BIOL 1113 Final Studying

Choanoflagellates

Single-celled protists considered the closest relatives of animals; key evidence for the origin of multicellularity

Diploblastic

Having two germ layers (ectoderm and endoderm with mesoglea between); characteristic of Cnidaria/Radiata

Triploblastic

Having three germ layers (ectoderm, mesoderm, endoderm); characteristic of all Bilateria

Acoelomate

Animal lacking a true coelom; relies on solid tissues; restricts organ complexity (e.g., flatworms)

Pseudocoelomate

Animal with a false coelom lined only on the outside by mesoderm; partially derived from endoderm (e.g., nematodes)

Eucoelomate

Animal with a true coelom; mesoderm fully surrounds gut; allows highly specialized organ systems

Schizocoely

Coelom formation by splitting of the mesoderm; characteristic of protostomes

Enterocoely

Coelom formation by outpocketing of the archenteron; characteristic of deuterostomes

Determinate cleavage

Cell fate is fixed early in development; loss of one cell is fatal to the organism; produces mosaic embryo; protostome

Indeterminate cleavage

Cell fate is specified late; each blastomere retains full potential; basis for identical twins; produces regulative embryo; deuterostome

Spiral cleavage

Cells divide at 45-degree angles producing unequal blastomeres; characteristic of protostomes

Radial cleavage

Cells divide at 90-degree angles producing uniform blastomeres; characteristic of deuterostomes

Protostome

Blastopore becomes the mouth; schizocoely; spiral cleavage; determinate development

Deuterostome

Blastopore becomes the anus; enterocoely; radial cleavage; indeterminate development

Metamerism (segmentation)

Division of the body into repeating regions allowing regional specialization; found in annelids, arthropods, chordates

Cephalization

Concentration of sensory structures and nervous tissue at the anterior end; associated with bilateral symmetry and forward movement

Lophotrochozoa

Protostome clade defined by lophophore or trochophore larval stage; includes molluscs, annelids, flatworms, rotifers

Ecdysozoa

Protostome clade defined by molting (ecdysis) of cuticle; includes nematodes and arthropods

Lophophore

Crown of ciliated tentacles used for filter feeding

Trochophore larva

Free-swimming ciliated larval stage shared by annelids and molluscs; evidence of lophotrochozoan relationship

Paedomorphosis

Reproductive maturity reached before adult body form develops; offspring retain juvenile traits; proposed origin of vertebrates from tunicates

Choanocytes

Flagellated collar cells lining sponge interior; beat flagella to drive water currents for filter feeding

Archaeocytes

Amoeboid cells in sponges; phagocytize and transport food; can differentiate into any other sponge cell type

Mesohyl

Gelatinous extracellular matrix filling sponge body; houses archaeocytes and spicules

Spicules

Structural support elements secreted by archaeocytes in sponges; make sponges unpalatable

Gemmules

Environmentally resistant reproductive structures of sponges; allow survival through harsh conditions

Asconoid

Simplest sponge body form; small, tube-shaped; flagellated spongocoel; water flows ostia → spongocoel → osculum

Syconoid

Intermediate sponge complexity; flagellated canals; water flows ostia → incurrent canal → atrium → osculum

Leuconoid

Most complex sponge form; flagellated chambers; colonial; slowest water velocity; greatest feeding efficiency

Cnidocytes

Specialized stinging cells of cnidarians containing cnidae with nematocysts; fire with bullet-like force

Nematocyst

Fluid-filled capsule inside cnidocyte that explosively discharges to capture prey or defend against predators

Gastrovascular cavity

Single-opening digestive cavity of cnidarians and flatworms; functions as both mouth and anus

Mesoglea

Jelly-like non-cellular layer between epidermis and gastrodermis in cnidarians; thick in scyphozoans

Polymorphism / dimorphism

Existence of two body forms (polyp and medusa) within one cnidarian species; homologous origins

Scyphozoa life cycle

Egg/sperm → zygote → planula → scyphistoma (polyp) → strobilation → ephyra → medusa

