4Phylum porifera *Cellular Level of Organization Organisms in the phylum Porifera are among the simplest animalsMany sponges are radially symmetricalTheir parts are arranged around a central axisChoanocytes are specialized cells that make up poriferans.Central axis
5Phylum porifera Filter feeders: Flagellated choanocytes filter food from the water passing through the porous bodySessile: stay in one placeChoanocyte in contact with an amoebocytePoresWATER FLOWSkeletal fiberCentral cavityChoanocyteFlagellaAmoebocyteFigure 18.3C
6The sponge lineage arose very early. Phylum poriferaThe sponge lineage arose very early.They probably evolved from multicellular choanoflagellates, the group that most likely gave rise to the animal kingdom.Single cellStalk
7Phylum Cnidaria *Tissue level organization Cnidarians are the simplest animals with tissues.These animals exist in two radially symmetrical forms:PolypMedusa
8Phylum Cnidaria Cnidocytes on their tentacles sting prey The tentacles, controlled by nerves, then push the food through the mouth into a gastrovascular cavity.In the cavity, the food is digested and then distributed.Only one opening in digestive system.
9Phylum Platyhelminthes *Organ level of Organization Flatworms are the simplest bilateral animals.Flatworms have organs.Planarians have a simple nervous system consisting of a brain, sense organs, and branching nerves.As in cnidarians, the mouth of a flatworm is the only opening for its gastrovascular cavity.Digestive tract (gastrovascular cavity)Nerve cordsMouthEyespotsNervous tissue clustersBilateral symmetry
10Flukes and tapeworms are parasitic flatworms with complex life cycles Mature flukes in blood vessels of intestineMaleHuman hostFemale1Sexual reproduction of flukes in human; fertilized eggs pass out in feces6Larva penetrates skin and blood vessels2Eggs hatch in water5Larva that infects human3Larva that infects snail4Asexual reproduction of flukes in snailSnail host
11Phylum Platyhelminthes Tapeworms can be eaten by cattle and burrow into the intestines and muscles.If meat is not properly inspected, humans can be infected by eating rare or undercooked beef.Units with reproductive structuresHeadHooksSucker
12Quick evolution checkpoint Porifera, Cnidaria, and Platyhelminthes lack a body cavity.Nearly all other animals have a body cavity called a coelom.This cavity is a fluid-filled space between the digestive tract and the body wall.The cavity aids in movement, cushions organs, and it may help in circulation.
14Phylum nematoda *Pseudocoelom AKA: RoundwormsNematodes have a body cavity not completely lined by mesoderm called a psuedocoelom.Like most animals, they possess a complete digestive tract.This is a tube with a mouth and an anus. (One-way tract)Many nematodes are free-living.Others are parasites.Trichinella juvenileMuscle tissue
15Phylum Mollusca *Coelom Phylum Mollusca is a large and diverse phylum that includesgastropods, such as snails and slugsbivalves, such as clams and scallopscephalopods, such as squids and octopuses
16Phylum Mollusca Mollusks have a true coelom and a circulatory system All mollusks have a muscular foot and a mantleThe mantle may secrete a shell which encloses the visceral massMollusks have a true coelom and a circulatory systemMany mollusks feed with a rasping radula
17Quick evolution checkpoint: After a Body cavity evolved… Segmentation is the subdivision of some or most of the body into a series of repeated parts, or segments.AnusBrainMain heartCoelomDigestive tractSegment wallsMouthAccessory heartNerve cordBlood vesselsExcretory organ
18Segmentation probably evolved as an adaptation for movement
19Quick Evolution checkpoint: Protostomal larval development Earliest type of larval development according to evolutionMouth is the first opening to develop.Cells of the embryo cannot be altered.
20Phylum Annelida *body segmentation & protostomes Earthworms and other annelids are segmented worms whose mouths develop first in the larval stage.The segmented bodies of annelids give them added mobility for swimming and burrowing.An earthworm eats its way through soil.Most leeches are free-living carnivores, but some suck blood.
21Phylum arthropoda *jointed appendages CephalothoraxAbdomenArthropods are the most numerous and widespread of all animals.They are segmented animals with exoskeletons and jointed appendages.ThoraxHeadAntennae (sensory reception)Swimming appendagesWalking legsPincer (defense)Mouthparts (feeding)
22Phylum arthropodaIn terms of numbers, distribution, and diversity, they are the most successful phylum of animals.Diversity:InsectsCrustaceans (marine arthropods)ArachnidsMillipedes & centipedesHorseshoe crabs are ancient marine arthropods
23Phylum arthropoda Insects are the most diverse group of organisms. They have a three-part body consisting of head, thorax, and abdomen.The development of many insects includes metamorphosis.HeadThoraxAbdomenAntennaForewingEyeHindwingMouthparts
24Phylum arthropoda Metamorphosis: Larvae: specialized for eating and growingAdults: specialized for dispersal and reproduction
25Phylum Echinodermata *deuterostome, endoskeleton, radial symmetry Echinoderms have spiny skin, an endoskeleton, and a water vascular system for movement.Phylum Echinodermata includes organisms such as sea stars and sea urchinsThese organisms are radially symmetrical as adults
26Phylum echinodermataThe water vascular system has suction-cup-like tube feet used for respiration and locomotion.AnusSpinesStomachTUBE FEETCANALS
27Phylum chordata *notochord Notochord: flexible, tough rod that provides support for the animal and gives muscles a place to attach
28Phylum chordata *notochord Organisms in this phylum (LIKE US) are segmented animals with four distinctive features:Dorsal hollow nerve cordStiff notochordPharyngeal slits behind the mouthMuscular post-anal tailWe’ll study this phylumseparately.