Problem 73 - Objective Biology for NEET

Question

Common features of Chordata are (a) The presence of notochord in any stage of life (b) Dorsal hollow neural system (c) Paired pharyngeal gill slits (d) All of these

Step-by-Step Solution

Answer

The correct answer is (d) All of these. Each feature provided: the presence of notochord at any stage of life, a dorsal hollow neural system, and paired pharyngeal gill slits, are common features of Chordata.

Step 1: Understanding Chordata

Chordata is a diverse phylum of animals that comprises species like mammals, birds, reptiles, amphibians, and fish. All chordates have several common features at stage of their life.

Step 2: Option (a) Analysis

The presence of a notochord is, indeed, a defining characteristic of the phylum Chordata. The notochord is a flexible rod that provides support in most species, it's present only in the embryonic stages.

Step 3: Option (b) Analysis

The dorsal hollow neural system is also a unique feature of chordates. It includes the brain and spinal cord. This system provides a pathway for the quick transmission of signals from the brain to the rest of the body and vice versa.

Step 4: Option (c) Analysis

The presence of paired pharyngeal gill slits is another characteristic of chordates. In aquatic species, these slits can mature into gills. In terrestrial species, they can develop into various structures depending on the species.

Step 5: Answer Analysis

After analyzing each option, it's clear that all presented features: presence of notochord, dorsal hollow neural system and paired pharyngeal gill slits, are defining characteristics of the Chordata phylum. Therefore, each statement individually is accurate. However, taking them collectively provides a more comprehensive definition.

Key Concepts

Notochord

The notochord is a key feature of chordates and plays a crucial role during the early development of these organisms. It's a flexible, rod-like structure that runs along the length of the body. The main function of the notochord is to provide skeletal support.
It acts as a firm axis that the rest of the body can move around, ensuring proper structure and movement.

• In many chordates, like fish, the notochord persists throughout life.
• In mammals and birds, it is replaced by the vertebral column or spine, contributing to the unique structural architecture of these animals.

The development of the notochord is essential for the proper alignment and positioning of other developing organs and systems. It is one of the earliest structures to form and prompts the development of the dorsal hollow nerve cord right above it.

Dorsal Hollow Neural System

The dorsal hollow neural system is another defining feature of chordates. This system is essentially the pathway that helps transmit signals from the brain to the body and back.
It is unique because, unlike many other organisms, it is hollow and located dorsally (toward the back of the body).

• This structure differentiates into the central nervous system, comprising the brain and the spinal cord.
• Immense nervous function is supported through this organization, which has evolved to enhance the rapid transmission of neural signals.

In embryonic developments, the dorsal hollow neural system begins as a simple neural tube. Through intricate developmental processes, this tube transforms into a complex network that controls sensory and motor functions. Such significant evolutionary advantage helps chordates to swiftly adapt and react to their environments.

Pharyngeal Gill Slits

Pharyngeal gill slits are openings found on the lateral sides of the throat region in chordates. These slits serve diverse functions depending on the species and the environment.
In aquatic environments, such as in fish, these slits often develop into gills, facilitating respiration by allowing water to pass through.

• In terrestrial chordates, these slits typically evolve into different anatomical structures during embryonic development.
• For example, in humans, they contribute to the formation of the ears, tonsils, and other neck structures.

The presence of pharyngeal gill slits during some stage of development is a quintessential example of evolutionary repurposing. While they may not serve the same function in all chordates, their presence indicates shared ancestry and evolutionary insight into the adaptive strategies of different species within the phylum Chordata.