Chordata Characteristics and Cephalochordata
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Questions and Answers

Which feature is NOT characteristic of organisms in Phylum Chordata?

  • Notochord at some life stage
  • Closed circulatory system
  • Ventral nerve cord (correct)
  • Dorsal hollow nerve cord

What structure in higher Chordata develops from the notochord?

  • Visceral clefts
  • Endoskeleton
  • Dorsal nerve cord
  • Vertebral column (correct)

Which of the following is true about the circulatory system of most chordates?

  • It is closed with a heart (correct)
  • It is open and involves sinuses
  • It varies widely among species
  • It lacks a heart

What is the function of the endostyle in Tunicata?

<p>To capture food particles (D)</p> Signup and view all the answers

Which statement accurately describes visceral clefts in Chordata?

<p>They occur as perforations during embryonic development. (A)</p> Signup and view all the answers

Which class of Chordata is characterized by living in marine environments, often in colonies?

<p>Urochordata (A)</p> Signup and view all the answers

What is a defining feature of the digestive system in Tunicata?

<p>Presence of a distinct stomach and intestines (C)</p> Signup and view all the answers

Which of the following statements about the notochord is true?

<p>It provides support and may be lost in some adult forms. (C)</p> Signup and view all the answers

Which characteristic is unique to adult Appendicularia compared to other classes in Tunicata?

<p>Retains a notochord throughout life (A)</p> Signup and view all the answers

What is the primary function of nephrocytes in the excretory system of Tunicata?

<p>Excretion of waste (C)</p> Signup and view all the answers

Which of the following statements about Cephalochordates is incorrect?

<p>They are part of the subphylum Vertebrate. (B)</p> Signup and view all the answers

Which class of Tunicata is characterized by its sessile, filter-feeding lifestyle?

<p>Ascidiacea (A)</p> Signup and view all the answers

Which feature do larvae of Tunicata have that adults lack?

<p>Postanal tail (D)</p> Signup and view all the answers

What is a common characteristic of all classes within the Tunicata?

<p>They possess a notochord at some stage. (D)</p> Signup and view all the answers

Which term best describes the habitat of Thaliacea?

<p>Pelagic (C)</p> Signup and view all the answers

Comparatively, how do the reproductive systems of Tunicata classes differ from those of vertebrates?

<p>Tunicates are hermaphrodites. (B)</p> Signup and view all the answers

What characteristic distinguishes lancelet larvae from adult lancelets?

<p>Lancelet larvae are asymmetrical and simpler in structure. (D)</p> Signup and view all the answers

Which feature of segmentation is stated to enhance locomotion in lancelets?

<p>It provides more effective body coordination. (A)</p> Signup and view all the answers

What type of habitat do lancelets prefer?

<p>Soft bottoms, including various types of sand and gravel. (B)</p> Signup and view all the answers

What is the primary body cavity present in lancelets called?

<p>Enteron (A)</p> Signup and view all the answers

Which descriptor accurately reflects the fins of lancelets?

<p>They are equipped with dorsal, caudal, and ventral odd fins. (B)</p> Signup and view all the answers

How is the coelom developed in lancelets during embryonic development?

<p>As outpouchings in the gut of the embryo. (D)</p> Signup and view all the answers

What general behavior do lancelets exhibit in their natural environment?

<p>They seek proper habitat and escape from predators. (A)</p> Signup and view all the answers

What does the segmentation in the bodies of lancelets include?

<p>Blocks of muscles and related nerve supplies. (B)</p> Signup and view all the answers

What is the significance of lancelets in evolutionary studies?

<p>They serve as a model for understanding vertebrate characteristics. (C)</p> Signup and view all the answers

Which of the following accurately describes the digestive system of lancelets?

<p>They utilize an endostyle for trapping food. (C)</p> Signup and view all the answers

How do lancelets excrete waste products?

<p>Through the anus and atriopore. (B)</p> Signup and view all the answers

What characteristic of lancelets indicates their classification as chordates?

