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►The Linnaeus Classification System►Prokaryotes-Small yet Significant►Marine Algae►Marine Plants►Sponges-Filters of the Sea►Corals, Anemones, Sea Fans, and Jellies►Simple Marine Worms►Mollusks-A Bag, a Scraper, and a Foot►Complex Worms

► Crustaceans-Underwater Arthropods► Echinoderms-Stars of the Sea

► Invertebrate Chordates► Vertebrate-Top of the Food Web

► Sharks and Rays-Teeth and Wings► Bony Fish-Half the World’s Vertebrates

►Marine Reptiles-Cold Blood and Warm Water

► Seabirds-At Flight Over and In the Ocean►Marine Mammals-Warm Blood in Cold W

ater

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A Survey of Life in the Sea

It’s not hard to imagine how difficult it would be for scientists to discuss biological questions without a classification system for life.

The Need for Classification Three reasons for classifying organisms:

1. It helps identify the relationships between organisms. 2. It requires scientists to clearly identify

key characteristics of each organism. 3. It avoids confusion. Common names differ

with cultures. Scientists in the US and Japan can identify exactly what they are both talking about by using the species’ Latin name.

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Classification Taxa

An organism’s scientific name represents two taxa. They are: 1. Species – is the most specific of the taxa. Species is usually considered to be a group of

organisms that can reproduce together. 2. Genus – is the taxon above species. Genus grouped species are considered to be closely related,

i.e., there are 34 species of reef shark belonging to genus Carcharhinus.

Species are identified by referring to both the genus and the species, with the genus capitalized and the species name in lower case.

There are seven main taxa into which organisms are classified; from the general to specific:

1. Kingdoms are groups of phyla (plural of phylum). 2. Phylum (or division) is a group of classes. 3. Classes are groups of related orders. 4. Orders are groups of related families. 5. Families are groups of genera that share characteristics. 6. Genus (plural genera) groups species that are closely related. 7. Species is the Latin name for an individual organism.

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Determining Taxa

How organisms are classified: Originally by using anatomical features. The prevailing view now is that taxonomy generally reflects theoretical

evolutionary relationships. Classifying by anatomical features remains an important classification method.

However, the study of genetics has become more important.

A common problem taxonomists have inclassifying organisms is thatsome organisms don’t fit neatly intodefined classifications. An organism canhave characteristics that fit in one and othersthat separate it from that same classification.

The answer is to insert intermediate classification levels. By assigning superlevels to create new higher divisions within a classification. By assigning sublevels to create lower divisions within a classification.

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Six - Kingdom System and Three - Domain System

Until recently taxonomists recognized five kingdoms: kingdom Monera, kingdom Protista, kingdom Fungi, kingdom Plantae, and kingdom Animalia.

The six-kingdom system divides kingdom Monera into two new kingdoms: kingdom Eubacteria and kingdom Archaebacteria.

The three-domain system method is based on genetic and biochemical research.

Domain Archaea is composed of organisms scientists think evolved first.

In this system domain Eukarya includes the Protista, Plantae, Fungi and Animalia kingdoms.

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Taxa tree

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Old and Simple

Prokaryotes are among the most important of the primary producers in the ocean. They don’t have the same complex internal

membrane structure. They lack chromosomes or a nucleus. Instead

they have a ring of DNA or RNA. They don’t have mitochondria and

lack chloroplasts. They are structurally simple – molecules

are surrounded by a membrane and cell wall. They are believed to be the oldest types of

organisms – archaea originated 3.5 billion years ago.

Scientists think that the process ofphotosynthesis began with cyanophytesof domain Bacteria, an early prokaryote.

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Archaea and Bacteria

Domain Archaea and domain Bacteria are best known for being extremophiles – living in environments that are inhospitable to most life.

Bacteria can do things no other known organisms can do: Certain species can create organic nitrogen compounds by fixing inorganic nitrogen

from the air – an essential element of life.

The most important bacteria are in the phylum Cyanophyta. Scientists think that these bacteria are crucial to life because: Photosynthesis evolved in the cyanophytes. Cyanophytes were the primary organisms that created the oxygen in

the atmosphere. Cyanophytes are among the bacteria responsible for nitrogen fixation.

