Dorsal hollow nerve cord

Definition

The dorsal hollow nerve cord is a unique structure found in chordates, consisting of a hollow tube of nervous tissue located along the dorsal side of the body. This feature is significant as it serves as the basis for the central nervous system, developing into the brain and spinal cord in vertebrates. It distinguishes chordates from other animal phyla, highlighting their evolutionary adaptations and complexity.

5 Must Know Facts For Your Next Test

1. The dorsal hollow nerve cord is formed from ectodermal tissue during embryonic development, specifically through a process called neurulation.
2. In vertebrates, this nerve cord differentiates into the central nervous system, which includes the brain and spinal cord, integral for processing sensory information and coordinating bodily functions.
3. The presence of a dorsal hollow nerve cord is one of the defining characteristics of the phylum Chordata, alongside notochord, pharyngeal slits, and a post-anal tail.
4. In some non-vertebrate chordates like tunicates and lancelets, the dorsal hollow nerve cord is simpler but still indicates evolutionary relationships within the phylum.
5. This nerve cord represents an evolutionary advancement over solid nerve cords found in other animal groups, enabling more complex behaviors and reflexes.

Review Questions

• How does the dorsal hollow nerve cord develop during embryonic stages in chordates?
  • During embryonic development in chordates, the dorsal hollow nerve cord forms from ectodermal tissue through a process called neurulation. This involves the folding of the ectoderm to create a neural tube that eventually becomes the central nervous system. The formation of this structure is crucial as it lays the foundation for complex nervous system development, including the formation of the brain and spinal cord.
• Compare the dorsal hollow nerve cord found in vertebrates with that of non-vertebrate chordates. What evolutionary implications can be drawn from these differences?
  • In vertebrates, the dorsal hollow nerve cord develops into a highly organized central nervous system that includes a complex brain and spinal cord. In contrast, non-vertebrate chordates like tunicates possess a simpler form of this structure, which may not evolve into a fully developed nervous system. The differences suggest an evolutionary trend towards greater complexity in vertebrates, highlighting how adaptations have allowed for enhanced sensory processing and behavioral responses over time.
• Evaluate how the presence of a dorsal hollow nerve cord influences the classification of organisms within Chordata and its role in their evolutionary significance.
  • The presence of a dorsal hollow nerve cord is a key feature that influences the classification of organisms within Chordata. It serves as an important criterion for grouping species and understanding their evolutionary relationships. By differentiating chordates from other animal groups based on this unique structure, researchers can trace back common ancestry and study how evolutionary adaptations have led to diverse forms of life with varying complexities in nervous system function.

Related terms

Notochord: A flexible rod-like structure that provides support and is present in all chordate embryos; it is replaced by the vertebral column in most vertebrates.

Pharyngeal Slits: Openings that occur in the pharynx region during development; they play roles in respiration and filter feeding, and are characteristic features of chordates.

Tail: An extension of the body past the anus; in chordates, it is used for locomotion and balance, contributing to their mobility in aquatic environments.