Biology Chapter 20
Terms
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- Analogy
- Correspondence in function or position between organs of dissimilar evolutionary origin or structure
- Binomial System
- A taxonomic name in binomial nomenclature
- Character
- structure, function, or attribute determined by a gene or group of genes
- Clade
- A group of organisms, such as a species, whose members share homologous features derived from a common ancestor
- Cladogram
- branching, treelike diagram in which the endpoints of the branches represent specific species of organisms. It is used to illustrate phylogenetic relationships and show points at which various species have diverged from common ancestral forms
- Class
- A taxonomic category ranking below a phylum or division and above an order
- Common Ancestor
- in genealogy, any person to whom two or more persons claim descent; also, the most recent ancestral form or species from which two different species evolved
- convergent evolution
- The adaptive evolution of superficially similar structures, such as the wings of birds and insects, in unrelated species subjected to similar environments.
- Family
- A taxonomic category of related organisms ranking below an order and above a genus
- Homology
- The relation of the organic compounds forming a homologous series
- Molecular Clock
- a measure of evolutionary change over time at the molecular level that is based on the theory that specific DNA sequences or the proteins they encode spontaneously mutate at constant rates and that is used chiefly for estimating how long ago two related organisms diverged from a common ancestor
- Phenetic Systematics
- based on natural evolutionary relationships
- Phyloge
- The evolutionary development and history of a species or higher taxonomic grouping of organisms
- Specific Epithet
- The uncapitalized Latin adjective or noun that follows a capitalized genus name in binomial nomenclature and serves to distinguish a species from others in the same genus
- Systematics
- The systematic classification of organisms and the evolutionary relationships among them; taxonomy
- Taxon
- A taxonomic category or group, such as a phylum, order, family, genus, or species
- Taxonomy
- The classification of organisms in an ordered system that indicates natural relationships
- archaea
- A unique group of microorganisms. They are called bacteria (Archaeobacteria) but they are genetically and metabolically different from all other known bacteria
- Bacteria
- Any of the unicellular prokaryotic microorganisms of the class Schizomycetes, which vary in terms of morphology, oxygen and nutritional requirements, and motility, and may be free-living, saprophytic, or pathogenic in plants or animals.
- Bacteriaphage
- A virus that infects and lyses certain bacteria
- Binary Fission
- A method of asexual reproduction that involves the splitting of a parent cell into two approximately equal parts.
- Capsid
- The protein shell that surrounds a virus particle
- Chemoautotroph
- An organism, such as a bacterium or protozoan, that obtains its nourishment through the oxidation of inorganic chemical compounds as opposed to photosynthesis.
- chemoorganotroph
- An organism which oxidizes chemical bonds for energy but requires organic carbon compounds to grow
- Cynobacteria
- photosynthetic bacterium of the class Coccogoneae or Hormogoneae, generally blue-green in color and in some species capable of nitrogen fixation. Cyanobacteria were once thought to be algae. Also called blue-green alga.
- Endospore
- A small asexual spore, as that formed by some bacteria
- Facultative anaerobe
- An organism, such as a bacterium, that can live in the absence as well as in the presence of atmospheric oxygen
- Fimbriae
- fringelike part or structure, as at the opening of the fallopian tubes
- Flagella
- A long, threadlike appendage, especially a whiplike extension of certain cells or unicellular organisms that functions as an organ of locomotion
- Halophile
- An organism that requires a salty environment
- Lichen
- A fungus, usually of the class Ascomycetes, that grows symbiotically with algae, resulting in a composite organism that characteristically forms a crustlike or branching growth on rocks or tree trunks
- mad cow disease
- fatal disease of cattle that affects the central nervous system; causes staggering and agitation
- Methanogen
- Any of various anaerobic methane-producing bacteria belonging to the family Methanobacteriaceae
- Nucleoid
- The part of a bacterium or virus that contains nucleic acid and is analogous in function to the nucleus of a eukaryotic cell
- Obligate anaerobe
- An organism, such as a bacterium, that can live only in the absence of oxygen
- Peptidoglycan
- A polymer found in the cell walls of prokaryotes that consists of polysaccharide and peptide chains in a strong molecular network. Also called mucopeptide, murein.
