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Questions and Answers
What is the primary characteristic that defines all members of the phylum Chordata?
What is the primary characteristic that defines all members of the phylum Chordata?
- A notochord (correct)
- A vertebral column
- A dorsal fin
- A complex nervous system
The notochord is a rigid structure that remains present in all adult chordates.
The notochord is a rigid structure that remains present in all adult chordates.
False (B)
Name two of the fundamental characteristics of chordates.
Name two of the fundamental characteristics of chordates.
Notochord and nerve cord
The nerve cord in chordates develops as a _____ tube lying just above the notochord.
The nerve cord in chordates develops as a _____ tube lying just above the notochord.
Match the following terms with their definitions:
Match the following terms with their definitions:
How many species are included in the phylum Chordata?
How many species are included in the phylum Chordata?
Cephalochordates are exclusively vertebrates.
Cephalochordates are exclusively vertebrates.
What are the soft and skeletal tissues between adjacent pharyngeal gill clefts called?
What are the soft and skeletal tissues between adjacent pharyngeal gill clefts called?
What distinguishes Urochordata from other sub-phylums?
What distinguishes Urochordata from other sub-phylums?
All Urochordates are terrestrial organisms.
All Urochordates are terrestrial organisms.
What is the primary food source of tunicates?
What is the primary food source of tunicates?
Urochordates are also known as _______ because their body is enclosed in a sac.
Urochordates are also known as _______ because their body is enclosed in a sac.
Which statement reflects the respiratory system of tunicates?
Which statement reflects the respiratory system of tunicates?
Match each component of the tunicate anatomy with its function:
Match each component of the tunicate anatomy with its function:
Most tunicates are hermaphrodites.
Most tunicates are hermaphrodites.
What type of circulatory system do tunicates have?
What type of circulatory system do tunicates have?
What is the primary function of the gill cleft?
What is the primary function of the gill cleft?
All chordates possess a post-anal tail at all stages of their life cycle.
All chordates possess a post-anal tail at all stages of their life cycle.
What transformation occurs to the anterior most cleft in adult amphibians?
What transformation occurs to the anterior most cleft in adult amphibians?
In non-vertebrate chordates, the clefts and arches are primarily involved in __________.
In non-vertebrate chordates, the clefts and arches are primarily involved in __________.
Match the subphylum with its characteristics:
Match the subphylum with its characteristics:
Which of the following is NOT a characteristic of chordates?
Which of the following is NOT a characteristic of chordates?
In fish-like vertebrates and juvenile amphibians, pharyngeal clefts develop into gills.
In fish-like vertebrates and juvenile amphibians, pharyngeal clefts develop into gills.
What is the term for the membranous tissue that suspends internal organs in the coelomic cavity?
What is the term for the membranous tissue that suspends internal organs in the coelomic cavity?
What happens to tunicate larvae as they mature?
What happens to tunicate larvae as they mature?
Cephalochordates have well-developed sense organs.
Cephalochordates have well-developed sense organs.
What is the primary mode of respiration in cephalochordates?
What is the primary mode of respiration in cephalochordates?
The larval stage of tunicates compares to a ______ as it resembles a mobile form.
The larval stage of tunicates compares to a ______ as it resembles a mobile form.
Match the following characteristics with their respective groups:
Match the following characteristics with their respective groups:
How do cephalochordates reproduce?
How do cephalochordates reproduce?
The digestive system of cephalochordates is incomplete.
The digestive system of cephalochordates is incomplete.
How many species of cephalochordates are estimated to exist?
How many species of cephalochordates are estimated to exist?
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Study Notes
Definition and Overview of Chordata
- Chordata derives from Greek, "chorde" meaning cord and "ata" meaning bearing, indicating animals with a notochord.
- Approximately 45,000 species fall under this phylum, including significant vertebrates and invertebrates like amphioxus and tunicates.
Fundamental Characteristics
- Chordates exhibit three core traits:
- Notochord
- Dorsal nerve cord
- Pharyngeal gill slits
- Post-anal tail
Notochord
- An elongated, flexible, cartilaginous structure located dorsally over the gut and ventrally beneath the nerve cord.
- In most adults, it either disappears or transforms into the vertebral column, while some non-vertebrates retain it in a modified form.
Nerve Cord
- Develops as a fluid-filled, hollow longitudinal tube lying above the notochord.
- Differentiates into the brain and spinal cord, forming the central nervous system connected to peripheral nerves.
Pharyngeal Gill Slits
- Present at various life stages, allowing water passage from the pharynx to outside, aiding in respiratory functions and filter feeding.
- Fate varies across groups; non-vertebrates use them for feeding, while vertebrates develop them into gills or other structures.
General Characteristics of Chordates
- Possess bilateral symmetry, are triploblastic, and belong to a deuterostome group.
- Have a complete digestive tract and well-developed coelom, with internal organs suspended in coelomic cavities via mesentery.
- Reproduce sexually and feature a post-anal tail.
Classification of Chordates
- Phylum Chordata is divided into:
- Acraniata (Protochordata)
- Craniata (vertebrates)
- Subphyla include:
- Urochordata (tunicates)
- Cephalochordata (lancelets)
- Agnatha (jawless fish)
- Gnathostomata (jawed vertebrates)
Group Acraniata (Protochordata)
- Characterized by the absence of a cranium and a less prominent brain than in Craniata.
- Notochord does not evolve into a vertebral column.
Sub-Phylum Urochordata
- Known as tunicates; have a notochord extending only in the tail.
- Body encased in a tunic, mainly composed of tunicine, similar to cellulose.
- Adaptations for feeding include two siphons for water intake and waste expulsion.
- Primarily filter-feeders, consuming plankton trapped by mucous secreted from the endostyle.
Urochordate Physiology
- Respiratory process involves gill slits capturing water and facilitating gas exchange; lacks kidney-like organs.
- Simple blood vascular system containing high levels of vanadium and specialized proteins.
- Most tunicates are hermaphrodites with a larval stage that exhibits chordate characteristics but undergo metamorphosis into a sedentary adult.
Sub-Phylum Cephalochordata
- Comprised of small, eel-like marine animals that retain the notochord and nerve cord throughout life.
- Have a complete digestive system and filter feed using pharyngeal slits.
- Respiration occurs through the body's surface; no specialized respiratory organs.
- Reproduction is sexual with separate sexes, and fertilization happens externally.
- Approximately 30 recognized species within this sub-phylum.
Additional Information
- Hemichordata is recognized as a sister group to echinoderms; they are marine, bilaterally symmetrical, and triploblastic animals.
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