Chapter 15 Marine Animals Oceanography An Invitation to Marine Science, 7th Tom Garrison

Chapter 15 Study Plan Animals Arose Near the End of the Oxygen Revolution Invertebrates Are the Most Successful and Abundant Animals The Worm Phyla Are the Link to Advanced Animals Advanced Invertebrates Have Complex Bodies and Internal Systems Construction of Complex Chordate Bodies Begins on a Stiffening Scaffold Vertebrate Evolution Traces a Long and Diverse History Fishes Are Earth’s Most Abundant and Successful Vertebrates Fishes Are Successful because of Unique Adaptations Sea Turtles and Marine Crocodiles Are Ocean-Going Reptiles Some Marine Birds Are the World’s Most Efficient Flyers Marine Mammals Include the Largest Animals Ever to have Lived

Chapter 15 Main Concepts Animals could not evolve until atmospheric oxygen was abundant. Photosynthetic autotrophs (mainly cyanobacteria) changed the composition of the atmosphere during the “oxygen revolution.” More than 90% of all living and fossil animals, including all of the earliest multi-cellular animals, are invertebrates – animals without backbones. By nearly any criterion, arthropods – a group that includes lobsters, shrimp, crabs, and insects – are the most successful of Earth’s animals. The Chordates possess a stiffening scaffold – a notochord – on which they are constructed. In vertebrate chordates, this structure persists as a vertebral column. Fishes are Earth’s most abundant and successful vertebrates. Marine mammals include the whales, the largest animals ever to have lived on Earth.

Animals Arose near the End of the Oxygen Revolution During the oxygen revolution (2 billion to 400 million years ago), photosynthetic autotrophs – mostly bacteria – caused a rapid rise in the amount of oxygen in the air, which made possible the evolution of animals. Animals are thought to have arisen between 900 and 600 million years ago.

Phylum Porifera Contains the Sponges -Suspension feeders- strain plankton from surrounding water. -Utilize diffusion for excretion/movement. -Spongin and spicules-prevent sponge from collapsing. -No digestive, circulatory, respiratory, or nervous systems.

Fig. 15-3b-d, p. 406 Water out Central cavity Water in Collar cell Flagellum Flattened surface cells Mesoglea Pore Amoeboid cell Spicules Stepped Art Nucleus Microvilli

Stinging Cells Define the Phylum Cnidaria Jellyfish, sea anenomes, corals; carnivorous. -Cnidoblasts- large stinging cells on tentacles; repel aggressor, release toxin, tangle prey. -Digestive cavity has one opening: -Built of two layers of cells- inner layer (gastrodermis) and outer layer (epidermis). -Radial symmetry- radiate from central axis. -Occur in two forms: medusa (jellyfish)- swim by contraction; and polyps (sea anenomes and corals)- no skeleton/ calcareous skeleton

Phylum Platyhelminthes, Nematoda, Annelida- Flatworms and Roundworms Phylum Annelida- –most evolutionary advanced worms. –Metamerism- segmentation; each segment has its own set of systems. Phylum Nematoda- Roundworms –Flow- through digestive system Phylum Platyhelminthes- –Parasitic; free-living predators and scavengers. –Found in shady underside of rocks; primitive in nature; possess CNS –No respiratory/excretory system; rely on diffusion

Phylum Mollusca- Clams, Snails, Octopuses, Squid Mostly marine; have internal/external shell. Bilaterally symmetrical; possess heads, flow through digestive tracts, nervous system. –Gastropoda- snails; large shells for refuge; suspension feeders; shell enlarges as snail grows. –Bivalvia- clams, oysters, mussels –Cephalopoda- nautiluses, octopuses, cuttlefish, and squid. Head surrounded by foot; divided into tentacles. Catch prey with stiff adhesive discs on their tentacles that function as suction cups. Squid and octopus- release ink when threatened; confuse predators.

Advanced Invertebrates Have Complex Bodies and Internal Systems Bivalves are suspension feeders that make their living by filtering the water for edible particles. In this diagram (showing a bivalve with its left shell removed), water and tiny bits of food are swept into the animal by the movement of tracts of cilia on the gills. Food settles onto the gills and is then driven toward the mouth and swallowed.

Phylum Arthropoda- lobsters, shrimp, crab, krill, and barnacles Most successful of phyla. Clear segmentation with pairs of appendages per segment. Bilaterally symmetrical. Possess three unique characteristics: –1) Exoskeleton- made of chitin; molted at regular intervals; when molted, generates a new one one size larger –2) Striated muscle. –3) Articulation- Between segments and appendages.

-Lack eyes or brains; radially symmetrical. -Body plan based on 5 sections/projections; move slowly. -Spiny projections on top; tubed feet beneath. Water enters the animal’s body through a sieve plate, and circulates through canals. To eat- expels stomach through mouth and eats victim in place If grabbed by predator, detaches arm (regenerates later) Sea Stars Are Typical of the Phylum Echinodermata

Construction of Complex Chordate Bodies Begins on a Stiffening Scaffold Chordata is the most advanced animal phylum. All chordates have, at some time during development, a notochord. Both invertebrate and vertebrate chordates are represented in ocean environments. In some chordates the notochord is lost during development. These are the invertebrate chordates. Most chordates (about 95%) retain the notochord in some form. These are the vertebrate chordates.

Vertebrate Evolution Traces a Long and Diverse History One proposed family tree for the vertebrates and their relatives, the invertebrate chordates. All vertebrates appear to be derived from fish-like ancestors.

