Invertebrates Chapter 33

Animal Origins

Chlorophyta Plantae Ancestral eukaryote Rhodophyta Fungi Diplomonadida Parabasala Euglenozoa AlveolataStramenopila Cercozoa Radiolaria Amoebozoa Animalia Choanoflagellates 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

A great diversity of body plans occur; some key features include: Organized federation of cells vs. cells in tissues Characteristics of the Animal Kingdom 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

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: Characteristics of the Animal Kingdom Fig Zygote Blastula Gastrulatio n Gastrula Blastocoel Endoderm Ectoderm Blastopore Archenteron

Two embryonic tissue layers: Characteristics of the Animal Kingdom Gastrula Blastocoel Endoderm Ectoderm Blastopore Archenteron Endoderm – Innermost “germ layer”; differentiates into some of the internal tissues and the lining of most hollow organs, if these are present Ectoderm – Outermost “germ layer”; differentiates into tissues that cover the body and into the nervous tissues Fig. 32.2

Three embryonic tissue layers: Characteristics of the Animal Kingdom 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 Fig. 32.9

Characteristics of the Animal Kingdom A great diversity of body plans occur; some key features include: Radial vs. bilateral symmetry 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 Fig. 32.7

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 Characteristics of the Animal Kingdom A great diversity of body plans occur; some key features include: Acoelomate: lack a coelom, i.e., lack a body cavity between digestive track and body wall Fig. 32.8

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: Pseudocoelomate: Fluid-filled body cavity between digestive tract and body wall partially lined by mesoderm Fig. 32.8

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: Coelomate: fluid-filled body cavity between digestive tract and body wall completely lined by mesoderm Fig. 32.8

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

The Animal Kingdom ~ 35 phyla Calcarea Silicarea Ctenophora Cnidaria Echinodermata Chordata Brachiopoda Phoronida Ectoprocta Platyhelminthes Nemertea Mollusca Annelida Rotifera Nematoda Arthropoda “Radiata” “Porifera” Deuterostomia Lophotrochozoa Ecdysozoa Bilateria Eumetazoa Metazoa Ancestral colonial flagellate Fig & Table 33.7

Phylum Porifera – Sponges Ancestral colonial choanoflagellate Eumetazoa Bilateria Deuterostomia Porifera Cnidaria Other bilaterians (including Nematoda, Arthropoda, Mollusca, and Annelida) Echinodermata Chordata Figure 33.2

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 Phylum Porifera – Sponges

Eumetazoa All animals except sponges belong to the clade Eumetazoa All eumetazoans have true tissues Ancestral colonial choanoflagellate Eumetazoa Bilateria Deuterostomia Porifera Cnidaria Other bilaterians (including Nematoda, Arthropoda, Mollusca, and Annelida) Echinodermata Chordata 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

Tentacles contain cnidocytes Fig Phylum Cnidaria – Corals, Jellyfish, Anemones

Polyp and medusa forms Fig Phylum Cnidaria – Corals, Jellyfish, Anemones

Polyp and medusa forms Phylum Cnidaria – Corals, Jellyfish, Anemones

Phylum Ctenophora – Comb jellies 8 rows of comblike plates of cilia

Bilateria Bilaterally symmetric, cephalized animals with 3 germ layers Ancestral colonial choanoflagellate Eumetazoa Bilateria Deuterostomia Porifera Cnidaria Other bilaterians (including Nematoda, Arthropoda, Mollusca, and Annelida) Echinodermata Chordata Figure 33.2

Gastrovascular cavity (if a gut is present) P. Platyhelminthes – Flat worms Some true organs are present (tissues grouped into functional structures) Hermaphroditic and capable of self-fertilization Acoelomate

Mostly free-living P. Platyhelminthes – Flat worms

Mostly free-living P. Platyhelminthes – Flat worms Some parasitic E.g., tapeworms

Distinguishing feature is a “crown of cilia” around the mouth P. Rotifera – Rotifers 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 Colonial Many contribute to marine reefs a.k.a. bryozoans

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, two- part 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 Closed circulatory system Coelom

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 Mouth Gut Anus

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 Free living or parasitic Pseudocoelomate 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 spider (tarantula) scorpion tick mite Cheliceriforms: Arachnids – spiders, ticks, scorpions, mites

P. Arthropoda Adults generally have 4 pairs of walking legs Some produce silk Cheliceriforms: Arachnids – spiders, ticks, scorpions, mites

P. Arthropoda Simple eyes (each with a single lens) Eyes of black widow spider Cheliceriforms: Arachnids – spiders, ticks, scorpions, mites

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 Adult often has 2 pairs of wings Hexapods: insects

P. Arthropoda Sometimes 1 pair of wings; sometimes none Hexapods: insects

P. Arthropoda Adult generally has 3 pairs of legs Hexapods: insects

P. Arthropoda Metamorphosis – transition between distinct (often dramatically different) developmental stages Larva (maggot, caterpillar) Pupa (transition to adult) Adult (often winged) Hexapods: insects

P. Arthropoda Metamorphosis – transition between distinct (often dramatically different) developmental stages Larva (maggot, caterpillar) Pupa (transition to adult) Adult (often winged) Hexapods: insects

P. Arthropoda Adult generally has compound eyes Hexapods: insects

Insects Some of the major orders (26 in total): Order Coleoptera Order Coleoptera – Beetles Order Hemiptera Order Hemiptera – True Bugs Order Homoptera Order Homoptera – Aphids and their kin Order Hymenoptera Order Hymenoptera – Ants, Bees, Wasps Order Isoptera Order Isoptera – Termites Order Lepidoptera Order Lepidoptera – Butterflies and Moths Order Odonata Order Odonata – Dragonflies and Damselflies Order Orthoptera Order Orthoptera – Crickets, Grasshoppers, Katydids Order Siphonaptera Order Siphonaptera – Fleas See also Fig

P. Arthropoda Crustaceans As in all arthropods, crustaceans have segmented body plans

P. Arthropoda waterflea sowbug hermit crabbarnacle Crustaceans

P. Arthropoda Often have 5 or more pairs of legs Crustaceans

P. Arthropoda Generally have compound eyes Crustaceans

Deuterostomia Deuterostome developmental pathway Ancestral colonial choanoflagellate Eumetazoa Bilateria Deuterostomia Porifera Cnidaria Other bilaterians (including Nematoda, Arthropoda, Mollusca, and Annelida) Echinodermata Chordata Coelomates Figure 33.2

P. Echinodermata

At first glance they may seem more radially than bilaterally symmetrical…

P. Echinodermata However, their larvae are obviously bilaterally symmetrical Sea star larva Sea star adult

P. Echinodermata Sea cucumber Brittle star Sea urchin Sand dollar

P. Echinodermata Sea cucumber Brittle star Sand dollar Sea urchin Calcium carbonate endoskeleton

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: