Chapter 33: An Introduction to Invertebrates
Head of Planarian
Light-sensitive eyespots, lateral flaps to detect specific chemicals
Parapodia
Paddlelike appendages that assist aquatic annelids in locomotion. Each parapodium has numerous chaetae. In some species, they function as gills and may have many blood vessels.
Chelicerae
Pair of mouthparts in chelicerates that contain fangs and are used to stab and paralyze prey. Functions as pincers or fangs.
Trematodes
Parasites (such as blood flukes) have complex, alternating life cycles. Usually they have to infect a preliminary host where larvae grow before infecting the final host.
Trichinella spiralis
Parasitic nematode occurring in the intestines of pigs, rats, and humans, producing larvae that form cysts in skeletal muscles
Acanthocephala
Parasitic worms with a spiny proboscis for host attachment. Some can manipulate intermediate host behavior for transmission to final host.
Acoela
Refers to acoel flatworms that have a simple nervous system and a saclike gut. Not included in Platyhelminthes.
Ophiuroidea
Refers to brittle stars and basket stars, which have a distinct central disk and long, flexible arms. They move by lashing their arms in serpentine motions and lack the flattened disk found at the base of seastars.
Polyplacophora
Refers to chitons
Nematodes
Refers to roundworms like pinworms, Trichinella worms, and Ascaris worms. They have a fine tip at the posterior end and a blunt tip at the anterior end. They also have a tough cuticle that is shed periodically in accordance with growth. Though they do have an alimentary canal, they do not have a circulatory system. They are pseudocoelomates, free-living, and are known for their parasitism.
Crinoidea
Refers to sea lilies and feather stars. They use their long, flexible arms for suspension feeding and these arms encircle the mouth that faces upward away from the substrate.
Annelida
Refers to segmented worms that are coelomates. Divided into Polychaeta, Oligochaeta, and Hirudinea.
Pseudocoelomates with alimentary canal (digestive tube with mouth and anus); jaws (trophi); head with ciliated crown
Rotifera (rotifers)
Sixth mass extinction
Scientists have predicted/identified a new mass extinction is underway and an estimated 2-25 percent of species will go extinct; it is caused by humans
What groups are included in Medusozoa?
Scyphozoans, cubozoans, and hydrozoans
Cnidocytes
Special stinging structures on cnidarians that look like small harpoons and aid in defense and prey capture.
Why are hosts often oblivious to leech incisions?
They secrete an anesthetic
Like gastropods, how do earthworms expel waste?
Through the metanephridia, which are excretory tubules
Hemiptera
True bugs that are hemimetabolous and include stink bugs, bed bugs, and assassin bugs. They have two pairs of wings (one membranous, the other leathery), piercing/sucking mouthparts, and undergo incomplete metamorphosis (ENA).
Diptera
True flies, mosquitoes, gnats, midges. Has one pair of wings, halteres for balance, mouthparts for sucking, piercing, or lapping, and compound eyes.
What Dipterans are known for carrying disease? Name two.
Tsetse flies may carry African Sleeping Sickness (Trypanosoma) and mosquitoes may carry Malaria (Plasmodium vivax)
Leeches
Sedentarians that typically inhabit freshwater (though can be found in other habitats). Some are predators of other invertebrates, while still others are parasitic and obtain blood from a host by temporarily attaching themselves.
Leeches and earthworms are types of
Sedentarians, a type of Annelid
Centipedes
Segmented bodies, 1 pair of legs per segment, predators with a pair of venomous claws
What are the two variations to cnidarian body plans?
Sessile polyp and more motile medusa
Ammonites
Shelled cephalopod animals that were the dominant invertebrate predators for millions of years ending with the mass extinctions at the end of the Cretaceous period.
Cone snails
Shoot harpoon-like radula (laden with toxin) at prey (special Gastropod adaptation)
Zygentoma
Silverfish that are small and wingless with a flattened body and reduced eyes.
Nematocysts
Small capsules that contain a toxin which is injected into the prey or predators of cnidarians
Lancelets
Small, blade-like chordates that live in marine sands
How do Cnidarians respond to stimuli?
They have a nerve net - conducts nerve impulse to and from all parts of their body. They have no circulatory, respiratory or excretory systems.
Siphon
Tubelike structure through which water enters and leaves a mollusc's body. Water enters a bivalve's mantle cavity through an incurrent siphon and exits through an excurrent siphon.