<p>Presence of a dorsal hollow nerve cord. (C)</p> Signup and view all the answers

Which statement about the reproductive system of lancelets is correct?

<p>They exhibit external fertilization with separate sexes. (C)</p> Signup and view all the answers

Which feature limits the ecological role of lancelets in nutrition?

<p>They are not abundant enough to be significant in the food chain. (D)</p> Signup and view all the answers

What is true regarding the pharyngeal structure of lancelets?

<p>It plays a role in both feeding and respiration. (D)</p> Signup and view all the answers

Which of the following best describes the circulatory system of lancelets?

<p>It is a closed system with a simple heart. (A)</p> Signup and view all the answers

Flashcards

What is a notochord?

A stiff, flexible rod running along the back of chordates, providing support. In higher chordates, develops into a vertebral column.

What is the dorsal hollow nerve cord?

A tube of nerve tissue located on the dorsal side of chordates. It's the central control system for the nervous system.

What are pharyngeal slits?

Openings in the pharynx of chordates that allow for filter feeding in some species. Modified into gills in some aquatic chordates.

What is a post-anal tail?

One of the defining features of Chordates, it protrudes beyond the anus. May be reduced or lost in adult stages.

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What are Tunicates?

A group of invertebrate chordates found in marine environments, they are typically attached to surfaces and filter feed.

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What is tunicin?

A sticky substance secreted by Tunicates to capture food particles in their pharyngeal slits.

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What is an endostyle?

A structure in the pharynx of Tunicates where food particles are collected and processed.

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How do Tunicates feed?

The process of Tunicates feeding by straining food particles from the water.

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What is the function of the visceral clefts in tunicates?

The opening in the pharynx of tunicates through which water enters, bringing in food and oxygen.

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Describe the circulatory system of tunicates.

A simple, open circulatory system, meaning that blood flows freely through the body cavities instead of within a network of vessels.

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What are nephrocytes and where are they found?

Specialized excretory cells that filter waste from the body fluids.

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What is a nerve ganglion and where is it located in a tunicate?

A group of nerve cells, usually forming a central point for controlling the nervous system.

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What are the defining features of a chordate and how do they relate to tunicate development?

In most tunicates, these key chordate features are only present during the larval stage, highlighting the evolutionary connection between tunicates and vertebrates.

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Describe the characteristics and lifestyle of Ascidiacea.

Also known as sea squirts, these tunicates live attached to surfaces, often forming colonies.

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Describe the characteristics and lifestyle of Thaliacea.

Tunicates that are free-floating, making up a part of the plankton.

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What is unique about the Appendicularia compared to other tunicates?

The only group of tunicates that retains the notochord throughout its entire life.

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Cephalochordates: Evolutionary Significance

The cephalochordates are a group of invertebrate chordates that evolved around 525 million years ago, during the Cambrian period. They are transitional forms, linking invertebrates to vertebrates, offering insights into the history of human lineage.

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Lancelet Size

Lancelets are a common example of cephalochordates. These creatures are small, usually reaching about 6-7 centimeters in length.

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Lancelet Importance

While edible, lancelets aren't a major food source for humans or in the natural food chain. They're primarily important because they reveal how early chordates evolved.

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Lancelet Mouth

Lancelets have a mouth with special structures called an oral hood, which helps them gather food. They also possess 'ciri,' sensory tentacles around the mouth.

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Lancelet Pharynx

The lancelet pharynx is perforated with openings called visceral clefts. These slits, along with the endostyle, help capture food using a mucus-based filter feeding method.

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Lancelet Endostyle

The endostyle is a specialized tissue in the lancelet's pharynx. It produces mucus that traps tiny food particles in the water, facilitating filter feeding.

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Lancelet Digestive and Circulatory Systems

Lancelets lack a true stomach but have a simple, closed circulatory system, meaning the blood is contained within vessels.