Also, some scientists think we presently underestimate the role cyanophytes play in primary productivity. Their pigments can contribute to the color of other organisms.

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A Broadly Applied Name

Algae is defined by taxonomists as those organisms that belong in one of seven specific phyla or divisions in kingdom Protista.

1. Chlorophyta 2. Rhodophyta 3. Phaeophyta 4. Dinophyta 5. Bacillariophyta 6. Euglenophyta 7. Chrysophyta

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Phylum Bacillariophyta – The Diatoms

Phylum Bacillariophyta is made up of diatoms, the most productive phytoplankton.

These primary producers are a widely diverse group. Between 5,000 to 50,000 species may

make up this phylum. Diatoms are larger than prokaryotes

– from 20 to 80 microns across. They have two-part silicon shells in

an amazing array of shapes. They are photosynthesizers that are

relatively dormant during the winter months.

Diatoms reproduce quickly when sunlight levels rise and are thought to account for 25% of all the photosynthetic biomass on Earth.

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Phylum Dinophyta – The Dinoflagellates

Dinoflagellates make up phylum Dinophyta (also called phylum Pyrrophyta or phylum Dinoflagellata).

In size they are 30 to 150 microns across and are the second most productive group of primary producers. Symbiodinium are particularly important

autotrophic dinoflagellates. They live within the zooxanthellate

coral polyps. They provide their host with food via

photosynthesis. In return Symbiodinium get nitrogenous

wastes from the coral. These are the only coral that build massive coral reefs. Without Symbiodinium, coral could not exist as we know it.

Without coral and coral reefs there would not be the unique organisms that make up the world’s most productive and beautiful ecosystems.

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Phylum Chlorophyta – Green Algae

Phylum Chlorophyta is made up of the macro algae – a term that applies to several algae phyla, but refers to multicellular species like seaweed.

They share the same green color as land plants. Both green algae and land plants have: Chlorophyll a – a pigment directly involved

with photosynthesis. Chlorophyll b – assists chlorophyll a in capturing light

for use in photosynthesis. Chlorophyll a and b absorb different colors of light, thus using light more efficiently. Scientists think the presence of chlorophyll a and b has evolutionary significance. It may

indicate that land plants evolved from green algae. Green algae and land plants also have other pigments in common and have cell walls made of

cellulose.

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Phylum Rhodophyta – Red Algae

Red algae is red because they have pigments called phycoerythrins which give it their color. This pigment has not been found in any other eukaryote, though it does exist in

cyanophytes.

Phycoerythrins allow some red algae to live deeper than any other algae – some as deep as 200 meters (656 feet). Red algae also has chlorophyll a, but not b.

Red algae is important to coral reefsbecause it is the cement that holdsthe coral reefs together.

Red algae species that live on coral reefssecrete a calcium carbonate shell. Their secretions bond coral colonies and debris

together which in turn holds the reef together.

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Phylum Phaeophyta – Brown Algae

Phylum Phaeophyta (brown algae), is more structurally complex. Manybrown algae species have: Holdfasts – anchor the algae to the bottom. Leathery stipes – provide support like plant

stems, but with no vascular system. Blades – equivalent of leaves. Pneumatocysts – gas filled float structures

that lift the algae off the bottom and keep the blades close to the surface and sun.

Kelp is the largest of the brown algae. Kelp is important because it is the foundation for

many temperate coastal ecosystems.

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Plant Adaptation to the Marine Environment

Salinity in the water is the greatest challenge to which plants must adapt. Salt causes dehydration in plants. Marine plants resist dehydration through several adaptations such as waxy coverings or other

protection that reduces water loss and prevention of dehydration.

Submergent and Emergent Plants Submergent plants live entirely underwater – seagrasses for example. Emergent plants live with their roots underwater, but with a significant portion of the plant

growing above the surface – mangroves for example. Other than producing food and oxygen, marine plants provide important habitats for other

marine organisms. Mangrove swamps are important to the environment:

1. They act as nurseries for adjacent marine ecosystems. 2. They filter runoff water protecting sensitive offshore ecosystems that would be harmed or killed by

settling sediment. 3. They hold sediments in place. They slow waves and reduce erosion while retaining nutrients used

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Characteristics of Sponges

Like all members of phylum Porifera, sponges aren’t very animal-like. Besides being multicellular heterotrophs, they have structural

organization and different cell types. 1. Collar cells have flagella that waft water into the sponge’s

epithelium (a tissue that protects the outer surface). 2. Amoebocytes (second cell type) pick up nutrient particles

as the water flows through the sponge walls.

