Question

Choose the correct options from the alternatives given.
Which of the combinations of phyla and characteristics is incorrect?
a. Nematoda- roundworms, pseudocoelomate
b. Cnidaria- radial symmetry, polyp and medusa body forms
c. Platyhelminthes- flatworms, gastrovascular cavity, acoelomate
d. Porifera- gastrovascular cavity, mouth from blastopore

Answer 1

Phylum is a level of classification in biology which lies below kingdom and above class. Organisms in a phylum share characteristics that distinguish them from other phyla. The term phylum was given by Ernst Haeckel. Some examples of phyla are Mollusca, porifera, etc.

Complete answer:
Ernst Haeckel coined the term phylum. It is taken from the Greek language. Phylum is a taxonomic classification which lies below kingdom and above class. Organisms in a phylum share characteristics that distinguishes them from other phyla.
From the given option the incorrect combination with characteristics is of Porifera.

The correct characteristics of phylum porifera are as follows:
• They are multicellular organisms.
• They have small pores on their body which are called ostia. In these ostia water canals, chambers form a unique system of water currents on which these organisms depend for food and water.
• They have radial symmetry.
• They have intracellular digestion and excretion and respiration is carried out by diffusion.
• They have choanocytes (flagellated cells) which help pump water in and out of their body. ‘
• They have no nervous system.
• Reproduction is both sexual and asexual. Asexual reproduction is carried out by buds or gemmules and sexual reproduction by sperms or eggs.
• They have three types of canal system, asconoid, syconoid and leuconoid.

Hence, the correct answer is option (D).

Note: Porifera are further divided into calcarean, demospongiae and hexactinellid. Calcarean have calcium carbonate spicules, have an internal system of pores and canals for water flow. Demispongiae have siliceous spicules and spongin networks are often present. Hexactinellid have syncytial trabecular reticulum.