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Questions and Answers
What are the two major groups of polychaetes?
What are the two major groups of polychaetes?
What is the defining characteristic of the class Polychaeta?
What is the defining characteristic of the class Polychaeta?
Many setae
Polychaete fertilize eggs internally.
Polychaete fertilize eggs internally.
False
The larva of sipunculans develops to form ______ larva.
The larva of sipunculans develops to form ______ larva.
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Match the following species with their classification groups:
Match the following species with their classification groups:
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What is the common name for Echiurus echiurus?
What is the common name for Echiurus echiurus?
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Which of the following is a defining characteristic of Subclass Oligochaeta?
Which of the following is a defining characteristic of Subclass Oligochaeta?
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Leeches fertilize eggs internally.
Leeches fertilize eggs internally.
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The anterior part of the body of peanut worms forms an eversible and fully retractable ________ with the mouth at the end.
The anterior part of the body of peanut worms forms an eversible and fully retractable ________ with the mouth at the end.
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Match the following features with their corresponding annelid class:
Match the following features with their corresponding annelid class:
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What is the process called when arthropods shed their existing exoskeleton?
What is the process called when arthropods shed their existing exoskeleton?
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Which molecule evolved from hemocyanin and is required in the formation of exoskeleton among crustaceans?
Which molecule evolved from hemocyanin and is required in the formation of exoskeleton among crustaceans?
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In arthropods, the circulatory system is closed with blood leaving the heart through closed vessels.
In arthropods, the circulatory system is closed with blood leaving the heart through closed vessels.
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Y-organ, located in the head of crustaceans, produces ______ hormones.
Y-organ, located in the head of crustaceans, produces ______ hormones.
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Match the following arthropod visual system components with their descriptions:
Match the following arthropod visual system components with their descriptions:
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What is the function of chelicerae in chelicerates?
What is the function of chelicerae in chelicerates?
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Which pair of appendages in chelicerates is responsible for grabbing, killing, reproducing, and sensory functions?
Which pair of appendages in chelicerates is responsible for grabbing, killing, reproducing, and sensory functions?
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In spiders, the prosoma and opisthosoma are never fused.
In spiders, the prosoma and opisthosoma are never fused.
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Respiration in chelicerates is through internalized book gills and ____________ called spiracles.
Respiration in chelicerates is through internalized book gills and ____________ called spiracles.
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Match the chelicerate species with the diseases they transmit:
Match the chelicerate species with the diseases they transmit:
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What are the defining characteristics of Class Insecta?
What are the defining characteristics of Class Insecta?
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What is the primary end product of insect metabolism?
What is the primary end product of insect metabolism?
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Insect flight requires lift and drag.
Insect flight requires lift and drag.
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Insect body is divided into 3 tagmata: head, thorax, and ___.
Insect body is divided into 3 tagmata: head, thorax, and ___.
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Match the following representative species with their corresponding classification type:
Match the following representative species with their corresponding classification type:
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Which of the following are arthropod-like characteristics of onychophorans?
Which of the following are arthropod-like characteristics of onychophorans?
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Nematodes have a closed circulatory system of discrete blood vessels.
Nematodes have a closed circulatory system of discrete blood vessels.
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Nematodes move by ________ waves.
Nematodes move by ________ waves.
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Match the following representative species with their phylum:
Match the following representative species with their phylum:
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What is the resting state of crustaceans like copepods and branchiopods?
What is the resting state of crustaceans like copepods and branchiopods?
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What is the unique feature of the head and thorax in insects?
What is the unique feature of the head and thorax in insects?
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Insects and myriapods have 2 pairs of antennae.
Insects and myriapods have 2 pairs of antennae.
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Arachnid species and snapping shrimp have ______ pairs of antennae.
Arachnid species and snapping shrimp have ______ pairs of antennae.
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Match the following orders with their representative species:
Match the following orders with their representative species:
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What are pheromones?
What are pheromones?
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Why are amphids and phasmids important in nematodes?
Why are amphids and phasmids important in nematodes?
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How many fertilized eggs does a single female Ascaris release per day?
How many fertilized eggs does a single female Ascaris release per day?
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Match the parasitic nematodes with their representative species:
Match the parasitic nematodes with their representative species:
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Nematodes lack free-swimming larval stages. True or False?
Nematodes lack free-swimming larval stages. True or False?
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What are the defining characteristics of Caligus curtus?
What are the defining characteristics of Caligus curtus?
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Which class includes species that are exclusively sedentary organisms with a greatly reduced head?
