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Triploblastic, metamerically segmented, dioecious and coelomate animals are

BASIS OF CLASSIFICATION
NEET
1

Apis, Hirudinaria

2

Nereis, Locusta

3

Pheretima, Periplaneta

4

Nereis, Pila

Solution:

Let's analyze the characteristics mentioned and evaluate each option:

Characteristics:

  • Triploblastic: Organisms developing from three embryonic germ layers (ectoderm, mesoderm, endoderm). This includes Annelids, Arthropods, Molluscs, Echinoderms, Hemichordates, and Chordates.

  • Metamerically segmented: The body is divided into a series of similar segments, both externally and internally. This feature is characteristic of Phylum Annelida and Phylum Arthropoda.

  • Dioecious: Sexes are separate (male and female reproductive organs are in different individuals).

  • Coelomate: Possessing a true coelom, a body cavity lined by mesoderm. This includes Annelida, Arthropoda, Mollusca, Echinodermata, Hemichordata, and Chordata.

Combining these, we are looking for animals that are triploblastic, coelomate, and metamerically segmented, which narrows down to Annelida and Arthropoda. Among these, we need to find examples that are also dioecious.

Evaluation of Options:

  • (1) Apis (Honeybee), Hirudinaria (Leech):

    • Apis (Phylum Arthropoda): Triploblastic, metamerically segmented, coelomate, dioecious. Fits the criteria.

    • Hirudinaria (Phylum Annelida): Triploblastic, metamerically segmented, coelomate. However, leeches (like Hirudinaria) are typically monoecious (hermaphroditic), not dioecious. So, this option is incorrect.

  • (2) Nereis (Ragworm), Locusta (Locust):

    • Nereis (Phylum Annelida): Triploblastic, metamerically segmented, coelomate, and dioecious. Fits all criteria.

    • Locusta (Phylum Arthropoda): Triploblastic, metamerically segmented, coelomate, and dioecious. Fits all criteria.

    Both organisms in this option satisfy all the given characteristics.

  • (3) Pheretima (Earthworm), Periplaneta (Cockroach):

    • Pheretima (Phylum Annelida): Triploblastic, metamerically segmented, coelomate. However, earthworms (like Pheretima) are monoecious (hermaphroditic), not dioecious. So, this option is incorrect.

    • Periplaneta (Phylum Arthropoda): Triploblastic, metamerically segmented, coelomate, dioecious. Fits the criteria.

  • (4) Nereis (Ragworm), Pila (Apple Snail):

    • Nereis (Phylum Annelida): Fits all criteria.

    • Pila (Phylum Mollusca): Triploblastic and coelomate. However, molluscs are not metamerically segmented. So, this option is incorrect.

Based on the analysis, only option (2) contains animals that are both triploblastic, metamerically segmented, dioecious, and coelomate.

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