Phylum Mollusca Snails, slugs, oysters, clams, octopuses, and squids Nephridium Most are marine Visceral mass Soft-bodied animals, but most are protected by a hard shell Coelom Digestive tract Gonads Shell Radula cavity Three similar structures: muscular foot, visceral mass, mantle Gill Nerve cords Foot Radula Esophagus 33.16 Separate sexes with gonads in the visceral mass 1 Phylum Mollusca Classes Class Polyplacophora - oval-shaped marine animals encased in an armor of eight dorsal plates Class Gastropoda - snails (shells), slugs (lack shell or very small shell) 33.16 33.21 (a) A land snail Both marine and freshwater Torsion - anus and mantle above head (b) A sea slug (nudibranch) Class Bivalvia - clams, oysters, mussels, and scallops (shell divided in t wo halves) Squid Have gills used for feeding as well as gas exchange Class Cephalopoda - squids, octopuses cavity Coelom Hinge area Gut Digestive gland Adductor muscle (one or two) Octopus Beak-like jaws surrounded by tentacles of modified foot Shell Chambered nautilus Palp Foot cavity Gonad Gill Water flow Incurrent 2 Molluscs: Silent Extinction Group with the largest number of recent extinctions Most threatened groups are freshwater bivalves and terrestrial gastropods Threatened by habitat loss, pollution, and non-native species Other invertebrates Molluscs ns Insects Birds Fishes Mammals An endangered Pacific island land snail, Partula suturalis Recorded extinctions of animal species (Data: International Union for Reptiles (excluding birds) Conservation of Nature, 2008) Workers on a mound of pearl mussels killed to make buttons (ca. 1919) 33.22 3
Phylum Annelida Cuticle Septum (partition between segments) Metanephridium Segmented worms (bodies composed of fused rings) Longitudinal muscle Dorsal vessel Chaetae Class Oligochaeta contain chaetae (bristles made of chitin) Earthworms eat their way through soil extracting nutrients as the soil moves through the canal Coelom Epidermis Circular muscle Skin Ventral vessel Fused s Nephrostome Metanephridium Clitellum Esophagus Crop Pharynx Giant Australian earthworm Gizzard Cerebral ganglia Subpharyngeal Circulatory system vessels ganglion Ventral s with segmental ganglia Class Polychaeta - possess paddlelike parapodia that function as gills and aid in locomotion Class Hirudinea - bloodsucking parasites (ex. leaches) 33.2333.25 Parapodia 4 Porifera Cnidaria Lophotrochozoa Ecdysozoa Deuterostomia Phylum Nematoda Nonsegmented Among the most widespread of animals Found in aquatic habitats, in the soil, in tissues of plants, and in the body fluids and tissues of animals 25 µm Encysted juveniles Muscle tissue 50 µm Bodies are covered in a tough cuticle Parasites of plants and animals 33.2633.27 Phylum Arthropoda 5 33.28-33.30 Two out of every three known species of animals are arthropods EXPERIMENT Early arthropods (trilobites) show variation from segment to segment Other ecdysozoans Origin of Ubx and abd-a Hox genes? Arthropods Onychophorans Common ancestor RESULTS Segmented coelomates that have an exoskeleton made of chitin and jointed appendages As they evolved the segments fused and the appendages became more specialized Ant = antenna J = jaws L1 L15 = body segments Cephalothorax Antennae (sensory reception) Head Abdomen Thorax Have an open circulatory system Fluid called hemolymph is circulated into the spaces surrounding tissues and organs Swimming appendages (one pair per abdominal segment Pincer (defense) parts (feeding) Walking legs 6
Phylum Arthropodia 33.31-33.34 Four Subphyla Cheliceriforms clawlike feeding appendages (chelicerae) (ex. spiders, ticks, mites, scropions, and horseshoe crabs) Arachnids have an abdomen and a cephalothorax with six pairs of appendages Myriapoda - millipedes (t wo pairs of legs per segment) and centipedes (one pair of legs per segment) Brain Digestive gland Eyes Ovary Poison gland Book lung Spinnerets Silk gland Gonopore (exit for eggs) Sperm receptacle Chelicera Pedipalp 50 µm Scorpion Dust mite (a) Millipede Web-building spider (b) Centipede Phylum Arthropodia Abdomen 7 Thorax Head Compound eye Antennae Four Subphyla Hexapoda - insects Dorsal artery Cerebral ganglion Crop More species-rich than all other forms of life combined Flight key to evolutionary success Vagina Malpighian tubules Ovary Tracheal tubes Nerve cords parts Many undergo metamorphosis Incomplete metamorphosis - the young (nymphs) look like adults but go through a series of molts Complete metamorphosis larval stages specialized for eating and entirely different from adult stage (maggot, grub, or caterpillar) (a) Larva (caterpillar) (b) Pupa (c) Later-stage (d) Emerging pupa adult (e) Adult 33.35-33.37 8 Phylum Arthropodia Four Subphyla Crustacea - have biramous, branched, appendages that are extensively specialized for feeding and locomotion (a) Ghost crab Decapods are large crustaceans (lobsters, crabs, crayfish, and shrimp) Planktonic crustaceans include many species of copepods (may be the most numerous of all animals) Barnacles - sessile crustaceans whose cuticle is hardened into a shell (b) Krill 33.39 (c) Barnacles 9