Describe the predation habits of cephalopods
Use tentacles to grasp prey, have beak-like jaws to bite and transmit venom into prey
Pharynx in planarians
Used to spill digestive juices on to prey so that small pieces of food can be transferred to the gastrovascular cavity for further digestion
Priapula
Worms with a large, rounded proboscis at the anterior end; named after the Greek god of fertility, Priapos (who had a large, well... you get the idea)
-Unique stinging structures (nematocysts) housed in specialized cells (cnidocytes) -diploblastic -radially symmetrical - gastrovascular cavity (digestive compartment with a single opening)
Cnidaria (jellies, hydras, sea anemones, corals)
Corals
Cnidaria, Anthozoa - often secretes a hard exoskeleton of calcium carbonate, reefs are being destroyed by pollution, overharvesting, global warming, and ocean acidification
Sea Anemones
Cnidarians; have tentacles and a nerve net; live as sessile polyps - type of Anthozoan
Name six orders of winged insects
Coleoptera, Diptera, Hymenoptera, Lepidoptera, Hemiptera, Orthoptera
Which of the six previous insects undergo complete metamorphosis?
Coleoptera, Diptera, Hymenoptera, and Lepidoptera
Choanocytes
Collar cells that line the body cavity and have flagella that circulate water in sponges - engulfs food particles by phagocytosis
What developmental patterns do brachiopods and ectoprocts both have?
Deuterostomes
Ectoprocta
Ectoprocts (bryozoans) live as sessile colonies and are covered by a tough exoskeleton.
The gastrodermis of cnidarians is derived from
Endoderm
In Porifera, the outer layer consisting of tightly packed epidermal cells
Epidermis
What two clades are Annelids divided into?
Errantia and Sedentaria
Bivalves
Molluscs that have two shells held together by hinges and strong adductor muscles. No distinct head and no radula, some have eyes and sensory tentacles along the outer edge of their mantle.
Rotifera
Multicellular with specialized organs enclosed in pseudocoelom, complete digestive tract (alimentary canal); filter-feeder.
Tube feet
Extensions of an echinoderm's water vascular system that stick out from the body and function in movement and obtaining food.
Describe the head of Gastropods
Eyes are at the tip of tentacles
Compound eyes
Eyes made of many individual light detectors, each with its own lens
Mantle cavities of bivalves have what functions?
Feeding and gas exchange
What are the six major types of Lophotrochozoans?
Flatworms, rotifers, ectoprocts, brachiopods, molluscs, and annelids
Spongin
Flexible material that make up the skeleton of some sponges.
Spongocoel
Found in sponges, it is the central cavity into which water is drawn to filter nutrients
Molluscs are the animal group with the most documented extinctions. What two groups are at the greatest risk?
Freshwater bivalves and terrestrial gastropods
Ventral nerve cords
From the ganglia, a pair of ventral nerve cords runs the length of the body.
Tracheal tubes
Gas exchange in insects is accomplished by a branched, chitin-based trancheal system that carries oxygen directly to cells. Opens to the outside of the body via spiracles, which open and close to control air flow and water loss.
Decapods
Group of crustaceans that includes crabs and lobsters. The cuticle is reinforced, forming a dorsal shield on the cephalothorax called the carapace. The cuticle is hardened by calcium carbonate.
What threats do freshwater and terrestrial molluscs face?
Habitat loss, pollution, competition or predation by non-native species introduced by humans
Trophi
Hard, jaw-like elements within the mastax of rotifers
Ampulla
In echinoderms, the muscular sac that contracts to force water into the tube foot, allowing it to extend
Gonads
Ovaries and testes
What are the three main subgroups of crustaceans?
Isopods, decapods, and copepods
What is the purpose of the gastrovascular cavity of Cnidarians in contraction?
It acts as a hydrostatic skeleton in which contractile cells of the epidermis and gastrodermis can work.
Scyphozoans
Jellies
Describe the gills of terrestrial snails
Lack typical gills that compare to aquatic snails. Lining of the mantle cavity functions as a lung to exchange respiratory gases with the air.
What is another name for brachiopods?
Lampshells
Bdelloid rotifers
Large and ancient group that appears to have been completely asexual (parthenogenic) for a long time
Describe the shell in cephalopods
Largely reduced and internal, only chambered nautiluses have the exoskeletal shells
Mastax
The muscular pharynx in rotifers
Mollusca
(Snails, clams, squids, octopuses) have a soft bodies that in many species are protected by a hard shell
Describe the process by which trematodes infect their final host.