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Lancelet Nervous System

Lancelets have a basic nervous system with a dorsal hollow nerve cord. However, they don't have a recognizable brain. They do possess pairs of peripheral nerves extending from the nerve cord.

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Lancelet Larva

The larval stage of a lancelet, resembling the adult but smaller, simpler, and asymmetrical with fewer gill slits.

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Metamorphosis in Lancelets

The process of transforming from the larval stage into the adult form.

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Lancelet Movement

Lancelets can move both forward and backward through the gravel in their habitat.

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Segmentation in Lancelets

The body of a lancelet is divided into repeating segments, similar to vertebrates.

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Coelom in Lancelets

The secondary body cavity in lancelets, containing internal organs.

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Coelom Development

The coelom in lancelets develops as outpouchings from the gut of the embryo.

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Lancelet Habitat

Lancelets are found in tropical and temperate coastal waters.

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Lancelet Bottom Habitat

Lancelets inhabit soft bottoms, ranging from sand to gravel in shallow coastal waters.

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Study Notes

Phylum Chordata: Characteristics

  • Bilaterally symmetrical
  • Triploblastic, coelomate
  • Metamerically segmented
  • Deuterostomia
  • Notochord: A slender, stiff, flexible rod running along the back at some life stage, developing into a vertebral column in higher chordates.
  • Dorsal hollow nerve cord: Unlike protostomes, which have a ventral nerve cord.
  • Pharyngeal slits: Perforations on each side of the pharynx present in all chordate embryos. They may develop into gills in some species and are reduced or lost in later adult stages.
  • Postanal tail: Present in some stage of the life cycle, may be reduced or lost in adult forms.

Chordate Subphylum: Cephalochordata

  • Small, fish-like marine invertebrates
  • Close relatives of vertebrates.
  • Notochord, dorsal hollow nerve cord, pharyngeal gill slits, postanal tail present throughout life.
  • About 20 species in two families (with one genus) (e.g. Branchiostoma).
  • Fossil record dates back to the early Cambrian period (around 525 million years ago.)
  • Adults approximately 6 to 7 centimeters in length.

Chordate Subphylum: Urochordata (Tunicata)

  • 3,000 species.
  • Numerous gill slits on pharynx for suspension feeding.
  • Notochord and nerve cord in larval stages only
  • Adult body has a polysaccharide tunic (secreted coating).
  • Three classes: Ascidiacea (ascidians), which are benthic, often colonial; Thaliacea (salps), pelagic, colonial; and Appendicularia (larvaceans), pelagic, solitary.
  • Adults often retain larval characteristics

General Features of Chordates

  • Digestive System: Mouth, pharynx with gill slits, intestines, and anus. They can be filter feeders.
  • Breathing System: Pharynx with gill slits, atrium, atriopore.
  • Circulatory System: Closed system with a simple heart in most cases.
  • Excretory System: Nephrocytes and excretion through the atrial siphon or anus.
  • Nervous System: Dorsal hollow nerve cord, but central nervous system isn't a visible brain in some.
  • Reproductive System: Mostly separate sexes, external fertilization, and larval development phases similar to those of vertebrates and tunicates are possible.

Chordate Ecology, Importance, and Movement

  • Ecology: Inhabit soft bottoms of shallow, coastal waters.
  • Importance: Provides information about evolutionary transition from invertebrates, to vertebrates.
  • Movement: Lancelets can swim forward and backwards quickly; have segmented muscles and fins for movement.
  • Segmentation: Body segmentation (metamerism) extends to body cavities, nerves, and excretory structures, which contributes to overall body coordination.

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Phylum Chordata Study Guide PDF

Description

Explore the fascinating features of Phylum Chordata, including their unique anatomical structures like the notochord and dorsal hollow nerve cord. Additionally, dive into the subphylum Cephalochordata and learn about these small, fish-like marine invertebrates that share a close relationship with vertebrates. Test your knowledge with this informative quiz!

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