Sponges are filter feeders – the amoebocytes distributenutrients throughout the sponge.

Special Attributes of Sponges Sponge larvae are more animal-like than adult sponges because they are free-swimming

organisms with flagella. The larvae swim and drift until they fix themselves in place on the reef and grow into adult sponges.

Most sponges are tough and fibrous, many produce toxic defense chemicals. After being torn apart, remaining pieces in contact may grow together. Isolated pieces can regenerate into entirely new sponges.

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Characteristics of Phylum Cnidaria

Phylum Cnidaria includes soft and hard corals, sea anemones, hydroids, sea fans, jelly fish, and siphonophores.

Anatomical characteristics include: They are radially symmetrical – symmetry

around a central point. They have a cup or bag-like body made of two

layers of cells, with tentacles around the rim. They have a mouth that opens into the gastro-

vascular cavity (a space in the middle of their body used for digestion/reproduction).

They are structurally uncomplicated, with simple nerves,muscle nets, and light receptors.

Colonial organisms are called polyps. Individuals are free-floating and are called medusae. All share the ability to defend themselves with nematocysts.

These stinging structures are composed of special cells called cnidocytes.

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Special Attributes of Coral and Anemones

The largest class in phylum Cnidaria is class Anthozoa, the coraland anemones. Members of this class are polyps that attach to the reef or other substrate. Coral and soft coral are colonial, anemones are individual organisms.

Hard coral are the most ecologically significant thanks to the massive calcium carbonate reefs they build. They are sensitive to runoffs, fertilizers, etc. that

can cause damage. When coral are stressed they become colorless.

This is called coral bleaching – a sign of a diseased and dying colony.

Soft coral and sea fans grow into tree-like structures built on protein skeletons. They are not reef builders.

Anemones have a mutualistic relationship with various species of anemonefish. The fish receive protection by living in the anemone

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Special Attributes of Fire Coral and Siphonophores

Both fire coral and siphonophores belong in the class Hydrozoa. Fire coral is one of the cnidarians that can sting humans.

It gets its name from the mild burn you get from touching them.

Siphonophores exist as planktonic colonies, yet within the colonies are special organisms adapted to feeding, reproduction, movement and other functions. The Portuguese man-of-war is an example of this. Siphonophores can exceed 40 meters

(131 feet) in length.

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Special Attributes of Jellyfish

The Portuguese man-of-war is in class Hydrozoa. It is not a jellyfish.

Jellyfish are members of class Scyphozoa.

Box jellyfish are members of class Cubozoa.

Comb jellyfish appear to be jellyfish, but are members of phylum Ctenophora. Comb jellies lack the bag-like

cnidarian body shape. Unlike jellies they have

cilia on their surfaces to help them move.

They lack stinging cnidocytes.

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Characteristics of Simple Worms

Phylum Platyhelminthes is made up of flat worms. They have a flattened tube of muscle, simple digestive system,

a single opening that serves as both mouth and anus.

Phylum Nemertea are more complex with a flat shape. They have a simple blood vascular system, one-way digestive

system, separate mouth, and anus. They are carnivores.

Phylum Nematoda are structurally simple round worms. More complex than the other two phyla. Most are parasitic

worms, some live in sea animals. This phylum also includes human parasite forms.

Special Attributes of Simple Worms Lineus longissimus, a nemertean, found in the

North Sea is perhaps the longest known creature in theworld – more than 60 meters (197 feet).

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Characteristics of Mollusks

Phylum Mollusca – the mollusks – ranges from squid and octopuses to sea slugs, snails, oysters, clams, and conches.

Three characteristics all members share: 1. A muscular bag called the mantle. 2. A muscular foot beneath the head. 3. The radula – a tongue with rough

scraping teeth used for feeding.

