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68 Cards in this Set
- Front
- Back
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What does echinodermata mean?
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Spiny skin- endoskeleton of dermal ossicles with projecting spines
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How big is the phylum echinodermata?
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Not particularly large (in terms of number of species)- about 6000 species (small)
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Why do we study echinoderms?
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They are very important ecologically and evolutionarily; abundant in marine ecosystems
humans are more closely related to echinoderms that to any other invertebrate group, based on RNA analysis |
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What type of symmetry do adult echinoderms have?
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Radial symmetry
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What type of symmetry do larval echinoderms have?
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Bilateral symmetry
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What does radial symmetry in adult form tell us about echinoderms?
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This tells us that the radial symmetry is secondarily derived, meaning that it is an advanced feature. not a primitive feature.
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What is secondary radial symmetry?
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It is evolved from bilateral ancestor, but evolved back to radial symmetry.
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How well developed is cephalization in echinoderms?
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Cephalization is reduced or absent in this group
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How well developed is the echinoderm's nervous system?
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Nervous system is decentralized- no "brain"
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What do echinoderms feed on?
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Small organic particles or algae, or small prey. Some, however, (sea stars & sea urchins) are efficient predators despite the lack of a central nervous system & cephalization.
Most are active, mobile animals |
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What organ system is unique to the echinoderms?
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Water vascular system with tube feet for locomotion
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What are the functions of the water vascular system?
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Respiratory, locomotion, excretory
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The water flow of the echinoderm's water vascular system..
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Madreporite --> internal system of canals --> ampulla and tube feet
(stone canal --> ring canal --> radial canal --> lateral canal --> ampulla --> tube foot |
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What is the function of the relatively large eucoelom?
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circulation, respiration, and excretion
fluid is circulated by cilia on the peritoneum lining the eucoelom |
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Also note large true coelom- Excretion and gas exchange via....?
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Papulae and tube feet which project out between ossicles.
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Exoskeleton Dermal ossicles are...
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- little bony plates under skin, joined by connective tissue
- some project outward as spines |
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What is pedicillariae?
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- small pincers extending from skin.
- clean skin of debris, project papulae, may aid in food capture in some. - only applies to sea stars and urchins. |
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Does osmoregulation occur in echinoderms?
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No, they are restricted to marine ecosystems and do not occur in the brackish waters of estuaries or freshwater.
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What is the reproduction of an echinoderm?
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Mostly dioecious, automy is common, can regenerate complete organism with one arm and 1/5th of oral disc!
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What class includes the sea stars (starfish)?
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Class Asteroidea
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How do sea stars (Asteroidea) feed?
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They are Predators: feed on crustaceans, polychaetes, small fish, and other sea stars.
-Eversible stomach: insert cardiac stomach into open bivalve to digest and absorb soft parts |
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What are sea stars tube feet often used for in this group?
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-locomotion and gripping bivalve shells so that the shells can be pulled open
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What class includes the sea urchins?
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Class Echinoidea
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What are the major body modification in Class Echinoidea?
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- oral surfaces has expanded around to the aboral side.
- fused dermal ossicles form a rigid test with long, movable spines, tube feet, and pedicellariae. |
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What is the diet of sea urchins?
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- They are grazers: feed on algae, detritus, or small particles of food, although some feed on larger prey such as abalone.
- complex 5-part jaw structure called Aristotle's Lantern |
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The red sea urchin is one of the longest living creatures on earth, with some living more than ____?
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200 years!
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What is in Class Echinoidea, but a different animal from sea urchin?
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Sand dollars
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Sand dollars have very small....
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spines used to burrow just below the sand.
- fused dermal ossicles form a rigid test, with tube feet, and pedicellariae. - organic particles settle on aboral surface, and cilia move them down to mouth. |
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Sometimes a sand dollar chews its food for...
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-fifteen minutes before swallowing. It can take two days for the food to digest.
-scientists can age a sand dollar by counting the growth rings n the plates of the exoskeleton. Sand dollars usually live six to 10 years. |
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What is the largest class of echinoderms, and what is the common name of organisms in this group?
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Class Ophiuroidea (brittle stars and basket stars)
-abundant in oceans, often covering sea bottom |
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What do brittle stars and basket stars feed on and how do they do it?
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They are detritivores: they feed on decaying matter and plankton via moveable jaws.
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How do brittle stars differ from sea stars?
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- locomotion by movable arms (tube feet are not involved)
- no intestine or anus (incomplete digestive system) - no pedicellariae or papullae - automy and regeneration even better developed than in sea stars- they lose arms easily and grow them back readily. |
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What class includes the sea cucumbers?
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Holothuroidea
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How does Holothuroidea differ from other echinoderms?
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-they are greatly elongated on the oral aboral axis.
-ossicles reduced so body is relatively soft, use a hydrostatic skeleton. -arrangement of tube feet modified for crawling |
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How do the sea cucumbers feed?
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They feed by picking up food or trapping food on tentacles and stuffing them into mouth one by one.
- to defend themselves, they expel parts of viscera which are sticky may contain toxins - or they can "throw up" their digestive system! |
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What class includes the mos ancient and primitive echinoderms, those with a plant-like body?
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- Crinoidea (sea lilies and feather stars)
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What is the difference between a sea lily and a feather star?
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- both start out attached to the substrate via a stalk, and continue much of life sessile, adult feather stars detach and can swim.
- arms are tentacle-like with leathery skin and small branches and mucus for trapping and eating suspended phytoplankton. |
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Why did radial symmetry first evolve in Class Crinoidea?
