Phylum Echinodermata Introduction. About 6000 species, all marine Echinodermata.
Chapter 16-The Echinoderms Phylum Echinodermata- Spiny- skinned animals ...
-
Upload
amelia-baker -
Category
Documents
-
view
236 -
download
0
Transcript of Chapter 16-The Echinoderms Phylum Echinodermata- Spiny- skinned animals ...
Chapter 16-The Echinoderms
Phylum Echinodermata- Spiny-skinned animals
http://videos.howstuffworks.com/hsw/11762-the-world-of-animals-phylum-echinodermata-video.htm
Animal Development
AcoelomateAcoelomate- An animal that lacks a coelom, or body cavity.
CoelomateCoelomate- An animal that has a body cavity in which the internal organs are located.
Gastrula stage during embryo development- opening to the outside called a blastopore.blastopore.ProtostomesProtostomes- Animals with mouths that develop from
or near the blastopore; mouth before anusEX: Annelids, Mollusks and Arthropods
DeuterostomesDeuterostomes- Animals in which the anus develops from the blastopore; anus before mouthEX: Echinoderms and Chordates
Embryonic Development
Modern Echinoderms
First animals to develop an endoskeleton Marine, radially symmetrical as adults Evolved more than 650 million years ago Mostly free-living predators; some algae-eaters
Modern EchinodermsAll Echinoderms share four fundamental
characteristics:EndoskeletonEndoskeleton- Calcium-enriched, spine-bearing, and
composed of individual plates called ossiclesossiclesCovered by a thin layer of skin which sometimes wears offSometimes fuse for muscle attachment and shell-like protection
Five-part Radial Symmetry- Mouth on bottom (oral), anus on top (aboral)Bilaterally symmetrical as larvaeArms, called rays, radiate from central point with no head or
brainCan regenerate arms; Complete animal can regenerate from
an arm connected to a portion of the central disk
Pentaradial Symmetry
http://player.discoveryeducation.com/index.cfm?guidAssetId=61763568-F5A4-470B-98E5-059CE2C4AB99
Moving Sea Star
Modern EchinodermsWater-vascular systemWater-vascular system- Water-filled system of
interconnected canals and thousands of tiny hollow tube feet Tube feetTube feet with suckers at each end extend outward through
openings in ossicles;used to crawl; each is connected to a water-filled sac called an ampullaampulla
Water enters and leaves through pores in the madroporitemadroporite- a sieve-like structure that filters out large particles
Also functions in feeding and gas exchange- tube feet pull valves of bivalve open to exchange gas and excrete waste
Coelomic circulation and respiration-Skin gillsSkin gills- Small, finger-like projections grow among
spines to create an increased surface area through which gases can be exchanged
Also function as excretory structures
Modern EchinodermsNervous System
Central ring of nerves branches into each arm allowing for independent movement
Radial nerves run along each rayEyespots- at tips of rays, detects light and dark
Digestive systemUses water-vascular system to open bivalvesPushes stomach through mouth into shell (evisceration);
enzymes digest solid food into liquid absorbed by the stomach
Stomach is pulled back into mouth and food travels through intestines where nutrient absorption occurs
ReproductionSeparate sexesGametes located in
arms (rays)Sexual
reproduction- external fertilization
Larvae undergo metamorphosis – bipinnaria larvae
Body Structure
Echinoderm Diversity20 extinct classes; 6
livingSuper-class Stelleroidea
Class AsteroideaSea starsCarnivoresOssicles produce pincerlike
structures called pedicellaria pedicellaria with their own muscles and nerves
Snap at anything that touches them
“Crown-of-thorns” sea star responsible for massive coral reef loss
Echinoderm Diversity
Class OphiuroideaBrittle Stars and Sea
Baskets Largest classSlender, branched arms
that move in pairsBreak easilyThey stay hidden in reefs
and under rocksFilter feeders
Echinoderm Diversity
Class Crinoidea Sea Lilies and Feather Stars Most ancient and primitive Mouth is located on the upper,
rather than lower surface Sessile Feather stars have hook-like
projections to attach themselves directly to the ocean bottom or coral reef
Echinoderm Diversity
Class Echinoidea Sea Urchins and Sand
Dollars Lack distinct arms Sea urchins found on the
ocean bottom Sand dollars live on sand
bars along coasts Spines provide protection
and sometimes contain a venom
Some sea urchins use paralytic toxins
Echinoderm Diversity Class Holothuroidea
Sea Cucumbers
Soft-bodied, slug-like animals without arms
Ossicles small and unfusedMostly separate sexes, some
hermaphroditesMouth surrounded by tube
feet modified into tentacles covered with a sticky mucus
Draws tentacles into mouth to clean off plankton and mucus
Can release sticky threads from anus to trap attackers
Echinoderm Diversity Sea Daisies
Discovered in 1986Strange, disk-shaped
animals with no arms Found off New Zealand
coast Less than 1 cm in
diameterTube feet located
around edge of disk rather than along radial lines
http://player.discoveryeducation.com/index.cfm?guidAssetId=1EE88D80-43B6-
453A-9EFF-48B6CA8A64CB