Phylum Chordata Overview

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Questions and Answers

How long ago did the fossil record of cephalochordates begin?

About 525 million years ago.

What is the maximum length adult Branchiostoma can reach?

Six to seven centimeters.

What is the primary significance of lancelets in the study of evolution?

They are invertebrates transitional to vertebrates, providing clues for human lineage.

Describe the function of the endostyle in lancelets.

The endostyle produces slime to trap food in the perforated pharynx. Signup and view all the answers

What type of circulatory system do lancelets possess?

A closed circulatory system. Signup and view all the answers

How do lancelets reproduce, and where does fertilization occur?

Lancelets have separate sexes and reproduce by shedding eggs and sperm into the water for external fertilization. Signup and view all the answers

What feature distinguishes the nervous system of lancelets?

They have a dorsal hollow nerve cord and a central nervous system without a visible brain. Signup and view all the answers

How does the excretory system of lancelets function?

Excretion occurs through the anus and atriopore, utilizing nephridia. Signup and view all the answers

What unique feature do cephalochordates retain into adulthood that distinguishes them from most vertebrates?

The notochord is retained into adulthood in cephalochordates. Signup and view all the answers

Describe the key reproductive characteristic of organisms within the Class Ascidiacea.

Organisms in Class Ascidiacea are hermaphrodites, possessing both male and female reproductive organs. Signup and view all the answers

How do Thaliacea differ in size and habitat compared to Ascidiacea?

Thaliacea are generally 1 mm to 15 cm small and are pelagic, while Ascidiacea are larger and mainly benthic. Signup and view all the answers

What components of the nervous system are present only in the larval stage of Ascidiacea and Thaliacea?

The notochord, dorsal hollow nerve cord, and postanal tail are present only in the larval stage. Signup and view all the answers

What method do organisms in the subphylum Tunicata use for feeding?

Organisms in Tunicata are filter-feeders, extracting nutrients from water. Signup and view all the answers

What are the distinguishing ecological behaviors of Appendicularia compared to Ascidiacea?

Appendicularia do not form colonies and live near the surface, whereas Ascidiacea live mostly in colonies on the sea floor. Signup and view all the answers

In what way does the circulatory system of tunicates differ from that of typical vertebrates?

Tunicates have an open circulatory system with a simple heart and no blood vessels. Signup and view all the answers

Identify the types of excretory structures present in tunicates.

Tunicates utilize nephrocytes for excretion, primarily through the anus and atrial siphon. Signup and view all the answers

What structural characteristics make lancelet larvae distinct from adult lancelets?

Lancelet larvae are asymmetrical, smaller, simpler, with fewer gill slits and no atrium. Signup and view all the answers

How does segmentation contribute to the movement of lancelets?

Segmentation provides effective body coordination during locomotion, enabling both forward and backward swimming. Signup and view all the answers

What is the significance of the coelom in lancelets and how does it develop?

The coelom is a well-developed secondary body cavity that forms from outpouchings in the gut of the embryo. Signup and view all the answers

Describe the habitats where lancelets are typically found.

Lancelets inhabit soft bottoms ranging from sand to coarse shelly sand or gravel in shallow coastal waters. Signup and view all the answers

What types of fins do lancelets possess, and what is their function?

Lancelets have dorsal, caudal, and ventral odd fins that aid in movement. Signup and view all the answers

In what way do lancelets exhibit simple behavior in their environment?

Their behavior primarily involves locating suitable habitats and avoiding predators. Signup and view all the answers

What similarities exist between the segments of lancelets and vertebrates?

The segments of lancelets and vertebrates are similar, suggesting a common ancestry. Signup and view all the answers

What is meant by 'odd fins' in lancelets, and how do they differ from other fin types?

'Odd fins' refer to the unique configuration of their fins that provide specific swimming adaptations. Signup and view all the answers

What is the primary function of the notochord in Chordata and how does it change in higher Chordata?

The notochord provides structural support and flexibility; in higher Chordata, it develops into the vertebral column. Signup and view all the answers

Describe the significance of the dorsal hollow nerve cord in Chordata and how it differs from Protostomia.