Special Attributes of Class Gastropoda Snails, whelks, slugs, and most single-shelled mollusks belong in class Gastropoda. Torsion is a developmental process.

It occurs after the veliger settles and begins maturing. Its body twists into a permanent loop thatrearranges the organs and brings them together allowing the body to draw into the spiral shell common to this class.

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Special Attributes of Class Bivalvia

Belonging to class Bivalvia (bi meaning two) are mollusks that have twohinged shells.

Mussels, clams, oysters, and scallops are all bivalves.

Special Attributes of Class Cephalopoda This class includes cuttlefish, squid and octopuses.

Cuttlefish (order Sepioidea) differ from squid and octopuses by having an internal shell used primarily for buoyancy.

Squid (order Teuthoidea) differ from cuttlefish and octopuses with their streamlined, torpedo-shaped bodies adapted to life in open water.

Octopuses (order Octopoda) differ from squid and cuttlefish by having no shell and living in rocky reefs and coral.

Octopuses are probably the most intelligent invertebrates.

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Characteristics of Annelids

Worms in phylum Annelida stand apartbecause of their structural complexity. They have a heart, nephridia, and sometimes, jaws.

Most important, they exhibit metamerism– the division of the body into repeating blocks or segments.

Special Attributes of Annelids Of particular relevance to oceanography – class

Polychaeta, because many polychaete worms live in the marine environment. 1. Tubeworms have flower-like “antennae.” 2. Bristleworms sting when touched. 3. Spongeworms live on sponges. 4. Fireworms live on the surface of fire coral.

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Characteristics of Crustaceans

Phylum Arthropoda is the most numerous of multicellular animal phyla. There are several intermediate classifications. There may be as many as one million arthropod species. Characteristics: segmented bodies, jointed legs, a chitinous exoskeleton.

Superclass Crustacea – an intermediate classification. Characteristics include:

A pair of appendages on each body segment. Two pairs of antennae. Mandibles for chewing. Teardrop-shaped larvae. Exoskeletons are shed

as they grow.

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Special Attributes of Class Cirripedia

Barnacles unique lifestyle sets them apart into class Cirripedia.

Life begins as free-swimming larvae like other crustaceans. When the larva finds a surface on which to live (rocks, boats,

etc.) it fuses itself in place “upside down.” The exoskeleton forms the carapace (hard shell) the barnacle

can withdraw into for protection.

Special Attributes of Copepods Copepods play a central role in the ocean food webs.

They are important primary and secondary consumers ofphytoplankton and zooplankton.

Relatively few larger animals can consume the tiniest plankton,but many can eat the larger copepods. Fish, krill, and giant planktonfeeders, including whale sharks, baleen whales, and manta rays all eat copepods.

Copepods are important to ocean food webs because they link thetiny primary producers and consumers to the large animalshigher up the web.

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Special Attributes of Decapods and Krill

Class Malacostraca includes two orders of interest due to their roles as food for humans and food for nature.

Order Decapoda: lobsters, shrimps, and crabs Have 10 functional legs (deca meaning ten and

poda meaning foot). Have claws and an extended carapace that

encloses the gills. Because humans eat these shellfish, they are

an important food source and resource on which the fishing industry relies.

Order Euphausiacea: krill Krill are important primary and secondary consumers

that link smaller plankton to larger consumers. In subpolar food webs, they are vital. Whales, seals,

sea birds, and penguins only survive in highly productive waters. Much of the food web above krill depends on it for life.

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Characteristics of Echinoderms

Even though the organisms in phylum Echinodermata don’t at first look and act much like animals, they are. They move. They attack prey. They defend themselves.

They just tend to do so very slowly.

They all share: A radially symmetrical body divided into five parts. Most have hundreds of tiny tube feet to crawl and climb. Most have a water vascular system that

brings oxygen to the body cells.

Echinoderms have some traits closeto chordates. The adult is radially symmetrical. The larvae are bilaterally symmetrical.

Bilateral symmetry, along a vertical axis,is what mammals, fish, etc. have.

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Special Attributes of Crinoids

Class Crinoidea include feather stars and sea lilies. The primary characteristics of this class are:

Long feather-like arms and short, hook-like legs called cirri.