1. Mature flukes live in the blood vessels of the human intestine. 2. A female fluke will fit into a groove on the male's body and sexual reproduction will occur in the human host. The fertilized eggs exit the host in feces. 3. The feces enter a water source where the eggs develop into ciliates larvae, which will infect snails, the intermediate host. 4. Asexual reproduction occurs within the snail and the new motile larva exits the intermediate host. 5. Larvae penetrates the skin and blood vessels of humans working in fields irrigated with water contaminated with fluke larvae.
Cephalopods
A member of a group of molluscs that include squids and octopi. Only molluscs that have a closed circulatory system. They have well-developed sense organs and a complex brain.
Echinoderms
A member of a group of slow moving or sessile marine animals characterized by a rough or spiny skin, a water vascular system, a hard calcareous endoskeleton, and a radial symmetry in adults (larvae have bilateral symmetry), with examples such as sea stars, sea urchins and sand dollars
Chaeta
A chitinous projection from the cuticle found in annelids. Polychaeta have far more projections per segment than do Oligochaeta.
What life stage do some molluscs have that marine annelids and some other lophotrochzoans also have?
A ciliated larval stage, called the trochophore
Closed circulatory system
A circulatory system in which the oxygen-carrying blood cells never leave the blood vessels. Hence, the blood is distinct from the fluid in the body cavity.
Closed circulatory system
A circulatory system in which the oxygen-carrying blood cells never leave the blood vessels. The blood remains separate from the fluid in the body cavity.
Hydrozoans
A class of Cnidaria where most of the organisms alternate between polyp and medusa except hydras, which are only polyp. They can reproduce both asexually and sexually.
Lophophore
A crown of ciliated tentacles that function in feeding
Mantle
A fold of tissue that drapes over the visceral mass and secretes a shell (usually). In many molluscs, the mantle extends beyond the visceral mass, producing a water-filled chamber.
Planarians
A free-living flatworm found in unpolluted ponds and streams that can be predators or scavengers. They move by using cilia on their ventral surface and gliding along the mucus they secrete. Some swim using an undulating motion.
Mesohyl
A gelatinous region between the two layers of cells of a sponge
Pearl mussels
A group of freshwater bivalves that can make natural pearls, among the world's most endangered animals.
Arthropods
A group of organisms that are coelomates and have jointed appendages, a segmented body, an exoskeleton, bilateral symmetry, and reproduce sexually; insects, arachnids, millipedes and cenitpedes, and crustaceans. Thought to have arisen from Lobopods from the Cambrian explosion, which had body segments that were not diversified. Changes to existing Hox genes are hypothesized to have led to body segment diversity in modern species.
Arthropods
A group of organisms that have jointed appendages, a segmented exoskeleton, bilateral symmetry, and reproduce sexually; insects, arachnids, millipedes and cenitpedes, and crustaceans
Osculum
A large opening on a sponge through which filtered water is expelled
Chelicerates
A lineage of arthropods that includes horseshoe crabs, scorpions, ticks, and spiders. They have chelicerae for feeding, have an anterior cephalothorax, a posterior abdomen, simple eyes, and lack antennae.
Arachnids
A member of a major arthropod group that includes spiders, scorpions, ticks, and mites. They all have six pairs of appendages including the chelicerae for feeding, pedipalps, and four pairs of walking legs.
Gastropods
A mollusc with a single shell or no shell. Refers to snails and slugs.
Foot
A muscular organ that is used for locomotion and takes a variety of forms depending on the animal (trait of molluscs)
Water vascular system
A network of hydraulic canals unique to echinoderms that branches into extensions called tube feet, which function in locomotion, feeding, and gas exchange
Sea daisies
A new species found in 1986, small disk shaped animals with no arms. Tube feet are around the edges. Only three species are known.
Tapeworms
A parasitic flatworm characterized by the absence of a digestive tract (no gastrovascular cavity or mouth, absorbs nutrients from the host's intestine)
Madreporite
A perforated plate by which the entry and exit of seawater into and out of the vascular system of an echinoderm is controlled.
Lorica
A pocket formed by six plates surrounding the abdomen from which the head, neck, and thorax of a Loriciferan can project
Ectoprocts
A sessile, colonial lophophorate; also called a bryozoan. They superficially resemble clumps of moss. Often, the colony is encased in a hard exoskeleton studded with pores fro, which lophophores extend.