- Photoautotroph
- An organism capable of synthesizing its own food from inorganic substances using light as an energy source. Green plants and photosynthetic bacteria are photoautotrophs
- Plasmid
- A circular, double-stranded unit of DNA that replicates within a cell independently of the chromosomal DNA. Plasmids are most often found in bacteria and are used in recombinant DNA research to transfer genes between cells.
- Prion
- A microscopic protein particle similar to a virus but lacking nucleic acid, thought to be the infectious agent responsible for scrapie and certain other degenerative diseases of the nervous system.
- Prokaryote
- An organism of the kingdom Monera (or Prokaryotae), comprising the bacteria and cyanobacteria, characterized by the absence of a distinct, membrane-bound nucleus or membrane-bound organelles, and by DNA that is not organized into chromosomes. Also called moneran.
- Retrovirus
- Any of a group of viruses, many of which produce tumors, that contain RNA and reverse transcriptase, including the virus that causes AIDS.
- Symbiotic
- A close, prolonged association between two or more different organisms of different species that may, but does not necessarily, benefit each member
- Thermoacidophile
- archaebacteria that thrive in strongly acidic environments at high temperatures
- Transduction
- Transfer of genetic material or characteristics from one bacterial cell to another by the incorporation of bacterial DNA into a bacteriophage
- Transformation
-
The change undergone by an animal cell upon infection by a cancer-causing virus.
The alteration of a bacterial cell caused by the transfer of DNA from another bacterial cell, especially a pathogen - Viroid
- An infectious particle, similar to but smaller than a virus, that consists solely of a strand of RNA and is capable of causing disease in plants
- Virus
- Any of various simple submicroscopic parasites of plants, animals, and bacteria that often cause disease and that consist essentially of a core of RNA or DNA surrounded by a protein coat. Unable to replicate without a host cell, viruses are typically not considered living organisms
- Algae
- Any of various chiefly aquatic, eukaryotic, photosynthetic organisms, ranging in size from single-celled forms to the giant kelp. Algae were once considered to be plants but are now classified separately because they lack true roots, stems, leaves, and embryos.
- Amoeboid
- or resembling an amoeba, especially in changeability of form and means of locomotion
- Brown algae
- algae having the chlorophyll masked by brown and yellow pigments
- Cellular Slime mold
- Any of various primitive organisms of the phylum Acrasiomycota, especially of the genus Dictyostelium, that grow on dung and decaying vegetation and have a life cycle characterized by a slimelike amoeboid stage and a multicellular reproductive stage
- Ciliate
- Any of various protozoans of the class Ciliata, characterized by numerous cilia
- Colony
- visible growth of microorganisms, usually in a solid or semisolid nutrient medium
- Conjugation
-
The temporary union of two bacterial cells during which one cell transfers part or all of its genome to the other.
A process of sexual reproduction in which ciliate protozoans of the same species temporarily couple and exchange genetic material.
A process of sexual reproduction in certain algae and fungi in which temporary or permanent fusion occurs, resulting in the union of the male and female gametes. - Cyst
- A small capsulelike sac that encloses certain organisms in their dormant or larval stage. A thick-walled resting spore, as in certain algae or fungi
- Diatom
- Any of various microscopic one-celled or colonial algae of the class Bacillariophyceae, having cell walls of silica consisting of two interlocking symmetrical valves.
- Dinoflagellate
- Any of numerous minute, chiefly marine protozoans of the order Dinoflagellata, characteristically having two flagella and a cellulose covering and forming one of the chief constituents of plankton. They include bioluminescent forms and forms that produce red tide.
- Euglenoid
- any flagellate of the order Euglenida
- Filament
- The stalk that bears the anther in a stamen.
