Phylum Chordata

What five characteristics define chordates?

Notochord, pharyngeal slits, endostyle/thyroid, dorsal hollow nerve cord, and post-anal tail.

What is a notochord?

A flexible supportive rod along the dorsal side of the body.

What is the function of the notochord?

Provides structural support and helps organize development.

Is the notochord the same as a vertebral column?

No.

What happens to the notochord in invertebrate chordates?

It may persist into adulthood.

What happens to the notochord in vertebrates?

It becomes associated with or is replaced by the vertebral column during development.

What are pharyngeal slits?

Openings in the pharyngeal region.

What are pharyngeal slits used for in aquatic chordates?

Feeding and/or respiration.

What happens to pharyngeal structures in terrestrial vertebrates?

They are modified during embryonic development.

What are homologous structures?

Structures inherited from a common ancestor, possibly with different functions.

What does the endostyle produce?

Mucus that traps food during filter feeding.

What vertebrate organ is homologous to the endostyle?

The thyroid gland.

What is the endostyle's function in tunicates?

Produces mucus for filter feeding.

What is the thyroid gland's function in vertebrates?

Produces hormones.

What does dorsal mean?

Toward the back.

What does ventral mean?

Toward the belly or underside.

What does the dorsal hollow nerve cord develop into in vertebrates?

The brain and spinal cord.

What type of nerve cord do arthropods have?

Ventral nerve cord.

What type of nerve cord do chordates have?

Dorsal hollow nerve cord.

What is a post-anal tail?

A tail extending beyond the anus.

What are the functions of a post-anal tail?

Locomotion, balance, or communication.

Do humans develop a post-anal tail?

Yes, temporarily during embryonic development.

What are the three major chordate groups?

Urochordata, Cephalochordata, and Vertebrata.

What animals belong to Urochordata?

Tunicates or sea squirts.

What animals belong to Cephalochordata?

Lancelets.

What animals belong to Vertebrata?

Vertebrates, including fishes, amphibians, reptiles, birds, and mammals.

Are all chordates vertebrates?

No, but all vertebrates are chordates.

What are tunicates also called?

Sea squirts.

What is the habitat of tunicates?

Marine environments.

Are adult tunicates usually mobile or sessile?

Usually sessile.

What is the outer covering of a tunicate called?

A tunic.

How do tunicates feed?

Water enters the incurrent siphon, food is trapped in mucus in the pharyngeal basket, and water exits.

What is the function of a tunicate's pharyngeal basket?

Filters food from water.

Which chordate characteristics do adult tunicates mainly retain?

Pharyngeal slits and endostyle.

How can tunicates be chordates if adults lack some chordate characteristics?

Their larvae possess all five defining chordate characteristics.

Which five chordate characteristics are present in tunicate larvae?

Notochord, dorsal hollow nerve cord, pharyngeal slits, endostyle, and post-anal tail.

What happens to a tunicate larva before becoming an adult?

It swims, settles on a surface, and undergoes metamorphosis.

What does a tunicate larva lose during metamorphosis?

The notochord, dorsal hollow nerve cord, and post-anal tail.

What does a tunicate retain after metamorphosis?

Pharyngeal slits and endostyle.

Why do adult tunicates lose swimming structures?

Sessile adults no longer need them for swimming.

What are lancelets?

Small, fish-shaped marine invertebrate chordates.

What are the main characteristics of lancelets?

Marine, bilateral, fish-shaped, and filter-feeding.

Where do lancelets usually live?

In sandy substrates, often with their anterior end exposed.

How do lancelets move and live in the substrate?

They are poor swimmers and often burrow into sand.

Do lancelets retain chordate characteristics as adults?

Yes, they retain all five defining characteristics.

How do lancelets feed?

Water and food enter the mouth, and food is filtered through the pharyngeal region.

How do tunicates and lancelets differ in retaining chordate characteristics?

Tunicates show them most clearly as larvae; lancelets retain them as adults.

What is the key evolutionary modification in vertebrates?

The notochord becomes associated with or is replaced by a vertebral column during development.

Which chordate group includes humans?

Vertebrata.

Which chordate characteristic is a flexible supportive rod?

Notochord.

Which chordate characteristic develops into the brain and spinal cord?

Dorsal hollow nerve cord.

Which chordate characteristic extends beyond the anus?

Post-anal tail.

Which chordate characteristic is associated with filter feeding and homologous to the thyroid?

Endostyle.

Which chordate characteristic consists of openings in the pharyngeal region?

Pharyngeal slits.

Which chordate group retains all five characteristics as an adult?

Cephalochordata, represented by lancelets.

Which chordate group displays all five characteristics most clearly during its larval stage?

Urochordata, represented by tunicates.

Which chordate group contains vertebrates?

Vertebrata.

Can an adult animal be a chordate without a notochord and post-anal tail?

Yes, if it possessed the defining characteristics at some point during development.

Why don't all adult chordates retain all five characteristics?

Some characteristics are lost or modified during development.

What is the main difference between chordates and vertebrates?

All vertebrates are chordates, but some chordates lack a vertebral column.

What are the five defining chordate characteristics?

Notochord, pharyngeal slits, endostyle/thyroid, dorsal hollow nerve cord, and post-anal tail.