Molluscs
A soft-bodied animal characterized by a muscular foot, mantle, mantle cavity, and radula; includes gastropods (snails and slugs), bivalves (clams, oysters, and scallops), and cephalopods (squids and octopuses). Many species secrete a hard protective shell made of calcium carbonate.
Radial canal
A structure in echinoderms that runs the length of the arm, is part of the water vascular system
Tunicates
A subphylum of Chordata that includes about 3000 species of filter-feeding marine animals, such as sea squirts and salps. They are sessile marine chordates that lack a backbone.
Millipedes
A terrestrial arthropod that has two pairs of short legs for each of its numerous body segments and that eats decaying plant matter.
Myriapods
A terrestrial arthropod with many body segments and one or two pairs of legs per segment. Millipedes and centipedes comprise the two classes of living myriapods. Have antennae and three pairs of appendages modified as mouthparts, including the mandibles.
Cuticle
A tough external coat that ecdysozoans excrete as they grow by ecdysis
Mantle cavity
A water-filled chamber that houses the gills, anus, and excretory pores of a mollusc.
Hemichordata
Acorn worms (enteropneusts) and pterobranchs. They have gill slits and a dorsal nerve chord, members of the deuterostome clade.
Cells that can transport phagocytized nutrients to other cells of the sponge body, produce materials for skeletal fibers (spicules), or differentiate into any sponge cell needed
Amoebocytes
Metanephridium
An excretory organ found in many invertebrates that typically consists of tubules connecting ciliated internal openings to external openings. Removes wastes from the hemolymph.
Malpighian tubules
An excretory organ that is unique to insects, empties into digestive tract and removes nitrogenous wastes from the hemolymph, also plays a role in osmoregulation.
Eurypterids
An extinct carnivorous cheliceriform also called a water scorpion.
Radula
An organ covered with teeth that molluscs use to scrape food into their mouths
Porifera
Animal phylum that includes sponges, which are sessile and lack true tissues. They are filter-feeders, meaning that they trap particles that pass through the internal channels of their bodies.
Placozoa
Animalia phylum with only one species: Trichoplax adhaerens. They are thought to be basal and they consist of a simple bilayer of a few thousand cells.
Flatworms (Phylum Platyhelminthes)
Animals in this group exhibit bilateral symmetry and moderate cephalization (a head). They include planaria (nonparasitic), as well as flukes and tapeworms (Both parasitic). They are triploblastic and aceolomates
Loricifera
Animals only 0.1-0.4 mm in length; can move its head, neck, and thorax out of its lorica (pocket formed by six plates surrounding the abdomen)
Invertebrates
Animals that lack a backbone
Coelomates with segmented body wall and internal organs (except unsegmented digestive tract)
Annelida (segmented worms)
Cibrostatin
Antibiotic produced by sponges which holds promise due to its ability to kill penicillin resistant strains of streptococcus and some cancer cells.
Crustaceans
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. Only Arthropods with two pairs of antennae. Have appendages on their abdomen.
Visceral mass
Area beneath the mantle of a mollusc that contains the internal organs
Coelomates with segmented body, jointed appendages, and exoskeleton made of protein and chitin
Arthropoda (spiders, centipedes, crustaceans, insects)
Describe the circulatory system of Arthropods
Arthropods have an open circulatory system in which hemolymph is propelled by a heart through short anterior and then into spaces called sinuses surrounding the tissue and organs. Hemolymph reenters the heart through pores that are usually equipped with valves.
Insects
Arthropods with three body sections, six legs, one pair of antenna, and usually one or two pairs of wings that emerge from the dorsal side of the thorax (extensions of the cuticle)
How do lophophores function?
As the cilia draw water toward the mouth, the tentacles trap suspended food particles
Parthenogenesis
Asexual reproduction in which females produce offspring from unfertilized eggs.
What are the five clades of Echinoderms?
Asteroidea, Ophiuroidea, Echinoidea, Crinoidea, and Holothuroidea
Sponges are near the root of the phylogenetic tree for animals, so they are called
Basal animals
Describe the circulatory system in cephalopods
Closed circulatory system, only mollusc group with this quality
Brachiopoda
Brachiopods (lamp shells) that are often confused with Mollusca. The difference lies in the fact that brachiopods have a unique stalk for anchorage to the substrate and a crown of cilia (lophophore).
