Vertebrates and Phylum Chordata

Vertebrates Overview

• Characterized by having an endoskeleton with a backbone that supports the dorsal nerve cord and muscle attachment.
• Possess a distinct skull, exhibiting cephalization.
• They are widespread across marine, freshwater, and terrestrial environments.
• Vary significantly in their ability to fly.
• Exhibit bilateral symmetry and are segmented.
• Segmentation is often inconspicuous.
• Triploblastic organisms possess a well-developed coelom.
• Feature closed circulation and chambered hearts.
• Most are free-living, but some species display ectoparasitic behavior.
• Deuterostomes that belong to Echinodermata and Chordata.
• Reproduce mainly through sexual reproduction.

Phylum Chordata

• Chordates exhibit four key characteristics at some point in their development
  • A notochord
  • A nerve cord
  • Pharyngeal gill slits
  • A post-anal tail

Notochord Characteristics

• Notochords are flexible and extend along the length of the body.
• They function as hydrostatic organs.
• Also offer skeletal support to the organism.
• Muscle attachment is facilitated by the notochord, enabling lateral bending movements without shortening.
• Crucial for undulatory locomotion within vertebrates.
• The vertebral column usually replaces the notochord in adult chordates

Nerve Cord details

• As a tube, it runs dorsally relative to the digestive tract.
• Gives rise to the spinal cord and brain.

Pharyngeal Slits functions

• Aid in filter feeding.
• Serve as gill supports.
• Provide jaw support.
• Eventually contributing to the development of ears and tonsils in tetrapods.

Post Anal Tail details

• Functions as a locomotory structure in aquatic species.
• Tetrapods have it for balance.
• Use them for courtship.
• Also used for communication.

Subphylum Urochordata

• Commonly known as tunicates or tail-chordates, with about 3000 species.
• Usually sessile in the sea as adults, although some can also be free-living.
• Contain a tough, non-living tunic made of cellulose that surrounds the animals.
• Larval forms have all chordate characteristics.
• During metamorphosis, the notochord and tail disappear, and the nerve cord is reduced to a single ganglion.

Urochordata Classes:

• Ascidiacea
• Appendicularia
• Thaliacea

Ascidians/Sea Squirts

• Most common and well-known among tunicates.
• Most species attach to rocks or other hard surfaces, thus are sessile
• Exteriorly, defined by two siphon projections, incurrent and excurrent, required for filter feeding
• Incurrent siphon allows food particle containing water to enter.
• The same siphon water carries the digested food into the siphon.
• Waste is excreated through the anus.
• They have ability to regenerate.
• Most are asexual and are hermaphroditic with external fertilization

Subphylum Cephalochordata

• Cephalochordates are lancets.
• They are slender compressed translucent animals.
• Their length is between 3-7 cm.
• Found all over coastal waters of the world that have sandy sediments.
• Named because of their bladelike shape.
• Possess a slightly swollen tip on the anterior end of their dorsal nerve cord, however have no true brain.
• Colorless blood moves through a ventral vessel.
• Similar body structure compared to tunicates.
• Possess smaller atrium and mouth .
• Larvae eat planktons.
• Adults burry themselves in the sand and filter the water for food.
• Water is pumped out using the atriopore which separates it from waste.
• They have segmented muscles which makes them able to undulate.
• They contain tentacles for sensing.
• Sexes are separate.
• Fertilization occurs using the atrium to release gametes to the outside through an atripore.

Subphylum Vertebrata

• Large and diverse group referred to as Craniata.
• The vertebrate endoskeleton supports virtually unlimited body sizes.
• Possess a stiff vertebral column.
• Hollow nervous tissue spinal column is present as well.
• Central nervous system is also present.
• Have a mouth that is at the very anterior.
• The anus is found before posterior end.
• Animal develops a tail posterior to anus during at least one phase.
• Vertebrate organisms contain a chambered heart.
• Size has a wide range, starting from 7.7 mm to 33 meters.
• Approximately 4% of all animal species can be classifies as vertebrates.

The Earliest Vertebrates details

• Jawless organisms with a fish anatomy that appeared in the Cambrian period.
• Belonged to Agnatha, and are modern vertebrate ancestors.
• The organisms Myllokunmingia and haikouichthys were discovered is China and are among the earliest vertebrates.
• The organisms were small, and also had notochords, gill slits, along with primitive craniums.
• Cartilaginous skeletal parts that lacked jaws, paired fins, and vertebrea.
• The Pteraspidomorphs appeared during the Ordovician period, and where jawless fish with head shields made of bone to protect themselves.
• During the Silurian period, the Ostracoderms were next to radiate, and like the previous where armored, jawless vertebrates.
• During the Devonian period, Placoderms radiated and eventually evolved to be the the first jawed vertebrates.
• Placoderms also developed true jaws.
• The plates covering their bodies made them the dominant marine predators.

Superclass Agnatha Characteristics

• Known as jawless fishes.
• Contains 119 species that contain:
  • Myxini
  • Petromyzontida is also known as lampreys.
• Lack internal ossification and jaws as well.
• Have paired fins with scales as well.
• Have eel like body structure.
• Contain openings in pore- like form at the gills.
• Skeleton is purely cartilage.
• Reproduce using oviparous methods.
• Two chambered heart.
• Predation is common.

