Exam 3 Flashcards
Protostomes
Extremely diverse, monophyletic group in the animal phyla
Includes insects, earthworms, bees, common seafoods, etc.
Embryonic development of protostomes
Protostome = “mouth first”
Spiral cleavage
Mouth develops before anus
Two major protostome subgroups
Lophotrochozoa and ecdysozoa
Lophotrochozoa
Includes mollusca, rotifera, annelida, and platyhelminthes
Monophyletic group defined by lophophore, trochophore, spiral cleavage, and tube-like bodies
Lophophore
Specialized feeding structure that rings the mouth and functions by suspension feeding
Trochophore
Type of larva (present in some phyla) that has a ring of cilia around the middle that functions for sweeping and sometimes feeding
Development of tube-like body
Ectoderm becomes the outer tube (skin), endoderm becomes the inner tube (gut), and the mesoderm becomes muscles and organs between outer and inner tubes
Flatworms
Lophotrochozoa
Has a broad, flat body and lacks a coelom and other structures necessary for gas exchange and circulation
Includes planarians, which regenerate if cut in half
Annelids
Lophotrochozoa
Segmented worms
Include polychaeta, oligochaeta (earthworms), and hirudinea (leeches)
Mollusks
Lophotrochozoa
Highly diverse and monophyletic
Have a characteristic body defined by a foot, a visceral mass, a mantle, and usually a radula
Includes chitons, bivalves, gastropods, and cephalopods
Chitons
Dorsal shell made of plates
Foot is large and muscular; works as hydrostatic skeleton called muscular hydrostat
Bivalves
Clams and mussels
Foot is modified as a digging appendage
In clams, mantle has two siphons extending into a water column, controlling incurrent and excurrent water flow over the gills
Cephalopods
Squid and octopus
Foot is modified to form tentacles
Mantle cavity fills with water, muscle contracts, and stream of water is forced out to create a jet propulsion
Gastropods
Slugs and snails
For snails, foot works as a muscular hydrostat
Visceral mass
Region containing most of the main internal organs and the external grill
Separates the internal organs from the hydrostatic skeleton
Has a key adaptation separating it from the foot
Mantle
Outgrowth of body wall that covers visceral mass, forming enclosure cavity
Secretes a shell made of calcium carbonate
Many diverse adaptations and functions
Ecdysozoa
Includes arthropods
Defined by intermittent growth via molting
Molting
Shedding of soft cuticle or hard exoskeleton followed by fluid causing the body to expand and a larger cuticle/exoskeleton forms
Species undergo a succession of molts over time, sometimes with dramatic morphological changes
Arthropods
Defined by key body features: segmentation, exoskeleton, and jointed appendages
Includes myriapods, insects, crustaceans, and chelicerates
Segmentation
Segmented body is organized into prominant regions called tagmata
Insects are divided into head, thorax, and abdomen
Spiders and crayfish are divided into cephalothorax and abdomen
Convergent evolution of segmentation
Annelids also have body segmentation, although they are in a different lineage from arthropods
Exoskeleton
Made primarily of chitin, strengthened by calcium carbonate in crustaceans
Jointed appendages
Enable the rigid body to move
Myriapods
Arthropods
Millipedes and centipedes
Have long, segmented trunks
Insects
Arthropods
Three tagmata, unbranched appendages, and one pair of antennae
Crustaceans
Arthropods
Two to three tagmata, branched appendages, and two pairs of antennae
Chelicerates
Arthropods
Spiders and scorpions
Two tagmata
Deuterostomes
Large and complex animals, mostly vertebrates
Meaning “second mouth” because the anus develops before the mouth in embryonic stages
Includes echinoderms and chordates
Echinoderms
Includes sea stars, sea urchins, and other marine animals
Monophyletic, contains three main synapomorphies: radial symmetry, endoskeleton, and water vascular system
Endoskeleton
Hard protective and supportive structure
Formed by secretion of calcium carbonate inside the skin; in some species plates fuse together and in others plates stay flexible
Water vascular system
Series of branching, fluid-filled tubes and chambers that form a hydrostatic skeleton
Controls tube feet: elongated, fluid-filled appendages with an ampulla inside the body and tube-like podium projecting on outside
Radial symmetry
Most species are bilaterally symmetrical as larvae and later develop pentaradial symmetry (see diagram)
Chordates
Include vertebrates, urochordates, and cephalochordates
Synapomorphies include pharyngeal gill slits, dorsal hollow nerve cord, notochord, and muscular post-anal tail
Cephalochordates
Include lancets and amphioxus
Small, mobile suspension feeders that resemble fish, burrow in sand, and have no eyes or jaw
Have a dorsal hollow nerve cord that runs parallel to notochord
Notochord stiffens body and results in muscular contractions and movement
Urochordates
Includes tunicates
Both larvae and adults have pharyngeal gill slits for feeding and gas exchange
Notochord, dorsal hollow nerve cord, and tail only occur in larvae or sexually mature forms of motile species
Vertebrates
Includes hagfish, lampreys, sharks, rays, bony fish, amphibians, mammals, reptiles, and birds
Dorsal hollow nerve cord becomes the spinal cord
Pharyngeal pouches and notochord present in embryos but not once born
Synapomorphies: vertebrae and cranium
Vertebrae
