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vertebrates are a subphylum inside of what phylum?
Chordata
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what two groups of invertebrate deuterostomes are more closely related to vertebrates than invertebrates?
urochordates and cephalochordates
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how did vertebrates get their name?
get their name from vertebrae, the series of bones that make up the backbone
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Chordates
are bilaterian animals that belong to the clade of animals known as Deuterostomia
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how many species in vertebrates and diversity
- ~52,000 species of vertebrates, including the largest organisms ever to live on the Earth
- Vertebrates have great diversity, a wide range of differences within the group
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Four key characters of chordates
- Notochord
- Dorsal, hollow nerve cord
- Pharyngeal slits or clefts
- Muscular, post-anal tail
- Some species have some of these traits only during embryonic development
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Notochord
- is a longitudinal, flexible rod between the digestive tube and nerve cord
- support for organs
- provides skeletal support throughout most of the length of a chordate
- In most vertebrates, a more complex, jointed skeleton develops, and the adult retains only remnants of the embryonic notochord
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Nerve cord
- of a chordate embryo develops from a plate of ectoderm that rolls into a tube dorsal to the notochord
- The nerve cord develops into the central nervous system: the brain and the spinal cord
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Pharyngeal clefts
- grooves in the pharynx
- develop into slits that open to the outside of the body
- Functions of pharyngeal slits:
- –Suspension-feeding structures in many invertebrate chordates
- –Gas exchange in vertebrates (except vertebrates with limbs, the tetrapods)
- –Develop into parts of the ear, head, and neck in tetrapods
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Tail
- posterior to the anus
- In many species, the tail is greatly reduced during embryonic development
- The tail contains skeletal elements and muscles
- It provides propelling force in many aquatic species
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lancelets
(Cephalochordata)
- named for their bladelike shape
- They are marine suspension feeders that retain characteristics of the chordate body plan as adults
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tunicates
(urochordata)
- are more closely related to other chordates than are lancelets
- They are marine suspension feeders commonly called sea squirts
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Crainates
- The origin of a head opened up a completely new way of feeding for chordates: active predation
- share some characteristics: a skull (at least a partial skull), brain, eyes, and other sensory organs
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Derived characters of crainates
- One feature unique to craniates is the neural crest, a collection of cells near the dorsal margins of the closing neural tube in an embryo
- Neural crest cells give rise to a variety of structures, including some of the bones and cartilage of the skull
- Craniates have a heart with at least two chambers, red blood cells with hemoglobin, and kidneys
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Myxini
- The least derived surviving craniate lineage is Myxini, the hagfishes
- Hagfishes have a cartilaginous skull and axial rod of cartilage derived from the notochord, but lack jaws and vertebrae
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Vertebrates are?
Vertebrates are craniates with a backbone
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Characters of vertebrates
- Vertebrae enclosing a spinal cord
- An elaborate skull
- Fin rays, in the aquatic forms
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Petromyzontida
- Lampreys represent the oldest living lineage of vertebrates
- They are jawless vertebrates inhabiting various marine and freshwater habitats
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Gnathostomes
- vertebrates with jaws
- Today, jawed vertebrates, or gnathostomes, outnumber jawless vertebrates
- An enlarged forebrain associated with enhanced smell and vision
- In aquatic gnathostomes, the lateral line system, which is sensitive to vibrations
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lateral line system is what?
a pressure sensor
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Chondrichthyes
- have a skeleton composed primarily of cartilage
- The cartilaginous skeleton evolved secondarily from an ancestral mineralized skeleton
- The largest and most diverse group of chondrichthyans includes the sharks, rays, and skates
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3 ways embryo (shark) can develop: Chondrichthyes
- Shark eggs are fertilized internally but embryos can develop in different ways:
- –Oviparous: eggs hatch outside the mother’s body
- –Ovoviviparous: the embryo develops within the uterus and is nourished by the egg yolk
- –Viviparous: the embryo develops within the uterus and is nourished through a yolk sac placenta from the mother’s blood
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osteichthyes
- includes the bony fish and tetrapods
- Nearly all living osteichthyans have a bony endoskeleton
- Aquatic osteichthyans are the vertebrates we informally call fishes
- Most fishes breathe by drawing water over gills protected by an operculum
- Fishes control their buoyancy with an air sac known as a swim bladder
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