- Green algae
- algae that are clear green in color; often growing on wet ricks or damp wood or the surface of stagnant water
- Holozoic
- Obtaining nourishment by the ingestion of organic material, as animals do.
- Phagocytize
- To ingest by phagocytosis; phagocytose.
- Phytoplankton
- Minute, free-floating aquatic plants
- Plankton
- The collection of small or microscopic organisms, including algae and protozoans, that float or drift in great numbers in fresh or salt water, especially at or near the surface, and serve as food for fish and other larger organisms.
- Plasmodial slime mold
- slime mold of the class Myxomycetes
- Protozoan
- Any of a large group of single-celled, usually microscopic, eukaryotic organisms, such as amoebas, ciliates, flagellates, and sporozoans
- Pseudopod
- A temporary projection of the cytoplasm of certain cells, such as phagocytes, or of certain unicellular organisms, especially amoebas, that serves in locomotion and phagocytosis.
- Radiolarian
- Any of various marine protozoans of the order Radiolaria, having rigid siliceous skeletons and spicules.
- Red algae
- marine algae in which the chlorophyll is masked by a red or purplish pigment; source of agar and carrageenan
- Seaweed
-
Any of numerous marine algae, such as a kelp, rockweed, or gulfweed.
Any of various marine plants - Sporozoan
- Any of numerous parasitic protozoans of the class Sporozoa, most of which reproduce sexually and asexually in alternate generations by means of spores. They are frequently transmitted by bloodsucking insects to different hosts, where they cause many serious diseases, such as malaria and coccidiosis.
- Test
- A hard external covering, as that of certain amoebas, dinoflagellates, and sea urchins
- Trichocyst
- stinging or grasping organ in the outer cytoplasm of certain protozoans, especially ciliates, consisting of a threadlike or bristlelike filament that can be discharged suddenly from a minute capsule.
- Trypanosome
- Any of various parasitic flagellate protozoans of the genus Trypanosoma, transmitted to the vertebrate bloodstream, lymph, and spinal fluid by certain insects and often causing diseases such as sleeping sickness and nagana.
- water mold
- Any of various parasitic or saprobic fungi of the phylum Oomycota, living chiefly in fresh water or moist soil.
- zooflagellate
- A flagellated protist that ingests food and lacks chlorophyll
- zooplankton
- Plankton that consists of animals, including the corals, rotifers, sea anemones, and jellyfish
- Ascus
- A membranous, often club-shaped structure in which typically eight ascospores are formed through sexual reproduction of ascomycetes
- Basidium
- A small, specialized club-shaped structure typically bearing four basidiospores at the tips of minute projections. The basidium is unique to basidiomycetes and distinguishes them from other kinds of fungi
- Budding
- An asexual reproductive structure, as in yeast or a hydra, that consists of an outgrowth capable of developing into a new individual
- Clubfungi
- any of a family (Clavariaceae) of basidiomycetes with a simple or branched often club-shaped sporophore
- Condiospore
- an asexually produced fungal spore formed on a conidiophore
- Dikaryotic
- characterized by the presence of two nuclei in each cell
- Fruiting body
- A specialized spore-producing structure, especially of a fungus.
- Fungus
- Any of numerous eukaryotic organisms of the kingdom Fungi, which lack chlorophyll and vascular tissue and range in form from a single cell to a body mass of branched filamentous hyphae that often produce specialized fruiting bodies. The kingdom includes the yeasts, molds, smuts, and mushrooms.
- Hypha
- Any of the threadlike filaments forming the mycelium of a fungus
- Imperfect fungi
- Any of various fungi of the order Fungi Imperfecti, which reproduce only by asexual means
- Mycelium
-
The vegetative part of a fungus, consisting of a mass of branching, threadlike hyphae.
