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31.1 What Is a Protostome?
They are bilaterally symmetrical and triploblastic.
They likely evolved from an ancestor with a coelom, but some have lost it.
Protostomes independently moved onto land, developing waterproof shells, exoskeletons, and adaptations for water conservation.
compartmentalized body plans allow parts to evolve separately, leading to greater diversity.
31.2 What Is a Lophotrochozoan?
Flatworms, annelids, and mollusks are main phyla which made the water-to-land transition.
Flatworms are unsegmented and lack specialized structures for gas exchange or circulation and live in aquatic or moist environments
Annelids have segmented bodies and include marine worms, earthworms, and leeches.
Mollusks have a body plan with a foot, visceral mass, and mantle. They occupy aquatic and some terrestrial habitats, with groups like clams, snails, and octopuses.
31.3 What Is an Ecdysozoan?
Key groups: roundworms (tiny, unsegmented) and arthropods (insects, spiders, crabs).
Roundworms live in almost all habitats.
Arthropods have segmented bodies, a chitin exoskeleton, and jointed legs. They include myriapods (millipedes, centipedes), insects, crustaceans (shrimp, crabs), and chelicerates (spiders, scorpions).
Metamorphosis can be incomplete (nymphs look like adults) or complete (larvae and adults are very different).
What is a lophophore?
a. a specialized filter-feeding structure
b. the single opening in species with a blind gut
c. a distinctive type of larva with a band of cilia d. a synapomorphy at defines lophotrochozoans
a. a specialized filter-feeding structure
What is the function of the arthropod exoskeleton?
a. The presence of an exoskeleton has given arthropods a good fossil record, because hard parts fossilize more readily than do soft tissues.
b. It has no well-established function. (Trilobites had an exoskeleton, and they went extinct.)
c. It provides protection on and functions in locomotion.
d. It makes growth by molting possible.
c. It provides protection on and functions in locomotion.
One trait that is shared by the Lophotrochozoa and Ecdysozoa is _______ .
bilateral symmetry
Which protostome phyla successfully made the transition from water to land? Select True or False for each phylum.
T/F Mollusca
T/F Arthropoda
T/F Annelida
T/F Nematoda
True
True
True
True
Propose an explanation for why annelids and arthropods were 1ought to be closely related, before phylogenetic analyses in the late 1990s.
Annelids and arthropods were thought to be closely related because both have segmented bodies, which suggested a common ancestry.
Use your understanding of insect evolution to predict two adaptations for terrestrial living that occurred in spiders.
Waterproof exoskeleton to prevent dehydration.
Book lungs or tracheae for efficient gas exchange in air.
Pose a hypothesis to explain why 1e evolution of the wing was such an important event in the evolution of insects.
evolution of wings in insects allowed for increased mobility, helping them find food, escape predators, and spread to new habitats, which contributed to their diversification and success.
