Are seabirds and sea squirts are more closely related to one another than r bivalves & brachiopods?
You need to look at the relative taxonomic levels. Sea squirts and sea birds are both in the same phylum Chordata, albeit in separate subphyla Urochordata and Vertebrata respectively. They share chordate characteristics of a notochord (primitive spinal chord, not spine) and post-anal tail, which appear only in larvae of urochordates. Brachiopods and molluscs (which include bivalves) are in different phyla and so are more distantly related. Depending on which taxonomic scheme you follow Brachiopoda is a phylum/class within the superphylum/phylum Lophophorata, while Mollusca is a phylum/class within superphylum/phylum Trochozoa. Which ever way you look at it, they are not closely related. Don’t be fooled by superficial morphological similarity – convergent evolution can produce similarities in distant relatives. Whales do look more like fish than they do cattle, among their closest relatives, but living in the sea produces certain constraints. Sea squirts and sea birds are more closely r