A similar mass of fibers formed by certain bacteria. - Mycorrhiza
- The symbiotic association of the mycelium of a fungus with the roots of certain plants, such as conifers, beeches, or orchids
- Nonseptate
- not divided by or having a septum
- Sac fungi
- Any of various members of a large group of fungi characterized by the presence of sexually produced spores formed within an ascus
- Septate
- Divided by a septum or septa
- Sporangium
- A single-celled or many-celled structure in which spores are produced, as in fungi, algae, mosses, and ferns. Also called spore case
- Spore
-
A small, usually single-celled reproductive body that is highly resistant to desiccation and heat and is capable of growing into a new organism, produced especially by certain bacteria, fungi, algae, and nonflowering plants.
A dormant nonreproductive body formed by certain bacteria in response to adverse environmental conditions - Yeast
- Any of various unicellular fungi of the genus Saccharomyces, especially S. cerevisiae, reproducing by budding and from ascospores and capable of fermenting carbohydrates
- Zygospore
- A large multinucleate spore formed by union of similar gametes, as in algae or fungi
- Adventitious root
- root growing in an unusual location e.g. from a stem
- Annual ring
- The layer of wood formed in a plant during a single year. Annual rings appear concentric when viewed in cross section
- Apical meristem
- meristem at the tip of a plant shoot or root that causes the shoot or root to increase in length
- Axillary bud
- A lateral bud.
- Bark
- The tough outer covering of the woody stems and roots of trees, shrubs, and other woody plants. It includes all tissues outside the vascular cambium
- Collenchyma
- A supportive tissue of plants, consisting of elongated living cells with unevenly thickened walls
- Cork
- nonliving, water-resistant protective tissue that is formed on the outside of the cork cambium in the woody stems and roots of many seed plants. Also called phellem
- Cork cambium
- A lateral ring of meristematic tissue found in woody seed plants, producing cork on the outside of the ring and parenchyma on the inside of the ring. Also called phellogen
- Cortex
- The region of tissue in a root or stem lying between the epidermis and the vascular tissue. An external layer, such as bark or rind
- Cotyledon
- leaf of the embryo of a seed plant, which upon germination either remains in the seed or emerges, enlarges, and becomes green. Also called seed leaf.
- Cuticle
- The layer of cutin covering the epidermis of the aerial parts of plants
- Endodermis
- The innermost layer of the cortex that forms a sheath around the vascular tissue of roots and some stems
- Epidermis
-
The outermost layer of cells covering the leaves and young parts of a plant.
The outer, protective, nonvascular layer of the skin of vertebrates, covering the dermis - Herbaceous stem
-
Relating to or characteristic of an herb as distinguished from a woody plant.
Green and leaflike in appearance or texture. - Internode
- section or part between two nodes, as of a nerve or stem
- Leaf
- A usually green, flattened, lateral structure attached to a stem and functioning as a principal organ of photosynthesis and transpiration in most plants
- Leaf vein
- One of the vascular bundles or ribs that form the branching framework of conducting and supporting tissues in a leaf or other expanded plant organ. Also called nervure
- Meristem
- The undifferentiated plant tissue from which new cells are formed, as that at the tip of a stem or root.
- Mesophyll
- The photosynthetic tissue of a leaf, located between the upper and lower epidermis.
- Monocot
- a monocotyledon - Any of various flowering plants, such as grasses, orchids, and lilies, having a single cotyledon in the seed.
- Node
- The point on a stem where a leaf is attached or has been attached; a joint.
- Parenchyma
- The primary tissue of higher plants, composed of thin-walled cells and forming the greater part of leaves, roots, the pulp of fruit, and the pith of stems
- Perennial
- Lasting an indefinitely long time; enduring. Appearing again and again; recurrent
- pericycle
- A plant tissue characteristic of the roots, located between the endodermis and phloem
- pith
- The soft, spongelike, central cylinder of the stems of most flowering plants, composed mainly of parenchyma
- pits
- A cavity in the wall of a plant cell where there is no secondary wall, as in fibers, tracheids, and vessels.
