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Invertebrates Chapter 33 Animal Origins Euglenozoa Parabasala Diplomonadida Alveolata Stramenopila Radiolaria Cercozoa Amoebozoa Plantae Chlorophyta Rhodophyta Animalia Choanoflagellates Fungi Animal Origins Ancestral eukaryote Figure 28.4 Characteristics of the Animal Kingdom None of the following are unique to animals, but together distinguish animals from other organisms: Multicellular Heterotrophic No cell walls Motile during some stage(s) in life Characteristics of the Animal Kingdom A great diversity of body plans occur; some key features include: Organized federation of cells vs. cells in tissues Tissue – integrated group of cells with a common structure and function Tissues are generally further integrated into organs Organs are generally further integrated into organ systems Characteristics of the Animal Kingdom A great diversity of body plans occur; some key features include: For organisms with tissues: two vs. three principal embryonic tissues Characteristics of the Animal Kingdom Two embryonic tissue layers: Blastocoel Zygote Blastula Blastocoel Endoderm Ectoderm Archenteron Blastopore Gastrula Gastrulatio n Fig. 32.2 Characteristics of the Animal Kingdom Two embryonic tissue layers: Endoderm – Innermost “germ layer”; differentiates into some of the internal tissues and the lining of most hollow organs, if these are present Blastocoel Endoderm Ectoderm – Outermost “germ layer”; differentiates into tissues that cover the body and into the nervous tissues Ectoderm Archenteron Blastopore Gastrula Fig. 32.2 Characteristics of the Animal Kingdom Three embryonic tissue layers: Fig. 32.9 Endoderm – Innermost “germ layer”; differentiates into some of the internal tissues and the lining of most hollow organs, if these are present Mesoderm – Middle “germ layer”; differentiates into muscles, circulatory and skeletal systems, and sex organs, if these are present Ectoderm – Outermost “germ layer”; differentiates into tissues that cover the body and into the nerve tissues Characteristics of the Animal Kingdom A great diversity of body plans occur; some key features include: Radial vs. bilateral symmetry Fig. 32.7 Any plane that passes through the central axis produces roughly mirror-image halves A single midline plane produces roughly mirror-image halves; generally accompanied by distinct cephalization Characteristics of the Animal Kingdom A great diversity of body plans occur; some key features include: Among organisms with 3 germ layers: Acoelomate, pseudocoelomate, or coelomate Characteristics of the Animal Kingdom A great diversity of body plans occur; some key features include: Among organisms with 3 germ layers: Acoelomate, pseudocoelomate, or coelomate Fig. 32.8 Acoelomate: lack a coelom, i.e., lack a body cavity between digestive track and body wall Characteristics of the Animal Kingdom A great diversity of body plans occur; some key features include: Among organisms with 3 germ layers: Acoelomate, pseudocoelomate, or coelomate Fig. 32.8 Pseudocoelomate: Fluid-filled body cavity between digestive tract and body wall partially lined by mesoderm Characteristics of the Animal Kingdom A great diversity of body plans occur; some key features include: Among organisms with 3 germ layers: Acoelomate, pseudocoelomate, or coelomate Fig. 32.8 Coelomate: fluid-filled body cavity between digestive tract and body wall completely lined by mesoderm Characteristics of the Animal Kingdom A great diversity of body plans occur; some key features include: Protostome vs. deuterostome development Characteristics of the Animal Kingdom A great diversity of body plans occur; some key features include: Protostome vs. deuterostome development See Fig. 32.9 Arthropoda Nematoda Rotifera Annelida Mollusca Nemertea Platyhelminthes Ectoprocta Phoronida Brachiopoda Chordata Echinodermata Cnidaria Ctenophora Silicarea Calcarea “Radiata” “Porifera” Deuterostomia Lophotrochozoa Ecdysozoa Bilateria Eumetazoa Metazoa Ancestral colonial flagellate Fig. 32.11 & Table 33.7 The Animal Kingdom ~ 35 phyla Ancestral colonial choanoflagellate Chordata Echinodermata Other bilaterians (including Nematoda, Arthropoda, Mollusca, and Annelida) Cnidaria Porifera Phylum Porifera – Sponges Deuterostomia Bilateria Eumetazoa Figure 33.2 Phylum Porifera – Sponges Organized aggregation of cells Probably the most similar extant group to the protistan colonial precursors to the animals Phylum Porifera – Sponges Organized aggregation of cells Three main cell types, but no true tissues Asymmetric body plan Mostly marine, but some inhabit fresh water Phylum Porifera – Sponges Internal skeleton of protein spicules E.g., natural bath sponge Eumetazoa Chordata Echinodermata Other bilaterians (including Nematoda, Arthropoda, Mollusca, and Annelida) Cnidaria All eumetazoans have true tissues Porifera All animals except sponges belong to the clade Eumetazoa Deuterostomia Bilateria Eumetazoa Ancestral colonial choanoflagellate Figure 33.2 Phylum Cnidaria – Corals, Jellyfish, Anemones Radially symmetric animals with 2 germ layers (true tissues), but generally lacking true organs Gastrovascular cavity; mouth and anus are the same opening Rudimentary nerve net and contractile tissue Phylum Cnidaria – Corals, Jellyfish, Anemones Tentacles contain cnidocytes Fig. 33.6 Phylum Cnidaria – Corals, Jellyfish, Anemones Polyp and medusa forms Fig. 33.5 Phylum Cnidaria – Corals, Jellyfish, Anemones Polyp and medusa forms Phylum Ctenophora – Comb jellies 8 rows of comblike plates of cilia Bilateria Chordata Echinodermata Other bilaterians (including Nematoda, Arthropoda, Mollusca, and Annelida) Cnidaria Porifera Bilaterally symmetric, cephalized animals with 3 germ layers Deuterostomia Bilateria Eumetazoa Ancestral colonial choanoflagellate Figure 33.2 P. Platyhelminthes – Flat worms Gastrovascular cavity (if a gut is present) Some true organs are present (tissues grouped into functional structures) Hermaphroditic and capable of self-fertilization Acoelomate P. Platyhelminthes – Flat worms Mostly free-living P. Platyhelminthes – Flat worms Mostly free-living Some parasitic E.g., tapeworms P. Rotifera – Rotifers Distinguishing feature is a “crown of cilia” around the mouth Complete digestive tract surrounded by pseudocoelom Parthenogenesis (development from unfertilized eggs) is the most common mode of reproduction P. Ectoprocta P. Phoronida P. Brachiopoda All bear a lophophore – fold of the body wall bearing ciliated tentacles surrounding the mouth Coelomate P. Ectoprocta a.k.a. bryozoans Colonial Many contribute to marine reefs P. Phoronida A group of tube-dwelling marine worms P. Brachiopoda a.k.a. lamp shells Marine, mostly extinct P. Nemertea a.k.a. proboscis or ribbon worms Structurally acoelomate, with a small fluid-filled sac that may be a vestigial coelom Closed circulatory system, but no heart P. Mollusca a.k.a. mollusks P. Mollusca a.k.a. mollusks Coelomate body with a muscular foot, visceral mass, and mantle (which secretes a shell in many species) P. Mollusca a.k.a. mollusks 8 classes, including: C. Polyplacophora (chitons) Shell divided into 8 plates P. Mollusca a.k.a. mollusks 8 classes, including: C. Gastropoda (snails and slugs) Single shell or lacking shell P. Mollusca a.k.a. mollusks 8 classes, including: C. Gastropoda (snails and slugs) Single shell or lacking shell P. Mollusca a.k.a. mollusks 8 classes, including: C. Bivalvia (clams, oysters, mussels, etc.) Hinged, twopart shell P. Mollusca a.k.a. mollusks 8 classes, including: C. Cephalopoda (squids, octopuses, nautiluses) Only mollusks with closed circ. system and complex brain P. Mollusca a.k.a. mollusks 8 classes, including: C. Cephalopoda (squids, octopuses, nautiluses) Only mollusks with closed circ. system and complex brain P. Annelida a.k.a. segmented worms P. Annelida a.k.a. segmented worms Segmented Coelomate Coelom Closed circulatory system P. Annelida a.k.a. segmented worms 3 classes: C. Oligochaeta Earthworms and their kin Coelom P. Annelida a.k.a. segmented worms 3 classes: C. Polychaeta Bristled