The dorsal hollow nerve cord is a key characteristic enabling complex nervous system development; unlike Protostomia, which have a ventral nerve cord, Chordata possess a dorsal arrangement. Signup and view all the answers

Explain the role of visceral clefts in Chordata and their modifications in different groups of Chordates.

Visceral clefts serve as openings in the pharynx for feeding and respiration; they can develop into gills in some species or be reduced in higher Chordates. Signup and view all the answers

Identify two defining characteristics of the Tunicata (Urochordata) and describe their habitat.

Tunicata are characterized by their barrel shape and colonial or solitary lifestyle; they inhabit marine waters while being attached to the substrate. Signup and view all the answers

What is the function of the endostyle in the digestive system of Tunicata?

The endostyle releases mucus to capture food particles, which are further processed in the stomach. Signup and view all the answers

How are Chordates categorized based on their circulatory system, and what is the exception?

Chordates generally possess a closed circulatory system with a heart; however, Tunicata are the exception as they do not follow this pattern. Signup and view all the answers

Discuss the importance of metameric segmentation in the body structure of Chordates.

Metameric segmentation allows for increased complexity and flexibility in movement and specialization of body segments. Signup and view all the answers

What does the term 'triploblastic' refer to in the context of Chordata, and what are the three germ layers?

'Triploblastic' indicates that Chordates develop from three germ layers: ectoderm, mesoderm, and endoderm. Signup and view all the answers

Study Notes

Phylum Chordata

Characteristic features:
- Bilaterally symmetrical
- Triploblastic, coelomate
- Metamerically segmented
- Deuterostomia
- Notochord (a slender, stiff, flexible rod) present at some stage of life cycle; develops into vertebral column in higher chordates
- Dorsal hollow nerve cord (protostomes have a ventral nerve cord)
- Visceral clefts (pharyngeal slits): perforations on each side of the pharynx, present in all chordate embryos; in some, they develop into gills; reduced in higher chordates
- Postanal tail at some stage of their life, can be reduced or lost in some adult chordates
Other features:
- Possess an endoskeleton
- Closed circulatory system with a heart (except tunicates)
- Central nervous system (CNS)

Subphylum Urochordata (Tunicata)

Characteristics:
- 3,000 species
- Numerous gill slits on the pharynx for suspension feeding
- Oral and atrial siphons
- Notochord and nerve cord present in tadpole larvae
- No coelom or bony tissue
- Secrete tunic (a polysaccharide coating) for their adult body
Classes:
- Ascidiacea (ascidians): benthic (live on the bottom); solitary or colonial
- Thaliacea (salps): pelagic; colonial
- Appendicularia (larvaceans): pelagic; solitary; adults retain larval characteristics
Lifestyle: Live in marine waters; colonies or as individuals; attached to the bottom; barrel-shaped, covered with a tunic (contains tunicin/polysaccharide similar to cellulose)

Subphylum Cephalochordata

Characteristics:
- Small, fish-like, marine invertebrates
- Closest living relatives of vertebrates
- Have a hollow, dorsal nerve cord, pharyngeal gill slits, a notochord, and a postanal tail
- Notochord persists into adulthood, never replaced by vertebrae
- Approximately 20 species in two families, each with a single genus ( Branchiostoma)
Key Features:
- Oral hood with tentacles
- Notochord
- Dorsal nerve cord
- Intestine
- Gill slits in pharynx
- Gonads
- Atrium
- Atriopore
- Anus
Size: Adult lancelets reach lengths of 6-7 cm.

Importance

Edible, but not a significant food source
Serve as a simple example of vertebrate characteristics and evolutionary features. Provide clues for the history of human lineage.

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Description

Explore the fascinating characteristics of Phylum Chordata, including key features such as bilateral symmetry, notochord, and dorsal nerve cord. This quiz also delves into the unique aspects of the subphylum Urochordata, covering their feeding mechanisms and structural attributes. Test your knowledge of these essential biological concepts!