Chapter 24 Animal Evolution The Invertebrates

Chapter 24 Animal Evolution The Invertebrates

24.1 Medicines from the Sea Invertebrates No backbone Most diverse and numerous of land and ocean animals Marine invertebrates Many produce secondary metabolites that help them survive Some can be useful as medicines

Medicines from the Sea Fish-eating cone snails produce venom Paralyzes a fish during capture Same compound affects the human nervous system Synthetic version currently used to relieve severe pain Other peptides from cone snail venom being tested as treatments for epilepsy, cancer, and diabetes

Medicines from the Sea AZT Medicine used to treat AIDS First derived from a sponge Gorgonians (relatives of sea anemones) Source of a variety of anti-inflammatory compounds

24.2 Animal Traits and Body Plans Animals Multicelled heterotrophs Ingest food, digest it, and absorb the released nutrients Develop from embryo to adult forms Most reproduce sexually All move during their lifetime

Sponges Cnidarians Flatworm s Annelids Mollusks Roundworms Arthropod s Echinoderms Chordates Trochophore Larva Molting 5 Protostome Development 6 Deuterostome Development 3 Radial Symmetr y 4 Bilateral Symmetry 2 Tissues 2016 Cengage Learning 1 Multicellularity Ancestral protist

Animal Traits and Body Plans Embryo structure Jellies and other cnidarians have two tissue layers Outer ectoderm and inner endoderm Other animals include a mesoderm (middle layer) Internal organs develop from the mesoderm

ectoderm mesoderm endoderm 2016 Cengage Learning

Animal Traits and Body Plans Sponges are asymmetrical Jellies and other cnidarians have radial symmetry Animals with three-layer body plan have bilateral symmetry Cephalization Evolutionary process in which cells and sensory structures become concentrated at the front of the body Helps animal find food or avoid threats

Animal Traits and Body Plans Protostomes First opening on an embryo becomes the mouth Most bilateral invertebrates Deuterostomes Mouth develops from second embryonic opening Includes some invertebrates, and all vertebrates

Animal Traits and Body Plans Digestion In sponges, digestion is intracellular Cnidarians and flatworms digest in the gastrovascular cavity Most bilateral animals have a complete digestive tract

epidermis (from ectoderm) tissues, organs (from mesoderm) gut cavity gut tissue (from endoderm) A Flatworms have no body cavity ex cept their gut. pseudocoelom epidermis (from ectoderm) tissues, organs (from mesoderm) gut cavity gut tissue (from endoderm) B Roundworms have a fluid-filled pseudocoelom. coelom epidermis (from ectoderm) mesenter y tissues, organs (from mesoderm) gut cavity gut tissue (from endoderm) C Annelids have a fluid-filled coelom with sheets of tissue (mesentery) that hold the gut in place. 2016 Cengage Learning

24.3 Animal Origins and Adaptive Radiation Colonial theory of evolution First animals evolved from a colonial protist Colonies had specialized cell types Eventually process produced the first animal Choanoflagellate cells resemble cells in modern sponges Earliest evidence of animals Biomarker characteristic of sponges found in 635 million year old sedimentary rock

Animal Origins and Adaptive Radiation 570 million year old fossils of marine invertebrates discovered in Australia Dramatic adaptive radiation occurred during the Cambrian (542-488 million years ago) All animal lineages present by the end of the period Environmental factors were probable influences Global climate warmed Oxygen concentration increased

Animal Origins and Adaptive Radiation Biological factors might have influenced diversification Evolution of novel prey defenses

24.4 Sponges Sponges have no tissues or organs Aquatic animals More than 5,000 species live in tropical seas Common shape: asymmetrical vase-like or columnar Live attached to a surface Suspension feeders Filter food from the surrounding water

water out glassy structural elements amoeboid cell central cavity pore semifluid matrix flattened surface cells water in water in collar cell flagellum collar of microvilli nucleus 2016 Cengage Learning

Sponges Reproduction Most sponges are hermaphrodites Each individual can produce both eggs and sperm Sperm released into the water Fertilization produces a zygote Develops into a ciliated larva Gemmules Tiny clumps of resting cells encased in a hard coat Wind-dispersed, they grow into new sponges

24.5 Cnidarians Predators with Stinging Cells Phylum Cnidaria 10,000 species Includes corals, sea anemones, and jellies Body plans of cnidarians Medusa: bell shaped Polyp: tubular Use tentacles to sting and capture prey No brain, but have interconnecting nerve cells

Cnidarians Predators with Stinging Cells Cnidarian classes Hydrozoans Example: Hydra, a freshwater predatory polyp Anthozoans Corals and sea anemones Cubozoans Box jellies Scyphozoans Jellies that wash up on beaches Portuguese man-of-war

2016 Cengage Learning lid capsule s trigger (modified cilium) barbs on discharged thread exposed barbed thread in capsule nematocyst (capsule at free surface of epidermal cell)

lid capsule's trigger (modified cilium) barbs on discharged thread exposed barbed thread in capsule nematocyst (capsule at free surface of epidermal cell) Stepped Art

Cnidarians Predators with Stinging Cells Some marine hydrozoans Life cycle includes polyp, medusa, and larval stages

6 reproductive polyp female medusa male medusa ovum sperm 1 zygote 5 feeding polyp 3 2 4 one branch of a colony growth of a polyp ciliated bilateral larva Stepped Art

A Hydrozoan. Hydra, a freshwater species, capturing and digesting a water flea. B Anthozoans. A reef-building coral with polyps extended for feeding (top), and a sea anemone (bottom). C Cubozoan. The box jelly Chironex makes a toxin that can kill a person. D Scyphozoan. The Portuguese man-ofwar (Physalia ) is a colony. The purplishblue, air-filled float is a modified polyp. Courtesy of Dr. William H. Hamner Kim Taylor/Bruce Coleman, Ltd. A.N.T./Science Source. Expeditieteam Aldabra, Foto Natura/Minden Pictures Etha Daniels/Shutterstock

24.6 Flatworms Simple Organ Systems Flatworms Simplest protostomes Flattened body Organ systems, but no body cavity Move nutrients through their system using diffusion Majority are hermaphrodites Some are free-living and some are parasites

Flatworms Simple Organ Systems Free living flatworms propelled by cilia Planarian Type of free living flatworm common in ponds Muscular tube called pharynx sucks food into gastrovascular cavity Chemical receptors on the head detect light Simple brain of paired ganglia Higher solute concentration than surrounding water Water moves into the body by osmosis

branching gastrovascular cavity paired groups of nerve cells that serve as simple brain pair of highly branched tubules that adjust water and solute levels in body ovary testis oviduct mouth pair of nerve cords that have lateral branchings genital pore A Digestive system. B Nervous system. C Solute-regulating system. D Reproductive system. 2016 Cengage Learning

Parasitic Flatworms Flukes and tapeworms Life cycle generally includes multiple hosts Reproduce asexually in early hosts before developing into adults Reproduce sexually in the final host Schistosomaisis Human disease caused by blood fluke Affects 200 million people Most cases in Southeast Asia and Northern Africa

Parasitic Flatworms Tapeworms Live and reproduce in the vertebrate gut Head structure includes hooks or suckers to attach to the gut wall Do not have a gastrovascular cavity Absorb nutrients across the body wall Beef tapeworm life cycle Humans are the final host See Figure 24.15 on next slide

1 2 proglottid scolex tapeworm in cattle muscle 5 beef with larval tapeworm 4 larva 3 proglottid with fertilized eggs Stepped Art

24.7 Annelids Segmented Worms Bilateral worms with segregation both inside and outside the body Have a closed circulatory system Blood flows through a series of vessels Polychaetes and oligochaetes Have chitin-reinforced bristles on their segments Sandworm is the best known polychaete

Annelids Segmented Worms Leeches Can live in the ocean and damp land habitats Most common in fresh water Body has a sucker at each end Many are scavengers or predators to small invertebrates Some suck blood from vertebrates Saliva protein keeps blood from clotting while it feeds

Annelids Segmented Worms Earthworm: an oligochaete Body is coated with secreted proteins Gas exchange occurs across the body surface Circulatory system helps distribute oxygen Scavenger Has both longitudinal and circular muscles Hermaphrodite, but needs to be fertilized by another worm

24.8 Mollusks Animals With a Mantle Bilaterally symmetrical invertebrates with a mantle Skirtlike extension of the upper body Encloses a space called the mantle cavity Vast majority are marine, but some live in fresh water Respiratory system Aquatic mollusks have gills Land mollusks have lungs

Mollusks Animals With a Mantle 100,000 living species Four main classes Chitons Marine; feature a dorsal shell with eight plates Gastropods Snails and slugs Bivalves Mussels, oysters, clams, and scallops Cephalopods Squids, octopuses, and cuttlefish

24.9 Rotifers and Tardigrades Tiny and Tough Rotifers Live in fresh water and damp land habitats Most are less than one millimeter long Have constantly moving cilia on the head Movement directs food into the mouth Tardigrades Commonly live alongside rotifers Suck juices from plants or algae Survive dry periods by becoming dormant Can live for years in dormant state

24.10 Roundworms Unsegmented Worms That Molt Unsegmented worms with a cylindrical body Collagen-rich cuticle is periodically molted As the worm grows 20,000 species live in fresh water, seas, damp soil, and inside other animals Most are free living decomposers less than one millimeter long Several types of parasitic roundworms infect humans

A Intestinal parasite, Ascaris, passed by a child. B The grossly enlarged leg of the man on the left is a sign of lymphatic filariasis. C Plant-infecting roundworm entering a root. Courtesy of Emily Howard Staub and The Carter Center CDC/ Henry Bishop William Wergin and Richard Sayre. Colorized by Stephen Ausmus.

24.11 Arthropods Molting Animals With Jointed Legs Arthropods have a hard, jointed external skeleton Most diverse invertebrate group Adaptations that helped them succeed Exoskeleton Jointed appendages allow movement Highly modified segments perform special tasks Compound eyes and antennae Body plan that changes during life cycle

24.12 Chelicerates Spiders and Their Relatives Examples: spiders, scorpions, ticks, horseshoe crab Two body regions: fused head and thorax, and abdomen Arachnids live on land 38,000 spider species Ticks are parasites of vertebrates Mites are less than one millimeter long Some can burrow beneath the skin

24.13 Myriapods Centipedes Nocturnal ground dwellers Have a flattened body with many similar segments Have 30 to 50 legs Fast moving predators Millipedes Few hundred pairs of legs Slower moving than centipedes Feed on decaying vegetation

24.14 Crustaceans Most marine arthropods are crustaceans Body has two distinctive regions Cephalothorax and abdomen Examples: lobster, shrimp, crayfish, and crabs Decapods: five pairs of walking legs Krill and copepods Small swimmers that feed on plankton Group includes larval barnacles and pillbugs

A Antarctic krill ( Euphausia superba). Individuals can be up to 6 centimeters long. David Tipling/Photographer s Choice/Getty Images Peter Parks/Image Quest Marine. Herve Chaumeton/Agence Nature B Female copepod with eggs. C Barnacle extending feathery legs.

24.15 Insects Diverse and Abundant Three part body Head, thorax, and abdomen Group is largely terrestrial Earliest insects were ground dwelling Did not undergo metamorphosis Most modern insects have wings and undergo metamorphosis Stages: larvae, pupa, adult Ants make up 10 percent of world s terrestrial biomass

Insects Diverse and Abundant Ecological impact of insects Pollinate flowering plants Important as food for wildlife Insects dispose of wastes and remains Insects are humans main competitors for crops About one-third of all crops in the United States are lost to insects Insects can spread human diseases

24.16 The Spiny-Skinned Echinoderms Echinoderms include 6,000 marine invertebrates Example: sea stars Active predators that move on tiny, fluid-filled tube feet Feed on bivalve mollusks Can regenerate lost body parts Brittle stars are seafloor scavengers Sea urchins have a spiny, rounded covering

upper stomach anus lower stomach spine gonad coelom digestive glan d eyespot Herve Chaumeton/Agence Nature 2016 Cengage Learning spine ossicle (tiny skeletal structure) ampullae tube feet

Points to Ponder Some people don t consider an organism a true animal unless it bleeds red when injured. Do any of the animals presented in this chapter fit this definition? Why is the word primitive not accurate in describing early groups like sponges and cnidarians?