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diploblast : animal that develops from two germ layers | https://openstax.org/books/biology/pages/27-key-terms |
Ecdysozoa : clade of protostomes that exhibit exoskeletal molting (ecdysis) | https://openstax.org/books/biology/pages/27-key-terms |
Ediacaran period : geological period (630â542 million years ago) when the oldest definite multicellular organisms with tissues evolved | https://openstax.org/books/biology/pages/27-key-terms |
enterocoely : mesoderm of deuterostomes develops as pouches that are pinched off from endodermal tissue, cavity contained within the pouches becomes coelom | https://openstax.org/books/biology/pages/27-key-terms |
eucoelomate : animal with a body cavity completely lined with mesodermal tissue | https://openstax.org/books/biology/pages/27-key-terms |
Eumetazoa : group of animals with true differentiated tissues | https://openstax.org/books/biology/pages/27-key-terms |
gastrula : stage of animal development characterized by the formation of the digestive cavity | https://openstax.org/books/biology/pages/27-key-terms |
germ layer : collection of cells formed during embryogenesis that will give rise to future body tissues, more pronounced in vertebrate embryogenesis | https://openstax.org/books/biology/pages/27-key-terms |
Hox gene : (also, homeobox gene) master control gene that can turn on or off large numbers of other genes during embryogenesis | https://openstax.org/books/biology/pages/27-key-terms |
indeterminate cleavage : early stage of development when germ cells or âstem cellsâ are not yet pre-determined to develop into specific cell types | https://openstax.org/books/biology/pages/27-key-terms |
Lophotrochozoa : clade of protostomes that exhibit a trochophore larvae stage or a lophophore feeding structure | https://openstax.org/books/biology/pages/27-key-terms |
mass extinction : event that wipes out the majority of species within a relatively short geological time period | https://openstax.org/books/biology/pages/27-key-terms |
Metazoa : group containing all animals | https://openstax.org/books/biology/pages/27-key-terms |
organogenesis : formation of organs in animal embryogenesis | https://openstax.org/books/biology/pages/27-key-terms |
Parazoa : group of animals without true differentiated tissues | https://openstax.org/books/biology/pages/27-key-terms |
protostome : blastopore develops into the mouth of protostomes, with the second opening developing into the anus | https://openstax.org/books/biology/pages/27-key-terms |
pseudocoelomate : animal with a body cavity located between the mesoderm and endoderm | https://openstax.org/books/biology/pages/27-key-terms |
radial cleavage : cleavage axes are parallel or perpendicular to the polar axis, resulting in the alignment of cells between the two poles | https://openstax.org/books/biology/pages/27-key-terms |
radial symmetry : type of symmetry with multiple planes of symmetry, with body parts (rays) arranged around a central disk | https://openstax.org/books/biology/pages/27-key-terms |
schizocoely : during development of protostomes, a solid mass of mesoderm splits apart and forms the hollow opening of the coelom | https://openstax.org/books/biology/pages/27-key-terms |
spiral cleavage : cells of one pole of the embryo are rotated or misaligned with respect to the cells of the opposite pole | https://openstax.org/books/biology/pages/27-key-terms |
triploblast : animal that develops from three germ layers | https://openstax.org/books/biology/pages/27-key-terms |
Animals included in phylum Porifera are Parazoans because they do not show the formation of true tissues (except in class Hexactinellida). These organisms show very simple organization, with a rudimentary endoskeleton. Sponges have multiple cell types that are geared toward executing various metabolic functions. Althou... | https://openstax.org/books/biology/pages/28-chapter-summary |
Cnidarians represent a more complex level of organization than Porifera. They possess outer and inner tissue layers that sandwich a noncellular mesoglea. Cnidarians possess a well-formed digestive system and carry out extracellular digestion. The cnidocyte is a specialized cell for delivering toxins to prey as well as ... | https://openstax.org/books/biology/pages/28-chapter-summary |
Phylum Annelida includes vermiform, segmented animals. Segmentation is seen in internal anatomy as well, which is called metamerism. Annelids are protostomes. These animals have well-developed neuronal and digestive systems. Some species bear a specialized band of segments known as a clitellum. Annelids show the presen... | https://openstax.org/books/biology/pages/28-chapter-summary |
Flatworms are acoelomate, triploblastic animals. They lack circulatory and respiratory systems, and have a rudimentary excretory system. This digestive system is incomplete in most species. There are four traditional classes of flatworms, the largely free-living turbellarians, the ectoparasitic monogeneans, and the end... | https://openstax.org/books/biology/pages/28-chapter-summary |
The rotifers are microscopic, multicellular, mostly aquatic organisms that are currently under taxonomic revision. The group is characterized by the rotating, ciliated, wheel-like structure, the corona, on their head. The mastax or jawed pharynx is another structure unique to this group of organisms. | https://openstax.org/books/biology/pages/28-chapter-summary |
The nemertini are the simplest eucoelomates. These ribbon-shaped animals bear a specialized proboscis enclosed within a rhynchocoel. The development of a closed circulatory system derived from the coelom is a significant difference seen in this species compared to other pseudocoelomate phyla. Alimentary, nervous, and e... | https://openstax.org/books/biology/pages/28-chapter-summary |
Phylum Mollusca is a large, marine group of invertebrates. Mollusks show a variety of morphological variations within the phylum. This phylum is also distinct in that some members exhibit a calcareous shell as an external means of protection. Some mollusks have evolved a reduced shell. Mollusks are protostomes. The dor... | https://openstax.org/books/biology/pages/28-chapter-summary |
Nematodes are pseudocoelomate animals akin to flatworms, yet display more advanced neuronal development, a complete digestive system, and a body cavity. This phylum includes free-living as well as parasitic organisms likeCaenorhabditis elegansandAscarisspp., respectively. They include dioeceous as well as hermaphroditi... | https://openstax.org/books/biology/pages/28-chapter-summary |
Arthropods represent the most successful phylum of animal on Earth, in terms of the number of species as well as the number of individuals. These animals are characterized by a segmented body as well as the presence of jointed appendages. In the basic body plan, a pair of appendages is present per body segment. Within ... | https://openstax.org/books/biology/pages/28-chapter-summary |
Echinoderms are deuterostomic marine organisms. This phylum of animals bears a calcareous endoskeleton composed of ossicles. These animals also have spiny skin. Echinoderms possess water-based circulatory systems. A pore termed the madreporite is the point of entry and exit for water into the water vascular system. Osm... | https://openstax.org/books/biology/pages/28-chapter-summary |
The characteristic features of Chordata are a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail. Chordata contains two clades of invertebrates: Urochordata (tunicates) and Cephalochordata (lancelets), together with the vertebrates in Vertebrata. Most tunicates live on the ocean floor and are... | https://openstax.org/books/biology/pages/28-chapter-summary |
amoebocyte : sponge cell with multiple functions, including nutrient delivery, egg formation, sperm delivery, and cell differentiation | https://openstax.org/books/biology/pages/28-key-terms |
Annelida : phylum of vermiform animals with metamerism | https://openstax.org/books/biology/pages/28-key-terms |
archenteron : primitive gut cavity within the gastrula that opens outwards via the blastopore | https://openstax.org/books/biology/pages/28-key-terms |
Arthropoda : phylum of animals with jointed appendages | https://openstax.org/books/biology/pages/28-key-terms |
biramous : referring to two branches per appendage | https://openstax.org/books/biology/pages/28-key-terms |
captacula : tentacle-like projection that is present in tusks shells to catch prey | https://openstax.org/books/biology/pages/28-key-terms |
cephalothorax : fused head and thorax in some species | https://openstax.org/books/biology/pages/28-key-terms |
chelicera : modified first pair of appendages in subphylum Chelicerata | https://openstax.org/books/biology/pages/28-key-terms |