Which class includes species that are exclusively sedentary organisms with a greatly reduced head?
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In Class Insecta, digestion and absorption primarily occur in the hindgut.
In Class Insecta, digestion and absorption primarily occur in the hindgut.
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The larval stages of Balanus sp. are known as __________.
The larval stages of Balanus sp. are known as __________.
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Match the order of arachnids with their corresponding species:
Match the order of arachnids with their corresponding species:
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Study Notes
Phylum Annelida
- Defining characteristics:
- One or more pairs of chitinous setae
- Polychaetes can be divided into 2 general groups: Errantia (errant species) and Sedentaria
- General Annelid Characteristics:
- All adult annelids except sipunculans possess at least one pair of chitinous setae
- All are vermiform (worm-shaped) and longer than they are wide
- Soft-bodies, circular in cross-section
- Exhibit metameric segmentation or metamerism
- Thin body wall can serve as a surface for gas exchange
- Septa - thin sheets of mesodermally derived tissue (peritoneum)
- Excretion occurs through nephridia (little kidneys)
- Coelomic fluid is drawn into nephridium at the nephrostome
- Function of nephridium: regulate water content of coelomic fluid, outlet for metabolic waste products, and discharge gametes and urine
Polychaeta
- Defining characteristics:
- Paired lateral outfoldings of the body wall (parapodia)
- 65% of annelids are polychaetes; nearly all live in saltwater
- Have at least one pair of eyes and at least one pair of sensory appendages (tentacles) on the anterior-most part of the body
- Parapodia are outgrowths of the body wall that function in gas exchange and locomotion
- Setae - calcareous bristles protruding from each parapodium
- Reproduction:
- Exclusively sexual; most are gonochoristic
- Gametes are produced by peritoneal tissue
- At least 6 adjacent segments are involved in gamete production
- Some polychaetes undergo epitoky - morphological preparation for reproductive activity
Echiurans
- Defining characteristics:
- Muscular organs (anal sacs) outpocketing from the rectum into the coelomic space, bearing numerous funnels that discharge coelomic fluid (and wastes) through the anus
- Segmentation confined to small rear portion of animal (opisthosoma)
- Anteriormost region of body bears cephalic lobe or "beard"
- Trunk contains uninterrupted coelomic cavities and major organs within trunk: gonads and trophosome
- Representative species:
- Urechis caupo
- Bonellia viridis
Sipunculans
- Defining characteristics:
- Anterior part of body forms an eversible and fully retractable introvert, with the mouth at its end
- Multicellular bodies (urns) in the coelomic fluid, specialized for accumulating particulate wastes
- Anterior tentacles connected to a series of muscular sacs (compensatory sacs) that pump fluid into the tentacles and store fluid when the tentacles retract
- Representative species:
- Sipunculus nudus
- Phascolosoma gouldi
Clitellata
- Defining characteristics:
- Pronounced cylindrical glandular region of the body (clitellum) that plays important roles in reproduction
- Permanent gonads
- Hermaphroditic
- Representative species:
- Lumbricus terrestris (common earthworm)
- Tubifex (sludge-worms)
Leeches (Hirudinea)
- Defining characteristic:
- Posterior sucker
- Representative species:
- Hirudo medicinalis (medicinal leech)
- Limnatis sp. (common carabao leech)### Regulation of Reproductive Cycle
- Regulation of reproductive cycle, body fluid osmotic concentration, migration of light-screening pigments in the eye, and movement of pigment granules within chromatophore cells leading to gradual changes in body color
- Tagmatization: specialization of groups of segments for highly specialized functions
Nerves and Muscles
- In vertebrates, each muscle fiber is innervated by a single neuron
- Strength of muscle contraction depends on the number of fibers contracting; number of fibers contracting depends on the number of axons fired
- In arthropod muscle, strength of contraction depends on the rate at which nerve impulses are delivered to the fibers
- Single muscle fiber may be innervated by 5 types of neurons
- Arthropod neuron may innervate a large number of muscle fibers
Exoskeleton
- Differences in exoskeleton between arthropods and molluscs:
- Molluscan shell functions to protect soft parts within
- In arthropods, exoskeleton functions as a locomotory skeleton
- Components of arthropod exoskeleton:
- Epicuticle: waxy outermost layer, composed of firm lipoprotein layer and lipid layers, water-impermeable, and thin
- Procuticle: bulk of exoskeleton, composed of polysaccharide chitin