Fish/Chondrichthyes Gills for breathing. Fins for swimming. Ectothermic- internal temperature is the same as surrounding environment. 40%- freshwater, 60%- saltwater Paired fins-help to stabilize movement. Chondrichthyes- sharks, rays, skates, chimeras -Skeleton made of elastic tissue- cartilage. -Jaws with teeth, paired fins, active lifestyles.

Class Osteichthyes Comprises the Familiar Bony Fishes -Bony fish -Hard, strong, lightweight skeleton. -Most abundant and diverse About 90% of all living fishes are contained within the order Teleostei- cod, tuna, halibut, goldfish, and other familiar species; independently movable fins, great speed, camoflauge.

Fishes Are Well Adapted to Their Environment What are some problems posed by living in a marine environment? Movement, shape and propulsion - fish must be able to move through water, which is 1,000 times denser and 100 times more viscous than air Maintenance of level - fish tissue is usually denser than the surrounding water, so fish must have a system to keep from sinking Gas exchange – water and blood circulate in opposite directions as it passes through gill membranes; 85% O2 extracted. Osmotic considerations - fish need a system to maintain proper salt levels in their bodies Feeding and defense - evolution of a wide variety of habits; sight (see/avoid prey), hearing (vibrations), smell of substances, schooling (no leader; movement by lateral lines), bioluminescence.

Turbulence and drag. At the same speed, with the same frontal area, shape (a) will have about 15 times as much drag as shape (c). Shape (b) shows only a small improvement in drag over the disk. Fishes Are Well Adapted to Their Environment

Gas Exchange Is Accomplished through Gills Cutaway of a mackerel, showing the position of the gills (a). Broad arrows in (b) and (c) indicate the flow of water over the gill membranes of a single gill arch. Small arrows in (c) indicate the direction of blood flow through the capillaries of the gill filament in a direction opposite to that of the incoming water. This mechanism is called countercurrent flow.

Successful Fishes Quickly Adapt to Their Osmotic Circumstances Osmoregulation in freshwater and marine fishes.

Some Birds Are the World’s Most Efficient Flyers Birds evolved from small, fast running dinosaurs over 160 million years ago. Reptilian heritage- scaly legs and claws Success is due to evolution of feathers. Birds are endothermic- internal temperature is higher than surroundings. Light, thin, hollow bones; highly efficient respiratory systems; lay eggs on land.

Like All Birds, Marine Birds Evolved from Dinosaur-Like Ancestors Only 270 of the known species of birds qualify as seabirds. Seabirds have salt excreting glands to eliminate salt taken in with their food. There are four groups of seabirds: –Tubenoses - this group includes the albatrosses and petrels –Pelicans - this group includes relatives of the penguins that have webbed feet and throat pouches –Gulls - these birds are found along the shore, where they scavenge for food. –Penguins - these birds have lost the ability to fly, but are excellent swimmers

Marine Mammals Share Common Features Mammalia- most advanced vertebrate group; 4,300 species of mammals are known. What are the three groups of marine mammals? Cetacea – porpoises, dolphins and whales Carnivora - seals, sea lions, walruses and sea otters Sirenia – manatees and dugongs Share common features- streamlined body shape, generate internal body heat, modified respiratory system, osmotic adaptations.

Order Cetacea- Whales Whales are known for having no teeth and instead use baleen (bristles) for filter feeding. -Paddle forelimbs- steering. -Propelled by horizontal tail flukes. -Oily blubber- insulation. Special valves- prevent intake of water (submerged) -Large brains

-Some representatives of the order Cetacea. -Whales are known for being active predators who use teeth for feeding. The toothed whales search for food using echolocation, a biological equivalent to sonar. Marine Mammals Share Common Features

Marine animals have evolved effective adaptations for capturing prey, avoiding danger and maintaining thermal and fluid balance with their environment. (above) Echolocation, used by toothed whales to locate and perhaps stun their prey; sharp clicks and other sounds that bounce off prey species and return to be recognized. The Order Cetacea Includes the Whales

A plate of baleen and its position in the jaw of a baleen whale. For clarity, the illustration shows an area of the mouth cut away.

Chapter 15 in Perspective In this chapter you learned that animals must ultimately depend on primary producers (autotrophs) for nutrition. Animals could not exist on Earth until increasing levels of free oxygen in the atmosphere permitted them to metabolize food obtained from autotrophs. And remember, it was the photosynthetic autotrophs themselves that contributed huge quantities of oxygen to the environment. True multi-cellular animals arose between 900 and 700 million years ago, near the end of this “oxygen revolution.” Their variety is astonishing – a tribute to millions of years of complex interplay between environment, producer, and consumer. Our survey of marine animals followed the course of their evolution. The complexity of animals increased as we moved from groups (phyla) whose basic structure seems to have solidified relatively early in the history of animals to groups that evolved more recently. Every marine animal has evolved effective adaptations for capturing prey, avoiding danger, maintaining thermal and fluid balance with their surroundings, and competing for space, and our survey of marine animals stressed these adaptations. In the next chapter you will learn how these animals interact with one another and with their environment. The organisms you met in the last two chapters do not live alone. They are distributed throughout the marine environment in specific communities: groups of interacting producers, consumers, and decomposers that share a common living space. The types and variety of organisms found in a particular community depend on the physical and biological characteristics of that living space.