They have upward-facing mouths. Most are nocturnal feeders. At night, they unfurl

their arms to capture plankton and nutrients carriedinto their paths by the current.

By day they coil up tightly and hide in the reef. Most crinoids attach to the bottom by their cirri.

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Special Attributes of Sea Stars

Sea stars belong to class Asteroidea. They are predators with downward-facing mouths. They have tube feet covering their undersides. They usually have five arms. A few species have toxic spines for protection. Each arm carries an equal share of the

animal’s systems and organs. They can regenerate a lost limb, some grow

into several new animals when cut into pieces.

Special Attributes of Brittle Stars Brittle stars belong to class Ophiuroidea.

This class has slender legs that are proportionatelylonger and thinner than those on sea stars.

Brittle stars feed on detritus and small animals. They use arms and tube feet for locomotion.

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Special Attributes of Sand Dollars and Sea Urchins

Sand dollars and sea urchins are part of class Echinoidea. They have the five-section body, but no arms. Sand dollars and sea urchins share a disk-shaped body. They have tube feet on the underside. Sea urchins graze on algae. Swimmers avoid sea urchins because of their spines.

Some species have toxins in the spines for self-defense. Urchins can move their spines to assist in locomotion.

Special Attributes of Sea Cucumbers Sea cucumbers are part of class Holothuroidea.

They have an elongated five-segment body with tentacles around the mouth.

Most feed by moving with their mouths open, allowing sandto flow through. A few are filter feeders.

Some expel a sticky mass of white tubes covered in toxin. They are protected by tough skins and by the ability to expel

part of their internal organs for predators while saving the rest to survive.

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Characteristics of Chordates

Phylum Chordata are characterized by having a notochordand a dorsal nerve cord at some point in their life cycle. A notochord is a firm tissue mass along the dorsal side. A dorsal nerve cord is a tube of nervous tissue just above

the notochord.

Special Attributes of Subphyla Urochordata and Cephalochordata

Subphylum Urochordata includes tunicates, colonialdrifting salps, and larvacean.

Tunicates pump water to filter feed. Salps are gelatinous free-floating organisms. Larvaceans are tadpole-like planktonic organisms thought to

resemble the theorized ancestor of vertebrates.

Subphylum Cephalochordata includes 25 species of lancelet. These small filter feeders of genus Amphioxus are significant because they resemble vertebrates, except they lack vertebrae.In

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Characteristics of Subphylum Vertebrata

A notochord that has developed into a spinal cord protected byvertebrae and a head with a brain characterize organisms inthis subphylum. Vertebrates consist of the most complex, large, fast, and conspicuous organisms.

They include us, the organism that has had the most effect on the global biosphere.

Significance of Class Agnatha This is the class of the jawless fish.

Species include lampreys and hagfish.

Organisms in this class are significant because they mayrepresent the ancestor of bony fish/sharks. Scientists theorize that during the Cambrian period the first

of three gill arches on a jawless fish evolved into the first jaws. Having jaws allowed vertebrates to become very successful predators. Having jaws put organisms in class Chondrichthyes (sharks and rays) and class

Osteichthyes (bony fish) near the top of marine food webs.

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Characteristics of Sharks and Rays

Class Chondrichthyes includes sharks, rays and their close relatives. Sharks and rays don’t look similar on the outside, but

share a basic anatomy that classifies them together. Sharks and rays are jawed fish, that lack a swim

bladder, and have cartilaginous skeletons.

Special Attributes of Sharks and Rays Sharks and rays are successful predators:

Subclass Elasmobranchii have cartilaginous skeletons. This characteristic saves energy. Saving energy is one of the

things that have made them successful predators.

Sharks have a sense of smell that detect incrediblydiluted substances.

Sharks have a “conveyor belt” of multiple rows of teeth. They swing into place as old teeth wear out and fall away.

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Special Attributes of Sharks and Rays (continued)

Sharks and rays have other interesting characteristics: Both have lateral lines – lines of sensory hair along the length of the body

that detect water motion and vibrations. Unique to elasmobranchs is electroreception – the ability to sense minute electricity

created by muscles and nerves. Sharks and rays have organs called ampullae of Lorenzini which you can see as

visible pits near their snouts used to detect the electrical current.