Archaeognatha
Bristletails (wingless, monocondylic).
How is the shell of Gastropods produced?
By the glands of the mantle
Cnidae
Capsule-like organelles that are contained in cnidocytes that can explode outward
What are the two clades of flatworms?
Catenulida and Rhaditophora
Totipotent
Cells that are able to develop into any type of cell found in the body. Helpful to sponges which must be able to adjust to an ever-changing environment.
Amoebocytes
Cells that move using pseudopods and digest food particles from choanocytes as well as carry nutrients to other cells. They also manufacture tough skeletal fibers within the mesohyl and are totipotent.
Describe the nervous system of insects.
Cerebral ganglion where the two nerve cords meet at the head. The antennae, eyes, and other sense organs are concentrated on the head.
Catenulida
Chain worms that reproduce asexually by budding at their posterior end
What are the three major lineages of Arthropods?
Chelicerates, myriapods, and pancrustaceans
Flagellated cells that line the spongocoel and create a current that draws in water through the pores and out through the osculum
Choanocytes
What two types of cells does Porifera have?
Choanocytes and amoebocytes
Coelomates with notochord; dorsal, hollow nerve cord; pharyngeal slits; post-anal tail
Chordata (vertebrates, lancelets, tunicates)
Eumetazoa
Clade of animals with true tissues
Medusozoa
Clade of cnidarians that produces a medusa
Lophotrochozoa
Clade of protostomes that exhibit a trochophore larvae stage or a lophophore feeding structure. Most diverse clade in terms of body plan. Includes flatworms, rotifers, ectoprocts, brachiopods, molluscs, and annelids.
Sedentarians
Clade that contains leeches and earthworms. Usually less mobile than errantians
Chitons
Class Polyplacophora. Has an oval-shaped body and a shell composed of eight dorsal plates (body is unsegmented, however)
Earthworms
Class Sedentaria of Annelida that have an alimentary canal and are hermaphrodites that do also cross-fertilize. Sexual reproduction occurs when earthworms align themselves in opposite directions to exchange sperm and asexual reproduction may occur by fragmentation and then regeneration. They also have cerebral ganglia and a closed circulatory system.
Anthozoans
Class of Cnidaria that occurs only as polyps, including coral and sea anemones.
Cubozoans
Class of Cnidaria with a box-shaped medusa stage and complex eyes. Often equipped with toxic cnidocytes. "Box-jellies" - an example would be sea wasps, which have a poison that is more deadly than cobra venom
Holothuroidea
Class of echinoderms including the sea cucumbers that lack spines, have reduced exoskeletons, are elongated at their oral-aboral axis, and five rows of tube feet.
Asteroidea
Class of echinoderms that includes sea stars and sea daisies. They have arms radiating from a central disk; have tube feet under their arms that can attach to substrate, enable locomotion, and grasp prey; can begin digestion externally; and can regenerated lost limbs.
How does digestion occur in planarians?
Completed within the cells lining the gastrovascular cavity, which has many fine subbranches to maximize surface area. Undigested wastes are ejected through an opening at the tip of the pharynx.
Describe the life cycle of hydrozoan Obelia (Similar in most other Cnidarians)
Consists of two stages, one that is asexual and another that is sexual. 1. Budding, a form of asexual reproduction, produces a colony of interconnected polyps. 2. The polyps are specialized for different purposes. Some have tentacles for feeding, while others lack tentacles and produce medusae by budding. 3. Medusae swim off, grow, and then reproduce sexually by meiosis and fertilization. 4. The zygote then develops into a solid ciliates larva called a planula. The planula will eventually settle and develop into a new polyp. The process can then restart.
What conditions may promote sexual reproduction in rotifers?
Crowding that produces dormant embryos
What do Echinoderms and Chordates have in common?
Deuterostome mode of development, such as radial cleavage and formation of the anus from the blastopore
Gastrovascular cavity
Digestive chamber with a single opening, in which cnidarians, flatworms, and echinoderms digest food
Alimentary canal
Digestive tube that extends from the mouth to the anus
Cnidarians have two layers of cells (ectoderm and endoderm) so they must be
Diploblastic
Trochophore larva
Distinctive larval stage observed in some lophotrochozoan animals, including some annelids and molluscs.
