Question

Tube-within-tube body plan is shown by
(a) Coelenterates
(b)Flatworms
(c)Annelida
(d)Sponges

Answer 1

Hint: They are from the group of segmented worms found in marine, freshwater, or the moist terrestrial environment.

Complete answer:
The Tube-within-tube body plan is shown by the phylum Annelida. They are also known as ringed worms belonging to a large phylum with species including earthworms, ragworms, and leeches. The tube-within-tube body plan involves two tubes or openings from one food entering (mouth) and from another, the wastes are excreted outside the body (anus).

Additional Information: -A Tube-within-tube body plan is generally found in higher animal groups from nematodes to chordates.
-The body plan has two openings one for ingestion and another for excretion. It is of two types:
        - Protostomous plan – having a mouth towards the first end while the anus is derived later.
         -Deuterosromous plan – the anus is derived first and the mouth opposite to it.
-The body is long, cylindrical, bilaterally symmetrical, and segmented.
-The body is covered by a cuticle below which a layer of cells made of collagen is present which secretes them.
-The body is coelomate having true coelom which is lined by the epidemics epidermis.
-Respiration occurs through the skin or gills.
-The excretory organ is metanephridia which does not have them, they use protonephridia to remove waste products.
-The locomotory organ is setae and parapodia which helps them in swimming and crawling.
-They can reproduce by both means; sexual and asexual reproduction.
So, the correct answer is ‘Annelida'.

Note: -The oldest known fossil of Annelida comes from the early Cambrian period around 518 million years ago.
-Fossils of most polychaetes appear at the end of the Carboniferous period about 299 million years ago. -The earliest fossil of the group oligochaetes appears in the tertiary period about 66 million years ago.