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Special Attributes of Sharks and Rays (continued)

Elasmobranchs differ in their reproductive strategy. Sharks and rays produce fewer, but more mature offspring. Most fertilize their eggs internally.

The male deposits sperm in the female via a pair of copulatory organs called claspers found at the base of the pelvic fins.

The female lays an egg case in which the juveniles develop for up to six months at which time one or more sharks or rays emerge.

A few shark species are ovoviviparous – the eggs hatch within the mother’s body. They give birth to live young rather than egg cases.

The largest fish in the ocean. Shark size ranges from hand-sized to the

whale shark – the largest fish in the ocean. Whale sharks can reach 14 meters (46 feet). Basking sharks can reach 10 meters (33 feet). Megamouth sharks can reach 6 meters (20 feet).

All three are filter feeders that consume plankton.

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Special Attributes of Rays

Superorder Batidoidimorpha of subclass Elasmobranchii consists of therays, which includes skates and guitarfish. Ray anatomy is well suited to life on sandy

bottoms or midwater. Specially adapted to life in midwater are

the eagle ray and manta ray. Pectoral fins have become “wings” that

stretch forward over the gills and are fused to the sides of the head.

Shoulder girdles are flattened and many bones are fused together for rigidity.

No longer need a tail for swimming, the tail has become a defensive whip in some species.

Rays literally fly through the water. The largest rays are mantas with wingspans

exceeding 8 meters (26 feet). Like the largest shark, the mantas feed on plankton.C

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Characteristics of Bony Fish

Class Osteichthyes are jawed fish with bone skeletons. Most have a swim bladder and scales. Most control buoyancy by adding or releasing gas to/from their swim bladder.

They control the swim bladders with oxygen gas exchanged to and from blood circulation. Many have a special organ called the gas gland and the rete mirabile that take up gases from

the bloodstream for the swim bladder. This allows many species to hover nearly motionless in midwater.

Most bony fish reproduce externally. The female lays her eggs, the male

immediately fertilizes them. Their strategy is to produce a vast number

of off-spring with only a few expected to survive to maturity.

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Characteristics of Bony Fish (continued)

Bony fish have characteristics for life on the reef and for life in theopen ocean: Bony fish have lateral lines that detect water

motion and vibrations. Most open ocean and schooling fish have a torpedo-like

streamlined shape that minimizes drag and turbulence. This fusiform shape is spindle-like, slightly broader at the

head and a V-shaped tail. This makes them fast swimmers.

Most open-ocean and schooling fish have a lighter underside and dark topside for concealment.

Bony fish living in reefs and on the bottom usesurvival strategies more diverse and includeconcealment and armor instead of swimming. For this reason, you see far more diversity in color,

shape, and size among reef and bottom fish.

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Special Attributes of Orders Clupeiformes and Gadiformes

Two orders in class Osteichthyes have an importantplace in worldwide fisheries. 1. Order Clupeiformes which includes herrings,

pilchards, sardines, and anchovies. About one-quarter of all fish caught come from this order.

2. Order Gadiformes which includes cod, pollack, haddock, whitings, and their relatives.

This order continues to produce about a sixth of theworld’s fish catch.

Alaskan pollack, the haddock and whitings havebecome important fisheries.

Historically, worldwide fisheries have influencedpolitics and caused wars.

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Characteristics of Reptiles

Organisms in class Reptilia mostly live on land or in freshwater. Relatively few live in the ocean. They have these characteristics in common:

Are generally cold-blooded and have scales. Reproduce (most species) by laying internally fertilized eggs. Breathe with lungs at all stages of their lives.

Special Attributes of Marine Crocodiles,Turtles, Snakes, and Lizards

Three orders of reptiles having marine species are: Order Crocodilia – alligators, crocodiles, and caimans.

Members of this order are semi-aquatic with most living infreshwater. Exception is the giant saltwater crocodile.

Order Chelonia – turtles and tortoises. There are seven species of marine turtles – all live in

warm waters.

Order Squamata – snakes and lizards. 61 species of sea snake are true marine organisms.