Hermaphrodites
Each individual functions as both male and female in sexual reproduction by producing both sperm and eggs. Porifera reproduce by a sequential male releasing sperm, which then joins with the egg in another sponge that is functioning as a female. The flagellated larvae then swims to a suitable substrate for its sessile adult development.
Pedipalps
Each of the second pair of appendages attached to the cephalothorax of most arachnids. They are variously specialized as pincers in scorpions, sensory organs in spiders, and locomotory organs in horseshoe crabs. Function for sensing, feeding, defense, or reproduction.
Coelomates with bilaterally symmetrical larvae and five-part body organization as adults; unique water vascular system; endoskeleton
Echinodermata (sea stars, sea urchins)
What are the two groups in Deuterostomia?
Echinoderms and Chordates - grouped together based on DNA similarities
The epidermis of cnidarians is derived from
Ectoderm
Triploblastic
Has three germ layers: the ectoderm, endoderm, and mesoderm.
Schistosomiasis
Helminth infection acquired from contact with water containing infected snails. (Blood flukes)
What groups belong to Deuterostomia?
Hemichordata, Chordata, and Echinodermata
What two orders of insects undergo incomplete metamorphosis?
Hemiptera and Orthoptera
Halteres
Highly modified wings used for balance rather than flight. Usually are club- shaped structures; found on the metathorax of true flies (Diptera).
Cnidarians have a variety of sessile and motile forms including what three groups?
Hydras, corals, and jellies
Lophophore
In some lophotrochozoan animals, including brachiopods, a crown of ciliated tentacles that surround the mouth and function in feeding.
Where are the gonads located in molluscs?
In the visceral mass
Hymenoptera
Includes ants, bees, and wasps. Social insects with two pairs of membranous wings, a mobile head, and chewing/sucking mouthparts. Some females have posterior stinging organs and still others in this order build elaborate nests.
Lepidoptera
Includes butterflies and moths, which have a long feeding proboscis.
Ctenophora
Includes comb jellies, which are diploblastic and radially symmetric. They have eight "combs" of cilia that propel the animal through the water and make up much of the ocean's plankton. Contact with comb jellies often spurs specialized cells to break open and cover the prey in sticky threads.
Cnidaria
Includes corals, jellies, and hydras. They are diploblastic, radially symmetric, and have a gastrovascular cavity with a single opening that serves as the mouth and anus.
Lophophorates
Includes ectoprocts and brochiopods; all have a crown of cilia that helps in absorbing water and trapping suspended food particles (lophophores); have a U-shaped alimentary canal and no distinct head; have a true coelom and are sessile
Orthoptera
Includes grasshoppers, crickets, and katydids. Mostly herbivorous, have hind legs adapted for jumping, two pairs of wings (one leathery, one membranous), and biting/chewing mouthparts.
Echinoidea
Includes sea urchins and sand dollars, which have no arms, five rows of tube feet for slow movement, and muscles that pivot their long spines for locomotion and protection (urchins).
Hemimetabolous
Incomplete metamorphosis where the immature resemble the adults but some features are missing or different (wings, reproductive organs, color, shape, etc.).
What is the evolutionary advantage of lacking a body cavity and being relatively flat for flatworms?
Increases surface area to volume ratio. By placing all their cells close to water in the surrounding environment or their gut, gas exchange and the elimination of waste can occur by diffusion across the body surface.
Complete metamorphosis
Insect development consisting of four stages: egg, larva, pupa, and adult
Incomplete metamorphosis
Insect development consisting of three stages: egg, nymph, and adult (ENA). Nymphs resemble the adults but have different body proportions and lack wings. Each molting results in a nymph that looks increasingly like the adult. The final molt is where the insect reaches full size, acquires wings, and becomes sexually mature.
Pancrustaceans
Lobsters and other crustaceans, as well as insects and their relatives
Coelomates with lophophores (feeding structures bearing ciliated tentacles)
Lophophorates (Ectoprocta and Brachiopoda)
What are the three groups of Bilateria?
Lophotrochozoa, Ecdysozoa, and Deuterostomia
What groups belong to Ecdysozoa?
Loricifera, Onychophora, Nematoda, Tardigrada, and Arthropoda
Ganglia
Masses of nerve cell bodies at the anterior end of flatworms used for sensory input.
Coelomates with three main body parts (muscular foot, visceral mass, mantle); coelom reduced; most have a hard shell made of calcium carbonate
Mollusca (squids, snails, clams)
What are the two divergent clades of Cnidaria?
