Basic biology and classification of marine invertebrates Metazoan

Basic biology and classification of marine invertebrates

-Metazoan animal origins: 700 million to 1. 4 billion ybp -Cambrian explosion: 600 mybp -evolution is not progressive, no increase in complexity after origination of phyla -many body plans are no longer around -What caused the dramatic radiation of metazoans?

Burgess shale fossil quarry in the Canadian Rockies

Some major phyla of marine invertebrates Porifera sponges Cnidaria jellyfish, anemones, corals Annelida segmented worms (e. g. polychates) Mollusca clams, mussels, octopus, squid Bryozoa bryozoans Arthropoda crabs, shrimp, copepods, Echinodermata urchins, holothuroids, sea stars Urochordata ascidians/tunicates You should know the phyla and examples and general characteristics of animals in each

Some basic terms: Benthic vs. Pelagic Sessile vs. Mobile Solitary vs. Colonial Sexual vs. Asexual Encrusting vs. Upright Autotrophic, Chemoautotrophic, Heterotrophic Predation, Herbivory, Omnivory, Primary production

Phylum: Porifera: Sponges -simplest multicellular animals, but not ancestral! -no true tissues -cells are independent and perform specialized functions -very efficient filter feeders -good spatial competitors -incurrent and excurrent canals -asymmetrical

Sponge anatomy-built around a system of pores, chambers, and canals -choanocyte -spicules

Phylum Cnidaria jellyfish, anemones, corals What makes something a Cnidarian? -all are aquatic -tissues present but no organs -2 basic shapes or phases: polyp & medusa -nematocyst -tentacles -1 opening

Phylum Cnidaria Physalia: man-o-war jellyfish, anemones, corals Cassiopia

Phylum Cnidaria Hydroid jellyfish, anemones, corals Sea Pen

Phylum Cnidaria Colonial reef coral Sea fan jellyfish, anemones, corals Solitary reef coral Anemone

Phylum Annelida Class Polychaeta segmented marine worms Fire worm 6000 species Segmentation Setae A variety of feeding modes: Active predators, mucus bag feeders, mud-munchers and passive filter feeders

Feather duster worm -serpulids: secrete Ca. Co 3 shell -filter feeders Christmas tree worm

Phylum Mollusca Cyphoma Class Gastropoda: snails and limpets Cassis -second most diverse marine animal phyla (100, 000+ species) -no segmentation -have complete gut -usually have a calcareous shell Class Polyplacophora chitons

Phylum Mollusca Class Gastropoda: snails and limpets Cone shell Conus geographus “mini melo” -many predatory snails are highly specialized

Phylum Mollusca Bivalves: clams, oysters, mussels, scallops Tridacna Giant Clam -some have autotrophic symbionts -most are active filter feeders

Phylum Mollusca Cephalopods: octopods, squid, nautilus Octopus-8 arms Squid-8 arms + 2 longer tentacles

Phylum Mollusca Nudibranchs: sea slugs -most are specialized predators Aplysia Sea Hare

Phylum Bryozoa: -passive filter feeders -colonial -zoids bryozoans

Phylum Arthropoda Subphylum Trilobita Subphylum Chelicerata horseshoe crabs, sea spiders Subphylum Crustaea crabs, shrimp, barnacles, copepods Subphylum Uniramia insects -by far the largest animal phylum -could represent several independent phyla -mono vs. polyphyletic -all are segmented, but segments are divided into different body regions -appendages are paired and jointed -all have an external skeleton -probably derived from annelids