Which member of the phylum Porifera is the oldest metazoan group still existing on our planet?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. Sponges.
- Sponges, members of the phylum Porifera is the oldest metazoan group still existing on our planet.
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Sponges are regarded as the oldest living metazoans, with fossil evidence dating back to the Precambrian era (~600 million years ago).
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Body Structure: They are simple multicellular organisms that lack true tissues, organs, and a nervous system, but contain specialized cells (e.g., choanocytes for feeding, amoebocytes for transport).
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Feeding Mechanism: Sponges use a water canal system for filter feeding, efficiently extracting nutrients and oxygen from water.
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Evolutionary Significance: Fossil records indicate that sponges played a crucial role in early marine ecosystems, making them key to understanding animal evolution.
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Habitat: They are exclusively aquatic—predominantly marine, though a few species also inhabit freshwater environments.