Medusozoans and Anthozoans
Bilateria
Members of the branch of eumetazoans possessing bilateral symmetry and have triploblastic development. Most have a digestive tract with two openings (a mouth and an anus) and a coelom
Bilateria
Members of the branch of eumetazoans possessing bilateral symmetry. Includes Lophotrochozoa, Ecdysozoa, and Deuterostomia
The bilayer of a sponge is separated by this gelatinous matrix
Mesohyl
Copepods
Minute shrimp-like crustaceans; often they are the most common zooplankton in estuarine waters. Some are grazers, while others are predators. A surprising example would be barnacles.
Errantians
Mobile, mostly marine organisms that have parapodia on each body segment
Planarian Nervous System
More complex and centralized than the nerve nets of cnidarians
Rhabditophora
More diverse and include both free-living and parasitic species of flatworms
Medusa
Motile stage of the life cycle of a cnidarian that has a bell-shaped body. Free-swimming and resembles a flattened, mouth-down version of the polyp.
Describe the sensory system of Arthropods
Much more complex, yet focused at the anterior end with eyes, olfactory receptors, and antennae
Cylindrical pseudocoelomates with tapered ends; no circulatory system; undergo ecdysis
Nematoda (roundworms)
Mollusc nervous system
Nerve ring around the esophagus, from which nerve cords extend
Protonephridia
Networks of tubules with ciliated structures called flame bulbs that pull fluid through branched ducts opening to the outside
Mandibles
One of a pair of jaw-like feeding appendages found in myriapods, hexapods, and crustaceans.
Isopods
One of the largest groups of crustaceans, primarily aquatic, but including pill bugs common under logs and moist vegetation next to the ground.
Proglottids
One of the segments of a tapeworm, sacs containing both male and female reproductive organs. After sexual reproduction, these sacs are released via the posterior end of the tapeworm and later in the feces of the host.
Mollusc hearts
Open circulatory system that has a dorsal heart that pumps hemolymph (circulatory fluid) through arteries into sinuses (body cavities), continuously bathing organs in hemolymph
What type of circulatory system do insects have?
Open circulatory system where the heart drives the hemolymph through the system.
Spiracles
Openings in the exoskeleton of arthropods, such as the grasshopper, that connect to internal cavities called hemocoels where respiratory gases are exchanged
Coleoptera
Order of beetles that have two pairs of wings (one is stiff, the other is membranous), an armored exoskeleton, and mouthparts for biting and chewing
Filter feeders
Organism that takes in water to filter out the food and then releases the extra water (clam, oysters, sponge)
Book lungs
Organs of gas exchange in spiders, consisting of stacked plates contained in an internal chamber.
Why can't Polychaeta, Oligochaeta, and Hirudinea (leeches) be characterized as such?
Phylogenomic studies have indicated that oligochaetes are a subgroup of polychaetes and that leeches are a subgroup of oligochaetes
Platyhelminthes
Phylum of flatworms, including tapeworms, planarians, and flukes. They have bilateral symmetry and a central nervous system that processes information from sensory structures. They have no body cavity (acoelomates) or specialized organs for circulation.
Onychophora
Phylum of velvet worms that originated in the Cambrian explosion. They formerly inhabited the ocean, but now they are found only in humid forests. They have fleshy antennae and several dozen pairs of saclike legs.
Tardigrada
Phylum of water bears that can survive dormant in conditions less than -200 degrees Celsius. They have a rounded shape, stubby appendages, and a lumbering, bearlike gait.
How do planarians reproduce?
Planarians are hermaphrodites and can reproduce sexually, or asexually through fission
Dorsoventrally flattened acoelomates; gastrovascular cavity or no digestive tract
Platyhelminthes (flatworms)
What groups belong to Lophotrochozoa?
Platyhelminthes, Ectoprocta, Rotifera, Brachiopoda, Acanthocephala, Nemertea, Cycliophora, Annelida, and Mollusca
What are the four major clades of Molluscs?