- primary root
- An edible or esculent root, especially of such plants as produce a single root, as the beet, carrot, etc.; as, the root crop
- rhizome
- A horizontal, usually underground stem that often sends out roots and shoots from its nodes. Also called rootstalk, rootstock.
- root cap
- A thimble-shaped mass of cells that covers and protects the root tip
- root hair
- thin hairlike outgrowth of an epidermal cell of a plant root that absorbs water and minerals from the soil.
- root system
- All the roots of a plant.
- sclerenchyma
- A supportive plant tissue that consists of thick-walled, usually lignified cells
- sieve tube member
- A series of cells joined end to end, forming a tube through which nutrients are conducted in flowering plants and brown algae.
- spongy mesophyll
- A leaf tissue consisting of loosely arranged, chloroplast-bearing, usually lobed cells. Also called spongy parenchyma
- stem
- The main ascending axis of a plant; a stalk or trunk.
- stolon
- A shoot that bends to the ground or that grows horizontally above the ground and produces roots and shoots at the nodes
- stoma
- One of the minute pores in the epidermis of a leaf or stem through which gases and water vapor pass. Also called stomate
- taproot
- The main root of a plant, usually stouter than the lateral roots and growing straight downward from the stem
- tracheid
- A cell in the xylem of vascular plants
- vascular bundle
- A strand of primary conductive plant tissue consisting essentially of xylem and phloem. Also called fibrovascular bundle
- vascular cambium
- A lateral meristem that produces secondary xylem to the inside and secondary phloem to the outside
- vascular cylinder
- A lateral meristem that produces secondary xylem to the inside and secondary phloem to the outside
- vascular tissue
- The supportive and conductive tissue in plants, consisting of xylem and phloem
- wood
- The secondary xylem of trees and shrubs, lying beneath the bark and consisting largely of cellulose and lignin.
- xylem
- The supporting and water-conducting tissue of vascular plants, consisting primarily of tracheids and vessels; woody tissue.
- Companion cell
- A specialized parenchyma cell, located in the phloem of flowering plants and closely associated in development and function with a sieve-tube element.
- Epiphyte
- A plant, such as a tropical orchid or a staghorn fern, that grows on another plant upon which it depends for mechanical support but not for nutrients. Also called aerophyte, air plant.
- Girdling
- To remove a band of bark and cambium from the circumference of (a tree), usually in order to kill it.
- Guard cell
- One of the paired epidermal cells that control the opening and closing of a stoma in plant tissue
- Guttation
- The exudation of water from leaves as a result of root pressure
- Horizons
- A period during which the influence of a specified culture spread rapidly over a defined area:
- Humus
- A brown or black organic substance consisting of partially or wholly decayed vegetable or animal matter that provides nutrients for plants and increases the ability of soil to retain water.
- Hydroponics
- Cultivation of plants in nutrient solution rather than in soil.
- Macronutrient
- An element, such as carbon, hydrogen, oxygen, or nitrogen, required in large proportion for the normal growth and development of a plant.
- Micronutrient
- A substance, such as a vitamin or mineral, that is essential in minute amounts for the proper growth and metabolism of a living organism
- Mineral
- A naturally occurring, homogeneous inorganic solid substance having a definite chemical composition and characteristic crystalline structure, color, and hardness.
- Phloem
- The food-conducting tissue of vascular plants, consisting of sieve tubes, fibers, parenchyma, and sclereids. Also called bast
- Phytoremediation
- The use of plants and trees to remove or neutralize contaminants, as in polluted soil or water
- Root pressure
- Pressure exerted in the roots of plants as the result of osmosis, causing exudation from cut stems and guttation of water from leaves.
- Soil
- The top layer of the earth's surface, consisting of rock and mineral particles mixed with organic matter
- Soil erosion
- the washing away of soil by the flow of water
- Soil profile
- a vertical section of soil from the ground surface to the parent rock
- Transpiration
- The act or process of transpiring, especially through the stomata of plant tissue or the pores of the skin.
