chordates
Notochord-bearing creatures
Chordates are animals possessing a notochord—a flexible rod running along the back—at some stage of development.
The phylum Chordata includes vertebrates (mammals, birds, fish, reptiles, amphibians) as well as some invertebrates like sea squirts and lancelets.
In vertebrates, the notochord typically develops into the spinal column.
Chordates share certain anatomical features that distinguish them from invertebrates like insects or mollusks.
Sudden appearance of complex life
- fossilsPreserved ancient organism traces
- common ancestorOrigin point of descendants
- phylogenyEvolutionary relationships among organisms
- diversificationExpanding into varied areas
land invasion · ancestral · homology · extinction · speciation · natural selection · Paleozoic
Animals with internal skeletons
- tetrapodsAnimals having four limbs
- amniotesVertebrates with protective embryo sacs
- fishGilled aquatic vertebrate
- amphibiansVertebrates with aquatic larvae
reptiles · birds · mammals · hagfish · lampreys · sharks · bony fish · sea squirts
Embryonic axial support structure
- endoskeletonBody's inner framework
- neural tubeEmbryonic nervous system precursor
- bilateral symmetryEqual halves along midline
- coelomMesoderm-lined internal space
segmentation · vertebral column · cranium · branchial arches · cartilage · bone · skull · jaw
Equal halves along midline
- segmentationDivision into sections
- endothermyInternal body heat generation
- ectothermyTemperature from surroundings
- homeostasisBiological internal stability maintenance
gills · lungs · scales · feathers · fur · oviparous · viviparous · sensory organs
Major classification rank
- ChordataPhylum featuring notochords
- subphylumRank beneath phylum
- classGrouping by shared traits
- orderMethodical arrangement or request
family · genus · species · clade · monophyletic · phylogenetics · cladistics · classification
At earliest developmental stage
- larval stageEarly developmental form
- metamorphosisProfound biological restructuring
- gastrulationEmbryo forms primary layers
- mesodermEmbryonic tissue forming muscles
ectoderm · endoderm · organogenesis · tadpole
Cambrian explosion
Sudden appearance of complex life
- fossilsPreserved ancient organism traces
- common ancestorOrigin point of descendants
- phylogenyEvolutionary relationships among organisms
diversification · land invasion · ancestral · homology · extinction · speciation · natural selection · Paleozoic
vertebrates
Animals with internal skeletons
- tetrapodsAnimals having four limbs
- amniotesVertebrates with protective embryo sacs
- fishGilled aquatic vertebrate
amphibians · reptiles · birds · mammals · hagfish · lampreys · sharks · bony fish · sea squirts
notochord
Embryonic axial support structure
- endoskeletonBody's inner framework
- neural tubeEmbryonic nervous system precursor
- bilateral symmetryEqual halves along midline
coelom · segmentation · vertebral column · cranium · branchial arches · cartilage · bone · skull · jaw · fins
bilateral symmetry
Equal halves along midline
- segmentationDivision into sections
- endothermyInternal body heat generation
- ectothermyTemperature from surroundings
homeostasis · gills · lungs · scales · feathers · fur · oviparous · viviparous · sensory organs
phylum
Major classification rank
order · family · genus · species · clade · monophyletic · phylogenetics · cladistics · classification · taxon
embryonic
At earliest developmental stage
- larval stageEarly developmental form
- metamorphosisProfound biological restructuring
- gastrulationEmbryo forms primary layers
mesoderm · ectoderm · endoderm · organogenesis · tadpole
chordatesinvertebrates
Animals without vertebral columns
arthropods · mollusks · insects · annelids · echinoderms
chordatessponges
Porous absorbent masses
jellyfish · corals · sea anemones · flatworms · roundworms