishes: Jawless Fishes
Chordates consist of only three groups of invertebrates:
o Lancelets- bladelike, no cranium
o Tunicates- sea squirts, no cranium. Embryonic notochord. Adult=radial symmetry
o Hagfishes- eel-life, have a cranium but no spine
No cranium, no vertebrae
All other chordates are vertebrates
Fishes: Jawless Fishes
, Hagfish
o Cartilage
o Partial cranium
o Slime as a defense mechanism
Lampreys
o Cartilaginous backbone
o Cranium
o No jaws
o Some are parasites that attach to fish to suck out their blood
o Ancestral chordate may have looked similar to a lancelet
Fishes
Two major groups of living fish:
o Cartilaginous fish- flexible skeleton of catilage, jaws appear (ex. sharks and rays)
o Bony fishes- skeleton of calcium and bone
Ray finned fishes
Lungfishes
Lobe-finned fishes
Bony Fishes: Lobe fins
Lobe-fins are major lineage of vertebrate fishes
A key derived trait is the rod-shaped bones surrounded by a thick layer of muscle in their
pectoral and pelvic fins
The fins are very flexible and potentially useful for supporting the body on land. Tetrapods are
thought to have evolved from primitive lobe-finned fish
Bony fishes: Lungfish
Found only in the southern hemisphere
Adaptation to air sac that can function as lungs during periods of drought
Also have gills to obtain oxygen from water
They burrow into the mud and cover themselves in mucus to stay moist until the pond refills
Early Land Animals
Life on land provided advantages and posed challenges to early colonizers
o The atmosphere had higher oxygen concentration than aquatic environments
o There were new sources of food and fewer competitors
o Water was scarcer
o Temperatures fluctuated between greater extremes
o There was no support against gravity
o Arthropods were among the first animals to colonize the land about 450 million years
ago
o Vertebrates colonized land 365 million years ago
Tetrapods
Vertebrate Evolution and Diversity Phylum Chordata
Vertebrates have unique endoskeletons composed of
o Cranium
o Backbone made of a series of bones
Characteristics of Chordates
The last phylum in the animal kingdom is Chordata
Chordates all share four key features that appear in the embryo and sometimes the adult:
o A dorsal, hollow nerve cord
o A notochord
o Pharyngeal skills
o A post-anal tail
Another chordate characteristic is a body segmentation, apparent in the:
o Backbone of vertebrates
o Segmental muscles of all chordates
Trends in Vertebrate Evolution
Improvements in vertebral column- cartilage, bone
Gill slit supports- jaws, other head bones
Appendages- fins, legs, wings
Respiration- gills and lungs
Circulation- heart (4 chambered)
Reproduction- eggs, shells, “live” young
Phylum Chordata
Dorsal hollow nerve cord- brain and spinal cord develop from this
Notochord- beneath nerve cord, acts as an anchor for internal muscles, permitting rapid body
movement
Pharyngeal slits- slits behind the mouth into the pharynx. From this, ear bone, and the pharynx
or gills develop
Post anal tail- extends beyond the anus
Invertebrate Chordates: Fishes: Jawless Fishes
Chordates consist of only three groups of invertebrates:
o Lancelets- bladelike, no cranium
o Tunicates- sea squirts, no cranium. Embryonic notochord. Adult=radial symmetry
o Hagfishes- eel-life, have a cranium but no spine
No cranium, no vertebrae
All other chordates are vertebrates
Fishes: Jawless Fishes
, Hagfish
o Cartilage
o Partial cranium
o Slime as a defense mechanism
Lampreys
o Cartilaginous backbone
o Cranium
o No jaws
o Some are parasites that attach to fish to suck out their blood
o Ancestral chordate may have looked similar to a lancelet
Fishes
Two major groups of living fish:
o Cartilaginous fish- flexible skeleton of catilage, jaws appear (ex. sharks and rays)
o Bony fishes- skeleton of calcium and bone
Ray finned fishes
Lungfishes
Lobe-finned fishes
Bony Fishes: Lobe fins
Lobe-fins are major lineage of vertebrate fishes
A key derived trait is the rod-shaped bones surrounded by a thick layer of muscle in their
pectoral and pelvic fins
The fins are very flexible and potentially useful for supporting the body on land. Tetrapods are
thought to have evolved from primitive lobe-finned fish
Bony fishes: Lungfish
Found only in the southern hemisphere
Adaptation to air sac that can function as lungs during periods of drought
Also have gills to obtain oxygen from water
They burrow into the mud and cover themselves in mucus to stay moist until the pond refills
Early Land Animals
Life on land provided advantages and posed challenges to early colonizers
o The atmosphere had higher oxygen concentration than aquatic environments
o There were new sources of food and fewer competitors
o Water was scarcer
o Temperatures fluctuated between greater extremes
o There was no support against gravity
o Arthropods were among the first animals to colonize the land about 450 million years
ago
o Vertebrates colonized land 365 million years ago
Tetrapods