- anther
- The pollen-bearing part of the stamen
- carpel
- One of the structural units of a pistil, representing a modified, ovule-bearing leaf
- coevolution
- The evolution of two or more interdependent species, each adapting to changes in the other. It occurs, for example, between predators and prey and between insects and the flowers that they pollinate
- double fertilization
- The union in flowering plants of two sperm nuclei. One sperm nucleus unites with the egg to form the diploid zygote, from which the embryo develops, and the other unites with two polar nuclei to form the triploid, primary endosperm nucleus.
- embryo
- The minute, rudimentary plant contained within a seed or an archegonium
- embryo sac
- The female gametophyte of a seed plant, within which the embryo develops
- endosperm
- The nutritive tissue within seeds of flowering plants, surrounding and absorbed by the embryo
- flower
- The reproductive structure of some seed-bearing plants, characteristically having either specialized male or female organs or both male and female organs, such as stamens and a pistil, enclosed in an outer envelope of petals and sepals.
- fruit
- The ripened ovary or ovaries of a seed-bearing plant, together with accessory parts, containing the seeds and occurring in a wide variety of forms.
- gametophyte
- The gamete-producing phase in a plant characterized by alternation of generations
- megaspore
- The larger of two types of spores that give rise to a female gametophyte. Also called macrospore
- megasporocyte
- A cell that undergoes meiosis to produce four megaspores.
- microspore
- The smaller of two types of spores that give rise to a male gametophyte
- microsporocyte
- A cell that undergoes meiosis to produce four microspores.
- ovary
- The ovule-bearing lower part of a pistil that ripens into a fruit.
- ovule
- minute structure in seed plants, containing the embryo sac and surrounded by the nucellus, that develops into a seed after fertilization
- petal
- One of the often brightly colored parts of a flower immediately surrounding the reproductive organs; a division of the corolla
- plumule
- The rudimentary terminal bud of a plant embryo situated at the end of the hypocotyl, consisting of the epicotyl and often of immature leaves
- pollen grain
- A microspore of seed plants, containing a male gametophyte
- pollination
- To transfer pollen from an anther to the stigma of (a flower).
- protoplast
- The living material of a plant or bacterial cell, including the protoplasm and plasma membrane after the cell wall has been removed
- seed
- a ripened plant ovule containing an embryo
- sepal
- One of the separate, usually green parts forming the calyx of a flower
- sporophyte
- The spore-producing phase in the life cycle of a plant that exhibits alternation of generations
- stamen
- The pollen-producing reproductive organ of a flower, usually consisting of a filament and an anther
- stigma
- A small mark, spot, or pore, such as the respiratory spiracle of an insect or an eyespot in certain algae
- style
- The usually slender part of a pistil, situated between the ovary and the stigma
- tissue culture
- A culture of tissue grown by this technique or process
- totipotent
- The ability of a cell, such as an egg, to give rise to unlike cells and thus to develop into or generate a new organism or part.
- Animal
- A multicellular organism of the kingdom Animalia, differing from plants in certain typical characteristics such as capacity for locomotion, nonphotosynthetic metabolism, pronounced response to stimuli, restricted growth, and fixed bodily structure
- Bilateral symmetry
- Symmetrical arrangement, as of an organism or a body part, along a central axis, so that the body is divided into equivalent right and left halves by only one plane
- Cephalization
- An evolutionary trend in the animal kingdom toward centralization of neural and sensory organs in the head or anterior region of the body.
- Cestode
- Any of various parasitic flatworms of the class Cestoda, including the tapeworms, having a long flat body equipped with a specialized organ of attachment at one end
- Cnidarian
- Any of various invertebrate animals of the phylum Cnidaria, characterized by a radially symmetrical body with a saclike internal cavity, and including the jellyfishes, hydras, sea anemones, and corals.
