Question

Mention the animals that exhibited a 'tube-within-a-tube' organisation for the first time. Name their body cavity.

Answer 1

Organization of the Animal Body | Evolution and Classification of Animals | Trends in ... The Phylum Rotifera | The Tube-within-a-tube Body Plan: Phylum Nematoda ... animals) first appear 700 million years ago, during the Vendian time. ... of the Cambrian (named after Cambria, an ancient name for the country of Wales).

Answer 2

The animals such as Nematodes and Rotifers exhibited a 'tube-within-a-tube' organization for the first time.

Explanation:

• Tube within a tube organization refers to the body plan in which the organism posses two different opening in which one acts as mouth and other acts as anus.

• Through mouth opening the organism ingests food, whereas through the anus opening it ejects waste out of the body.

• Such type of arrangement was found initially in species such as nematodes and rotifers belonging to the phylum called Aschelminthes and they posses pesudoceloem type of body cavity.