Invertebrates

Chapter 33

• Most animals - invertebrates - do not have backbone.

http://www.edsci-affiliates.com/images/invertebrates_divider.jpg

1Phylum Porifera

• Sponges - lack nerves and muscles; sessile (non-motile).

• Most marine, live in water.• Most hermaphrodites - each

individual produces sperm and eggs.

• Can regenerate lost parts.

http://www.gcb.vic.gov.au/gallery/SEA%20SPONGE,%20PORIFERA.jpg

• Sponges perforated with holes so water can flow through them (suspension-feeding)

• Water drawn through pores into central cavity (spongocoel) and flows out through larger opening (osculum)

2Phylum Cnidaria• 1st organisms to have true tissues. • Basic body plan - sac with central

digestive compartment (gastrovascular cavity)

• Jellyfish, corals, sea anemones, and hydras.

• Have nerve nets - very primitive nervous systems that move towards stimuli.

• 2 body plans in cnidarians.• 1Polyp stage - sessile; some live

whole life this way.• 2Medusa stage - cnidarian can

swim freely.• Can move through both stages

during lifetime.

http://library.thinkquest.org/26153/marine/sketch/613.jpg

• Cnidarians have nematocysts - stinging cells.

• Phylum Cnidaria divided into 3 major classes: Hydrozoa (hydra), Scyphozoa (true jellyfish), and Anthozoa (sea anemones).

• Cnidarians - carnivores - use tentacles to push food into gastrovascular cavity.

3Phylum Ctenophora

• Comb jellies named for fused cilia.

• Resemble medusa stage of cnidarians.

• No stinging cells present.

4Phylum Platyhelminthes

• Flatworms, both parasitic and non-parasitic.

• Flatworms have mesoderm - middle layer of tissues - makes them bilateral.

http://www.waterworxbali.com/Images/Photos/Large/pseudoceros-ferrugineus.jpg

• Gastrovascular cavity with only 1 opening; absorb materials across tissue.

• Flatworms are divided into four classes: Turbellaria, Monogenia,Trematoda (flukes), and Cestoidea (tapeworms).

Turbellaria

http://en.wikipedia.org/wiki/Turbellaria

Trematoda

http://en.wikipedia.org/wiki/Trematodes

http://www.saudeanimal.com.br/imagens/platelmintos.jpg

Cestoidea

• Planaria - scavengers found in ponds.

• No organs specialized for circulation or respiration; exchange gases across membranes.

• Have eyespots for detecting light and lateral flaps for smell.

• Nervous systems more advanced than cnidarians; reproduce asexually through regeneration (can sexually reproduce).

Planaria

• Trematodes parasites with suckers to attach to victims.

• Blood fluke - parasite of humans.• Tapeworms have suckers and

hooks on head; anchor worm in digestive tract of host.

Blood fluke

5Phylum Rotifera• Rotifers - complete digestive tract

with separate mouth and anus. • Internal organs in pseudocoelom -

body cavity not completely lined with mesoderm.

• Functions as circulatory system -nutrients dissolved in cavity.

• Have hydrostatic skeleton - movement.

http://planktonweb.ifas.ufl.edu/Asplanchna.jpg

• Some rotifers exist only as females that produce more females from unfertilized eggs - parthenogenesis.

6Phylum Mollusca• Snails, slugs, clams, squid, and

octopus. • Mollusks soft-bodied animals -

most protected by hard shell of calcium carbonate.

• All have similar body plan with muscular foot (locomotion), visceral mass with most of internal organs, and mantle.

http://sps.k12.ar.us/massengale/clip0051.jpg

• Use radula to feed - allows them to scrape up food.

• Most mollusks have separate sexes.

• 4 common classes - Polyplacophora (chitons), Gastropoda (snails and slugs), Bivalvia (clams, oysters, and other bivalves), Cephalopoda (squids, octopuses, and nautiluses).

Chiton

http://cache.eb.com/eb/image?id=65301&rendTypeId=4

Gastropod

http://www.marinefoundation.org/mussels_600.jpg

Bivalves

http://home.earthlink.net/~snailstales/cephalopods.jpg

Cephalopod

• Gastropods have shells that they can retreat into (means stomach-foot)

• Lining of mantle acts like lungs - allows them to live on land (garden snails and slugs).

• Bivalves - 2-shelled - clams, oysters, mussels, and scallops.

• Most bivalves - suspension feeders, trapping fine particles in mucus that coats gills.

• Usually sessile - cannot move during lifetime.

• Cephalopods have reduced shell and include nautilus, squid, and octopus.

• Nautilus - external shell. • Have well-developed nervous

system with complex brain and well-developed sense organs.

• Cephalopods have closed circulatory system.

Nautilus

6Phylum Annelida

• Annelids - segmented worms. • Digestive system - pharynx,

esophagus, crop, gizzard, and intestine.

