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🦴 Phylum Chordata – NEET Notes, Examples, and Tips

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📚 Introduction

Phylum Chordata is one of the most important phyla in biology, as it includes vertebrates (animals with a backbone) and other related invertebrates. The members of this phylum are characterized by possessing a notochord, dorsal hollow nerve cord, pharyngeal gill slits, and a post-anal tail at some stage of their life cycle. For NEET, understanding the different subphyla and their distinguishing features is essential.

In this blog, we’ll break down the key features of Phylum Chordata, highlight important examples, and give you some useful NEET tips.

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🧬 Key Features of Chordata

Feature	Details
Notochord	Flexible rod-like structure supporting the body
Dorsal Hollow Nerve Cord	Nervous system running along the back
Pharyngeal Gill Slits	Openings in the throat for water filtering
Post-Anal Tail	Tail extending beyond the anus
Body Structure	Bilateral symmetry, triploblastic, coelomate
Circulatory System	Closed circulatory system
Digestive System	Complete digestive system
Reproductive System	Dioecious (except some species)
Respiration	Gills, lungs, or skin depending on the species

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🔬 Subphyla of Chordata – Focus on Major Examples

1. Cephalochordata (e.g., Lancelets)

   • These are small, fish-like organisms that retain a notochord throughout life. They are often used as examples of primitive chordates.

2. Urochordata (e.g., Tunicates or Sea Squirts)

   • Tunicates are marine organisms that have a notochord and a dorsal nerve cord only in their larval stage. As adults, they become sessile and lose many chordate features.

3. Vertebrata (e.g., Humans, Birds, Fishes, Reptiles, Amphibians)

   • Vertebrates are the most familiar and advanced members of this phylum. They have a vertebral column (backbone), cranium, and a highly developed nervous system.

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⚡ Unique Features of Chordata

• Notochord: The notochord is a long, flexible rod-like structure that provides support during development. In vertebrates, it is replaced by the vertebral column but remains in some non-vertebrate chordates like lancelets.

• Dorsal Hollow Nerve Cord: This nerve cord is located along the back of the organism and is the precursor to the spinal cord in vertebrates.

• Pharyngeal Gill Slits: These slits are used for filter feeding in some chordates and gas exchange in aquatic species. In vertebrates, they form the gills in fish or develop into parts of the ear and throat in higher organisms.

• Post-Anal Tail: Many chordates, especially invertebrates, retain a tail that extends beyond the anus. In humans, this structure is represented by the coccyx or tailbone.

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🧠 Smart Mnemonic

“Chords Don’t Play Much, But They Are Perfect Musicians.”

• Chords – Chordata

• Don’t – Dorsal hollow nerve cord

• Play – Pharyngeal gill slits

• Much – Muscular post-anal tail

• But – Bilateral symmetry

• Are – Advanced vertebrates

• Perfect – Presence of a notochord

• Musicians – Musculoskeletal support

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🔬 Structure of a Vertebrate (e.g., Human)

Let’s focus on humans, which are vertebrates:

• Notochord: The notochord is present during early embryonic development but is replaced by the vertebral column (spine) in humans.

• Dorsal Hollow Nerve Cord: This cord develops into the brain and spinal cord, central to the nervous system.

• Pharyngeal Slits: In humans, these slits are represented in embryonic stages but disappear by the time of birth. In fish, they develop into gills.

• Post-Anal Tail: In humans, the tail reduces to a coccyx, a small vestige at the end of the spine.

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🎯 NEET PYQ Alerts – Chordata

1. Which of the following is a characteristic of all chordates during at least some stage of their life cycle?
   ✅ Answer: Notochord

2. What is the notochord replaced by in vertebrates?
   ✅ Answer: Vertebral column (backbone)

3. Which of the following organisms is an example of a cephalochordate?
   ✅ Answer: Lancelet

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🧾 Summary Table

Feature	Chordata
Notochord	Present at some stage of life
Dorsal Hollow Nerve Cord	Precursor to the spinal cord
Pharyngeal Gill Slits	Filter feeding or gas exchange
Post-Anal Tail	Tail extends beyond the anus
Body Structure	Bilateral symmetry, coelomate
Circulatory System	Closed circulatory system
Digestive System	Complete digestive system
Reproductive System	Dioecious (except some species)
Respiration	Gills, lungs, or skin

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🔗 Stay Connected with Our NEET Bio Blogs:

• 📘 biologyatease1.blogspot.com – NEET Notes & Diagrams

• 🎯 neetpyqall.blogspot.com – NEET PYQs Solved Smartly

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📝 Conclusion

Phylum Chordata encompasses the most diverse and complex animals, from invertebrates like lancelets and tunicates to vertebrates such as humans, birds, and fishes. The key features of chordates—notochord, dorsal nerve cord, and pharyngeal slits—are critical for understanding their development and evolutionary significance. For NEET, be sure to focus on the defining characteristics of each subphylum and how they relate to human biology.

👉 Up next: Review of NEET PYQs for Chapter 10 – Animal Kingdom!