choanocyte : (also, collar cell) sponge cell that functions to generate a water current and to trap and ingest food particles via phagocytosis | https://openstax.org/books/biology/pages/28-key-terms |
Chordata : phylum of animals distinguished by their possession of a notochord, a dorsal, hollow nerve cord, pharyngeal slits, and a post-anal tail at some point in their development | https://openstax.org/books/biology/pages/28-key-terms |
clitellum : specialized band of fused segments, which aids in reproduction | https://openstax.org/books/biology/pages/28-key-terms |
Cnidaria : phylum of animals that are diploblastic and have radial symmetry | https://openstax.org/books/biology/pages/28-key-terms |
cnidocyte : specialized stinging cell found in Cnidaria | https://openstax.org/books/biology/pages/28-key-terms |
conispiral : shell shape coiled around a horizontal axis | https://openstax.org/books/biology/pages/28-key-terms |
corona : wheel-like structure on the anterior portion of the rotifer that contains cilia and moves food and water toward the mouth | https://openstax.org/books/biology/pages/28-key-terms |
ctenidium : specialized gill structure in mollusks | https://openstax.org/books/biology/pages/28-key-terms |
cuticle (animal) : the tough, external layer possessed by members of the invertebrate class Ecdysozoa that is periodically molted and replaced | https://openstax.org/books/biology/pages/28-key-terms |
cypris : larval stage in the early development of crustaceans | https://openstax.org/books/biology/pages/28-key-terms |
Echinodermata : phylum of deuterostomes with spiny skin; exclusively marine organisms | https://openstax.org/books/biology/pages/28-key-terms |
enterocoelom : coelom formed by fusion of coelomic pouches budded from the endodermal lining of the archenteron | https://openstax.org/books/biology/pages/28-key-terms |
epidermis : outer layer (from ectoderm) that lines the outside of the animal | https://openstax.org/books/biology/pages/28-key-terms |
extracellular digestion : food is taken into the gastrovascular cavity, enzymes are secreted into the cavity, and the cells lining the cavity absorb nutrients | https://openstax.org/books/biology/pages/28-key-terms |
gastrodermis : inner layer (from endoderm) that lines the digestive cavity | https://openstax.org/books/biology/pages/28-key-terms |
gastrovascular cavity : opening that serves as both a mouth and an anus, which is termed an incomplete digestive system | https://openstax.org/books/biology/pages/28-key-terms |
gemmule : structure produced by asexual reproduction in freshwater sponges where the morphology is inverted | https://openstax.org/books/biology/pages/28-key-terms |
hemocoel : internal body cavity seen in arthropods | https://openstax.org/books/biology/pages/28-key-terms |
hermaphrodite : referring to an animal where both male and female gonads are present in the same individual | https://openstax.org/books/biology/pages/28-key-terms |
invertebrata : (also, invertebrates) category of animals that do not possess a cranium or vertebral column | https://openstax.org/books/biology/pages/28-key-terms |
madreporite : pore for regulating entry and exit of water into the water vascular system | https://openstax.org/books/biology/pages/28-key-terms |
mantle : (also, pallium) specialized epidermis that encloses all visceral organs and secretes shells | https://openstax.org/books/biology/pages/28-key-terms |
mastax : jawed pharynx unique to the rotifers | https://openstax.org/books/biology/pages/28-key-terms |
medusa : free-floating cnidarian body plan with mouth on underside and tentacles hanging down from a bell | https://openstax.org/books/biology/pages/28-key-terms |
mesoglea : non-living, gel-like matrix present between ectoderm and endoderm in cnidarians | https://openstax.org/books/biology/pages/28-key-terms |
mesohyl : collagen-like gel containing suspended cells that perform various functions in the sponge | https://openstax.org/books/biology/pages/28-key-terms |
metamerism : series of body structures that are similar internally and externally, such as segments | https://openstax.org/books/biology/pages/28-key-terms |
Mollusca : phylum of protostomes with soft bodies and no segmentation | https://openstax.org/books/biology/pages/28-key-terms |
nacre : calcareous secretion produced by bivalves to line the inner side of shells as well as to coat intruding particulate matter | https://openstax.org/books/biology/pages/28-key-terms |
