Lecture11MarineAnimalsII - Ch 15 Marine Animals Marine •...

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Unformatted text preview: Ch. 15 Marine Animals Marine • Multicellular heterotrophic organisms • Obtain food (ultimately) from primary producers •Problems: Finding food Avoiding predators Finding mates (reproduction) • Use a variety of survival strategies Phylum Mollusca Phylum Diverse: includes clams, snails, octopuses and Diverse: squid squid Some have acute eyesight and considerable Some intelligence intelligence Common ancestry with annelids? Share a few Common basic characteristics… basic Bilateral symmetry, obvious heads, flow-through Bilateral digestive tracts, nervous systems digestive Unlike annelids, molluscs grow large, secrete Unlike shells, exhibit great structural diversity shells, Classes: Gastropoda, Bivalvia, and Cephalopoda Cephalopoda (are more classes than this) Gastropoda – the snails Gastropoda Bivalvia – clams, oysters, mussels Bivalvia Cephalopods – nautilus, octopus, cuttlefish, squid cuttlefish, Though diverse in shape and habits, you can see the link to a common ancestor through the similarity of underlying body parts. Gastropods – inhabit shells, used for refuge from predators •May graze, be suspension feeders, or predators •Most are benthic (except pteropods, which are planktonic) •Nudibranchs are naked gastropods Bivalves • animals enclosed in twin shells • good to eat (clams, oysters, mussels, scallops) • generally are suspension feeders • burrowing species will dig into sediment with foot; extend siphons to surface to obtain water, eject wastes Tiny cilia on gills sweep water into the bivalve, edible bits of food settle onto the gills, is driven towards the mouth and swallowed. Sand and debris are rejected in the exhalent flow Cephalopods • most highly evolved of the molluscs • includes nautilus, squid, octopus • head is surrounded by a foot divided into tentacles (hence the name) • some have retained the shell, others haven’t • move by creeping across the bottom, by swimming with special fins or by squirting jets of water from an interior cavity • capture prey with suction cups, tear open prey with beaks • squid & octopus can squirt ink • squid grow to extremely large size (giant squid) • octopus may be the “most intelligent of the invertebrates”… good eyesight, camouflage ability, can recognize keepers in captivity Immature female giant squid, almost 5 m long! Octopus Octopus Probably the most intelligent invertebrate Behavioral adaptations and protective coloration Although they have 8 legs, can use bipedal locomotion Phylum Arthropoda Phylum Arthron = joint, pod = foot Includes lobsters, shrimp, crabs, krill, and Includes barnacles barnacles Are the MOST SUCCESSFUL of animal Are phyla phyla Body plan: clear segmentation with a pair Body or pairs of appendages on each segment (like the Annelids) (like Bilaterally symmetrical Dungeness Crab (Cancer magister) wdfw.wa.gov/.../coast/graphics/crab_molt.jpg Evolutionary advances of arthropods arthropods An exoskeleton (strong, light, form-fitting; An exoskeleton made of chitin, an N rich carbohydrate) chitin Striated muscle (quick, strong, lightweight, allows rapid movement and flight) Articulation (appendages bend at specific points; not ball and socket, but each joint along an appendage moves in a different plane) plane) External skeletons must be molted in order for the organism to grow in Aquatic arthropods slowly substitute body mass for water held in the tissues between molts. When molting, the animal takes on water, then expands tissues without adding muscle mass. Shell splits and falls away. Arthropods do not have a steady growth pattern Phylum Arthropoda Phylum Class Crustacea Lobster, crayfish, crabs, copepods, krill, Lobster, barnacles barnacles Bodies have ~16 to 20 segments Appendages may be specialized for sensing, Appendages food handling, walking, fighting, defense (examples?) (examples?) 70% of all zooplankton are crustaceans (name 70% them) them) Largest crustacean is the King Crab (legspan = Largest 3.6 meters) 3.6 ...
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