Which phylum has the following features? (1) Digestive track...

Which phylum has the following features? (1) Digestive track is complete, straight or $\mathrm{U}$ shape. (2) Worm like, unsegmented marine animal. (3) Respiration is done by gills. (4) Excretion by single proboscis gland. (5) Circulatory system is naturally open. (a) Arthropoda (b) Mollusca (c) Hemichordata (d) Urochordata

Which phylum has the following features?
(1) Digestive track is complete, straight or $\mathrm{U}$ shape.
(2) Worm like, unsegmented marine animal.
(3) Respiration is done by gills.
(4) Excretion by single proboscis gland.
(5) Circulatory system is naturally open.
(a) Arthropoda
(b) Mollusca
(c) Hemichordata
(d) Urochordata

Key Concepts

Hemichordata

Hemichordata is a phylum of marine deuterostomes that exhibit features such as a complete digestive tract, pharyngeal gill slits, an open circulatory system, and a distinctive anterior proboscis which can be involved in various functions including excretion. Studying Hemichordata is important for understanding the evolutionary relationships among deuterostomes.

Unsegmented Marine Invertebrate Body Plans

A body plan characterized by an unsegmented, worm-like form is common in certain marine invertebrates. This simple organization supports lifestyles such as burrowing or navigating soft substrates and contrasts with segmented body plans found in other animal groups.

Complete Digestive Tract

A complete digestive system features two distinct openings, a mouth and an anus, allowing food to pass in a one-way stream through specialized regions for ingestion, digestion, and excretion. This organization enhances digestive efficiency and is found in many advanced metazoans.

Open Circulatory System

An open circulatory system refers to a design where the circulating fluid, or hemolymph, is not confined within well-defined blood vessels but instead freely bathes the internal organs in body cavities. This system is characteristic of many invertebrates and influences the way nutrients and gases are transported within the body.

Pharyngeal Gill Slits

Pharyngeal gill slits are openings in the pharynx that aid in respiration by allowing water to pass through, facilitating gas exchange. They play a critical role in aquatic animals and are a defining feature in several deuterostome groups, highlighting an evolutionary link among them.

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