InvertebrateDiversity

Comparison of Increasing Complexity

Highlight what is bold/underlined

What is an invertebrate?

Name some common invertebrates?

Are snakes invertebrates?

Introductory VocabularyInvertebrate – animal without a backbone

Coelom – fluid-filled space between body wall and intestine

Cephalization – sensory organs concentrated at the anterior end of the organism

Sexual reproduction – gametes are produced and fuse to form unique diploid offspring

Asexual reproduction – single parent produces offspring genetically identical to itself

Hermaphrodite – animals with both ovaries and testes

Sessile – nonmotile; animal that doesn’t move on its own

Open circulatory system – vessels empty into body spaces called sinuses

Closed circulatory system – blood never leaves vessels as it flows through the body

Compound eye – eye with many lenses; found in arthropods

Notochord – stiff rod found in chordates that becomes the vertebral column in vertebrates

Dorsal nerve cord – bundle of nervous tissue found in chordates that becomes the spinal cord in vertebrates

Pharyngeal slits – openings in the pharynx found in chordates that give rise to many structures in vertebrates

Kingdom Animalia

Invertebrate phyla:

Porifera -sponges

Cnidaria-sea anemones,coral and jelly fish

Platyhelminthes-flatworms (planaria, flukes, tapeworms)

Nematoda -roundworms

Mollusca-slugs, snails, “seashell animals”, octopii and squid

Annelida – segmented worms (marine worms, earthworms & leeches)

Arthropoda – insects, arachnids & crustaceans

Echinodermata – starfish, sand dollars, sea urchins, & sea cucumbers

Porifera• Sponges

– Multicellular; no true tissues; asymmetric; sessile

– spongin- protein fibers for structure; spicules for skeleton

– individual cells acting together as an organism

• filter feeders using collar cells (choanocytes) & amoebocytes

• Water enters pores and exits osculum

– Asexual reproduction• fragmentation

– sexual reproduction (hermaphroditic)

• External fertilization

Cnideria• Radial symmetry; true

tissues; sessile and/or motile

• Cnidocytes - stinging barbs to capture prey

• Tentacles to bring prey into gastrovascular cavity

• Two body forms– Polyp – sessile with

mouth dorsal– Medusa – motile with

mouth ventral (adult)• Asexual reproduction -

budding • Sexual reproduction -

external fertilization resulting in planulae larvae

Classes of cniderians:

Hydrozoa – hydra, Obelia, & Portuguese man-of-war

Scyphozoa – jellyfish

Anthozoa – sea anemones & coral

-bilateral symmetry; cephalization; acoelomate; organs-Nervous system: ganglia & nerve cords-Excretory system: flame cells-Digestive system: two-way digestive tract with common mouth/anus; gastrovascular cavity-Respiratory system: diffusion through epidermis -Circulatory system: none (diffusion)-Reproductive system:

-Sexual – internal fertilization; hermaphroditic; lay eggs-Asexual - fragmentation

Platyhelminthes - flatworms

Class Turbellaria

- planaria

- freeliving

- one of few freshwater species

“typical” flatworm

Class Cestoda•Tapeworms•Parasites•Attach to intestinal wall of host with scolex•proglottids – segments packed with reproductive organs•absorb nutrition from host –don’t need digestive system

Class Trematoda

- endoparasites OR ectoparasites

- complex life cycle with more than one host

- primitive or no digestive system

Schistosoma – major public health threat; cause liver damage

Phylum Nematoda - roundworms- pseudocoelomate- hydrostatic skeleton- one-way digestive

system with separate mouth/anus

- Respiration and circulation by diffusion

- Have longitudinal muscles - Reproduction – sexual;

complex life-cycle with multiple hosts

- Most are free-living predators in the soil

- Some are parasitic; hookworms, pinworms, Trichinella

                                                                                                        

                       

Mollusca• Coelomate; bilateral

symmetry; organs; exoskeleton (shell)

• 3-part body plan:– Visceral mass – contains

organs– Mantle – secretes shell– Foot – locomotion

• Radula – for feeding• cephalization • Open circulatory system• One-way digestive system• Nephridia – excretory organs• Respiration – gills, mantle

cavity, and/or diffusion across skin

• Reproduce sexually; many hermaphroditic; form trochophore larvae

Classes of mollusks – based on body plan:

*Gastropoda – stomach-foot; snails and slugs

*Bivalvia – two-shells; clams, oysters, mussels

*Cephalopoda – head-foot; nautilus, squid, octopi, cuttlefish

ANNELIDA• Oligochaeta –

earthworms• Hirudinea – leeches• Polychaeta – marine

worms

Major characteristics of all annelids:• Segmentation – separated by septa; each

segment has organs of each major system

• Cephalization – including cerebral ganglia

• Ventral nerve cord

• Coelom – hydrostatic skeleton

• Organ systems

• Setae – bristles for movement

• Parapodia – fleshy appendages for movement &/or respiration

Earthworms•Ecologically important scavengers

•Two layers of muscle: longitudinal & circular

•5 hearts; closed circulatory system

•Nephridia for excretion

•Respiration through epidermis

•Complex digestive system with mouth, pharynx, esophagus, crop, gizzard, intestine, and anus

•Sexual reproduction; hermaphroditic; clitellum forms mucus cocoon to protect fertilized eggs

How are HUMANS separated into body segments?

•Remnants of segmentation are visible in the embryo as

repeated blocks of tissue called somites and in the vertebral

column

Arthropods•largest and most diverse phylum; includes insects, crustaceans, spiders

•segmented bodies – head, thorax, & abdomen or cephalo-thorax & abdomen; segmentation apparent on abdomen

•jointed appendages (3, 4 or 5 pairs of walking legs plus assorted other specialized appendages)

•Respiration: spiracles into trachea; gills; book lungs

•Excretion through Malpighian tubules

•Incomplete or complete metamorphosis

•exoskeleton of chitin *complex muscular system

•ventral nerve cord & brain * open circulatory system

•compound eyes * ecdysis (molting)

Millipedes – 2 pairs of legs per segment

- herbivores or detritovores, but can be really smelly!

- one pair of antennae

Centipedes – 1 pair of legs per segment

- predators with jaws

- one pair of antennae

Insects – 3 body regions: head, thorax, abdomen

- 3 pairs of legs attached to thorax

- exoskeleton of chitin

- jaws (mandibles)modified for particular feeding method

- wings are extensions of the exoskeleton; 0, 1 or 2

pairs

- 1 pair of antennae

- compound eyes

Arachnids – spiders, scorpions, ticks, & mites

•Chelicerae – mouthparts modified into pincers or fangs

•Cephalothorax & abdomen

•4 pairs of walking legs

•No antennae

•Simple eyes

•Spinnerets & silk glands in spiders

•Book lungs in spiders

•Predators that consume liquified food

•Distantly related to horseshoe crabs

mite

tick

Crustaceans Ecologically important – copepods & krill are planktonic crustaceans that form the basis of many marine food chains

Crabs, lobsters, shrimp, & crayfish are other well-known crustaceans called decapods – “10 feet”

First pair of walking legs often modified into chelipeds (pincers)

2 pair of antennae

Compound eyes

Sexual reproduction

Cephalothorax covered by carapace

Small appendages on abdomen of of some called swimmerets

Barnacles are sessile crustaceans

Pill bugs (isopods) are terrestrial crustaceans with gills

ECHINODERMS

*most complex of the invertebrates

•Only live in salt water (oceans)

•Five-part radial symmetry in adults; larvae are bilaterally symmetrical

•Hard, bumpy, spiny ENDOskeleton composed of ossicles

•Water vascular system with 5 rows of tube feet that aid them in movement, gas exchange, food capture and waste excretion.

•Skin gills increase respiratory surface area & function in excretion

•Feeding in starfish involves everting stomach out of mouth, digesting prey outside of body, and then pulling the digested material into the body; other echinoderms tend to be filter feeds or detritivores

Ex: starfish, sand dollar, sea cucumber, sea urchin, sea cucumber, sea biscuit, brittle stars, sea lilies, sea daisies, sea pens, feather stars

Invertebrate Chordates

4 characteristics of all chordates:

*Notochord

*Dorsal hollow nerve cord

*Pharyngeal gill slits

*Postanal tail

Invertebrate chordates include tunicates & lancelets; all other chordates are vertebrates

tunicate

lancelet