Chordata

Chordata is a phylum in the animal kingdom that includes organisms with a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail at some stage in their life cycle.

Characteristics of Chordates

Chordates are characterized by the following features:

1. Notochord: A flexible rod-like structure that provides support to the body. In some chordates, it is replaced by the vertebral column.
2. Dorsal Hollow Nerve Cord: A hollow tube located dorsal to the notochord, which develops into the spinal cord in vertebrates.
3. Pharyngeal Slits: Openings in the pharynx that connect the pharynx to the outside environment, and in aquatic chordates, function in filter-feeding and gas exchange.
4. Post-Anal Tail: An extension of the body past the anal opening, which is present at some stage in the development of all chordates.

Classification of Chordates

Chordates are classified into three subphyla:

1. Urochordata (Tunicates): Marine organisms with a sac-like body structure and a notochord during their larval stage.
2. Cephalochordata (Lancelets): Small, fish-like marine organisms with a notochord and a dorsal nerve cord.
3. Vertebrata (Vertebrates): Chordates with a vertebral column, including fish, amphibians, reptiles, birds, and mammals.

Importance of Chordates

Chordates play crucial roles in various ecosystems and have significant economic and ecological importance. Vertebrates, in particular, are essential for maintaining ecological balance and serve as a source of food and livelihood for humans.

Study Guide Questions

1. What are the key characteristics of chordates?
2. Describe the functions of the notochord, dorsal hollow nerve cord, and pharyngeal slits in chordates.
3. Differentiate between the three subphyla of chordates.
4. Discuss the importance of chordates in ecosystems and their significance to humans.

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