Chapter 15 Biology Notes on Echinoderms and Chordates

General Characteristics of Echinoderms

• Deuterostome coelomates

• slow moving or sessile

• appears radially symmetrical

• water vascular system with tube feet

Water Vascular System and Tube Feet Movement

Diversity of Echinoderms

• Members of the group include:

  • Asteroids: Sea stars and sea daisies

  • Ophiuroidea: Brittle stars

  • Echinoidea: Sea urchins -and sand dollars

  • Holothuroidea: Sea cucumbers

  • crinoidea: feather stars and sea lilies

    Central Disk in Sea Stars

• has a nerve ring and nerve cords radiating from the ring into the 5 arms

Pentaradial Symmetry

• characteristic of echinoderm. five arms arranged in five rays of symmetry radiating from central disks

Madreporites used for

• allow water flow in or out of the water vascular system. when water flows in it produces a hydraulic motion for movement

Shared-Derived Characteristics of Chordates

• Notochord: longitudinal flexible rod found between the digestive tube and nerve cord ( primitive backbone)

  1. found in All embryos and some adults

  2. vestigal in human vertebrates

• Dorsal Hollow Nerve Cord: forms from ectoderm that rolls into a neutral tube in chordates embryos

  1. develops into the central nervous system ( brain and spinal cord)

• Pharyngeal Gill Slits: areas behind mouth ( pharynx) has arches separated by slits which open into the pharynx

  1. lets water enter through mouth opening into and out slits

  2. used for suspension feeding and gas exchange

• Muscular Post-Anal Tail: tail extends behind anus, muscular and contains bone in aquatic species for swimming reduced during embryonic development in many species

  Characteristics of Cephalochordates (Lancelets)

• Adults burrow into sand and filter-

  feed on phytoplankton, detritus

• capable of swimming using growth like fish

• feeding: H2O enter from mouth and food stuck on muscous in pharyngeal aches pass to intest

Characteristics of Urochordates (Tunicates)

• Chordate features most obvious in larvae.

  Most features lost as adults.

• free swimming larvae attach to substrate and undergo metaphorsis

• adults are sessible filter-feeder

Vertebrates

• are Chordates with a backbone, typically have a skull and a backbone made of vertebrae enclosed spinal cord but some species only have cartilaginous

• neural crest-cells located at the edges of neutral tube

describe jawless Fish and what are the features of Cyclostomes

• Jawless fish include hagfish and lampreys, characterized by:

  • Lack of jaws but possess structures for feeding (sucking mouth).

  • Mainly cartilaginous structures instead of bones.

1. round mouth no teeth no jaws, suckomh mouths ex: myxini and petromyzontida

characteristics: Long symmetrical body, rudimentary or no vertebrae, retain cartilaginous notochord

Features of Hagfish

• have cartilaginous skull but reduced vertebrae

• mouth have rows of teeth made of keratin

• produce slime when attacked

• bottom feeders scavengers

Characteristics of Lampreys

• have cartilaginous skull, skeleton and simple vertebrae

• parasitic clam feed off blood and other tissue

• juveniles live in freshwater stream, suspension feeders and resemble lancets

Gnathostomes

• jaw mouth animals sharks, reptiles, amphibians, mammals, ray-finned fish, lobe-finned fish

Purpose of Jaws

• hinged structures that along with teeth help to grip and slice food. improve prey capture

Mineralization and its Significance

• harden by incorporation of minerals like calcium in teeth and skull. Happen during the transition from suspension feeders to predators. it divided gnathostomes into Chondrichthyes (cartilage and osteocytes (bony)

Lateral Line System in Fish

• organs from a row in the side of the body and used to sense vibration

Chondrichthyans Characteristics

• cartilage fish sharks, rays, skates and ratfishes

• characteristics: paired fins, hinged jaws with mineralized teeth, skeleton made of cartilage that contains some calcium, and have spiractes bring in h20 for gas exchange

what are ways that sharks can detect their prey

• nostrils for smelling prey, regions on head detects electric field from prey muscle contraction

Definitions

• Oviparous: female lay egg that hatch outside mothers body

• Ovoviviparous: mother retain eggs oviduct, egg hatch internally

• Viviparous: young are nourished in uterus by a placenta give birth ( mamal)

Osteichthyans

• honey fish that contain an ossified bony skeleton with calcium phosphate matrix

Features of Bony Fish

• gills protected by flaps called operculum

• maintain buoyancy by filling air sac called swim bladder

• flattered scales all over body

Swim Bladder Used for?

• homologous with lungs fills and empties with muscle contraction and relaxation ti regulate buoyancy

Operculum Used for

• bony flap that cover the movement of operculum draws water into mouth through pharynx and out between gills

Features of Ray-Finned Fish

• bony rays that support fins

• freshwater and saltwater species

• oviparous

• body form, swimming style, feeding modes are specialized to environment

Features of Lobe-Finned Fish

• scarcopterygii: posses pectoral and pelvic that have rod snapped surrounded by muscle

  • evolved in coastal wetlands and similar environments likely used lobe fin to move through mud

    2. actinistia: (coelacanths) bottom dwellers huge

    3. Dipnoi( lungfish) : ride to the surface to gulpairin lungs homologous to those interapod

       • found freshwater swamps and ponds

       • survive dry seasons by burrowing in mud