Animal Web HomeDiversity of Animals

Kingdom Animalia•Multicellular•Eukaryotic•Heterotrophs•Cells lack cell wall

Trends in animal evolution:•Asymmetrical, radial symmetry, bilateral symmetry•Cephalization•Sessile, motile•Specialized cells, tissue, organs, systems•Body cavity formation (coelem)•Embryology and germ layer development

Phylum Porifera:The Sponges

Structure and Filter Feeding Mechnism

Diversity information, pictures, classification

Characteristics of Poriferans:•“pore bearers”•Sessile (attached to a fixed point)•Asymmetrical (no front or back, left or right)•No tissue or organs, only specialized cells•Filter feeders•Water flows in through pores and out through osculum•Choanocytes use flagella to move water through the sponge•Skeleton of spicules (silica or calcium carbonate) or spongin (flexible protein fibers)•Reproduce by budding or sexually•Provide habitats for smaller animals and form mutualistic relationships with photosynthetic organisms

Phylum Cnidaria:The Stinging Cell Animals

Diagram of a Cnidocyte

Diversity information, pictures, classification

Characteristics of Cnidarians:•Include jellyfish, coral, hydra, and sea anemones•Motile or sessile•Radial symmetry•Cnidocytes with nematocysts•Specialized tissue…primitive “nervous system” called a nerve net.•Polyp and/or medusa body forms.

Phylum Platyhelminthes:The Flatworms

Diversity information, pictures, classification

Characteristics of Flatworms:•Include free-living species, tapeworms, flukes•Have tissue and organ systems•Bilateral symmetry•Cephalization•Three embryonic germ layers•Acoelomates (no fluid filled body cavity)

•One-opening digestive system in planaria (Pharynx leads to mouth)•Diffusion for tapeworms (no digestive system)•Ganglia; gathering of nerve cells near anterior end (beginnings of a brain)•Nerve cords•Eyespots and other receptors•Circulation not necessary because they’re flat (diffusion is adequate)•Flame cells for excretion•Hermaphrodites (both male and female reproductive organs)•Complex life cycles for parasites

Phylum Nematoda:The Roundworms

Diversity information, pictures, classification

Characteristics of Roundworms:•Unsegmented, tapered ends•Free-living in soil and water•Parasites of many kinds of plants and animals•Trichinella, filarial worms, Ascaris, hookworms•Digestive system with two openings (mouth and anus)•Pseudocoelem (body cavity between endoderm and mesoderm)

Phylum Annelida:The Segmented Worms

Characteristics of Annelids:•Earthworms, leeches, sandworms, bloodworms•Segmented bodies•True coelem lined with mesoderm•More advanced body systems

•Digestion; pharynx, crop, gizzard, intestine•Circulation; closed circulatory system (blood vessels)

•Aortic arches act as tiny pumping hearts

•Excretion; Nephridia- organs that filter fluid in the coelem•Nervous; brain, ganglia, nerve cords•Reproduction; hermaphrodites…use clitellum to exchange sperm

Diversity information, pictures, classification

Ventral view

Digestive & Circulatory

Phylum Mollusca:The Soft-bodied Animals

Diversity information, pictures, classification

Characteristics of mollusks:•Snails, slugs, clams, oysters, scallops, octopi, squid, cuttlefish, nautilus•Soft-bodied animals that usually have an internal or external shell•Closely related to annelids…both have a free-swimming larval stage called a trochophore•Have a true coelem lined with mesoderm•Body plan contains four parts: foot, mantle, shell, and visceral mass•Open or closed circulatory system•Carnivores, herbivores, filter feeders, detritivores, parasites•Advanced and complex sense organs, intelligence in the cephalopods

Phylum ArthropodaThe Jointed-Leg Animals

Diversity information, pictures, classification

Characteristics of Arthropods:•Jointed appendages•Exoskeleton of chitin•Segmented bodies (like annelids)•Specialized appendages for feeding, movement, etc.•By far the most successful phylum of animals•85% of all living animal species are arthropods

Phylum includes:

Crustaceans (crab, shrimp, lobster, crayfish, barnacles)

Chelicerates (spiders, mites, ticks, scorpions, horseshoe crabs)

Uniramians (insects, millipedes, centipedes)

Factors leading to Insect success:

1. Small size2. Coevolution with flowering plants3. Metamorphosis (complete or incomplete)

Two specialized life stagesComplete; egg, larva, pupa, adult Incomplete; egg, nymph, adult

4. Tough exoskeleton (chitin with waxy covering in some)Molting to grow

5. Flight6. Rapid multiplication/short life cycle…evolve quickly7. Sense organs, specialized mouthparts and appendages

Insect Communication

Waggle Dance

Phylum Echinodermata:The Spiny Skin Animals

Characteristics of Echinoderms:•Include sea stars, brittle stars, sea urchins, sand dollars, sea cucumbers, sea lilies, feather stars•Spiny skin of calcium carbonate•Internal skeleton•Water vascular system•Tube feet (suction cups on legs)•Radial symmetry

Then why didn’t we study these with Cnidarians???

Diversity information, pictures, classification

Echinoderm larvae are bilaterally symmetrical indicating that symmetry evolved independently in this group.

In the embryonic development, echinoderms are more similar to chordates…they are both deuterostomes.

So although they exhibit radial symmetry, we do not consider echinoderms to be primitive animals.

Which group includes snails, clams, and squid?Which group is the sponges?Which are the flatworms?

…segmented worms?…roundworms?

Which group has jointed appendages & an exoskeleton?Which two groups are radially symmetrical?Which group has no symmetry?

Invertebrate quick check…