Figure 33.2 Review of animal phylogeny Ancestral colonial choanoflagellate Eumetazoa Bilateria Deuterostomia Porifera Cnidaria Other bilaterians (including

Figure 33.2 Review of animal phylogeny

Ancestral colonialchoanoflagellate

Eumetazoa

Bilateria

Deuterostomia

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- Invertebrates - no backbone- 95% of all animals

- Tree based on body plan

- Phylum Porifera (sponge)- No true tissue (parazoa)- Sessile & porous- Most are hermaphrodites

Chapter 33: Invertebrates

Figure 33.4 Anatomy of a sponge

Azure vase sponge (Callyspongia plicifera)

Osculum

Spicules

Waterflow

Flagellum

CollarFood particlesin mucus

Choanocyte

Phagocytosis offood particles Amoebocyte

Choanocytes. The spongocoel is lined with feeding cells called choanocytes. By beating flagella, the choanocytes create a current that draws water in through the porocytes.

Spongocoel. Water passing through porocytes

enters a cavity called the spongocoel.

Porocytes. Water enters the epidermis through

channels formed by porocytes, doughnut-shaped cells that span the body wall.

Epidermis. The outer layer consists of tightly

packed epidermal cells.

Mesohyl. The wall of this simple sponge consists of

two layers of cells separatedby a gelatinous matrix, themesohyl (“middle matter”).

The movement of the choanocyte flagella also draws water through its collar of fingerlike projections. Food particles are trapped in the mucus coating the projections, engulfed by phagocytosis, and either digested or transferred to amoebocytes.

Amoebocyte. Amoebocytes transport nutrients to other cells ofthe sponge body and also produce materials for skeletal fibers (spicules).

5

6

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Eumetazoa

Bilateria

Deuterostomia

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- Phylum Porifera (sponge)- No true tissue (Parazoa)- Sessile & porous- Most are hermaphrodites

- True tissue (Eumetazoa)- Phylum Cnidaria

- Radial symmetry & diploblastic- Gastrovascular cavity- 1 opening - both mouth & anus- Sessile polyp or floating medusa

Figure 33.5 Polyp and medusa forms of cnidarians

Mouth/anus

TentacleGastrovascularcavity

Gastrodermis

Mesoglea

Epidermis

Tentacle

Bodystalk

Mouth/anus

MedusaPolyp

Table 33.1 Classes of Phylum Cnidaria

Figure 33.7 Cnidarians

(a) These colonial polyps are members of class Hydrozoa.

(b) Many species of jellies (classScyphozoa), including thespecies pictured here, are bioluminescent. The largest scyphozoans have tentaclesmore than 100 m long dangling from a bell-shaped body up to 2 m in diameter.

(c) The sea wasp (Chironex fleckeri) is a member of class Cubozoa. Its poison,which can subdue fish andother large prey, is more potent than cobra venom.

(d) Sea anemones and othermembers of class Anthozoaexist only as polyps.

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“Porifera” Deuterostomia Lophotrochozoa Ecdysozoa

Bilateria

Eumetazoa

Metazoa

Ancestral colonialflagellate



Eumetazoa

Bilateria

Deuterostomia

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- Phylum Porifera (sponge)- No true tissue (parazoa)- Sessile & porous- Most are hermaphrodites

- True tissue (Eumetazoa)- Phylum Cnidaria

- Radial symmetry & diploblastic- Gastrovascular cavity- 1 opening - both mouth & anus- Sessile polyp or floating medusa

- Bilateral symmetry & triploblastic- Body cavities of lophotrochozoa

Figure 32.8 Body plans of triploblastic animals

CoelomBody covering(from ectoderm)

Digestive tract(from endoderm)

Tissue layerlining coelomand suspendinginternal organs(from mesoderm)

PseudocoelomMuscle layer(from mesoderm)

Body covering(from ectoderm)

Digestive tract(from ectoderm)

Body covering(from ectoderm)

Tissue-filled region(from mesoderm)

Digestive tract(from endoderm)

Coelomate. Coelomates such as annelids have a true coelom, a body cavity completely lined by tissue derived from mesoderm.

(a)

Pseudocoelomate. Pseudocoelomates such as nematodes have a body cavity only partially lined by tissue derived from mesoderm.

(b)

Acoelomate. Acoelomates such as flatworms lack a body cavity between the digestive tract and outer body wall.

(c)

- Invertebrates- True tissue (Eumetazoa)- Bilateral symmetry

- Body cavities of lophotrochozoa- Acoelomates

- Phylum Platyhelminthes – flat as a plate- Tapeworms & flukes- Gastrovascular cavity with 1 opening- Tapeworms absorb nutrients along

the length of their body

Proglottids withreproductive structures

200 µm

Hooks

SuckerScolex


Figure 33.10 Anatomy of a planarian, a turbellarian

Pharynx. The mouth is at thetip of a muscular pharynx thatextends from the animal’sventral side. Digestive juicesare spilled onto prey, and thepharynx sucks small pieces offood into the gastrovascularcavity, where digestion continues.

