EXAM4 BIO Study GUIDE

What are Porifera?

Lack tissues, organs, and symmetry; simple animals with complex multicellularity.

Where do sponges live?

Mostly marine (26k species), some freshwater.

How do adult sponges move?

They are sessile and attached to substrate.

What are ostia?

Small pores where water enters the sponge.

What is the osculum?

Large opening where water exits the sponge.

What is the mesohyl?

Gelatinous ECM layer containing amoebocytes, spicules, and spongin.

What are choanocytes?

Flagellated collar cells that create water flow, trap food, and move waste.

What do amoebocytes do?

Move nutrients, form spicules and spongin, and differentiate into sperm/egg.

How do sponges feed?

Filter feeding using choanocytes.

How do sponges breathe?

Diffusion across cell membranes.

How do sponges reproduce asexually?

By fragmentation.

How do sponges reproduce sexually?

Hermaphroditic; internal fertilization; ciliated larvae.

What defines eumetazoans?

Animals with true tissues, symmetry, and germ layers.

What symmetry do cnidarians have?

Radial symmetry.

How many germ layers do cnidarians have?

Two (diploblastic).

Do cnidarians have organs?

No; they have tissues but no organs.

What is the cnidarian nervous system?

Nerve net with no brain.

What are nematocysts?

Microscopic stinging capsules used for prey capture and defense.

What are cnidocytes?

Cells containing nematocysts.

What are the two cnidarian body forms?

Polyp (sessile) and medusa (free-swimming).

What is the gastrovascular cavity?

Single-opening cavity for digestion, circulation, and waste removal.

What type of digestion do cnidarians use?

Extracellular digestion in the gastrovascular cavity.

What is a planula?

Ciliated larval stage of cnidarians.

How do medusae reproduce?

Usually sexually; produce gametes.

What is mesoglea?

Gel-like layer between epidermis and gastrodermis.

What do circular muscles do in jellyfish?

Contract to propel the animal by shrinking the bell.

What do longitudinal muscles do in jellyfish?

Widen the bell when contracting.

What are the four major cnidarian classes?

Hydrozoa, Scyphozoa, Cubozoa, Anthozoa.

What is unique about Hydrozoa?

Both polyp and medusa; many freshwater; colonial forms.

What is the dominant stage in Scyphozoa?

Medusa.

Why are box jellies dangerous?

They have potent venom and image-forming eyes.

What animals belong to Anthozoa?

Corals and sea anemones.

Do Anthozoans have a medusa stage?

No; only polyps.

How do corals build reefs?

Polyps secrete calcium carbonate skeletons.

What causes coral bleaching?

Corals expel symbiotic dinoflagellates under stress.

What symmetry do ctenophores have?

Biradial symmetry.

How do comb jellies move?

Using rows of fused cilia called ctenes.

What are colloblasts?

Sticky prey-capturing cells in ctenophores.

Do ctenophores have mesoderm?

Yes; true muscles.

What defines Bilateria?

Bilateral symmetry and three germ layers.

What type of coelom do Platyhelminthes have?

Acoelomate.

Do flatworms have a complete gut?

No; they have an incomplete (blind) gut.

How do flatworms move?

Using ciliated epithelial cells and muscles.

What are flame cells?

Excretory/osmoregulatory cells that remove waste and regulate water.

Describe flatworm nervous system.

Cerebral ganglion with paired ventral nerve cords.

Are flatworms hermaphroditic?

Yes; most cross-fertilize.

What are the two major groups of Neodermata?

Trematodes (flukes) and cestodes (tapeworms).

How do flukes attach to hosts?

Using hooks, anchors, or suckers.

How many hosts does Clonorchis sinensis require?

Three: human → snail → fish → human.

What disease does Schistosoma cause?

Schistosomiasis.

How do blood flukes avoid immune detection?

By coating themselves in host antigens.

Where do tapeworms live?

In the intestines of vertebrates.

What is a scolex?

Anterior attachment organ with hooks and suckers.

What are proglottids?

Reproductive segments containing eggs.

Do tapeworms have a digestive system?

No; absorb nutrients across body surface.

What type of coelom do nematodes have?

Pseudocoelom.

Do nematodes have circular muscles?

No; only longitudinal muscles, causing thrashing motion.

What covers nematodes externally?

A tough cuticle that must be molted.

Do nematodes have a complete gut?

Yes; mouth to anus.

Do nematodes have separate sexes?

Yes; most are gonochoric.

What is eutely?

Fixed number of cells in the adult body.

What disease do hookworms cause?

Anemia by feeding on intestinal blood.

How is elephantiasis transmitted?

Parasitic nematodes spread by mosquitoes.

What phylum includes snails, clams, and squids?

Mollusca.

What is the mantle?

Tissue that secretes the shell.

What is the muscular foot?

Structure used for locomotion, digging, or feeding.

What is the radula?

Rasping tongue-like organ with chitinous teeth (absent in bivalves).

Do mollusks have a closed circulatory system?

No, except cephalopods.

What is a trochophore?

Free-swimming larval stage of mollusks and annelids.

What is a veliger?

Second larval stage in many mollusks.

Describe gastropods.

Include snails and slugs; undergo torsion and coiling.

What is torsion?

Twisting of body that moves mantle cavity and anus to the anterior.

What is coiling?

Spiral winding of the shell.

Describe bivalves.

Clams/mussels; two shells; filter-feeders; no radula.

How do bivalves feed?

Using cilia on gills and siphons to filter food.

What is unique about cephalopods?

Closed circulatory system, advanced brains, arms/tentacles.

How do cephalopods move?

Jet propulsion using siphon.

What are chromatophores?

Pigment cells allowing rapid color change.

Do cephalopods undergo direct or indirect development?

Direct development.

What defines Annelida?

Segmented worms with septa and chaetae.

What type of circulatory system do annelids have?

Closed circulatory system.

What are chaetae?

Chitinous bristles for traction.

What is the function of the gizzard in earthworms?

Grinding food.

How do earthworms reproduce?

Hermaphroditic but cross-fertilizing.

What is the clitellum?

Secretes mucus for copulation and egg cocoon.

How do annelids move?

Using hydrostatic skeleton and circular/longitudinal muscles.

What are errant annelids?

Active swimmers/crawlers (bristle worms).

What are sedentary annelids?

Burrowers and tube dwellers.

What are leeches?

Clitellata group; no chaetae; many are ectoparasitic.

What defines arthropods?

Segmented bodies, jointed appendages, chitin exoskeleton.

What is tagmata?

Body segments fused into functional units (head/thorax/abdomen).

What are the downsides of exoskeletons?

Limits size, requires molting.

What is ecdysis?

Molting of the exoskeleton.

Do arthropods have open or closed circulation?

Open circulation.

What are book lungs?

Respiratory structures in spiders.

What is the tracheal system?

Network of tubes delivering oxygen directly to tissues in insects.

What are spiracles?

External openings for gas exchange in arthropods.

What are Malpighian tubules?

Excretory organs producing uric acid in insects/arachnids.

What are ommatidia?

Units of compound eyes.

What are chelicerae?

Fang or pincer-like appendages in spiders, ticks, and scorpions.