32.1
What Is a Protostome? 691
Trochophores, lophophores, and spiral
cleavage evolved among the lophotrochozoans
692
Ecdysozoans must shed their exoskeletons
693
Arrow worms retain some ancestral
developmental features 694
32.2 What Are
the Major Groups of Lophotrochozoans?
695
Ectoprocts live in colonies 695
Flatworms, rotifers, and ribbon worms
are structurally diverse relatives
695
Phoronids and brachiopods use lophophores
to extract food from the water 697
The annelids and the mollusks are
sister groups 698
Annelids have segmented bodies 698
Mollusks have undergone a dramatic
evolutionary radiation 700 32.3
What Are the Major Groups of Ecdysozoans?
702
Several marine groups have relatively
few species 702
Nematodes and their relatives are
abundant and diverse 703
32.4 Why Do Arthropods Dominate Earth’s
Fauna? 705
Arthropod relatives have fleshy, unjointed
appendages 705
Jointed legs first appeared in the
trilobites 706
Crustaceans are diverse and abundant
706
Insects are the dominant terrestrial
arthropods 708
Myriapods have many legs 712
Most chelicerates have four pairs
of legs 712
An Overview of Protostome Evolution
714