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- Probably an adaptation for filter-feeding
- radial symmetry was then retained by other members of this phylum which now obtain food in different ways (sea stars, sea cucumbers, sea urchins and brittle stars) - many fossil crinoids can be found in the River Falls area. |
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Eucolomates in the Kingdom Animalia are divided into two major groups: what are they?
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Protostomes and deuterostomes
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Protostome group?
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Annelida, Mollusca, and Arthropoda
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Deuterostome group?
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Echinodermata, Hemichordata, and Chordata
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What type of cleaves occurs in the development of protostomes and deuterostomes, respectively?
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Spiral in protostomes, radial in deuterostomes
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What type of coelom formation occurs in both groups?
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schizocoelous in protostomes, enterocoelous in deuterostomes
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What type of embryos are formed in protostomes and deuterostomes?
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mosaic in protostomes, regulative in deuterostomes
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Where are acorn worms found?
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- mud or sand flats of intertidal zones
- sluggish, live in burrows or under stones - small phylum (only about 70 species) |
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What evolutionarily significant anatomical features do hemichordates have?
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- dorsal hollow nerve cord
- gill slits - two of five chordate characteristics |
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What type of larvae do hemichordates have, and what does it strongly resemble?
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- hemichordates have a tornaria larvae; it very strongly resembles the bipinnaria larvae of sea stars and may be evidence of an evolutionary link between the two groups.
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What evidence is there linking the phylum Hemichordata with the phyla Echinodermata and Chordata?
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- all three phyla belong to the deuterostome branch of the animal kingdom
- two of the five chordate characteristics are found in hemichordates - RNA evidence supports a common ancestory of the Echinodermata, Hemichordata,and Chordata. |
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What five features do all members of the phylum Chordata have in common?
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- notochord, dorsal nerve cord, pharyngeal gill slits, postanal tail, and endostyle or thyroid gland
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What is the function of the notochord?
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- first supporting structure of the chordate body
- present in all life stages of primitive chordates; present only in early stages in advanced chordates. - replaced by vertebral column during development in more advanced vertebrates. |
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What does the vertebral column project in higher chordates?
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- dorsal, hollow, nerve cord (often filled in during development)
- clusters of ganglia at the anterior end of the nerve cord (the "brain" or central nervous system) |
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Review: Where are the nerve cord and ganglia located in arthropods and annelids?
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- clusters of ganglia all along the ventral nerve cord
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What is the third characteristic that all chordates have in common?
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1. Pharyngeal gill slits
2. Outer ectoderm comes into contact with the endoderm of the pharynx and openings (slits) are formed. 3. original use was pharyngeal filter feeding, later, gills were added to arches between slits. |
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Why do non-aquatic chordates (vertebrates) still show evidence of these gill arches (and slits) in their embryos?
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- they have been retained and put to other uses.
- first forms jaws and inner ear - second, third, and fourth gill pouches contribute to the formation of the tonsils, parathyroid, thymus, and eustachian tube. |
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What the heck is an endostyle?
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- secretes mucus that traps small food particles brought into pharyngeal cavity
- secretes iodine- containing proteins - homologous to thyroid gland in vertebrates |
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What is the fifth fundamental chordate characteristic?
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- postanal tail
- tail extends beyond anus |
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What was its original purpose, that is still retained in some chordates?
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- propulsion through water
- retains this function in many chordates, but is present in the embryo of all chordates, including humans |
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What are the three subphyla in the phylum Chordata, and what organisms are included in them?
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1. Urochordata- includes the tunicates (also called sea squirts)
2. Cephalochordata- includes lancelets, also called amphioxus 3. Vertebrata- includes lamprey, fish, amphibians, reptiles, birds, and mammals. |
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What is a common name of the subphylum Urochordata?
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- tunicata because a covering ("tunic") containing cellulose surrounds the body.
- also called "sea squirts" because some species forcefully discharge a jet of water from their excurrent siphon when irritated |
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How many species are in the subphylum Urochordata?
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- about 2000 species, marine, mostly sessile.
- solitary, colonial, and compound forms all occur; compound forms share a single tunic (test) - solitary is the most common form |
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Why do adult tunicates have an excurrent siphon?
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- they are pharyngeal filter feeders that pull water into their basket-like pharynx via the action of cilia; water exits via the excurrent siphon.
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Why don't I see a postanal tail?
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- free swimming larva (tadpole-like) possesses all 5 of the chordate characteristics
- undergoes metamorphosis and loses the tail and the notochord, dorsal nerve cord is reduced - becomes a sessile adult |
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What is the second subphylum in the phylum Chordata, and what is the common name for the organism in this subphylum?
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Cephalochordata (includes lancelet)
- 2-3 inches long - inhabits the sandy bottoms of marine coastal areas around the world - anchors itself into bottom via its tail and filter-feeds (a pharyngeal filter feeder, like all primitive chordates) - only 25 species |
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Cephalochordates have all five chordate characteristics, which are:
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closed circulatory system, sexes separate, simple nervous system, simple sense organs, and also shows other vertebrate characteristics.
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Feeding mechanism is similar to...
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the Urochordata
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Water in mouth,...
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then through pharyngeal slits
- Endostyle produces mucus to capture particles; water exits pharynx then leaves body thru atriopore. - Food in mucus cord enters digestive tract |
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What is the third subphylum in the phylum Chordata?
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- subphylum Vertebrata (Craniata)
- cranium (braincase) - 3-part brain - head w/ paired sense organs - 2+ chambered heart |
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This subphylum is divided into two superclasses:
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first, superclass Agnatha (jawless vertebrates)
- only extant representatives: hagfish and lampreys |
