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Invertebrates!!

Review: What is an Animal? A multicellular eukaryotic heterotroph whose cells lack cell walls Invertebrates have no backbone or vertebral column. 95% of animals are invertebrates. Vertebrates have a backbone. Only 5% of animals are vertebrates.

What are the Invertebrates? Multicellular animals Heterotrophs – take in food, digest it, distribute it to cells No backbone Have locomotion, special parts for locomotion Some are sessile Some invertebrates can regenerate lost parts or even a complete individual from a broken piece.

Phylum Porifera Sea Sponges Means “pore bearing” Asymmetric Natural sea sponges: dead material that remains after decay

Sessile: live attached to a surface Do not have nerve cells or tissue Filter feeders: pump water in and out and feed on the organic material in water Many are hermaphrodites: able to produce male and female gametes – an advantage for sessile organisms Can reassemble when fragmented

Phylum Cnidaria Coral, jellyfish, sea anemones

Cnidocytes: cells that contain stinging poisonous barbs with which they paralyze prey Radial symmetry Two body forms: polyp: sessile, tentacles up (coral, hydra, anemone) medusa: free swimming, tentacles down (jellyfish)

Digestive body cavity surrounded by two layers of cells Sexual or asexual reproduction – hydra reproduces by budding Coral reefs build up and are important ocean habitats

Phylum Platyhelminthes Examples: flatworms, tapeworms, flukes

Many parasitic forms - cause many diseases of people and livestock Bilateral symmetry and cephalization One digestive opening (pharynx) to take in food and release waste – most don’t need complex digestive systems because food has already been digested by their host Most are hermaphroditic, some can regenerate lost body parts

Phylum Nematoda Examples: roundworms (pinworms, hookworms, heartworms)

Many are microscopic Two digestive openings: mouth and anus – food moves only one way Sexual reproduction Most are free-living, many are parasitic – you can be infected by consuming contaminated food/water or by being bitten by insects

Phylum Annelida Examples: segmented worms, earthworms, leeches

Closed circulatory system: blood stays within vessels Earthworm is hermaphroditic; others have separate sexes Earthworms are important in the soil ecosystem– provide passageways for plant roots and water. Aristotle called earthworms “the intestines of the soil”. What did he mean by this?

Phylum Mollusca Mollusks have an internal or external shell. Examples: snails, slugs, clams, octopus, squid, cuttlefish

Main groups of mollusks: 1. Gastropods are “stomach-footed” univalves: one shell (snail) bivalves: two shells (clam) 2. Cephalopods are “head-footed” Foot is modified into tentacles. They breathe with gills. (octopus, squid) Have you hugged your octopus today?

Sexual reproduction: most have separate sexes, some are hermaphrodites Most have an open circulatory system (blood is contained within vessels that empty into sinus cavities). Cephalopods have a closed system (blood remains within vessels). Most mollusks are marine, but some live in fresh water or on land

Phylum Arthropoda Arthropod means “jointed foot” Largest phylum – found almost everywhere!

Characteristics: 1. exoskeleton a. Outside the body b. Very good protection c. Does not grow, so it must be shed periodically (molting) 2. paired, jointed appendages (legs, antennae) 3. segmentation

Centipedes and Millipedes most primitive arthropods obvious segmentation Centipedes (Class Chilopoda) a. one pair of legs per segment b. venomous fangs for killing prey c. long antennae

Millipedes (Class Diplopoda) a. two pairs of legs per segment b. one pair of short antennae c. usually harmless vegetarians

Crustaceans (Class Crustacea) Examples: lobster, crayfish, shrimp, crab

Arachnids (Class Arachnida) Examples: spiders, ticks, mites, scorpions

two body regions: a. cephalothorax (where legs come from) b. abdomen no antennae simple eyes 4 pairs of walking legs mouthparts modified as fangs (chelicerae) to stab prey and suck out body fluids book lungs (gills modified for breathing on land)

Insects (Class Insecta) Over 75% of all animal species First animals to evolve the ability to fly 6 legs and 3 body parts

Insects undergo metamorphosis: a series of changes during which young insects develop into adults. Incomplete Metamorphosis (grasshopper) Gradual changes from nymph to adult 1. egg 2. nymph 3. adult

Complete Metamorphosis (butterflies, bees) 1. egg 2. larva (caterpillar) 3. pupa 4. adult

Phylum Echinodermata Name means “spiny skin” Marine environment Radial symmetry Deuterostomes - indicates a fairly close relationship to vertebrates

Water vascular system 1. system of internal tubes 2. carries out functions of circulation, respiration, and movement Tube feet 1. act like living suction cups 2. help in movement and feeding

Examples: sea urchins, sand dollars, starfish (sea stars)

Which invertebrate phyla are represented here?