Polyplacophora (chitons), Gastropoda (snails and slugs), Bivalvia (clams, oysters, and other bivalves), and Cephalopoda (squids, octopuses, cuttlefishes, and chambered nautiluses)
Areas on a sponge through which water enters that are formed by doughnut-shaped cells that span the body wall
Pores
Informally called "sponges"
Porifera
Lack true tissues; have choanocytes (flagellated collar cells for ingesting food)
Porifera (sponges)
Podium
Portion of the tube foot that expands and contacts substrate when the ampulla forces water in. Attachment to substrate occurs when the podium secretes adhesive chemicals and detach with de-adhesive chemicals and forcing water back into the ampulla to make the tube foot contract.
Free-living Rhabditophorans
Predators and scavengers in a wide range of aquatic habitats that are well-known for containing species of the genus Dugesia, or planarians.
Nemertea
Proboscis worms or ribbon worms; lack a true coelom but they have an alimentary canal and a closed circulatory system
Molting
Process in which an arthropod sheds its exoskeleton and manufactures a larger one to take its place. Also known as ecdysis.
What is the purpose of the shell of Gastropods?
Protecting the animal's soft body from injury and dehydration, protecting against predation
Echinodermata
Radially symmetrical marine invertebrates including e.g. starfish and sea urchins and sea cucumbers. They are deuterostomes and are bilaterally symmetrical as larvae but not adults. They use internal canals that pump water for locomotion and feeding.
Water passing through pores enter this cavity
Spongocoel
Brachiopods
Superficially resemble clams and other hinge-shelled molluscs, but the two halves of the shell are dorsal and ventral rather than lateral as in clams. All are marine and attach themselves to substrata by use of a stalk.
Ecdysozoa
Supergroup of protostomes; characterized by periodic molting of their exoskeleton. Includes the roundworms (nematodes) and arthropods.
What type of feeder are bivalves?
Suspension or filter feeders
Scolex
The anterior end (head) of a tapeworm, bearing suckers and hooks for attachment to the intestinal lining of the host.
Hirudin
The anticoagulant secreted by leeches into the wound they create to prevent clotting
Central disk
The central portion of a starfish. The arms of a starfish radiate from the central disk as well as a nerve ring and nerve cords.
What covers the body of an arthropod? What is this structure made of?
The cuticle, which is made of layers of protein and the polysaccharide chitin
Describe locomotion in cephalopods
The foot has been modified into an excurrent siphon. Squids dart around by drawing water into their mantle cavity and ejecting it through the excurrent siphon. They steer by pointing the siphon in different directions.
Mesoglea
The jellylike substance that separates the epithelial cells in a cnidarian
Proboscis
The long snout of an animal; a nose, especially a prominent one; a tubular organ
Cycliophora
The most recently named phylum; its only known member is Symbion pandora, a tiny invertebrate first identified in 1995 when a Danish biologist found specimens on the mouthparts of a Norwegian lobster. It is believed to be closely related to the marine phyla Entoprocta and Ectoprocta (Bryozoa), which are not discussed here. They have a bizarre life cycle in which males impregnate females while they are still developing in their mother's bodies. The females then escape to another part of the lobster and release the offspring, which will find a new lobster to restart this process.
Nematoda
The phylum of roundworms found in aquatic habitats, wet soil, moist tissues of plants, and body fluids of animals. They are parasitic and have a tough cuticle that coats their bodies.
Chordata
The phylum of the animal kingdom that includes vertebrates and two basal groups of invertebrates (lancelets and tunicates). They are bilaterally symmetrical, coelomates, and have segmented bodies.
Chordata
The phylum of the animal kingdom that includes vertebrates. The three groups of invertebrates in this phylum, however, are lancelets, tunicates, and hagfishes.
Annelida
The phylum to which segmented worms belong.
Hemocoel
The primary body cavity of most invertebrates, containing circulatory fluid. Name for the hemolymph-filled body sinuses.
Polyp
The sessile, tubular form of a cnidarian with a mouth and tentacles at one end and a basal disk at the other. The aboral (end opposite the mouth) end adheres to the substrate and they extend tentacles, waiting for prey. Examples include hydras and sea anemones.
Describe the body plan of molluscs.
They are coelomates and they have a foot, a visceral mass, and a mantle.
Rotifers
Tiny animals that inhabit fresh water, the ocean, and damp soil. They do not have a gastrovascular cavity and they instead have an alimentary canal. They are pseudocoelomates and they have a crown of cilia for drawing water into the mouth. Trophi at the back of the mouth enable rotifers to grind up food.
Parasitic Rhabditophorans
Trematodes and tapeworms, which live in or on other animals. Many have suckers or tough coverings.
