ECOL 182R - MIDTERM 4 WALSH STUDY SET

What are the two major subgroups of protostomes?

Lophotrochozoa and Ecdysozoa

What type of group are protostomes based on molecular phylogenies?

Monophyletic

Which protostome phyla are most diverse and species-rich?

Mollusca and Arthropoda

What key events triggered protostome diversification?

Water-to-land transition, diversification of appendages/mouthparts, evolution of metamorphosis

Examples of protostomes?

Arthropods (insects, spiders, crustaceans), Molluscs (snails, clams, octopuses, squids)

Cleavage pattern in protostomes?

Spiral cleavage

What does the blastopore become in protostomes?

Mouth

How does coelom form in protostomes?

Solid mesoderm splits to form coelom

Protostomes have what type of symmetry and tissue organization?

Bilateral symmetry, triploblastic, coelomate

How many major protostome phyla account for 99.5% of known species?

Eight

Difference in growth between Lophotrochozoa and Ecdysozoa?

Lophotrochozoans grow incrementally, Ecdysozoans grow by molting

How many total protostome phyla are there?

22

What is a lophophore?

Feeding structure surrounding the mouth for suspension feeding

What is a trochophore?

A larval form common to many lophotrochozoans

What defines ecdysozoan growth?

Molting a cuticle or exoskeleton

Two most prominent ecdysozoan phyla?

Nematoda and Arthropoda

Basic protostome body plan?

Tube-within-a-tube

What are flatworms (Platyhelminthes) lacking?

A coelom (they are acoelomate)

What are the functions of a coelom?

Fluid circulation and hydrostatic skeleton

Arthropod body plan features?

Segmented body (head, thorax, abdomen), jointed limbs, exoskeleton of chitin, hemocoel

Molluscan body plan features?

Foot, visceral mass, mantle

What replaced the coelom in molluscs?

Visceral mass and muscular foot

Which protostomes independently evolved to live on land?

Arthropods, molluscs, roundworms, annelids

What adaptations allowed land transition in protostomes?

Support/locomotion structures, new gas exchange and desiccation prevention adaptations

Forms of protostome locomotion?

Walking, running, jumping, flying, gliding, crawling, jet propulsion

How do protostomes reproduce?

Mostly sexual reproduction; some use asexual reproduction like parthenogenesis

Where does external fertilization occur in protostomes?

In sessile groups

What are the two reproductive innovations in protostomes?

Metamorphosis and desiccation-resistant eggs

Rotifer features?

Corona of cilia for feeding and swimming; found in damp, marine, and freshwater habitats

Three subgroups of flatworms?

Turbellarians (free-living), Cestodes (tapeworms), Trematodes (flukes)

Flatworm traits?

Flattened body, high surface area for gas exchange, digestive tract with one opening

Annelid traits?

Segmented body, coelom functions as hydrostatic skeleton

Two major annelid groups?

Polychaeta and Clitellata

Polychaeta features?

Marine, many bristle-like chaetae, size from 1 mm to 3.5 m

Clitellata subgroups?

Oligochaetes (earthworms), Leeches

Mollusca lineages?

Bivalves, Gastropods, Chitons, Cephalopods

Bivalve traits?

Two calcium carbonate shells, suspension feeders, external fertilization

Gastropod traits?

Includes snails, slugs, nudibranchs; torsion during development, radula for feeding

Function of radula?

Scraping food

Where do most molluscs live?

Marine environments (some freshwater and terrestrial)

Which molluscs have a single shell?

Snails

Which molluscs lack shells?

Slugs and nudibranchs

What are the two major subgroups of protostomes?

Lophotrochozoa and Ecdysozoa

What type of group are protostomes based on molecular phylogenies?

Monophyletic

Which protostome phyla are most diverse and species-rich?

Mollusca and Arthropoda

What key events triggered protostome diversification?

Water-to-land transition, diversification of appendages/mouthparts, evolution of metamorphosis

Examples of protostomes?

Arthropods (insects, spiders, crustaceans), Molluscs (snails, clams, octopuses, squids)

Cleavage pattern in protostomes?

Spiral cleavage

What does the blastopore become in protostomes?

Mouth

How does coelom form in protostomes?

Solid mesoderm splits to form coelom

Protostomes have what type of symmetry and tissue organization?

Bilateral symmetry, triploblastic, coelomate

How many major protostome phyla account for 99.5% of known species?

Eight

Difference in growth between Lophotrochozoa and Ecdysozoa?

Lophotrochozoans grow incrementally, Ecdysozoans grow by molting

How many total protostome phyla are there?

22

What is a lophophore?

Feeding structure surrounding the mouth for suspension feeding

What is a trochophore?

A larval form common to many lophotrochozoans

What defines ecdysozoan growth?

Molting a cuticle or exoskeleton

Two most prominent ecdysozoan phyla?

Nematoda and Arthropoda

Basic protostome body plan?

Tube-within-a-tube

What are flatworms (Platyhelminthes) lacking?

A coelom (they are acoelomate)

What are the functions of a coelom?

Fluid circulation and hydrostatic skeleton

Arthropod body plan features?

Segmented body (head, thorax, abdomen), jointed limbs, exoskeleton of chitin, hemocoel

Molluscan body plan features?

Foot, visceral mass, mantle

What replaced the coelom in molluscs?

Visceral mass and muscular foot

Which protostomes independently evolved to live on land?

Arthropods, molluscs, roundworms, annelids

What adaptations allowed land transition in protostomes?

Support/locomotion structures, new gas exchange and desiccation prevention adaptations

Forms of protostome locomotion?

Walking, running, jumping, flying, gliding, crawling, jet propulsion

How do protostomes reproduce?

Mostly sexual reproduction; some use asexual reproduction like parthenogenesis

Where does external fertilization occur in protostomes?

In sessile groups

What are the two reproductive innovations in protostomes?

Metamorphosis and desiccation-resistant eggs

Rotifer features?

Corona of cilia for feeding and swimming; found in damp, marine, and freshwater habitats

Three subgroups of flatworms?

Turbellarians (free-living), Cestodes (tapeworms), Trematodes (flukes)

Flatworm traits?

Flattened body, high surface area for gas exchange, digestive tract with one opening

Annelid traits?

Segmented body, coelom functions as hydrostatic skeleton

Two major annelid groups?

Polychaeta and Clitellata

Polychaeta features?

Marine, many bristle-like chaetae, size from 1 mm to 3.5 m

Clitellata subgroups?

Oligochaetes (earthworms), Leeches

Mollusca lineages?

Bivalves, Gastropods, Chitons, Cephalopods

Bivalve traits?

Two calcium carbonate shells, suspension feeders, external fertilization

Gastropod traits?

Includes snails, slugs, nudibranchs; torsion during development, radula for feeding

Function of radula?

Scraping food

Where do most molluscs live?

Marine environments (some freshwater and terrestrial)

Which molluscs have a single shell?

Snails

Which molluscs lack shells?

Slugs and nudibranchs

What are the two major subgroups of protostomes?

Lophotrochozoa (includes mollusks, annelids, flatworms—typically grow incrementally) and Ecdysozoa (includes arthropods and nematodes—grow by molting an exoskeleton).

What type of group are protostomes based on molecular phylogenies?

Monophyletic group, meaning all protostomes share a common ancestor and include all descendants of that ancestor.

Which protostome phyla are most diverse and species-rich?

Phyla Mollusca and Arthropoda—together, they make up the majority of protostome diversity.

What key events triggered protostome diversification?

The transition from aquatic to terrestrial habitats, the evolution of diverse body plans and appendages, complex mouthparts, and the innovation of metamorphosis.

Examples of protostomes?

Arthropods (e.g., insects, spiders, crustaceans), Mollusks (e.g., snails, clams, octopuses, squids), flatworms, annelids, rotifers, and nematodes.

Cleavage pattern in protostomes?

Spiral cleavage—cells divide at oblique angles in early embryonic development, resulting in a spiral arrangement.

What does the blastopore become in protostomes?

The mouth, distinguishing them from deuterostomes where it becomes the anus.

How does coelom form in protostomes?

By schizocoely—solid mesodermal mass splits to form the coelomic cavity.

Protostomes have what type of symmetry and tissue organization?

Bilateral symmetry; triploblastic (three germ layers: ectoderm, mesoderm, endoderm); most are coelomates.

How many major protostome phyla account for 99.5% of known species?

Eight major phyla make up nearly all known protostome species diversity.

Difference in growth between Lophotrochozoa and Ecdysozoa?

Lophotrochozoa grow incrementally by adding body mass, while Ecdysozoa grow by molting a cuticle (ecdysis).

How many total protostome phyla are there?

22 known protostome phyla in total, with 8 being the most dominant and diverse.

What is a lophophore?

A ring of ciliated tentacles surrounding the mouth used for suspension feeding, found in some Lophotrochozoans (e.g., brachiopods).

What is a trochophore?

A ciliated, free-swimming larval stage characteristic of many Lophotrochozoans like mollusks and annelids.

What defines ecdysozoan growth?

Periodic molting (ecdysis) of a protective cuticle or exoskeleton to allow growth.

Two most prominent ecdysozoan phyla?

Nematoda (roundworms) and Arthropoda (insects, arachnids, crustaceans).