Transcript Trichinella
I. Kingdom Animalia A. Most land animals in 3 phyla: 1. Arthropoda 2. Mollusca 3. Chordata B. Features (general) 1. diploid individuals 2. haploid gametes - swimming sperm 3. not the “alternation of generations” seen in plants Burgess Shale in Yoho National Park, Canada About 500 million years old II. Evolutionary Innovations A. Multicellularity 1. subkingdoms a. Parazoa - no symmetry or tissues b. Eumetazoa 2. simplest animals exhibit only multicellularity - sponges a. sponges lack tissues and organs b. “blob” of specialized cells - choanocytes (collect the food) - amoebocytes (deliver the food) - choanocytes are very similar to choanoflagellates (living Protists) B. Symmetry and tissues 1. embryonic layers (3) - each layer develops into specialized tissues a. endoderm - gastrointestinal tract b. mesoderm - muscles, bones c. ectoderm - external coverings, nervous system 2. radial symmetry 3. simplest: cnidarians a. polyps (mostly sessile) - sea anemones - hydras - many coral animals Coral polyps Sea anemones b. medusae (free-swimming) - marine jellys Purple jelly Lion’s mane jelly c. some alternate stages as part of their life cycle C. Bilateral symmetry - right and left (mirror images) - anterior/posterior (front/rear) - dorsal/ventral (back/belly) 1. no body cavity around gut (gastrovascular cavity) - no anus 2. flat worms (solid worms) a. Phylum Platyhelminthes b. free-living flatworms (planaria) c. flukes (animal parasites) d. tapeworms D. Body cavity (pseudocoelom filled with fluid) - pseudocoelomates 1. allows for: a. circulation - especially of nutrients b. movement - provides rigid structure to which muscles attach and are anchored for contraction - hydroskeleton c. organ function - organs can function during muscle contraction 2. pseudocoelom is between endoderm and mesoderm 3. nematodes a. have complete digestive tract b. many are parasitic - heartworms - Trichinella (trichinosis) E. Coelom 1. body cavity formed within mesoderm - allows endoderm to stay in contact with some mesoderm 2. gut tube is again enclosed by tissue - how do nutrients reach the tissues outside of the gut? - circulatory system 3. simplest: mollusks a. gastropods (snails and slugs) - mostly marine - some terrestrial (are the only terrestrial mollusks) b. cephalopods - large brains and complex sense organs c. bivalves - most are sessile c. bivalves - most are sessile - some can “swim” by “flapping” their shell sea scallop F. Segmentation - subdivision of the body into a series of repeated parts 1. annelids a. repeated segments b. some segments contain specialized structures c. segments “connected” by nerves and blood vessels 2. several types a. earthworms b. polychaetes - mostly marine - Christmas tree worms - tubeworms c. leeches - most actually eat small invertebrates 3. still apparent examples of segmentation in higher species - embryo 3. still apparent examples of segmentation in higher species - embryo - vertebrae G. Jointed appendages/exoskeleton (made of chitin) - Arthropods G. Jointed appendages/exoskeleton (made of chitin) - Arthropods 1. chelicerates: a. horseshoe crabs G. Jointed appendages/exoskeleton (made of chitin) - Arthropods 1. chelicerates: a. horseshoe crabs b. arachnids (scorpions, spiders, mites, ticks) 2. millipedes and centipedes a. millipedes - herbivores - two pair of legs per segment b. centipedes - poisonous carnivores (insectivores) - one pair of legs per segment 3. crustaceans - lobster/crayfish barnacles krill 4. insects (Class Insecta is by far the largest) a. head, thorax, abdomen b. three pair of legs c. most have 1 or 2 pair of wings H. Chordates (Phylum Chordata) 1. features: (some may be embryonic only) a. notochord: flexible rod along back b. nerve cord along back c. pharyngeal slits d. post-anal tail 2. invertebrate chordates - tunicates - lancelets 3. vertebrates a. head (with skull to protect brain) b. backbone (except hagfish: has head but lacks a backbone) - encloses the nerve (spinal) cord c. internal skeleton - bone (usually) - cartilage (sharks and rays)