- Sclerotization: tanning of procuticle's protein component
The Hemocoel
- Coelom in arthropod is greatly reduced
- Hemocoel: main body cavity
- Cryptocyanin: molecule that evolved from hemocyanin, required in formation of exoskeleton among crustaceans
Molting
- Ecdysis: process of removing existing exoskeleton
- New cuticle is secreted before old one is shed
- Soft-bodied crabs rely on internal blood pressure in the hemocoel to maintain locomotory function
- Biomass: growth of tissue, continuous process
Circulatory System
- Blood leaves heart through closed vessels and enters heart directly from the hemocoel through perforations called ostia
- Circulatory system is open
- One of the diagnostic features of arthropoda: heart with ostia
Arthropod Visual System
- Ocellus: small cup with light-sensitive surface backed by light-absorbing pigment
- Compound eyes:
- Can form images
- Common in insects and crustaceans; may be present in addition to ocelli
- Differences from human camera-type eye:
- Many lenses
- Focus of each lens cannot be varied
- Fewer receptor cells to sample the image, which is upright rather than inverted
- Ommatidium consists of:
- Fixed-focus lens (cornea)
- Underlying gelatinous crystalline cone
- Series of cylindrical bodies (photoreceptors) containing light-sensitive pigment
- Neural cartridge: cluster of neurons receiving information carried by photoreceptors and sending action potentials to optic ganglia### Myriapoda
- Defining characteristics:
- Many species conserve water by being nocturnal
- Chilopod head bears a single pair of antennae, pair of mandibles, and pair of first and second maxillae
- Unique proboscis at the anterior end with an opening at its tip
- Body characteristics:
- Not divided into distinct regions (tagmata)
- Head followed by 15 or more leg-bearing segments; first pair is called maxillipeds
- Some have repugnatorial glands on the ventral surface of each trunk segment
- Locomotion:
- Slow-moving
- Some produce silk; some burrow in soil (reduced legs and used properties of hydrostatic skeleton)
- Representative species:
- Scutigera coleoptrata
- Scolopendra gigantea
- Hydroschendyla submarina
Diplopoda
- Defining characteristics:
- Pair of segments fused; each segment (diplosegment) bears 2 pairs of legs, and 2 pairs of spiracles and ventral ganglia
- Body characteristics:
- Primarily slow-moving deposit feeders; some carnivorous
- In some millipedes, integument is impregnated with calcium salts, as in crustaceans; thus covering is more protective than centipedes
- Locomotion:
- Cuticle not waxy
- Representative species:
- Scutigerella sp.
- Symphella sp.
- Acladocricus sp.
Hexapoda
- Defining characteristics:
- Possess both uniramous and biramous appendages
- Includes 3 major groups: Myriapoda, Insecta, and Crustacea
- Body characteristics:
- Six-legged arthropods
- Most are insects; wingless hexapods (Entognatha); silverfish
- Respiratory system:
- Gas exchange surfaces are internalized; achieved by means of a tracheal system
Insecta
- Defining characteristics:
- Fusion of one pair of head appendages (the second maxillae) to form a lower lip (the labium)
- Loss of abdominal appendages
- Body characteristics:
- Most species are terrestrial; nearly one million species have been described
- Halobates – ocean striders; live in the surface waters of the open ocean
- Flight:
- Features that make flight possible:
- Abundance of striated muscle
- Muscle antagonism by means of lightweight, jointed skeleton
- Small body size
- Water-impermeable outer body covering, preventing dehydration
- Efficient systems for gas exchange, nutrient storage, and distribution of nutrients to the musculature
- Highly developed nervous and sensory systems for steering, navigating, and sensing wind direction
- Features that make flight possible:
Crustacea
- Defining characteristics:
- Head bears five pairs of appendages, including two pairs of antennae
- Development includes a triangular larval form (the nauplius) bearing three pairs of appendages and a single medial eye
- Body characteristics:
- 6 major classes
- Representative species:
- Campodea staphylinus
- Drosophila melanogaster
- Manduca sexta
- Aedes aegypti
- Ephemera varia
- Bellura sp.
Malacostraca
- Defining characteristics:
- Thorax with eight segments, abdomen with six to seven segments plus a telson
- Appendages on the sixth abdominal segment are flattened to form uropods
- Body characteristics:
- 60% of crustaceans; decapods, euphausiids, stomatopods, isopods, amphipods
- Malacostracan body is tripartite, consisting of a head, thorax, and abdomen
- Representative species:
- Shrimp-like; large; bottom dwelling; violent carnivores
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Description
Learn about the characteristics of Phylum Annelida, including their muscles, setae, and general features. This quiz covers the defining traits of Annelids and their subgroups.
