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Zoology, lecture 14
Invertebrates: Echinodermata
| Question | Answer |
|---|---|
| Echinodermata | רוק יצווק phylum of triploblastic deuterostomes |
| All of the phyla till now | Porifera, Cnidaria (diploblastic protostomes), Platyhelminthes, Annelida, Arthropoda (Triploblastic protostomes) |
| Two prominent deuterostomic phyla | Echinodermata and Chordata |
| Hemichordata | A small deuterostomic phylum significant for its evolutionary ties between Echinodermates and Chordates. |
| Deuterostome characteristics | Embryonic cleavage is radial, the coelom develops as an outpouching of the gastroderm, the initial opening closes, a mouth opens opposite it and an anus opens near the original opening. Development is indeterminate. |
| Enterocoelic | A trait of deuterostomes--the coelom develops as an outpouching of the endoderm (as opposed to schizocoelic--cell migration to form to masses that split). |
| Echinodermate characteristics | Deuterostomic, enterocoelic, nonsegmented, secondary radial symmetry, internal skeleton made of calciferous plates with spike like protrusions. |
| Basic echinodermate symmetry | Pentamerous (multiples of 5) with secondary radial symmetry in the adults. |
| Echinodermate larval symmetry | Initially they have bilateral symmetry and develop their pentamerous radial symmetry as their life cycle continues. |
| Oral/aboral orientation in echinodermates | The oral side is the side where the mouth opens. The aboral side is opposite it. In starfish the oral side is down |
| Echinodermate skeleton | They have an internal calciferous skeleton composed of plates. (with some magnesium). The skeleton is mesodermal below the external epithelium usually with spike-like protrusions. |
| Ambulacral system | Water-leg system in echinodermates used for walking, breathing and waste removal. |
| Development of the ambulacral system | Develops from the coelom. |
| Structure of the ambulacral system | A series of canals that branch into tubes with small bladders (ampullae) on one side and a flexible tube on the other. |
| Water entrance to the ambulacral system | It comes in through madreporites, down the stone canal, into the ring canal for distribution into radial canals. |
| Madreporites | Holes open to the outside through which water enters the ambulacral system. |
| Stone Canals | Tube that leads from the madreporites down into the ring canal. It is lined with calciferous spicules that give it shape. |
| Ring canal | Round tube in the center of the ambulacral system that receives water from the stone canal and distributes it to the radial canals. |
| Radial canal | There are five that branch from the ring canal, each with a series of wider bubbles called ampulla and a narrow extension called tube feet. |
| How do the echinodermates "walk"? | The ampulla contracts forcing water into the tube feet (hydrostatic pressure) through a one way valve extending the tube feet that retract with the help of longitudinal muscles. |
| Echinodermate nervous system | It's peripheral. There is no production of ganglia. There is a nerve ring around the mouth that branches into 5 radial nerves which further branch into a peripheral system. |
| Echinodermate sensory organs | They have simple eyes and are also capable of sensation with their tube feet. |
| Echinodermate digestive system | Complex and varied among different species. The intestine can be extended outward from the body secreting digestive enzymes on the prey. Sea urchins have a complex jaw structure called aristotle's lantern. |
| Details of the echinodermate digestive system | There is a central gut from which there are 5 extensions called pyloric ducts with blind secondary branches called pyloric cecum. |
| Aristotle's Lantern | Extendable jaw mechanism found in sea urchins |
| Pyloric ducts | 5 extensions from the main gut that make up the branches of the digestive system. |
| Pyloric cecum | Blind branches of the pyloric ducts that are active in digestion through diffusion. |
| Aristotle's Lantern structure | There are strong muscles operating the jaws allowing it to open and close on the prey. |
| Use of echinodermate tube feet | For walking, respiration and even for eating. They can use them to open bivalve shells. |
| Pedicillaria | Small protrusions from the sea urchin shell that function in removing stuff from the animal's surface. |
| Sea urchin respiration | They have small protrusions from their body surface that act as gills by increasing surface area for diffusion. |
