Chordates and Notochord Overview

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Questions and Answers

What is the primary reason for the development of the tripartite brain in vertebrates?

To improve reproductive strategies

To support respiratory functions

To enhance food capture capabilities (correct)

To facilitate swimming movements

What structures do neural crest cells contribute to in vertebrate development?

Endocrine glands and ventral heart

Cranium and some cranial nerves (correct)

Muscular pharynx and digestive tract

Paired glomeruli kidneys

Which sense organs evolved in vertebrates for distance perception?

Inner ear for balance

Eyes with inverted retinas (correct)

Lateral line for water vibrations

Taste and olfactory organs

Which embryonic innovations are key to the development of the vertebrate head and sense organs?

Neural crest and epidermal placodes Signup and view all the answers

What is a characteristic feature of the endoskeleton in vertebrates?

Composed primarily of cartilage or bone Signup and view all the answers

Which of the following best describes the composition of the vertebrate heart?

Ventral heart containing haemoglobin Signup and view all the answers

Which type of vertebrate fossils were previously considered the earliest known vertebrates?

Armoured jawless fishes known as ostracoderms Signup and view all the answers

What do epidermal placodes primarily give rise to in vertebrate development?

Inner ear and olfactory epithelium Signup and view all the answers

What is the primary adaptation of most batoids for their habitat?

Disk-like bodies for bottom dwelling Signup and view all the answers

What unique feature do electric rays possess for defense?

Electrical organs Signup and view all the answers

Which of the following is a characteristic of chimaeras?

Fused upper jaw with the cranium Signup and view all the answers

How do stingrays defend themselves?

Venomous spines on their tails Signup and view all the answers

What is the diet of chimaeras primarily composed of?

Seaweed and crustaceans Signup and view all the answers

What do the gill slits of batoids signify about their anatomy?

They are positioned beneath the pectoral fins Signup and view all the answers

What is a common feature of the subclass Holocephali?

Skeleton made of cartilage Signup and view all the answers

Which of the following statements about ancient Egyptians and electric rays is accurate?

They utilized them for electrotherapy treatments. Signup and view all the answers

What is the primary function of a tail in most mammals?

Assist in communication and balance Signup and view all the answers

What type of evidence suggests a common origin between chordates and echinoderms?

Fossil records Signup and view all the answers

What do homologous structures indicate?

A shared evolutionary origin Signup and view all the answers

What are pharyngeal slits considered in chordate evolution?

A shared derived characteristic with hemichordates Signup and view all the answers

Which group is suggested to be a direct ancestor of chordates?

Hemichordates Signup and view all the answers

Which function does not apply to the vestigial tail in humans?

Balancing during movement Signup and view all the answers

What is the primary role of the notochord in lower vertebrates?

To serve as the main axial support of the body Signup and view all the answers

What unique feature distinguishes the dorsal tubular nerve cord of chordates?

It is a single dorsal tube located above the alimentary canal Signup and view all the answers

Which of the following accurately describes analogous structures?

They share a similar function but differ in origin Signup and view all the answers

What is the evolutionary significance of the Calcichorda?

They exhibit traits linking them to chordates Signup and view all the answers

What do pharyngeal slits in primitive chordates primarily function as?

To filter food particles from water Signup and view all the answers

How are pharyngeal slits adapted in fish compared to their function in primitive chordates?

They are modified for respiration Signup and view all the answers

What structures arise from pharyngeal slits in tetrapods?

Eustachian tube, middle ear cavity, tonsils, and parathyroid gland Signup and view all the answers

What is the role of the endostyle in chordates?

It secretes mucus to trap food particles Signup and view all the answers

Which feature found in chordates has recently been recognized as crucial and is not found in other phyla?

Endostyle or thyroid gland Signup and view all the answers

What evolutionary purpose does the post-anal tail serve in chordates?

It contributes to locomotion Signup and view all the answers

Which characteristic differentiates Elasmobranchii from Holocephali?

Presence of ampullae of Lorenzini Signup and view all the answers

In what way do Elasmobranchii maintain osmotic pressure with the marine environment?

By excreting urea as a nitrogenous waste Signup and view all the answers

Which order of sharks is characterized by the absence of a nictitating membrane?

