* Earthworm, spider, centipede: These are all invertebrates, meaning they lack a backbone.
* Earthworm is an annelid (segmented worm).
* Spider is an arachnid (part of the arthropod family, which includes insects, crustaceans, and others).
* Centipede is also an arthropod, specifically a myriapod (meaning "many legs").
* Jellyfish: This is a cnidarian, a group that includes corals, sea anemones, and hydras.
* Frog, Trout: These are both vertebrates, meaning they have a backbone.
* Frog is an amphibian, meaning it spends part of its life in water and part on land.
* Trout is a fish, meaning it lives entirely in water.
Closest Relationships
1. Earthworm and Centipede are the most closely related, both being arthropods.
2. Spider is also an arthropod, but further away from the earthworm/centipede group.
3. Frog and Trout are both vertebrates, but belong to different classes (amphibians and fish).
4. Jellyfish is very distant from all the others, representing a different phylum entirely.
Key Takeaway: The more closely related organisms are, the more recently they shared a common ancestor. This is reflected in their shared physical characteristics and genetic makeup.
