Question:

Sycon belongs to a group of animals, which are best described as

Updated On: Jul 19, 2024
  • Unicellular or acellular
  • Multicellular without any tissue organization
  • Multicellular with a gastrovascular system
  • Multicellular having tissue organization, but no body cavity.
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The Correct Option is B

Solution and Explanation

Sycon, belonging to the phylum porifera, are multicellular organisms with cellular level of body organisation. The constituent cells perform their functions more or less independently. No distinct tissue or organs are present in it.
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Concepts Used:

Classification of Animals

Classification of Animal Kingdom:

One of the most fundamental forms of classification of animals is the presence or absence of the notochord. Hence, two major groups exist, namely: Chordates and Non-chordates

Non-chordates and the Chordates-

  • The notochord is a flexible rod made out of a material similar to cartilage. If an animal has a notochord during any stage of its life, it is classified as a chordate. Contrary to popular belief, chordates do not exclusively include vertebrates.
  • There are invertebrates that possess a notochord during some point in their lives and hence, are classified as chordates. Thus all vertebrates are chordates but not all chordates are vertebrates.

Non-chordates-

  • Non-chordates are animals without a notochord – the rod-like elastic structure that supports the body. This phylum consists of a small group of worm-like, marine species with an organ-system level of organization.
  • Members of phylum Porifera, Coelenterata, Ctenophora, Platyhelminthes, Aschelminthes, Annelida, Arthropoda, Mollusca, Echinodermata and Hemichordata fall under Non-chordates

Vertebrates Classification:

The subphylum Vertebrata is divided into five classes of vertebrates. These five classes of vertebrates comprise of all the species of animals and have developed vertebral column as well as an internal skeleton.

Other characteristic features of vertebrates are-

  • Presence of a true vertebral column and internal skeleton with muscle attachment points for body movement.
  • A front-side muscular heart with two, three or four chambers.
  • Kidneys for excretion and osmoregulation
  • A paired appendages which may be fins or limbs.
  • Possess notochord during the embryonic stage.
  • Vertebrates are the only chordates to possess a brain as a part of the central nervous system.

Classification of Vertebrates-

  • Pisces
  • Amphibia
  • Reptilia
  • Aves
  • Mammalia