- Coelom
- The cavity within the body of all animals higher than the coelenterates and certain primitive worms, formed by the splitting of the embryonic mesoderm into two layers. In mammals it forms the peritoneal, pleural, and pericardial cavities. Also called body cavity.
- Comb jelly
- biradially symmetrical hermaphroditic solitary marine animals resembling jellyfishes having for locomotion eight rows of cilia arranged like teeth in a comb
- Dimorphic
- Existing or occurring in two distinct forms; exhibiting dimorphism: a dimorphic crystal; dimorphic organisms
- Elephantiasis
- Chronic, often extreme enlargement and hardening of cutaneous and subcutaneous tissue, especially of the legs and external genitals, resulting from lymphatic obstruction and usually caused by infestation of the lymph glands and vessels with a filarial worm
- Flatworm
- Any of various parasitic and nonparasitic worms of the phylum Platyhelminthes, such as a tapeworm or a planarian, characteristically having a soft, flat, bilaterally symmetrical body and no body cavity. Also called platyhelminth.
- Heartworm disease
-
filarial worm (Dirofilaria immitis) transmitted by mosquitoes and parasitic in the heart and associated blood vessels of dogs and other canids.
The condition resulting from infestation with the heartworm - Hermaphroditic
- An anomalous condition in humans and animals in which both male and female reproductive organs and secondary sexual characteristics are present in the same individual.
- Hydra
- Any of several small freshwater polyps of the genus Hydra and related genera, having a naked cylindrical body and an oral opening surrounded by tentacles.
- Invertebrate
- Lacking a backbone or spinal column; not vertebrate
- Mesoglea
- The layer of gelatinous material that separates the inner and outer cell layers of a coelenterate
- Nematocyst
- A capsule within specialized cells of certain coelenterates, such as jellyfish, containing a barbed, threadlike tube that delivers a paralyzing sting when propelled into attackers and prey. Also called stinging cell.
- Nerve net
- A diffuse network of cells that conducts impulses in all directions from the area stimulated, forming a primitive nervous system in ctenophores, coelenterates, and certain other organisms.
- Proglottid
- One of the segments of a tapeworm, containing both male and female reproductive organs
- Pseudocoelom
- An internal body cavity of some primitive invertebrates, similar to a coelom but lacking a mesodermal lining
- Radial symmetry
- Symmetrical arrangement of constituents, especially of radiating parts, about a central point
- Ribbon worm
- Any of several velvety, usually brightly colored worms of the phylum Nemertina (or Nemertea) that have a flat, unsegmented body with an extensible proboscis and live in the sea or in the mud of the intertidal zone
- Rotifer
- Any of various minute multicellular aquatic organisms of the phylum Rotifera, having at the anterior end a wheellike ring of cilia.
- Roundworm
- Any of several worms of the phylum Nematoda, having unsegmented, cylindrical bodies, often narrowing at each end, and including parasitic forms such as the hookworm and pinworm
- Schistosomiasis
- Any of various generally tropical diseases caused by infestation with schistosomes, widespread in rural areas of Africa, Asia, and Latin America through use of contaminated water, and characterized by infection and gradual destruction of the tissues of the kidneys, liver, and other organs. Also called bilharziasis, snail fever.
- Scolex
- The knoblike anterior end of a tapeworm, having suckers or hooklike parts that in the adult stage serve as organs of attachment to the host on which the tapeworm is parasitic
- Segmentation
- Division into segments
- Sessile
- Stalkless and attached directly at the base: sessile leaves
- Spicule
- A small needlelike structure or part, such as one of the silicate or calcium carbonate processes supporting the soft tissue of certain invertebrates, especially sponges
- Sponge
- Any of numerous aquatic, chiefly marine invertebrate animals of the phylum Porifera, characteristically having a porous skeleton composed of fibrous material or siliceous or calcareous spicules and often forming irregularly shaped colonies attached to an underwater surface
- Trematode
- Any of numerous flatworms of the class Trematoda, including both external and internal parasites of animal hosts, that have a thick outer cuticle and one or more suckers or hooks for attaching to host tissue
- Trichinosis
- A disease caused by eating undercooked meat, usually pork, that contains trichinae, which develop as adults in the intestines and as larvae in the muscles, causing intestinal disorders, fever, nausea, muscular pain, and edema of the face.
