Deuterostomia Flashcards
What are the 3 phyla of Deuterostomia?
Hemichordata, Echinodermata, Chordata
Shared characteristics of Deuterostomia?
Deuterostome embryo development:
- raidial, indeterminate cleavage
- anus forms first from blastopore
- Coelom forms from outpocketing of mesoderm from archenteron
Which non-Deuterostomia undergo deuterostome development?
Brachiopoda and Ectoprota
What are the 5 characteristics of Echinoderms?
Radial symmetry in adults
Epidermis covers exoskeleton of ossicles
Unique water vascular system
Diffuse nervous system, no centralized brain
Separate sexes, broadcast spawners
What are ossicles?
calcareous plates which may have spines embedded in the dermis
the body wall can contain 1000s of ossicles
How does the water vascular system of echinoderms work?
- Derived from the coelom and consists of a ring canal in the central disk and a network of hydraulic canals running down each arm
- radial canals branch into hundreds of fluid-filled, muscular tube feet that can be adapted for locomotion, feeding, respiration etc
- tube feet are controlled by water pressure acting on the ampulla and podium allowing them to attach to substrates via suction and adhesive mucus production
- water vascular system is connected to sea water via a porous ossicle called the madreoporite
- system also used for circulation and respiration
- gas exchange occurs through gills and diffusion through feet
What is the structure of echnioderm nervous system?
A central disk with a nerve rung and radial nerves extending into the arms
How do echinoderms reproduce?
Gametes are released into the water for external fertilization
- no parental care of planktonic larvae
- in some species males free-spawn and female retains and broods eggs
What are the 5 clades of Echinodermata?
Crinoidea, Asteroidea, Ophiuroidea, Echinoidea, Holothuroidea
Asteroidea characteristics? anatomy? feeding? reproduction?
- 5 or more arms radiating from central disk
- each arm has tube feet on its undersurface to grip substrate
- predators that feed by prying open molluscs with tube feet
- evert stomach onto prey to engulf and digest food
- reproduce asexually via fission of central disk
- can regenerate lost arms
Echinoidea characteristics? Anatomy? Movement? Feeding?
- no arms, 5 rows of tube feet
- slow-moving, use spines (jointed ossicles) for locomotion and protection
- herbivorous, use jaw-like plates around mouth to grasp and grind algae
Holothuroidea characteristics? Anatomy? Symmetry? Feeding?
- tube-shaped and secondarily bilaterally symmetrical
- rows of tube feet along body
- may have tube feet around mouth as feeding tentacles
- detritivores; deposit or filter feeders
- no external spines, reduced endoskeleton with scattered osicles
What 3 groups are Chordates made of?
Vertebrata, Cephalochordata, Urochordata
Shared derived characteristics of Chordata (4)?
Notochord
Dorsal, hollow nerve cord
Pharyngeal slits
Muscular, post-anal tail
What is the notochord, how is it formed and what does it do?
Longitudinal, flexible rod located dorsally between digestive tract and nerve cord
- provides flexible skeletal support throughout the length of invertebrate chordates
- forms during embryogenesis when organ systems develop from embryonic layers
Do vertebrates have a notochord, explain?
Vertebral column replaces notochord before birth
- embryonic notochord retained as parts of the vertebral discs between vertebrae
How is the dorsal, hollow nerve cord developed?
- signalling molecules secreted by notochord and mesodermal cells induce neural plate formation from ectoderm
- neural plate curves inward forming the neural tube which develops into the CNS
- found ony in chordates, others have centrally located, hollow nerve cords
What are pharyngeal slits and what do they do?
embryonic arches in the pharynx
- in invertebrates they function as filter-feeding structures
- in aquatic vertebrates they facilitate gas exchange as gills develop along the pharyngeal arch and are ventilated when water is forced through gill slits
- allow water entering mouth to exit, preventing it from entering digestive tract
- only present during embryonic development in tetrapods
What kind of segmentation is present in Chordates and which group lacks it?
Not in Urochordata
- segmentally arranged muscle blocks in adult chordates develop from blockes of mesoderm called somites which flank the notochord
- arranged in chevron patterns
- alternating contractions of muscle blocks cause the notochord or vertebral column to flex side-side
Cephalochordata characteristics? Anatomy? Feeding? Relationships?
- blade-like body shape, resemble bony fish but are invertebrates
- sedentary suspension feeders
- wiggle backwards into sand and draw water into mouth via ciliary action
- particles extracted using mucus-covered pharyngeal slits
- mucus net and food is ingested
- water exits body through atriopore
- retain chordate body plan as adults
Urochordata characteristics? Movement? Relationships? development? anatomy? feeding? reproduction?
- more closely related to vertebrates
- larval stages have chordate body plan
- sessile suspension feeders either free-floating (pelagic) or attached to substrate
- after brief swimming phase, larvae attach to substrate by the head and metamorphose into sessile form
- adults have tough polysachharide tunic
- draw water in through incurrent siphon and filter through mucus-covered pharyngeal basket which collects food particles
- water exits through excurrent siphon
- may reproduce asexually by budding