Only one lizard is a true marine reptile – the marine iguana.Ma

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Characteristics of Birds

Birds are vertebrates in class Aves. They share several characteristics: Feathers, unique to this class. Forelimbs that are wings. A four-chambered heart and lay internally fertilized eggs.

Marine birds are important to the marine ecosystem: They are predators that consume

fish, crustaceans, and mollusks. In turn they are prey to marine mammals and sharks. They supply guano – a significant source

of nutrients, specially organic nitrogen important to sea life.

Many species of birds exhibit related adaptations to an aquatic life: Webbed feet for swimming and floating on the surface. Bill adaptations suited to their marine prey, like the pelican’s pouch. The cormorant flies over water, and dives in it in pursuit of prey. Birds, like the albatross, have wings and flight characteristics adapted to long-duration flying over

wide expanses of water.

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Special Attributes of Penguins

Penguins, order Sphenisciformes, all live in the Southern hemisphere. Penguins make up about 80% of all

Antarctic birds and by far outnumber even the massivemarine mammal populations.

Not all species live in cold places. Penguins are found on the coasts of

South America, Africa, Australia, New Zealand, and the nutrient-rich waterssurrounding the Galapagos Islandsnear the equator,

They cannot fly, but they’re as at homeunderwater as other birds are in the air. They dive hundreds of times daily hunting for food. They can reach depths of 100 meters (328 feet) and deeper.

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Characteristics of Marine Mammals

All organisms in class Mammalia share these characteristics: They have hair on some part of the body. They nourish their young with milk provided by mammary glands. Mammals are homeothermic (warm-blooded) with a

constant internal temperature. The majority give birth to live young.

The marine environment poses several challengesto mammalian physiology: 1. Compared to living in air, life in water demands high

oxygen consumption. Marine mammals meet this challenge by breathing air.

2. There is a need to dive holding their breath forlong periods.

They use myoglobin, a protein, to bind reversibly with oxygen to make it available for usein metabolism.

They use the mammalian diving reflex – is when diving pulse rate slows and blood flow diverts from the muscles to the heart and brain.

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Characteristics of Marine Mammals (continued)

3. The water pressure and a need to equalize. Marine mammals’ lungs and sinuses are very flexible, allowing compression

without pain or injury. Some dolphins and whales have lungs that engorge with blood thus offsetting

the compressed space.

4. The challenge of easy movement through the dense medium of water. The use of streamlining and hydrodynamics helps with this.

5. The challenge of the senses. They need to hear, see, and smell underwater. Dolphins and whales use echolocation (natural sonar) to determine distance,

size, density, and shape. Seals and sea lions have sensitive hearing and excellent underwater eyesight.

They see poorly above water, but have a keen sense of smell.

Special Attributes of Seals and Sea Lions The seals and sea lions belong in order Pinnipedia.

Seals: don’t have ear flaps, rear flippers point backward and cannotrotate forward, out of water seals crawl on their stomachs.

Sea Lions: have ear flaps, hind flippers rotate, can sit upright and run. Walrus: don’t have ear flaps, hind flippers rotate, can sit upright.C

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Special Attributes of Dolphins, Whales and Porpoises

Whales, porpoises, and dolphins come from different families organizedunder the order Cetacea. Cetaceans are divided into two suborders: Suborder Mysticeti: a group of filter feeders made up of baleen whales. Suborder Odontoceti: a group of toothed whales made up of sperm whales, dolphins

and porpoises. They are predators. Family Delphinidae: are the dolphins and orcas, one of the most varied and successful groups

among the toothed whales.

Most cetacea use echolocation and communicate by sound.

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Special Attributes of Dugongs and Manatees

Dugongs and manatees (sometimes called sea cows)belong to order Sirenia, which has four species.

All four are the only herbivorous marine mammals. Manatees are known for migrating to and from fresh- and

saltwater environments.

Marine Mammals and Human Interaction Human activities have endangered marine mammals and continue to do so.

Whaling brought whales to the verge of extinction. Banned or greatly limited by international convention

today, some species seem on the rise, others do notseem to be recovering.

People have hunted seals for their fur and manatees for meat. Dolphins have been killed as bycatch in tuna fishing. Pollution and overfishing raise new threats.

Because of their high metabolisms and energy demands,marine mammals require highly productive environmentsto survive.

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