Invertebrates Phylum Annelida Segmented Worms

◦ segmentation allows specialization of system

Body Plan: Tube-within-a-tube

Body Systems◦ Digestion

Pharynx, esophagus, crop, gizzard, intestine, accessory glands◦ Musculatory

Longitudinal and circular muscles in each segment◦ Circulatory

Closed system with pumping hearts◦ Nervous system

brain, ventral nerve cord, and ganglia in each segment◦ Excretory system

nephridia in most segments

Annelida cont’dClass Polychaeta

◦Largest class - marine worms◦Have setae-bristles for anchoring

worm or helping in locomotion Arranged in bundles on parapodia

Swimming, gas exchange◦Polychaetes are seasonal breeders

After fertilization, a trochophore larva develops-same larval type as molluscs

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Annelida cont’dClass Polychaeta cont’d

◦Representative Organisms Clam worms-Nereis

Predators-eat crustaceans and other small animals

Tube worms Tentacles that form a funnel-shaped fan Sessile filter feeders

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Polychaete diversity

Fig. 30.13

Annelida cont’dClass Oligochaeta

◦Earthworms◦Few setae per segment◦No obvious head◦Gas exchange across body wall◦Feed on leaves and other organic

matter Food is drawn into mouth by muscular

movements Digestive tract has a large surface area

Typhlosole-expanded region on dorsal surface of intestine

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Earthworm, LumbricusFig. 30.14

Annelida cont’dClass Oligochaeta cont’d

◦Segmentation Structure

External - evident by body rings Internal - septa

Nervous System Ventral nerve cord has ganglionic swellings in each

segment Lateral nerves extend from ganglions

Excretory Paired nephridia in each segment

1st funnel-like collects coelomic fluid 2nd exits through body wall

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Annelida cont’dClass Oligochaeta cont’d

◦Segmentation cont’d Circulation

Blood moves anteriorly through dorsal vessel Enters aortic arches- “hearts” Pump blood to ventral vessel

blood then moves posteriorly Branches in each segment

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Annelida cont’dClass Oligochaeta cont’d

◦Reproduction in earthworms Hermaphroditic

Male organs- testes, seminal vesicles, sperm ducts

Female organs-ovaries, oviducts, seminal receptacles

Worms lie parallel in opposite directions Clitellum produces mucus to keep sperm moist

After separation, produces a slime tube which moves eggs and sperm together for fertilization

Slime tube then produces a cocoon

Annelida cont’dClass Hirudinea

◦Leeches◦Most live in freshwater◦Most are ectoparasites- have suckers for

feeding Saliva contains hirudin-anticoagulant

◦Have same general body plan as other annelids Lack setae Each body ring has transverse grooves

Makes leech appear to have more segments

Invertebrates Phylum ArthropodaExoskeleton of chitin

◦ Must undergo molting to allow growth

Exhibit jointed appendages◦ Walking, swimming, reproduction, eating, sensory

reception

3 body regions◦ Head, thorax, abdomen

Well-developed nervous system◦ Brain and ventral nerve cord◦ Sense organs-compound eyes, antennae

Arthropod diversity

Fig. 30.15

Phylum Arthropoda cont’d.Subphylum

Crustacea◦ Barnacles,

shrimps, lobsters, crabs, crayfish

◦ Terrestrial - sowbug

Phylum Arthropoda cont’d.Subphylum Crustacea cont’d

◦Crayfish: Representative external structure Fused cephalothorax

Head has compound eyes and 5 pairs of appendages First 2 pairs are antennae, 3 pair are mouth

parts Thorax has 5 pair of appendages-walking legs

1st walking leg has a pinching claw Gills are situated above the walking legs

Abdomen- has swimmerets Last 2 segments have uropods and telson

Phylum Arthropoda cont’d.Subphylum Crustacea cont’d

◦Crayfish: Representative internal structure Digestive system

2 part stomach, green glands for waste excretion

Vascular system heart pumps blood with hemocyanin into

hemocoel Hemocyanin has blue pigment Hemolymph flows around organs

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Phylum Arthropoda cont’d.Subphylum Crustacea cont’d

◦Crayfish: Representative internal structure cont’d Nervous system

Brain and ventral nerve cord with segmental ganglia Sensitive hair like receptors on antennae

Mechanoreceptors: responds to physical stimuli Chemoreceptors: sensitive to chemicals in the water

Reproduction Sexes separate- sperm transfer by first pair of

swimmerets Ovaries open at base of third walking legs After fertilization, eggs attach to swimmerets of female

Male crayfish, Cambarus

Fig. 30.16

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Phylum Arthropoda cont’d.Subphylum Uniramia

◦Insects; largest and most diverse group

◦General structure Head with pair of compound eyes or

several simple eyes, a pair of antennae, mouthparts adapted to specific way of life

Thorax: 3 pairs of legs and wings if present

Abdomen: contains internal organs

Phylum Arthropoda cont’d.Subphylum Uniramia cont’d

◦Representative Organism: Grasshopper 3rd pair of legs is adapted for jumping 2 pairs of wings Tympanum on side of first segment of

abdomen Ovipositor of females- for digging a hole

in which to lay eggs.

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Phylum Arthropoda cont’d.Subphylum Uniramia cont’d

◦Grasshopper cont’d. Internal organs

Digestive system-stomach, intestine, rectum, anus

Excretory system - Malpighian tubules Uric acid-nitrogenous waste

Respiratory system-spiracles lead into trachae Air pumped by contraction and relaxation of

body wall Circulatory system-heart pumps hemolymph

into aorta, leads to a hemocoel Hemolymph has no specialized pigment and is

colorless

Phylum Arthropoda cont’d.Subphylum Uniramia cont’d

◦Grasshopper cont’d. Reproduction

Adapted to terrestrial life Internal fertilization protects zygotes and

gametes from drying Penis inserted into female, sperm stored in

seminal receptacle Fertilized eggs are deposited into ground

Metamorphosis change in form and physiology that occurs as a

larva becomes and adult Immature grasshopper called nymph

Female grasshoppers

Fig. 30.18 30-22

Phylum Arthropoda cont’d.

◦ Grasshopper: terrestrial Spiracles and trachae

for gas exchange O2 diffuses directly

through to reach cells Has tympanum for

reception of sound Use legs for hopping

and wings for flying Penis for passing

sperm to female to prevent drying

◦ Crayfish: aquatic Crayfish gills for

gas exchange require oxygen-

carrying pigment to carry oxygen to cells

Hair like receptors Utilize uropods for

swimming Sperm passed to

female, eggs carried externally.

Comparing Subphyla Uniramia and Crustacea

Phylum Arthropoda cont’d.Subphylum Chelicerata

◦Arachnids: Spiders, ticks, scorpions, mites

◦Cephalothorax 6 pairs of appendages Chelicerae, pedipalps, and 4 pairs of

walking legs◦Abdomen contains internal organs◦Ticks and mites are ectoparasites

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Phylum Arthropoda cont’d.Subphylum Chelicerata cont’d

◦Representative Organism: Spiders Narrow waist separates cephalothorax from

abdomen Fangs deliver poison to prey Pedipalps sense and hold prey Digestion:

Digestive juices released into prey, initial digestion is external

digested “broth” then is sucked into stomach Gas Exchange

lamellae of inner body wall for gas exchange “book lungs”

Silk glands for web-spinning

Arachnid diversity

Fig. 30.19

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