7.21 Invertebrates

65 question-and-answer flashcards reviewing anatomy, ecology, reproduction, and significance of major invertebrate phyla covered in the lecture.

What type of body symmetry do adult echinoderms exhibit?

Radial (usually pentaradial) symmetry.

Which unique organ system powers echinoderm locomotion and gas exchange?

The water vascular system.

Through which opening does water enter an echinoderm’s water vascular system?

The madreporite.

Trace the main pathway of water in a sea star’s vascular system.

Madreporite → stone canal → ring canal → radial canal → lateral canals → ampullae → tube feet.

Of what material are echinoderm ossicles made?

Calcium-carbonate (calcareous) plates.

What pincer-like structures around some echinoderm spines help with cleaning and defense?

Pedicellariae.

Name the five major echinoderm classes.

Asteroidea, Ophiuroidea, Echinoidea, Holothuroidea, Crinoidea.

How is fertilization usually accomplished in echinoderms?

Separate sexes release gametes externally into the water.

Which echinoderm is a keystone predator controlling kelp-grazing urchins?

The sunflower sea star.

What biomedical value do sea cucumber toxins show?

They can slow the growth of certain cancer cells.

What body symmetry characterizes flatworms (Platyhelminthes)?

Bilateral symmetry.

How many germ layers do flatworms possess?

Three (they are triploblastic).

Why are flatworms dorsoventrally flattened?

To increase surface area for diffusion of gases and nutrients.

What excretory unit in flatworms contains a flickering tuft of cilia?

A flame cell (protonephridium).

What structure functions as both digestive and circulatory cavity in flatworms?

The gastrovascular cavity.

List the four major classes of Platyhelminthes.

Turbellaria, Trematoda, Monogenea, Cestoda.

How do humans usually acquire tapeworm infections?

By eating undercooked or contaminated meat containing larval cysts.

Which parasitic flatworm causes schistosomiasis?

Blood flukes of the genus Schistosoma.

What adult stem cells drive planarian regeneration?

Neoblasts.

Give two methods of asexual reproduction in flatworms.

Fragmentation/fission and subsequent regeneration.

What type of body cavity is found in nematodes?

A pseudocoelom.

Which muscle type produces the thrashing motion of nematodes?

Longitudinal muscle only.

What protective layer do nematodes periodically shed?

A collagenous cuticle.

Is the nematode gut complete or incomplete?

Complete—from mouth to anus.

Name three common human-parasitic nematodes discussed.

Hookworms, pinworms, and filarial worms.

Which nematode infection can cause elephantiasis?

Lymphatic filarial worms (e.g., Wuchereria bancrofti).

How can hookworm infection be prevented?

Improve sanitation and avoid barefoot contact with contaminated soil.

Why are free-living nematodes ecologically important?

They recycle nutrients and can act as biological pest control.

What wheel-like ciliated structure crowns a rotifer’s head?

The corona.

What muscular organ with trophi grinds food in rotifers?

The mastax.

How do bdelloid rotifers maintain diversity without males?

By parthenogenesis and incorporating foreign DNA during desiccation dormancy.

What environmental condition triggers sexual reproduction in many monogonont rotifers?

Stress, such as crowding or limited resources.

Why are rotifers considered good bioindicators?

Their rapid response to pollutants reflects water quality changes.

List the three rotifer classes mentioned.

Bdelloidea, Monogononta, Seisonidea.

Which rotifer ability makes them models for desiccation studies?

Entering an anhydrobiotic dormant state and reviving when rehydrated.

What term describes repetition of body segments in annelids?

Metamerism.

Which bristle-like structures protrude from many annelid segments?

Setae (chaetae).

What annelid structure secretes mucus for sperm transfer and forms cocoons?

The clitellum.

Explain how circular and longitudinal muscles produce earthworm movement.

Circular muscles elongate each segment; longitudinal muscles shorten it, creating peristaltic waves.

What type of circulatory system do most annelids possess?

A closed circulatory system.

Name the excretory organ pair found in each annelid segment.

Metanephridia.

Which anticoagulant in leech saliva prolongs bleeding?

Hirudin (an anti-thrombin compound).

To which superphylum are arthropods assigned because they molt?

Ecdysozoa.

What is the main structural polymer in an arthropod exoskeleton?

Chitin.

Define holometabolous development.

Complete metamorphosis with egg, larva, pupa, and adult stages.

Which arthropod subphylum includes insects and has six legs?

Hexapoda.

What feeding appendages give Chelicerata their name?

Chelicerae.

How many legs do arachnids have?

Eight (four pairs).

Which copper-based molecule in horseshoe-crab blood is used to test medical equipment for bacteria?

Hemocyanin (via the Limulus Amebocyte Lysate test).

Which myriapod group are fast, venomous carnivores with one leg pair per segment?

Centipedes (Class Chilopoda).

What term describes the fused head-thorax region of many crustaceans?

Cephalothorax.

How many walking legs do decapod crustaceans possess?

Ten (five pairs).

Name the three main body regions of an insect.

Head, thorax, abdomen.

Which shared larval form links molluscs and annelids in Lophotrochozoa?

The trochophore larva.

List the three basic parts of a mollusc body plan.

Muscular foot, visceral mass, mantle.

What rasping organ is used by most molluscs to feed?

The radula.

Which mollusc class bears eight overlapping shell plates?

Polyplacophora (chitons).

How do cephalopods achieve rapid jet propulsion?

By expelling water from the mantle cavity through a siphon.

What pigment cells enable cephalopods to change color?

Chromatophores.

Which mollusc class lacks a radula and filter-feeds with gills?

Bivalvia.

What powerful muscles close a scallop’s or clam’s shells?

Adductor muscles.

What developmental process twists the body of many gastropods 180°?

Torsion.

What ecological service do burrowing sand dollars provide?

Bioturbation and oxygenation of seafloor sediments.

Which larval nematode stage is typically infective to plants?

The second-stage (J2) larva that hatches from the egg.