parapodia on each segment P. Annelida a.k.a. segmented worms 3 classes: C. Hirudinea Leeches P. Nematomorpha a.k.a. horsehair or gordian worms Not required to know P. Priapulida a.k.a. penis worms Not required to know P. Tardigrada a.k.a. water bears Not required to know P. Onychophora a.k.a. velvet worms Not required to know P. Nematoda a.k.a. roundworms Nonsegmented P. Nematoda a.k.a. roundworms Nonsegmented No circulatory or respiratory systems Anus Gut Mouth P. Nematoda a.k.a. roundworms Nonsegmented No circulatory or respiratory systems Pseudocoelomate P. Nematoda a.k.a. roundworms Nonsegmented No circulatory or respiratory systems Pseudocoelomate Free living or parasitic E.g., dog heartworm P. Arthropoda Segmented Coelomate Exoskeleton of chitin Jointed appendages P. Arthropoda Open circulatory system Hemolymph (the open-circulation system equivalent of blood) carries dissolved gases through short vessels and the hemocoel (main body cavity in adults, since coelom is reduced) P. Arthropoda As in much of modern systematics, classes are in flux; nevertheless, here are 5 main groups: Trilobites – all extinct during Permain mass extinction ~250 mya P. Arthropoda Cheliceriforms – horseshoe crabs P. Arthropoda Cheliceriforms – sea spiders P. Arthropoda Cheliceriforms: Arachnids – spiders, ticks, scorpions, mites P. Arthropoda Cheliceriforms: Arachnids – spiders, ticks, scorpions, mites spider (tarantula) mite tick scorpion P. Arthropoda Cheliceriforms: Arachnids – spiders, ticks, scorpions, mites Adults generally have 4 pairs of walking legs Some produce silk P. Arthropoda Cheliceriforms: Arachnids – spiders, ticks, scorpions, mites Eyes of black widow spider Simple eyes (each with a single lens) P. Arthropoda Myriapods – millipedes; 2 pairs of legs per segment P. Arthropoda Myriapods – centipedes; 1 pair of legs per segment P. Arthropoda Hexapods: insects P. Arthropoda Hexapods: insects Adult often has 2 pairs of wings P. Arthropoda Hexapods: insects Sometimes 1 pair of wings; sometimes none P. Arthropoda Hexapods: insects Adult generally has 3 pairs of legs P. Arthropoda Hexapods: insects Metamorphosis – transition between distinct (often dramatically different) developmental stages Larva (maggot, caterpillar) Pupa (transition to adult) Adult (often winged) P. Arthropoda Hexapods: insects Metamorphosis – transition between distinct (often dramatically different) developmental stages Larva (maggot, caterpillar) Pupa (transition to adult) Adult (often winged) P. Arthropoda Hexapods: insects Adult generally has compound eyes See also Fig. 33.37 Insects Some of the major orders (26 in total): Order Coleoptera – Beetles Order Hemiptera – True Bugs Order Homoptera – Aphids and their kin Order Hymenoptera – Ants, Bees, Wasps Order Isoptera – Termites Order Lepidoptera – Butterflies and Moths Order Odonata – Dragonflies and Damselflies Order Orthoptera – Crickets, Grasshoppers, Katydids Order Siphonaptera – Fleas P. Arthropoda Crustaceans As in all arthropods, crustaceans have segmented body plans P. Arthropoda Crustaceans waterflea hermit crab sowbug barnacle P. Arthropoda Crustaceans Often have 5 or more pairs of legs P. Arthropoda Crustaceans Generally have compound eyes Deuterostomia Deuterostome developmental pathway Chordata Echinodermata Other bilaterians (including Nematoda, Arthropoda, Mollusca, and Annelida) Cnidaria Porifera Coelomates Deuterostomia Bilateria Eumetazoa Ancestral colonial choanoflagellate Figure 33.2 P. Echinodermata P. Echinodermata At first glance they may seem more radially than bilaterally symmetrical… P. Echinodermata However, their larvae are obviously bilaterally symmetrical Sea star adult Sea star larva P. Echinodermata Brittle star Sand dollar Sea cucumber Sea urchin P. Echinodermata Calcium carbonate endoskeleton Brittle star Sand dollar Sea cucumber Sea urchin P. Echinodermata Unique water vascular system of hydraulic canals branching into tube feet for locomotion, feeding, and gas exchange P. Chordata At some stage in development, all chordates possess: