Animal Evolution –The Invertebrates Chapter 25 Part 3

25.11 Roundworms— Unsegmented Worms That Molt  Roundworms (phylum Nematoda) are unsegmented, pseudocoelomate worms with a secreted cuticle that is molted  Most are decomposers, some are parasites Parasitic roundworms include Trichinella, Ascaris, hookworms, Wuchereria, and pinworms

Roundworm Body Plan

Fig a, p. 420 pharynxintestineeggs in uterusgonad false coelom (unlined body cavity)muscular body wallanus

Animation: Roundworm body plan

Roundworms

25.12 Arthropods— Animals With Jointed Legs  Arthropods (phylum Arthropoda) are the most diverse animal phylum – with more than a million species Trilobites are an extinct group Modern arthropods include horseshoe crabs, spiders, ticks, crabs, lobsters, centipedes, and insects

Living Arthropod Subgroups

Key Arthropod Adaptations  A hardened exoskeleton (cuticle) Hormones control molting  Jointed appendages for movement Some legs are modified for special tasks  Highly modified segments Example: wings

Key Arthropod Adaptations  Sensory specializations Compound eyes Antennae that detect touch and chemicals  Specialized developmental stages Body plans may change by metamorphosis Example: Caterpillar and butterfly

Key Arthropod Adaptations

Fig a, p. 421

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25.13 Chelicerates— Spiders and Their Relatives  Chelicerates are arthropods without antennae Marine chelicerates include the oldest living arthropod lineage (horseshoe crabs) All land chelicerates are arachnids, including spiders, scorpions, ticks, and mites

Chelicerates

Fig a, p. 422 telson

Fig b, p. 422 telson (with stinger) pedipalpcephalothoraxabdomen

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Chelicerates: The Spiders  Spiders bite with fanglike chelicerae that deliver venom from poison glands  Paired spinners in the abdomen eject silk  Open circulatory system mingles blood with tissue fluids; Malpighian tubules move excess water and wastes to gut for disposal

Body Plan of a Spider

Fig , p. 422 digestive glandMalpighian tubules eyebrainheart poison gland anus pedipalp mouthbook lungovary spinners sperm receptaclesilk gland chelicera

25.14 The Mostly Marine Crustaceans  Crustaceans are mostly marine arthropods with two pairs of antennae Small crustaceans include krill, copepods, and barnacles Decapod crustaceans include lobsters, crayfish, crabs and shrimps

Crustaceans

Fig a, p. 423

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Body Plan of a Lobster

Fig , p. 423 abdomen segments cephalothorax (fused segments) eyes (two) antennae (two pairs) food-handling appendages (three pairs) tail fan swimmerets first leg walking legs (five pairs)

Crab Life Cycle

Fig , p. 423 juvenile adult female egg larva

Fig , p. 423 Stepped Art adult female egg larva juvenile

Animation: Crab life cycle

25.15 Myriapods—Lots of Legs  Myriapods (“many feet”) are arthropods with two antennae and many body segments  Centipedes are predators  Millipedes are scavengers

Myriapods  Centipede and millipede

25.16 The Insects  Insects have a three-part body plan The head has compound eyes, a pair of antennae, and specialized mouthparts The thorax has three pairs of legs; some lineages have wings Malpighian tubules in the abdomen eliminate wastes and save water

Insect Body Plan: Bedbug

Fig , p. 424 abdomen thorax with six legs head with two eyes, and two antennae

Specialized Mouthparts

Fig , p. 425 liplike labrum antenna compound mandible maxilla palps liplike labrum labium eye ac db

Animation: Insect head parts

Insects  Arthropods are the most successful animals, and insects are the most successful arthropods  Insects are adapted to life on land; a system of tracheal tubes delivers air to their tissues  Development may be direct, or through incomplete or complete metamorphosis

Insect Development

Fig , p. 425 a Direct development: Growth in size between molts but no change in body form eggyoungadult b Incomplete metamorphosis: gradual change with each molt until the nymph becomes adult eggnymphsadult c Complete metamorphosis: larvae grow, then molt into a pupa, which is remodeled into the adult form egglarvaepupaadult

25.17 Insect Diversity and Importance  It would be hard to overestimate the importance of insects, for either good or ill  Insects help provide us with food crops, are food for animals, and help dispose of wastes The four most diverse groups of insects all include pollinators of flowering plants  A few insects eat our crops or carry pathogens

Insect Diversity

Fig a, p. 427

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Fig l, p. 427

Key Concepts The Major Invertebrate Lineages  One major lineage of animals with tissues includes the flatworms, annelids, mollusks, nematodes, and arthropods  All are bilaterally symmetrical  The arthropods, which include the insects, are the most diverse of all animal groups

The Protostome-Deuterostome Split  So far, all of the animals with a three-layered embryo – from flatworms to arthropods – have been protostomes  All of the following animals – from echinoderms to vertebrates – are deuterostomes

25.18 The Spiny-Skinned Echinoderms  Echinoderms (phylum Echinodermata) have “spiny skins” embedded with interlocking spines and plates of calcium carbonate  They begin life as bilateral larvae and develop into spiny-skinned, radial adults  They are brainless and have a unique water- vascular system for locomotion

Echinoderm Body Plan: Sea Star

Fig , p. 428 upper stomach gonadspine lower stomach coelom digestive gland eyespot ampulla of a tube foot canal of water- vascular system spine ossicle (tiny skeletal structure) tube feet a c anus

Animation: Body plan of a sea star

Echinoderm Diversity  Echinoderms include about 6,000 marine invertebrates such as sea stars, brittle stars, sea urchins, and sea cucumbers  Echinoderms can regenerate lost body parts; any portion of a sea star with some of the central disc can regrow missing parts

Echinoderms

25.18 Key Concepts On the Road to Vertebrates  Echinoderms are on the same branch of the animal family tree as the vertebrates  They are invertebrates with bilateral ancestors, but adults now have a decidedly radial body plan

Animation: Chelicerates

Animation: Crustaceans

Animation: Insect development

Video: Old genes, new drugs

Video: Water vascular system

Video: Rotifers

Video: Beetle

Video: Brittle star

Video: Giant clam, octopus

Video: Nudibranch

Video: Otter eating

Video: Sea anemones