Animal Diversity

Animalia

Kingdom of multicellular, heterotrophic eukaryotes that lack cell walls.

Multicellular

Composed of many specialized cells working together.

Heterotroph

Obtains energy by consuming other organisms.

Collagen

Structural protein found in the extracellular matrix of animals.

Extracellular matrix

Network of proteins and carbohydrates surrounding animal cells.

Hox genes

Genes that control body plan development and organization.

Tissue

Group of similar cells performing a specific function.

True tissues

Organized cell layers specialized for particular functions.

Porifera

Animal phylum containing sponges.

Sponges

Simplest animals that lack true tissues.

Choanocytes

Collar cells that generate water currents and capture food in sponges.

Ostia

Pores through which water enters a sponge.

Osculum

Large opening where water exits a sponge.

Filter feeding

Obtaining food by straining particles from water.

Asymmetry

Body plan with no regular arrangement of parts.

Cnidaria

Animal phylum containing jellyfish, corals, hydra, and sea anemones.

Cnidocyte

Stinging cell unique to cnidarians.

Nematocyst

Harpoonlike stinging structure within a cnidocyte.

Radial symmetry

Body parts arranged around a central axis.

Diploblastic

Having two embryonic tissue layers.

Ectoderm

Outer embryonic tissue layer.

Endoderm

Inner embryonic tissue layer.

Mesoderm

Third embryonic tissue layer found in triploblastic animals.

Triploblastic

Having three embryonic tissue layers.

Bilateral symmetry

Body plan with matching right and left sides.

Cephalization

Concentration of sensory structures at the head end.

Acoelomate

Animal lacking a body cavity.

Pseudocoelomate

Animal with a cavity partially lined by mesoderm.

Coelomate

Animal with a true body cavity completely lined by mesoderm.

Coelom

Fluid-filled cavity surrounding internal organs.

Protostome

Animal whose blastopore develops into the mouth.

Deuterostome

Animal whose blastopore develops into the anus.

Lophotrochozoa

Protostome group including flatworms, annelids, and mollusks.

Ecdysozoa

Protostome group that molts an external covering.

Platyhelminthes

Phylum of flatworms.

Flatworms

Acoelomate worms with simple body organization.

Planarian

Free-living flatworm often used in studies of regeneration.

Fluke

Parasitic flatworm with complex life cycles.

Tapeworm

Parasitic flatworm that absorbs nutrients from its host.

Mollusca

Phylum containing snails, clams, squids, and octopuses.

Mollusk

Soft-bodied invertebrate usually possessing a mantle and muscular foot.

Mantle

Tissue that secretes the shell in many mollusks.

Muscular foot

Structure used for locomotion in mollusks.

Visceral mass

Region containing internal organs in mollusks.

Radula

Rasping feeding organ found in many mollusks.

Gastropod

Mollusk such as a snail or slug.

Bivalve

Mollusk with two shells such as a clam or oyster.

Cephalopod

Mollusk such as a squid, octopus, or cuttlefish.

Annelida

Phylum of segmented worms.

Annelid

Segmented worm with a true coelom.

Segmentation

Division of the body into repeating units.

Earthworm

Common annelid important in soil ecosystems.

Leech

Annelid that may be predatory or parasitic.

Closed circulatory system

Circulatory system where blood remains within vessels.

Nematoda

Phylum of roundworms.

Roundworm

Unsegmented pseudocoelomate worm.

Cuticle

Tough outer covering secreted by many invertebrates.

Molting

Process of shedding an external covering during growth.

Arthropoda

Largest animal phylum containing insects, spiders, and crustaceans.

Arthropod

Invertebrate with jointed appendages and an exoskeleton.

Exoskeleton

Hard external skeleton protecting the body.

Chitin

Strong polysaccharide forming arthropod exoskeletons.

Jointed appendages

Movable limbs connected by joints.

Metamorphosis

Developmental transformation from juvenile to adult form.

Chelicerate

Arthropod group containing spiders, ticks, and scorpions.

Arachnid

Chelicerate with four pairs of walking legs.

Spider

Arachnid that produces silk.

Scorpion

Arachnid with pincers and a venomous stinger.

Myriapod

Group including centipedes and millipedes.

Centipede

Predatory myriapod with one pair of legs per segment.

Millipede

Myriapod with two pairs of legs on many segments.

Crustacean

Arthropod group including crabs, shrimp, and lobsters.

Barnacle

Sessile crustacean that attaches to surfaces.

Hexapod

Six-legged arthropod group including insects.

Insect

Arthropod with three body regions and six legs.

Head

Insect body region containing sensory organs and mouthparts.

Thorax

Insect body region where legs and wings attach.

Abdomen

Insect body region containing digestive and reproductive organs.

Compound eye

Eye composed of many visual units.

Echinodermata

Phylum including sea stars, sea urchins, and sand dollars.

Echinoderm

Marine deuterostome with a water vascular system.

Water vascular system

Hydraulic system used for movement and feeding in echinoderms.

Tube feet

Extensions of the water vascular system used for locomotion.

Sea star

Common echinoderm also called a starfish.

Sea urchin

Spiny echinoderm with a rigid internal skeleton.

Chordata

Phylum defined by four key derived traits.

Chordate

Animal possessing a notochord at some stage of life.

Notochord

Flexible rod providing structural support.

Dorsal hollow nerve cord

Nervous system structure found in chordates.

Pharyngeal slits

Openings in the throat region of chordates.

Post-anal tail

Tail extending beyond the anus in chordates.

Vertebrate

Chordate possessing vertebrae and a skull.

Craniate

Chordate possessing a skull.

Hagfish

Jawless craniate lacking true vertebrae.

Lamprey

Jawless vertebrate that often feeds as a parasite.

Gnathostome

Jawed vertebrate.

Cartilaginous fish

Fish with skeletons made primarily of cartilage.

Shark

Predatory cartilaginous fish.

Ray

Flattened cartilaginous fish.

Bony fish

Vertebrate with a skeleton reinforced by bone.