Protostome Core Terms and Concepts (FB)

Flashcards reviewing key terms and concepts from a Protostome lecture, covering topics from body cavity types to specific phyla like Platyhelminthes, Mollusca, Annelida, Nematoda, and Arthropoda, including cross-phylum comparisons and healthcare relevance.

Acoelomate

An animal with no fluid-filled cavity; solid mesoderm fills the space (e.g., flatworms).

Pseudocoelomate

Animal whose body cavity is partly mesoderm, partly endoderm; acts as hydrostatic skeleton (e.g., nematodes).

Coelomate

Animal with a true coelom fully lined by mesoderm, allowing suspended organs and complex systems.

Cephalization

Concentration of brain & sensory organs at the anterior end, improving directed movement.

Bilateral symmetry

Single sagittal plane divides body into mirror-image left & right halves.

Protostome embryonic hallmark

Blastopore becomes mouth; spiral, determinate cleavage.

3 Segmentation advantages

Efficient movement, organ redundancy, segment specialisation.

Define complete digestive tract

Separate mouth & anus for one-way food processing.

which protostome phyla with complete gut

Nematoda, Mollusca, Arthropoda, Annelida.

Flatworms gut type

Incomplete; single opening gastrovascular cavity.

Stowers model: apple snail, why?

Eye closely resembles vertebrate eye and regenerates, informing eye-repair research.

Stowers model: fruit fly (Drosophila).

Shares human disease genes; classic genetics model.

Stowers model for planarian

Totipotent cells enable study of whole-body regeneration.

Body cavity of flatworms

Acoelomate.

Excretory cell in flatworms

Flame cell inside protonephridia.

How tapeworms obtain nutrients

Absorb across tegument; no digestive tract.

Tapeworm infection route

Eating undercooked meat with cysts (pork, beef).

Liver-fluke human infection route

Eating raw/undercooked freshwater fish or plants with metacercariae.

Disease site of liver flukes

Bile ducts / liver causing obstruction & inflammation.

Four core mollusc body parts.

Foot, visceral mass, mantle, head.

Function of the radula

“Tongue” with teeth to scrape/drill food (absent in bivalves).

What are ctenidia?

Gills located in mantle cavity for gas exchange.

Circulatory type in most molluscs vs cephalopods

Most = open hemocoel; cephalopods = closed vessels.

Gastropod signature developmental twist.

Torsion (180° rotation of visceral mass).

Bivalve feeding mechanism

Filter-feeding via gills; no radula.

Cephalopod locomotion method

Jet propulsion using siphon; foot modified into arms.

Why cephalopods need closed circulation

Supports high metabolic rate & active predation.

Snail’s medical link to liver flukes

Acts as first intermediate host in Clonorchis life cycle.

How segmentation aids annelid burrowing

Local muscle waves act on hydrostatic coelom for peristaltic motion.

Annelid excretory organ name

Metanephridium (paired per segment).

Annelid circulatory system

Closed; dorsal vessel pumps blood.

Medical use of leeches

Relieve venous congestion & deliver hirudin anticoagulant in microsurgery.

Nematode body cavity

Pseudocoelomate.

Nematode digestive layout

Complete tube: mouth → intestine → anus.

Vector transmitting elephantiasis.

Mosquito carrying filarial worms to lymphatics.

How hookworms enter the body

Larvae penetrate skin (bare feet) from contaminated soil.

Pinworm key symptom

Anal itching; eggs spread by hand-to-mouth contact.

Trichinosis infection source

Eating undercooked pork or game with Trichinella cysts.

Why C. elegans is a model organism

Transparent, ~1 000 cells, 3-day life cycle, sequenced genome → ideal for development & genetics.

Three key traits behind arthropod success.

Chitinous exoskeleton, segmentation with jointed appendages, metamorphosis.

Define tagma.

Fused segment block performing a unified function (e.g., head, thorax).

Role of an ommatidium

Single photoreceptive unit of a compound eye.

What ocelli detect

Light intensity/orientation (simple eyes).

Function of Malpighian tubules

Excrete uric acid & conserve water; osmoregulation.

Mouthpart pair unique to spiders & scorpions

Chelicerae (fangs/pincers).

Define Carapace in crustaceans

Hard exoskeletal shield covering head–thorax.

Insect respiratory network name

Tracheae with spiracles delivering air to tissues.

Arachnid primary respiratory organ

Book lungs (plus some tracheae in species).

Crustacean respiration structure

Gills under carapace.

Arthropod circulatory type

Open hemocoel, dorsal heart pumps hemolymph.

Mosquito disease example

Anopheles → malaria (Plasmodium).

Flatworm vs annelid circulation

Flatworm = none (diffusion); annelid = closed vessels.

Mollusc vs arthropod excretory organ

Mollusc = nephridia; arthropod = Malpighian tubules.

Annelid vs nematode body cavity

Annelid = true coelom; nematode = pseudocoelom.

Primary respiratory surface in earthworms.

Moist skin (diffusion).

Simplest nervous system phylum

Nematoda (nerve ring + longitudinal cords).

Invertebrate study matters to medicine for 2 reasons

(1) Many are pathogens/vectors (tapeworms, nematodes, mosquitoes). (2) Provide medical tools/models (leeches in surgery; Drosophila, planarians in research).