Strobilation

Asexual budding process in scyphozoan polyps that produces ephyrae (juvenile jellyfish)

Cubozoa

Box jellies; medusa phase only (no polyp); active hunters; includes deadly Chironex fleckeri (dermonecrotic, cardiotoxic, neurotoxic)

Gastrozooid

Feeding polyp in hydrozoan colonies; bears nematocyst-bearing tentacles

Gonozooid

Reproductive polyp in hydrozoan colonies; buds off new polyps and produces sexual medusae

Pedal laceration

Cloning method of sea anemones; a piece of the pedal disk is left behind when moving and regenerates into a new individual

Zooxanthellae

Photosynthetic dinoflagellates living within coral tissue; provide 20–90% of nutrients via photosynthesis; drive calcification and reef building

Coral bleaching

Expulsion of zooxanthellae from coral tissue due to stress; coral dies if zooxanthellae don't return within days

Ocean acidification

~30% increase in H+ ions in ocean; reduces carbonate availability; blocks calcification in corals and shellfish

Colloblasts

Sticky adhesive cells on ctenophore tentacles used for prey capture (unlike cnidarian nematocysts)

Flame cells

Excretory cells in flatworms that regulate osmotic balance and water excretion via tubules

Trematodes (flukes)

Parasitic flatworms with complex life cycles involving definitive and intermediate hosts (e.g., Schistosoma, Clonorchis sinensis)

Miracidium

First free-swimming larval stage of flukes; hatches from egg and infects first intermediate host (snail)

Cercariae

Free-swimming larval stage of flukes released from snail intermediate host; infects next host

Metacercariae

Encysted stage of flukes in second intermediate host; ingested by definitive host to complete life cycle

Scolex

Anterior attachment organ of tapeworms with hooks/suckers; anchors to intestinal wall

Proglottids

Repeating segments of tapeworms each containing complete male and female reproductive organs; self-fertilizing

Mastax

Muscular pharynx of rotifers used to hold food

Trophi

Jaw-like grinding structures inside the mastax of rotifers

Parthenogenesis

Asexual reproduction where females produce clonal offspring from unfertilized eggs via mitosis; seen in rotifers (amictic eggs)

Mictic eggs

Rotifer eggs produced by meiosis during sexual reproduction; if unfertilized → haploid males; if fertilized → dormant resting egg

Chaetae

Chitinous bristles in annelids that aid in locomotion and anchoring

Parapodia

Fleshy paired appendages of polychaetes bearing chaetae; aid in movement, burrowing, and gas exchange

Nephridia

Excretory organs of annelids that filter coelomic fluid and regulate water/ion balance

Epitoke

Posterior portion of polychaete that breaks off and swims to surface for mass spawning (epitoky)

Clitellum

Glandular band in oligochaetes that secretes mucus protecting sperm, produces cocoon, and secretes albumin to nourish embryos

Hirudin

Anticoagulant secreted by leeches that prevents blood clotting in host while feeding

Radula

Chitinous ribbon bearing teeth in molluscs; used to scrape or drill food; absent in bivalves

Mantle

Fold of tissue in molluscs that secretes the shell and encloses the mantle cavity housing gills or lungs

Countercurrent exchange

Blood and water flow in opposite directions across gill surfaces; maximizes O2 uptake; used by mollusc gills

Shell layers (mollusc)

Periostracum (conchiolin outer protection) → Prismatic (CaCO3 bulk) → Nacreous (CaCO3 over protein; innermost; thickens over time)

Byssal threads

Protein fibers secreted by bivalves to anchor themselves to substrate

Siphuncle

Gas-filled tube in nautilus shell used to regulate buoyancy by adjusting gas volume in chambers

Chromatophores

Pigment-containing cells in cephalopod skin enabling rapid color and pattern change

Eutely

Developmental condition in nematodes where cells lose the ability to divide after a fixed number; adult has exact same cell count

