Vertebrates

Superphylum Deuterostomia

PHYLUM CHORDATA

ALL EXHIBIT-

1) Body plan and Embryonic development: All bilateral deuterostomes

2) Germ Layers: Triploblastic eucoelomates

3) Digestive system: Complete

4) Excretory system: Kidneys to remove metabolic waste

5) Circulatory system: Closed system with heart

6) Nervous system: Brain with central nervous system

Respiratory System: Varies depending on group

-Gills

-Lung

-Skin

Most fall under Superphylum Vertebrata or Craniata, meaning they have a covering over their brain.

Two groups are an exception to this:

-Cephalochordata (lancelets)

-Urochordata (tunicates)

5 Defining Characteristics of all Vertebrates:

-Notochord

-Hollow dorsal nerve cord

-Pharyngeal slits

-Post-anal tail

-Endostyle/Thyroid gland

All at some point, can be embryonic development or adulthood

Notochord

Rod for structural support, flexible but stiff

Runs from anterior to posterior of the body

Located dorsal of the digestive tube and ventral of the nerve cord

Muscle attachment sites

Longitudinally incompressible but laterally and dorsally flexible (energy saver)

In true vertebrates it is replaced by the vertebral column

Hollow dorsal nerve cord

Derived from ectoderm

Runs anterior to posterior of the body/ consolidates into an anterior brain

Located just dorsal of notochord

Develops into brain and spinal cord (CNS)

Pharyngeal (gill) slits

Originated in filter feeders, allowing water to enter the mouth

-enters and leaves through pharynx

In aquatic vertebrate fishes:

-water enters mouth when feeding and exits through the gill slits

-these develop into gill support in jawless fishes, and jaw support in jawed fishes

In land vertebrates, these developed into the ear, tonsils, and thymus

Post-anal Tail

Extends beyond anus

Main purpose is locomotion (skeletal and musclar components)

In aquatic species: tail/caudal fin and used for locomotion

In terrestrial species it has adapted for balance

-reduced to coccyx in apes and humans

Endostyle/Thyroid gland

Mucus producing tissue on the floor of the pharynx

-produces substance similar to thyroid hormones

-important in iodine metabolism

In most vertebrates the endostyle is present at beginning of embryonic development, but continues into the thyroid gland

Urochordata and cephalochordata have endostyle as adults (HAVE ALL 5 AS ADULTS)

All other vertebrates have thyroid gland as adults

Two Chordate Clades are “Invertebrates”

Extremely primitive chordates

-Cephalochordata

Lancelets

Adults have all five characteristics

-Urochordata

Tunicates (sea squirts)

Larvae have all five

Adults have pharyngeal slits and endostyle only

Subphylum Vertebrata (Craniata)

Largest group of Chordata

Cranium is bony, or cartilaginous or ligamentous structure surrounding brain, includes jaw structures and facial structures

Bilateral animals have always have a head but not all have a cranium

Have five defining characteristics of Chordata

One major novel evolutionary adaptation:

-Vertebral column (spine) not just notochord

-Irregularly shaped bones joined together to form a backbone

Embryos have a notochord which develops into the vertebral segments of a true backbone

Segments can be cartilaginous or osseous

Agnathostomes- Animals without a jaw

Two classes: Myxini and Petromyzontidae

Myxini (Hagfish):

Scavengers

Blind but have sensory barbels around their mouth

Cartilaginous cranium

Have notochord, not vertebrae, for body support (one backbone)

Have keratin teeth on cartilage

Rasp pieces of food from dead animals

Not active hunters

More simple than lamprey

Petromyzontidae (lamprey)

Parastictic

Have eyes and cerebellum

Cartiliginous cranium

Have simple vertebrae

Have suction mouth with rasping tongue

They are ectoparasites

Usually do not kill host

More complex with vertebraes and tongue

Gnathostomes- animals with a jaw

Divided into:

Fishes

Tetrapods:

-four limbs: amphibians, reptiles, birds, mammals

Further divided into two groups

Amphibians

Amniotes

Animals with egg that contains extraembryonic membranes (yolk, amnion, chorion, allantois)

Adapted to terrestrial life

Mammals birds and reptiles