Porifera Cnidaria Lophotrochozoa Ecdysozoa Deuterostomia Phylum Echinodermata Share characteristics of deuterostomes with chordates (even though they are invertebrates) Short digestive tract Spine Gills Radial cleavage Central disk Development of the coelom from the archenteron Formation of the mouth at the end of the embryo opposite the blastopore Most echinoderms are slow-moving or sessile marine animals Madreporite Digestive glands Radial nerve Ring canal Radial canal 33.40 Gonads Ampulla Podium Tube feet Have a thin, bumpy or spiny skin that covers an endoskeleton of hard calcareous plates Have a water vascular system which is a net work of branching hydraulic canals into tube feet that function in locomotion, feeding, and gas exchange 10 Phylum Echinodermata Radial symmetry of many echinoderms evolved from bilateral ancestors Sea stars (Class Asteroidea) undersurfaces of arms have tube feet Brittle stars (Class Ophiuroidea) Sea urchins and sand dollars (Class Echinoidea) - have no arms, but they have five rows of tube feet Feather stars (Class Crinoidea) Sea cucumbers (Class Holothuroidea) - endoskeleton is reduced Sea daisies (Class Concentricycloidea) 33.41-33.45 11 Vertebrates 540 million years ago the first vertebrates began to evolve One lineage of vertebrates colonized land 365 million years ago 52,000 species of vertebrates which include the largest organisms ever to live on Earth 34.1 12
Vertebrates are a subphylum of the phylum Chordata Have a notochord and a dorsal, hollow nerve cord Bilaterian animals that belong to a clade known as Deuterostomia Two groups of invertebrate deuterostomes are the urochordates and cephalochordates are more closely related to vertebrates than to invertebrates ANCESTRAL DEUTEROSTOME Common ancestor of chordates Head Vertebral column Jaws, mineralized skeleton Lungs or lung derivatives Chordates Lobed fins Limbs with digits Amniotic egg Milk Echinodermata Tetrapods Amniotes Craniates Vertebrates Gnathostomes Osteichthyans Lobe-fins 34.2 Chordates 13 Chrodates All have a set of shared derived characters (some only express them during embryonic development - longitudinal, flexible rod located between the digestive tube and the Provides skeletal support throughout most of the length of a chordate In most vertebrates a complex, jointed skeleton develops Nerve cord - develops from a plate of ectoderm that rolls into a tube dorsal to the notochord Develops into the central nervous system Muscle segments Dorsal, hollow Muscular, post-anal tail Pharyngeal slits or clefts 34.3 14 Chordates Most have grooves in the pharynx called pharyngeal clefts that develop into slits that open to the outside of the body Function as suspension-feeding structures Modified for gas exchange in aquatic vertebrates Develop into parts of the ear, head, and neck in terrestrial vertebrates Chordates have a tail extending posterior to the anus (many lose it during embryonic development) 15
Subphylum (tunicates) deepest-branching lineage of chordates and are marine suspension feeders (sea squirts) Chordata Most closely resemble chordates during lar val stage Draws water through a to filter out food particles Subphylum (lancelets) named for blade-like shape Pharyngeal slits Atrium Gene expression in lancelets holds clues for the evolution of the vertebrate form 1 cm Atriopore Dorsal, hollow Segmental muscles Tail Incurrent to mouth Water flow Hox3 Dorsal, hollow Nerve cord of lancelet embryo BF1 Digestive tract Retain chordate body plan as adults Otx Cirri Marine suspension feeders BF1 Tail Muscle segments Hox3 Otx Incurrent Brain of vertebrate embryo (shown straightened) Atrium Midbrain Hindbrain Craniates Atrium Pharynx with numerous slits Tunic Pharynx with slits Forebrain 34.4-34.6 (a) Tunicate larva Dorsal edges of neural plate Esophagus (b) Adult tunicate Neural crest (c) Adult tunicate 16 Neural tube Chordates with a head Evolved 530 million years ago (Cambrian Explosion) Head allows a new way of feeding and active predation Share common characteristics: skull, brain, eyes, and other sensory organs Neural crest - collection of cells taht appears near the dorsal margins of the closing neural tube in an embryo Cells give rise to a variety of structures including some bones and cartilage in the skull Migrating neural crest cells (a) (b) Skull bones and cartilage derived from neural crest cells 34.7 (c) Slime glands Class (hagfish) - least derived lineage that still survives Jawless marine animals taht have a cartilaginous skull and an axial rod of cartilage derived from the notochord that lack vertebrae 34.9 17 Vertebrates Craniates that evolved a backbone Shared characteristics: vertebrae enclosing a spinal cord, an elaborate skull, and fin rays (in aquatic forms) 34.1034.12 Class Cephalaspidomorphi (Lampreys) Oldest living lineage of vertebrates Have cartilaginous segments surrounding the notochord and arching partly over the ner ve cord Conodonts and Ostracoderms are ancient vertebrates where mineralized skeletons first appeared Pteraspis Dental elements (within head) Pharyngolepis 18