| Echinodermate respiration | There is no respiratory system--they just respirate through diffusion and since the water passes through their whole body they can extract oxygen from the water (also they're not very active so they don't need a lot of oxygen) |
| Echinodermate reproduction | Asexual: removal of one part to produce a new individual and regeneration for both individuals. Sexual: Dieocious with gonads (not hermaphroditic) |
| Regeneration capabilities--principle | The more complex an organism, the more differentiation there is between cells and the less capable the organism is of regeneration. Simple organisms are significantly better at regeneration. |
| Iso-osmotic | The sea has the same nutrient and mineral concentration as the inside of echinodermates meaning that their gametes can survive in the ocean as long as they have an energy source. |
| Echinodermate sexual reproduction | Female and male individuals release gametes (synchronized release) into the open water where they meet for fertilization producing a zygote. |
| Echinodermate life cycle | Life-cycles vary among species but they have larval stages |
| Echinodermate ecological significance | Sea otters eat the sea urchins. Crown of thorns starfish eats corals and destroys reefs. It took over in australia. The assumption is that it started from increased nutrient content as a result. Some eat echin. gonads. |
| Charonia | A type of snail that eats star fish. |
| Echinodermate characteristics | Purely marine deuterostomic invertebrates, secondary radial symmetry, nonsegmented, mesodermal internal skeleton made of plates, move using tube feet system (developed from the coelom), no brain, peripheral nerve system |
| Echinodermate classes | Asteroidea (starfish), Ophiuroidea (brittle stars), Echinoidea (sea urchins), feather stars (crinoidea), holothuroidea (sea cucumbers) |
| Echinodermate reproduction | Asexual or sexual, dieocious, external fertilization, development in stages. |
| Chordates characteristics | Notochord (dorsal support cord), hollow dorsal nervous system, pharyngeal gill slits, tail. All of these appear during the pharyngula stage of the developmental cycle. |
| Pharyngula stage | Stage in embryonic development when all vertebrate embryos possess: a notochord, dorsal hollow nerve chord, post anal tail and paired pharyngeal gill slits. |
| Hemichordates | Organisms with some but not all of the chordate characteristics that appear in the pharyngula stage. |
| Hemichordate characteristics | Phylum of worm like marine organisms with gill slits in their pharynx and a tail bud. Dorsal nerves (not fused into a hollow chord) No notochord but they have cells that make a hard mass at the front of their bodies. |
| Acorn worms | Or tongue worms are a worm-like species of hemichordates |
| Phylogenesis of chordates | Echinodermates, hemichordates and chordates all have some common deuterostomic ancestor. |
| Dipleurula | Larvae with a ciliated band around the mouth and another around the edge of the body common to both hemichordates and some echinodermates vs the trochophore in protostomes |
| Trochophore | Larval type found in protostomes with no ciliated band around the mouth. |
| Similarities between echinodermates and chordates | Radial embryonic cleavage, nondeterministic development, deuterostomic. Both have coeloms. |
| Coelomic differences between echinodermates and chordates | Echinodermates are enterocoelic while chordates are schizocoelic |
| What characteristic differentiates between invertebrates and vertebrates? | Existence of a segmented spine made of bone vertebrae. Vertebrates therefore are some of the chordates, invertebrates are all the rest of the multicellular organisms. |
| Arthropod circulatory system | Open system with one dorsal tube that is open to the rest of the body. |
| Bilateral invertebrate vs. chordate body systems | They have the same body structures just in different places. Either the chordates flipped it or developed independently and the assumption is that the notochord development gave a push in the direction of the dorsal nerve chord development. |
| Schematic comparison of invertebrates vs. vertebrates: | First is an open unbranched circulatory system with a ventral nerve system and the digestive tract runs down the center as opposed to the vertebrates with a dorsal nervous system and ventral circulatory system (closed) |
| Development of the dorsal nervous system | Assumed to be a result of the development of the notochord that could protect it. |
Created by:
YaelNoa
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