nauplius : larval stage in the early development of crustaceans | https://openstax.org/books/biology/pages/28-key-terms |
nematocyst : harpoon-like organelle within cnidocyte with pointed projectile and poison to stun and entangle prey | https://openstax.org/books/biology/pages/28-key-terms |
Nematoda : phylum of worm-like animals that are triploblastic, pseudocoelomates that can be free-living or parasitic | https://openstax.org/books/biology/pages/28-key-terms |
Nemertea : phylum of dorsoventrally flattened protostomes known as ribbon worms | https://openstax.org/books/biology/pages/28-key-terms |
osculum : large opening in the spongeâs body through which water leaves | https://openstax.org/books/biology/pages/28-key-terms |
ostium : pore present on the spongeâs body through which water enters | https://openstax.org/books/biology/pages/28-key-terms |
oviger : additional pair of appendages present on some arthropods between the chelicerae and pedipalps | https://openstax.org/books/biology/pages/28-key-terms |
parapodium : fleshy, flat, appendage that protrudes in pairs from each segment of polychaetes | https://openstax.org/books/biology/pages/28-key-terms |
pedipalp : second pair of appendages in Chelicerata | https://openstax.org/books/biology/pages/28-key-terms |
pilidium : larval form found in some nemertine species | https://openstax.org/books/biology/pages/28-key-terms |
pinacocyte : epithelial-like cell that forms the outermost layer of sponges and encloses a jelly-like substance called mesohyl | https://openstax.org/books/biology/pages/28-key-terms |
planospiral : shell shape coiled around a vertical axis | https://openstax.org/books/biology/pages/28-key-terms |
planuliform : larval form found in phylum Nemertea | https://openstax.org/books/biology/pages/28-key-terms |
polymorphic : possessing multiple body plans within the lifecycle of a group of organisms | https://openstax.org/books/biology/pages/28-key-terms |
polyp : stalk-like sessile life form of a cnidarians with mouth and tentacles facing upward, usually sessile but may be able to glide along surface | https://openstax.org/books/biology/pages/28-key-terms |
Porifera : phylum of animals with no true tissues, but a porous body with rudimentary endoskeleton | https://openstax.org/books/biology/pages/28-key-terms |
radula : tongue-like organ with chitinous ornamentation | https://openstax.org/books/biology/pages/28-key-terms |
rhynchocoel : cavity present above the mouth that houses the proboscis | https://openstax.org/books/biology/pages/28-key-terms |
schizocoelom : coelom formed by groups of cells that split from the endodermal layer | https://openstax.org/books/biology/pages/28-key-terms |
sclerocyte : cell that secretes silica spicules into the mesohyl | https://openstax.org/books/biology/pages/28-key-terms |
seta/chaeta : chitinous projection from the cuticle | https://openstax.org/books/biology/pages/28-key-terms |
siphonophore : tubular structure that serves as an inlet for water into the mantle cavity | https://openstax.org/books/biology/pages/28-key-terms |
spicule : structure made of silica or calcium carbonate that provides structural support for sponges | https://openstax.org/books/biology/pages/28-key-terms |
spongocoel : central cavity within the body of some sponges | https://openstax.org/books/biology/pages/28-key-terms |
trochophore : first of the two larval stages in mollusks | https://openstax.org/books/biology/pages/28-key-terms |
uniramous : referring to one branch per appendage | https://openstax.org/books/biology/pages/28-key-terms |
veliger : second of the two larval stages in mollusks | https://openstax.org/books/biology/pages/28-key-terms |
water vascular system : system in echinoderms where water is the circulatory fluid | https://openstax.org/books/biology/pages/28-key-terms |
zoea : larval stage in the early development of crustaceans | https://openstax.org/books/biology/pages/28-key-terms |
The characteristic features of Chordata are a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail. Chordata contains two clades of invertebrates: Urochordata (tunicates) and Cephalochordata (lancelets), together with the vertebrates in Vertebrata. Most tunicates live on the ocean floor and are... | https://openstax.org/books/biology/pages/29-chapter-summary |
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