Digestion is completed withinthe cells lining the gastro-vascular cavity, which hasthree branches, each withfine subbranches that pro-vide an extensive surface area.

Undigested wastesare egestedthrough the mouth.

Ganglia. Located at the anterior endof the worm, near the main sourcesof sensory input, is a pair of ganglia,dense clusters of nerve cells.

Ventral nerve cords. Fromthe ganglia, a pair ofventral nerve cords runsthe length of the body.

Gastrovascularcavity

Eyespots

Table 33.2 Classes of Phylum Platyhelminthes


- Body cavities of lophotrochozoa- Acoelomates- Pseudocoelomates

- Phylum Nematoda (round worms)


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Bilateria

Eumetazoa

Metazoa



- Body cavities of lophotrochozoa- Acoelomates- Pseudocoelomates

- Phylum Nematoda (round worms)- Mostly aquatic habitats & in body fluids & tissues- Tough transparent cuticle & unsegmented body- Complete digestive tract- Nutrients spread in fluid of pseudocoelom- Trichinella spiralis – trichinosis in undercooked meat- C. elegans

25 µm


Figure 33.27 Juveniles of the parasitic nematode Trichinella spiralis encysted in human muscle tissue (LM)

50 µmEncysted juveniles Muscle tissue


- Body cavities of lophotrochozoa- Acoelomates- Pseudocoelomates- Coelomates

- Phylum Mollusca (snails, clams, oysters, octopus, etc)


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Bilateria

Eumetazoa

Metazoa




- Phylum Mollusca (snails, clams, oysters, octopus, etc)- Muscular foot, visceral mass, mantle- Soft-bodied but most are protected by shell secreted by mantle


Figure 33.16 The basic body plan of a mollusc

Visceral mass

Mantle

Foot

Coelom Intestine

Gonads

Mantlecavity

Anus

Gill

Nervecords Esophagus

Stomach

ShellRadula

Mouth

Mouth

Nephridium. Excretory organs called nephridia remove metabolic wastes from the hemolymph.

Heart. Most molluscs have an open circulatory system. The dorsally located heart pumps circulatory fluid called hemolymph through arteries into sinuses (body spaces). The organs of the mollusc are thus continually bathed in hemolymph.

The long digestive tract is coiled in the visceral mass.

Radula. The mouth region in many mollusc species contains a rasp-like feeding organ called a radula. This belt of backward-curved teeth slides back and forth, scraping and scooping like a backhoe.

The nervous system consists

of a nerve ring around the

esophagus, from which nerve

cords extend.

Table 33.3 Major Classes of Phylum Mollusca



- Phylum Mollusca (snails, clams, oysters, octopus, etc)- Muscular foot, visceral mass, mantle- Soft-bodied but most are protected by shell secreted by mantle

- Phylum Annelida – segemented worm – earthworms, leeches


Figure 32.11 One hypothesis of animal phylogeny based mainly on molecular data

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- Phylum Mollusca (snails, clams, oysters, octopus, etc)- Phylum Annelida – segemented worm – earthworms, leeches

- Damp climates- Divided coelom- Closed circulatory system- Digestive tract with specialized regions- Ventral nerve cord & cerebral ganglia


Figure 33.23 Anatomy of an earthworm

MouthSubpharyngealganglion

Pharynx EsophagusCrop

Gizzard

Intestine

Metanephridium

Ventralvessel

Nervecords

Nephrostome

Intestine

Dorsalvessel

Longitudinalmuscle

Circularmuscle

Epidermis Cuticle

Septum(partitionbetweensegments)

Anus

Each segment is surrounded by longitudinal muscle, which in turn is surrounded by circular muscle. Earthworms coordinate the contraction of these two sets of muscles to move (see Figure 49.25). These muscles work against the noncompressible coelomic fluid, which acts as a hydrostatic skeleton.

Coelom. The coelom of the earthworm is partitioned by septa.

Metanephridium. Each segment of the worm contains a pair of excretory tubes, called metanephridia, with ciliated funnels, called nephrostomes. The metanephridia remove wastes from the blood and coelomic fluid through exterior pores.

Tiny blood vessels are abundant in the earthworm’s skin, which functions as its respiratory organ. The blood contains oxygen-carrying hemoglobin.

Ventral nerve cords with segmental ganglia. The nerve cords penetrate the septa and run the length of the animal, as do the digestive tract and longitudinal blood vessels.