Lamniformes Signup and view all the answers

What feature is used for internal fertilization in male Elasmobranchii?

Pelvic fin modificaiton to form claspers Signup and view all the answers

Which of the following orders includes sawfish rays and electric rays?

Rajiformes Signup and view all the answers

Which is a notable feature of Carchardiniformes sharks?

Presence of an anal fin and nictitating membrane Signup and view all the answers

What distinguishes Squaliformes from other shark orders?

Lack of a nictitating membrane Signup and view all the answers

What significant group is believed to have given rise to Elasmobranchii during the Silurian or Early Devonian?

Extinct placoderm fishes Signup and view all the answers

Study Notes

Notochord and Nervous System

In lower vertebrates, the notochord serves as the primary axial support throughout life, while in higher vertebrates, it is replaced by the vertebral column.
Located on the ventral side of the neural tube, the notochord is critical for body support and development.
The dorsal tubular nerve cord, unique to chordates, is positioned above the alimentary canal and forms a tube through ectodermic folding during embryonic development.
The anterior portion of the nerve cord enlarges to form the brain, protected by a bony or cartilaginous cranium in vertebrates.
Pharyngeal slits develop from the endodermic lining of the pharynx and function in filter feeding in primitive chordates, while in fish, they adapt for respiration.

Pharyngeal Slits and Endostyle

Pharyngeal slits led to the evolution of structures like the Eustachian tube, middle ear cavity, tonsils, and parathyroid glands in tetrapods.
The endostyle, often considered part of the thyroid gland, secretes mucus and iodinated proteins, crucial for trapping food particles.
The post-anal tail, present in larval tunicates and amphioxus, is involved in locomotion and efficiency in movement, with mobility in mammals varying from lost (in humans as coccyx) to functional.

Evolutionary Origins

Chordates likely share a common ancestor with echinoderms and hemichordates, emerging during the Cambrian period around 570 million years ago.
The evolutionary connections between chordates and their primitive relatives are contested due to the lack of fossil evidence of early forms.
Shared derived characteristics like pharyngeal slits suggest close relations with hemichordates, while calcichorda fossils propose links to early chordates.

Nervous and Sensory Systems

As vertebrates transitioned from filter feeding to predation, their sensory systems adapted significantly, resulting in a tripartite brain.
Key sensory organs evolved for vision (eyes), hearing and balance (inner ears), taste, and electroreception, aiding in effective predation.
Neural crest and epidermal placodes in embryo development give rise to vital structures such as cranial features and sense organs.

Vertebrate Characteristics

All vertebrates possess five chordate features plus additional structures: endoskeleton, muscular pharynx, muscular digestive tract, and specialized sense organs.
Vertebrates generally have separate sexes with sophisticated reproductive structures, including gonads with ducts that connect to a cloaca or anal opening.
Limbs supported by girdles and an appendicular skeleton are characteristic of most vertebrates.

Early Vertebrate Fossils

Earliest vertebrate fossils (ostracoderms) trace back to the late Cambrian and Ordovician, but earlier fish-like vertebrates were discovered dating back to 530 million years ago.

Subclass Elasmobranchii

Elasmobranchii within Chondrichthyes include sharks (Euselachii) and rays (Batoidei), distinguished by separate gill openings and unique sensory systems.
Characteristics include a cartilaginous endoskeleton, placoid scales, urea retention mechanism, and claspers in males for internal fertilization.
Orders within Elasmobranchii encompass diverse species, exhibiting specific traits such as nictitating membranes or adaptations for pelagic living.

Subclass Holocephali (Chimaeras)

Chimaeras, also known as ratfish, diverged from shark lineage over 360 million years ago, with limited modern species (31).
Their diet is varied, focusing on seaweed and invertebrates, and they possess unique flat jaws and a venomous spine for defense.
Chimaeras inhabit temperate oceans and display a smooth, scale-less skin structure, further indicating their distinct evolutionary path.

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Description

Explore the anatomy and significance of the notochord in chordates versus lower vertebrates. Understand the unique features of the dorsal tubular nerve cord and its evolutionary implications. This quiz will enhance your knowledge of chordate evolution and anatomical structures.