- Vertebrate
- Having a backbone or spinal column
- Annelid
- Any of various worms or wormlike animals of the phylum Annelida, characterized by an elongated, cylindrical, segmented body and including the earthworm and leech
- Arthropod
- Any of numerous invertebrate animals of the phylum Arthropoda, including the insects, crustaceans, arachnids, and myriapods, that are characterized by a chitinous exoskeleton and a segmented body to which jointed appendages are articulated in pairs.
- Bivalve
- A mollusk, such as an oyster or a clam, that has a shell consisting of two hinged valves
- Centipede
- Any of various wormlike arthropods of the class Chilopoda, having a flattened body composed of segments, each bearing a pair of jointed appendages. The appendages of the foremost body segment are modified into venomous biting organs with which it preys on insects, such as cockroaches.
- Cephalopod
- Any of various marine mollusks of the class Cephalopoda, such as the octopus, squid, cuttlefish, or nautilus, having a large head, large eyes, prehensile tentacles, and, in most species, an ink sac containing a dark fluid used for protection or defense
- Cephalothorax
- The anterior section of arachnids and many crustaceans, consisting of the fused head and thorax
- Chelicerate
- or relating to or resembling chelicerae Either of the first pair of fanglike appendages near the mouth of an arachnid, such as a spider, often modified for grasping and piercing
- Chitin
- A tough, protective, semitransparent substance, primarily a nitrogen-containing polysaccharide, forming the principal component of arthropod exoskeletons and the cell walls of certain fungi
- Crustacean
- Any of various predominantly aquatic arthropods of the class Crustacea, including lobsters, crabs, shrimps, and barnacles, characteristically having a segmented body, a chitinous exoskeleton, and paired, jointed limbs
- Exoskeleton
- A hard outer structure, such as the shell of an insect or crustacean, that provides protection or support for an organism
- Gastropod
- Any of various mollusks of the class Gastropoda, such as the snail, slug, cowrie, or limpet, characteristically having a single, usually coiled shell or no shell at all, a ventral muscular foot for locomotion, and eyes and feelers located on a distinct head.
- Hemocoel
- A cavity or series of spaces between the organs of most arthropods and mollusks through which the blood circulates.
- Insect
- Any of numerous usually small arthropod animals of the class Insecta, having an adult stage characterized by three pairs of legs and a body segmented into head, thorax, and abdomen and usually having two pairs of wings. Insects include the flies, crickets, mosquitoes, beetles, butterflies, and bees
- Leech
- Any of various chiefly aquatic bloodsucking or carnivorous annelid worms of the class Hirudinea, of which one species (Hirudo medicinalis) was formerly used by physicians to bleed patients and is now sometimes used as a temporary aid to circulation during surgical reattachment of a body part.
- Malpighian tube
- Any of the excretory tubules leading from the posterior portion of the alimentary canal of insects and other arthropods
- Mantle
- The cerebral cortex.
- Metamorphosis
- A change in the form and often habits of an animal during normal development after the embryonic stage. Metamorphosis includes, in insects, the transformation of a maggot into an adult fly and a caterpillar into a butterfly and, in amphibians, the changing of a tadpole into a frog
- Millipede
- Any of various crawling herbivorous myriapods of the class Diplopoda, found worldwide and having a cylindrical segmented body with two pairs of legs attached to all segments except for the first four in the thoracic region
- Mollusc
- Any of numerous chiefly marine invertebrates of the phylum Mollusca, typically having a soft unsegmented body, a mantle, and a protective calcareous shell and including the edible shellfish and the snails