The circulatory system, a network of vessels, is closed. The dorsal and ventral vessels are linked by segmental pairs of vessels. The dorsal vessel and five pairs of vessels that circle the esophagus of an earthworm are muscular and pump blood through the circulatory system.

Cerebral ganglia. The earthworm nervous system features a brain-like pair of cerebral ganglia above and

in front of the pharynx. A ring of nerves around the pharynx connects to a subpharyngeal ganglion, from which a fused

pair of nerve cords runs posteriorly.

Chaetae. Each segment has four pairs of

chaetae, bristles that provide traction for

burrowing.

Many of the internal structures are repeated within each segment of

the earthworm.

Giant Australian earthworm

Clitellum

Table 33.4 Classes of Phylum Annelida



- Phylum Mollusca (snails, clams, oysters, octopus, etc)- Phylum Annelida – segemented worm – earthworms, leeches

- Damp climates- Divided coelom- Closed circulatory system- Digestive tract with specialized regions- Ventral nerve cord & cerebral ganglia

- Phylum Arthropoda – jointed feet – insects, spiders, crustaceans



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Bilateria

Eumetazoa

Metazoa




- Phylum Mollusca (snails, clams, oysters, octopus, etc)- Phylum Annelida – segemented worm – earthworms, leeches- Phylum Arthropoda – jointed feet – insects, spiders, crustaceans

- Regional segmentation & jointed appendages- Appendages for walking, eating, copulating, defense, sensing- Exoskeleton of chitin & proteins – molts- Extensive cephalization- Open circulatory system


Figure 33.29 External anatomy of an arthropod

Antennae(sensoryreception)

Head Thorax

Swimmingappendages

Walking legs

Mouthparts (feeding)Pincer (defense)

AbdomenCephalothorax

Table 33.5 Subphyla of Phylum Arthropoda




- Insects- Most have wings – 1 or 2 pair- Malpighian tubules remove waste from hemolymph- Tracheal system for gas exchange- Ventral nerve cords- Incomplete of complete metamorphosis- Pollination & crop destruction- Disease carriers


Figure 33.35 Anatomy of a grasshopper, an insect

Compound eye

Antennae

Anus

Vagina

OvaryDorsalartery Crop

Abdomen Thorax Head

The insect body has three regions: head, thorax, and abdomen. The segmentation of the thorax and abdomen are obvious, but the segments that form the head are fused.

Heart. The insect heart drives hemolymph through an open circulatory system.

Cerebral ganglion. The two nerve cords meet in the head, where the ganglia of several anterior segments are fused into a cerebral ganglion (brain). The antennae, eyes, and other sense organs are concentrated on the head.

Tracheal tubes. Gas exchange in insects is accomplished by a tracheal system of branched, chitin-lined tubes that infiltrate the body and carry oxygen directly to cells. The tracheal system opens to the outside of the body through spiracles, pores that can control air flow and water loss by opening or closing.

Nerve cords. The insect nervous system consists of a pair of ventral nerve cords with several segmental ganglia.

Insect mouthparts are formed from several pairs of modified appendages. The mouthparts include mandibles, which grasshoppers use for chewing. In other insects, mouthparts are specialized for lapping, piercing, or sucking.

Malpighian tubules. Metabolic wastes are

removed from the hemolymph by excretory organs called Malpighian

tubules, which are out-pocketings of the

digestive tract.




- Insects- Most have wings – 1 or 2 pair- Malpighian tubules remove waste from hemolymph- Tracheal system for gas exchange- Ventral nerve cords- Incomplete or complete metamorphosis- Significant ecological impact- Pollination & crop destruction- Disease carriers

- Deuterostomes



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Bilateria

Eumetazoa

Metazoa



- Body cavities of lophotrochozoa- Acoelomates- Pseudocoelmates- Coelomates- Deuterostomes

- Phylum Echinodermata –spiny skin – sea urchin, sea stars, - Sessile or slow movers as adults- Radial symmetry


Figure 33.40 Echinoderms

(a) A sea star (class Asteroidea) (b) A brittle star (class Ophiuroidea)

(c) A sea urchin (class Echinoidea) (d) A feather star (class Crinoidea)

(e) A sea cucumber (class Holothuroidea) (f) A sea daisy (class Concentricycloidea)


- Body cavities of lophotrochozoa- Acoelomates- Pseudocoelmates- Coelomates- Deuterostomes

- Phylum Echinodermata –spiny skin – sea urchin, sea stars, - Sessile or slow movers as adults- Radial symmetry

- Phylum Chordata – Ch 34 - vertebrates


Table 33.7 Selected Animal Phyla

Documents

Figure 33.2 Review of animal phylogeny Ancestral colonial choanoflagellate Eumetazoa Bilateria Deuterostomia Porifera Cnidaria Other bilaterians (including