Problem 151 - Objective Biology for NEET

Question

The fundamental character of chordate is (a) Notochord (b) Dorsal hollow nerve cord (c) Paired pharyngeal gill slits (d) All of these

Step-by-Step Solution

Answer

The correct answer is (d) All of these.

Step 1: Understanding Chordate Characteristics

Learn about chordates characteristics. The fundamental characteristics of a chordate include a notochord, a dorsal, hollow nerve cord, and pharyngeal slits.

Step 2: Comparing Choices

Go through each of the options given in the exercise. Option (a) refers to the notochord not being the only required characteristic for an animal to qualify as a chordate. The same applies to options (b) and (c). However, option (d) states 'all of these', implying that a chordate requires a notochord, a dorsal, hollow nerve cord, and pharyngeal slits.

Step 3: Choosing the Correct Answer

After comparing all the options, it is clear that 'all of these' or option (d) is the correct answer as it encompasses all required characteristics of chordates.

Key Concepts

Notochord

A notochord is a flexible, rod-like structure that acts as a primary support for chordates during their embryonic development. It runs along the body, usually encased in a sheath, and serves as a crucial anchor for muscle attachment.

• The notochord provides a scaffold that supports the developing body.
• It helps in defining the head-tail axis of the organism.
• In most vertebrates, the notochord is eventually replaced by the vertebral column.

In some non-vertebrate chordates, such as tunicates and lancelets, the notochord is maintained throughout the organism's life. This structural feature is one of the defining components that underscore the evolutionary step towards more complex spinal structures in vertebrates.

Dorsal Hollow Nerve Cord

The dorsal hollow nerve cord is a tube-like structure located dorsally, meaning along the back of the chordates. Unlike the solid nerve cords found in some other animals, this one is hollow and filled with fluid. This unique feature differentiates chordates from other phyla.

• The nerve cord develops into the central nervous system, specifically the brain and spinal cord in vertebrates.
• This formation allows for a more advanced and specialized nervous system.
• Its hollow nature facilitates the passage of nerve signals efficiently.

The position of the nerve cord is another distinguishing characteristic that sets chordates apart, with its dorsal placement enabling better protection and more optimal functioning of the nervous system through evolutionary adaptations.

Pharyngeal Gill Slits

Pharyngeal gill slits are small openings that appear in the pharynx region of chordate embryos. These slits contribute significantly to the versatility and adaptability of chordates.

• In aquatic species, these slits can develop into gills, which are used for breathing underwater.
• In terrestrial vertebrates, such as mammals, these structures transform into parts of the ear and throat.
• This adaptability showcases the evolutionary pivot from water to land in vertebrate history.

The gill slits indicate how chordates have evolved to adapt to various environments by modifying embryonic structures for different functional needs, balancing both survival and efficiency in diverse habitats.