• Closed circulatory system with 5 chambers act as heart to pump blood.

http://www.inhs.uiuc.edu/~sjtaylor/cave/cave_olig.jpg

• Each segment - pair of excretory tubes, (metanephridia) - remove wastes from blood and coelomic fluid exits through pores.

• Brainlike pair of cerebral ganglia lie above and in front of pharynx.

• Some earthworms reproduce asexually (regeneration), also reproduce sexually.

• Hermaphrodites - exchange sperm which are stored, then later fertilize egg.

• Phylum Annelida divided into 3 classes: Oligochaeta (earthworms), Polychaeta (bristle worms), and Hirudinea (leeches).

http://www.pmel.noaa.gov/vents/nemo/explorer/bio_gallery/biogallery-ImageF.00049.jpeg

Polychaeta

http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb6pg1_files/earthworm1.jpg

• Segmentation of worms allow for specialization.

• Hirudinea - leeches – parasitic, suck blood off hosts.

• Used in medicine because they promote circulation in areas of body.

Hirudinea

7Phylum Nematoda

• Roundworms - found in wet environments.

• Complete digestive tract - use fluid in pseudocoelom to transport nutrients (lack circulatory system)

• Reproduce sexually, can be parasitic (trichinosis)

8Phylum Arthropoda• Characterized by body

segmentation, a hard exoskeleton, jointed appendages.

• Body of arthropod completely covered by cuticle - exoskeleton constructed from layers of protein and chitin.

• Have to molt in order to grow.

• Arthropods have well-developed sense organs, including eyes for vision, olfactory receptors for smell, antennae for touch and smell.

• Arthropods - open circulatory system - fluid pumped by heart through short arteries into sinuses surrounding tissues and organs.

http://www.geocities.com/SouthBeach/7648/internal.jpg

• Aquatic arthropods - gills for breathing; terrestrial arthropods - internal structures for breathing.

• Insects - tracheal tubes to breathe.

http://www.dwm.ks.edu.tw/bio/activelearner/44/images/ch44c3.jpg

• Trilobites - extinct arthropods - no specialization.

• Chelicerates mostly extinct; 4 species, (i.e. horseshoe crab) still alive.

• Modern chelicerates members of class Arachnida (scorpions, spiders, ticks, and mites).

Trilobite

Horseshoe crab

• Most spiders - book lungs allow them to breathe.

• Some can inject poison to kill prey.

• Millipedes - worm-like with 2 pairs of walking legs on each segment.

• Centipedes - terrestrial carnivores.

• Insects (class Insecta) outnumber all other forms of life combined - 26 orders.

Millipede

• Insects - ability to fly. • Metabolic wastes removed from

fluid by Malpighian tubules, pockets of digestive tract.

• Respiration done by branched, chitin-lined tracheal system - carries O2 from spiracles directly to cells.

• Nervous system - pair of ventral nerve cords with several segmental ganglia.

• Metamorphosis occurs in insects; can be either incomplete (grasshoppers) or complete (butterflies).

• Reproduction in insects usually sexual, with separate male and females.

• Many arthropods live in water. • Crustaceans include lobsters,

crabs, crayfish, shrimp, and barnacles.

• Small crustaceans exchange gases across thin areas of cuticle; larger species have gills.

• Circulatory system open - heart pumps fluid into short arteries then into sinuses that bathe organs.

• Nitrogenous wastes excreted by diffusion through thin areas of cuticle, glands regulate salt balance of fluid (hemolymph).

http://limnology.wisc.edu/personnel/pieter/Hidden%20Stuff/Daphnia/SCDbody.jpg

• Crustaceans - different sexes.• 3 groups of crustaceans: isopods

(pill bugs, or wood lice), copepods (small crustaceans) and decapods (lobsters, crayfish, crabs, and shrimp).

• Barnacles also crustaceans.

http://farm1.static.flickr.com/1/380353_028542ead3.jpg

Phylum Echinodermata• Most echinoderms sessile, or

slow-moving.• Most - prickly skin.• Water vascular system - network

of hydraulic canals branching into extensions (tube feet) used for movement, feeding, gas exchange.

http://www.education.umd.edu/blt/pic/Echinoderm.jpg

• Sexual reproduction in echinoderms - release of gametes by separate males and females into seawater.

• 6 classes: Asteroidea (sea stars), Ophiuroidea (brittle stars), Echinoidea (sea urchins, sand dollars), Crinoidea (sea lilies, feather stars), Holothuroidea (sea cucumbers), Concentricycloidea (sea daisies)

http://www.arctic.noaa.gov/aro/russian-american/photo-gallery/brittle-stars-Photo-B-Bluhm.JPG

• Sea stars can attach to objects with tube feet.

• Can regenerate lost parts.• Brittle stars do not have suckers

on tube feet - have long and flexible arms.

Sea star

Brittle star

• Sea urchins and sand dollars - no arms, have 5 rows of tube feet used for locomotion.

• Sea lilies attached to objects by stalks, feather stars crawl using their long, flexible arms.

• Sea cucumbers lack spines - have tube feet.

Sea urchin

Sea lily

Sea cucumber