Question 3

Earthworm and squid are both examples of invertebrates.

Both the earthworm and the squid belong to groups of animals that do not possess a backbone, classifying them as invertebrates. This distinction is crucial in understanding the diversity of animal life.

A) Bird and bat

Birds and bats are both vertebrates, as they possess a backbone. Birds belong to the class Aves, while bats are mammals in the order Chiroptera. Therefore, this pair does not consist of invertebrates.

B) Oyster and fish

While oysters are invertebrates, being mollusks that lack a backbone, fish are vertebrates classified under the subphylum Vertebrata. Thus, this pair includes one invertebrate and one vertebrate, failing to meet the criteria.

C) Snake and snail

Snakes are vertebrates, belonging to the class Reptilia, characterized by their backbone. In contrast, snails are invertebrates under the phylum Mollusca. This pair, like the others, does not consist solely of invertebrates.

D) Earthworm and squid

Both the earthworm, a member of the phylum Annelida, and the squid, a cephalopod mollusk, are classified as invertebrates. Their lack of a backbone is a key feature that qualifies them as invertebrates, making this pair correct.

Conclusion

The correct answer, "Earthworm and squid," is definitive because both organisms are classified as invertebrates, exemplifying the absence of a backbone. In contrast, all other options include at least one vertebrate, which disqualifies them from being pairs of invertebrates. Understanding these classifications is essential in the study of animal biology.