e. Define arthropods with any four examples.
f. Write any three salient features of the animals belonging to Phylum Mollusca.
g. Why is octopus kept in Phylum Mollusca?
h. Define echinoderms with any two examples.
i. Why is earthworm kept in Phylum Annelida? How does it differ from Ascaris (Roundworm)?
Answer (2)
Arthropods are jointed invertebrates, including insects and crustaceans, while Phylum Mollusca features soft-bodied animals like octopuses, which have unique characteristics such as a mantle and muscular foot. Echinoderms, like starfish, are known for their radial symmetry, whereas earthworms belong to Phylum Annelida due to their segmented structure, differing from roundworms, which are unsegmented. Each phylum showcases distinct biological features and classifications.
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e. Arthropods are invertebrate animals that form the largest phylum in the animal kingdom, known as Arthropoda. They are characterized by having a segmented body, an exoskeleton made of chitin, and paired jointed appendages. Common examples include:
Insects (e.g., butterflies, beetles)
Arachnids (e.g., spiders, scorpions)
Crustaceans (e.g., crabs, lobsters)
Myriapods (e.g., centipedes, millipedes)
f. Three salient features of the animals belonging to Phylum Mollusca are:
Soft Body: Mollusks have a soft, unsegmented body that is often protected by a hard shell.
Muscular Foot: Most mollusks have a strong muscular foot used for locomotion or attachment to surfaces.
Mantle: This is a significant body part that secretes the shell in many mollusks and also houses the gills or lungs.
g. The octopus is kept in Phylum Mollusca because it shares key features with other mollusks such as a soft body and the presence of a mantle. Despite lacking a hard external shell, octopuses have an intricate internal structure that aligns with molluscan anatomy.
h. Echinoderms are marine invertebrates belonging to the Phylum Echinodermata, characterized by radial symmetry, a calcareous endoskeleton, and a water vascular system. Two examples include:
Starfish (or Sea Stars)
Sea Urchins
i. The earthworm is placed in Phylum Annelida due to its segmented body, which is a key characteristic of annelids. Earthworms have a coelom (body cavity) and exhibit bilateral symmetry. They are different from Ascaris (Roundworm) , which belongs to the Phylum Nematoda.
Earthworms have well-developed segmentation, whereas Ascaris has a tubular and unsegmented body.
Annelids like earthworms possess a true coelom, while nematodes have a pseudocoelom. This fundamental difference highlights the distinct structural organization between these two types of worms.