Hagfishes (Myxini)

• Lack vertebrae.
• Bodies consist of soft skin as well as scales.
• The species is mostly the same.
• The difference between species is number in positioning of gill apertures.
• Only reproduce through sexual means, but relatively unknown.
• The skin can cover the eyes, thus vision doesn't exist.
• Mostly dwell in the cold marine waters at the bottom.
• Eggs contain only Yolks without a laval stage.

Lampreys: Petromyzontida details

• Display a parasitic lifestyle, and commonly have no skin which is naked along with developed eyes.
• Commonly reside in marine waters as adults, but they reproduce with spawning in fresh waters.
• Swim by undulating the body.
• Typically known for attacking fish known as salmonid.
• Sucker is used to attach to prey.
• Lay small eggs that eventually transform to larvae.
• The larva will burrow into mud.

Chondrichthyes (Cartilaginous Fish)

• The cartilaginous skeletons are a defining trait.
• Skeletons are bones that calcify often and are absent.
• Polyphydont teeth and the presence of jaws are common, usually absent within chimaeras, can have a huge stomach.
• Size of liver is large that also contains a lot oil.
• Excellent senses with great development, includes vibration, electroreception, brain function, sense of smell, and vision.
• Each sex can be separate, having internal fertilization.
• Can be Ovoviviparous means there is no larva stage.
• Great blood and urea concentration.
• Gills come in 5-7 pairs.
• Lungs and swim bladder are absent.

Chondrichthyes divisions

• Elasmobranchi have sharks, skates, and rays.
• Holocephali have chimaeras.

Chondrichthyes Sharks details

• Consist of almost 45% of elasmobranks.
• Usually use fill splits and have 5-7 splits.
• Have sense of smell to find good or guide direction.
• Typically are predators.
• Can find prey using their lateral lines from very far distances.

Caudal Fin for bony fish:

• Heterocercal shark tail for sharks.
• Have Homocercal perches.
• Have Diphycercal lungfishes

Osteichthyes (Bony Fishes) details

• Consist completely of bones in it's skeleton, therefore also called bony fish.
• 30,00 + species can be classified within this vertebrates group.
• Bony plates known as operculum is placed over the gill.
• Composes of plates that are bony and are connected toward a series of muscles.
• Swim bladders for swim bladders
• Reproduction can be done sexually, internal or external.
• Development is variable, has Oviparous, Viviparous and Ovoviviparous.
• Made of two subclasses:
  • Ray skinned fish known as Actinopterygii.
  • Lobe finned fish known as Sarcopterygii.

Actinopterygii (Ray-Finned Fishes) characteristics

• Most of the ray finned fish consist of 31,000 species.
• Were assigned this name as a result of the fins being supported as bones that can parallel the rays.
• Fins are supported using bony support with rays/spines to stiffen.
• There aren't any muscles within this type of fin.
• Well ossified skeletons with some exceptions.
• Has Ganoid, cycloid, and cteniod of dermal origin
• Each sex is separate however can be hermaphroditic.
• Teleost is most largest and is more or less 29,600 species.

Sarcopterygii (Lobe-Finned Fish) Characteristics

• Fleshy has paired pectoral and pelvic finds.
• Contain a muscular lobe that is fleshy.
• External and intern fertilization.
• Swim bladder exist, mainly for respiration purposes.
• Cosmoid is scales presents
• Contains lungs in its fossils for freshwater
• A amphbian for there ancestor .
• Scales have potential to grow throughout life.

Class Amphibia characteristics

• Adapted from tetrapods and contains Cutaneous respiration and pulmonary.
• Most need freshwater
• The cycle habitat depends on species
• Legs is needed, lungs,respiration through cutaneous,divided heart
• The skin is always soft and has pigment
• Have a distinct head and is mostly been used for bone structure
• There is no webbed for feet
• large head that has small upper teeth and that can be external

Amphibia Orders:

• Caecilians order is called Gymnophiona (Apoda)
• Salamanders order is called Urodela (Caudata)
• Frogs has called Anura commonly referred and called (Salientia)

Caecilians (Order Gymnophiona) details

• Is limb less and can burrow deep within the soil (earth worms) can be mostly fed too.
• Eats insects
• Female has fertilization from males with protrusive copulatory organ
• Long slender contains ribs also small eyes.
• Most egg that deposite near grounds or water area.

Salamanders: Order Urodela Characteristics

• Can be aquatic as larva
• Can be carnivores in there stage larva or adults that pray on worms as they get to there full stage adults.
• Some eggs are fertilized internally from male that deposits on sticks for the female to catch

Frogs and Toads: Order Anura (Salientia) notes

• The most amphibians in the group
• No tail present and very good skilled for hopping
• Eggs comes in contact with larva
• Breeding can be known as noisy and makes alot of sounds
• Males tend to occupy the area that attracts females
• Some may contain long legs for best of there jumps

REPTILIA (Amniote)

• The amniota clade has reptila
• Is Anapsid, Diaosids and sunasoid has fenestrae and diversification of skull
• Some contains ventilation has side ventilation
• Amniotic eggs, albumin for and has albumen,allantole and chorion can be found.

Reptile physical features

• Very thick skin and dry, and also water loss
• Amniotic egg extraembryonic membranes
• The heart has an three- chambered body.
• Direct can be a external and or internal which has a separate sexes with fertilization.

Turtles, testudines (chelonia)

• Does not have teeth mostly for tough plates as used to food.
• Some shells consist of ventral which is also know as plastron all can have been bury.
• Some temperatures can determine the sex such that large turtles can also be gotten which can be also know as giants