Tagmata

Body regions formed by fusion of segments in arthropods (head, thorax, abdomen); allow regional specialization

Hemocoel

Blood-filled body cavity in arthropods and most molluscs; replaces true coelom; part of open circulatory system

Malpighian tubules

Excretory organs of insects and arachnids; extract nitrogenous wastes from hemolymph and deliver to gut

Tracheae / spiracles

Insect respiratory system; air enters through spiracles (external openings) and travels through tracheal tubes directly to tissues

Chelicerae

Fang-like first appendages of chelicerates used for feeding

Biramous appendages

Two-branched appendages of crustaceans (one branch for walking, one for swimming/respiration)

Holometabolous metamorphosis

Complete metamorphosis: egg → larva → pupa → adult; larva and adult occupy different niches reducing competition

Hemimetabolous metamorphosis

Incomplete metamorphosis: egg → nymph → adult; nymph resembles adult but lacks wings

Ambulacral grooves

Channels on echinoderm arms through which tube feet extend; associated with water vascular system

Water vascular system

Hydraulic system of canals and tube feet in echinoderms; madreporite → stone canal → ring canal → radial canals → tube feet

Pedicellariae

Movable pincer-like ossicles on echinoderm aboral surface; protect against settling of parasites and clean the body

Mutable connective tissue

Echinoderm connective tissue that rapidly changes rigidity via calcium signaling; enables autotomy and shape change

Autotomy

Self-amputation of a limb; echinoderms can regenerate entire body from one arm plus 1/5 of central disc

Notochord

Dorsal elastic rod providing support and muscle attachment in all chordates; becomes vertebral column in vertebrates

Dorsal hollow nerve cord

Hollow neural tube in chordates; anterior end enlarges to form the brain; distinguishes chordates from other phyla

Pharyngeal pouches (gill slits)

Perforated openings from pharyngeal cavity to exterior; originally for filter feeding; evolved into gills, parathyroid, and other structures

Paedomorphosis (chordate)

Tunicates reach sexual maturity in larval form; if adults lost sessile form, larval traits (notochord, nerve cord) could persist → fish-like ancestor

Lateral line system

Neuromast cells detecting water vibration and current in all fishes; allows detection of nearby objects and prey

Ampullae of Lorenzini

Electroreceptors in sharks detecting bioelectric fields, temperature, salinity, and pressure

Placoid scales (denticles)

Tooth-like scales of cartilaginous fishes pointing backward for streamlining; shark teeth are evolutionarily modified placoid scales

Squalene

Fatty lipid in shark liver providing buoyancy; compensates for lack of swim bladder

Heterocercal tail

Asymmetrical tail of cartilaginous fishes where the upper lobe is larger; generates lift

Homocercal tail

Symmetrical tail of most ray-finned bony fishes; most metabolically economical for sustained swimming

Swim bladder

Gas-filled buoyancy organ in bony fishes; homologous to tetrapod lungs; connected to esophagus via pneumatic duct in some species

Hypoosmotic regulator

Marine teleost strategy: body fluids less concentrated than seawater; compensate by drinking seawater and excreting salts via gills

Hyperosmotic regulator

Freshwater teleost strategy: body fluids more concentrated than surroundings; compensate with mucus/scales and kidneys that produce dilute urine

Positive pressure breathing

Amphibian lung ventilation: air is forced in by buccal pumping (swallowing air); opposite of mammalian negative pressure

Amniotic egg membranes

Amnion (fluid-filled sac around embryo) + Allantois (gas exchange/waste storage) + Chorion (outermost gas exchange) + Yolk sac (nutrients)

Kinetic skull

Reptile skull where jaws hinge to the skull (not each other); allows wider gape and more efficient prey capture

Synapsid vs. Diapsid skull

Synapsid (one temporal opening) → mammal lineage; Diapsid (two temporal openings) → reptile/bird lineage

Pneumatized skeleton

Bird bones with internal air cavities connected to air sacs; dramatically reduces body weight for flight