1. Choose to view chapter section with a click on the section heading.
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 Water
Chapter Topic Menu

2. 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.
The Linnaeus Classification System
Chapter 5 Page 5-4

3. 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.
The Linnaeus Classification System
Chapter 5 Pages 5-5 to 5-7

4. 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 in classifying organisms is that some organisms don’t fit neatly into defined classifications. An organism can have characteristics that fit in one and others that 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.
The Linnaeus Classification System
Chapter 5 Pages 5-8 & 5-9

5. Six - Kingdom System and Three - Domain System
© Current Publishing Corp. 2006
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.
The Linnaeus Classification System
Chapter 5 Page 5-10
Taxa tree

6. 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 of photosynthesis began with cyanophytes of domain Bacteria, an early prokaryote.
Prokaryotes – Small yet Significant
Chapter 5 Page 5-12

7. 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.
Prokaryotes – Small yet Significant
Chapter 5 Pages 5-13 to 5-15

8. 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
Marine Algae
Chapter 5 Pages 5-16 & 5-17

9. 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.
Marine Algae
Chapter 5 Pages 5-17 & 5-18

10. 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.
Marine Algae
Chapter 5 Page 5-19

11. 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.
Marine Algae
Chapter 5 Pages 5-20 & 5-21

12. 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 reefs because it is the cement that holds the coral reefs together.
Red algae species that live on coral reefs secrete a calcium carbonate shell.
Their secretions bond coral colonies and debris together which in turn holds the reef together.
Marine Algae
Chapter 5 Pages 5-21 & 5-22

13. Phylum Phaeophyta – Brown Algae
Phylum Phaeophyta (brown algae), is more structurally complex. Many brown 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.
Marine Algae
Chapter 5 Pages 5-23 & 5-24

14. 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 by organisms living there.
Marine Plants
Chapter 5 Pages 5-26 to 5-28

15. 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 distribute nutrients 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.
Sponges – Filters of the Sea
Chapter 5 Pages 5-30 to 5-32

16. 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.
Coral, Anemones, Sea Fans, and Jellyfish
Chapter 5 Pages 5-33 & 5-34

17. Special Attributes of Coral and Anemones
The largest class in phylum Cnidaria is class Anthozoa, the coral and 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 and the anemone receives food from the fish.
Coral, Anemones, Sea Fans, and Jellyfish
Chapter 5 Pages 5-34 to 5-36

18. 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.
Coral, Anemones, Sea Fans, and Jellyfish
Chapter 5 Pages 5-36 & 5-37

19. 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.
Coral, Anemones, Sea Fans, and Jellyfish
Jellyfish
Chapter 5 Pages 5-38 to 5-40

20. 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 the world – more than 60 meters (197 feet).
Simple Marine Worms
Chapter 5 Pages 5-41 & 5-42

21. 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 that rearranges the organs and brings them together allowing the body to draw into the spiral shell common to this class.
Mollusks – A Bag, a Scraper, and a Foot
Chapter 5 Pages 5-43 & 5-44

22. Special Attributes of Class Bivalvia
Belonging to class Bivalvia (bi meaning two) are mollusks that have two hinged 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.
Mollusks – A Bag, a Scraper, and a Foot
Chapter 5 Pages 5-45 to 5-48

23. Characteristics of Annelids
Worms in phylum Annelida stand apart because 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.
Complex Worms
Chapter 5 Pages 5-49 & 5-50

24. 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.
Crustaceans – Underwater Arthropods
Chapter 5 Page 5-51

25. 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 of phytoplankton and zooplankton.
Relatively few larger animals can consume the tiniest plankton, but many can eat the larger copepods. Fish, krill, and giant plankton feeders, including whale sharks, baleen whales, and manta rays all eat copepods.
Copepods are important to ocean food webs because they link the tiny primary producers and consumers to the large animals higher up the web.
Crustaceans – Underwater Arthropods
Chapter 5 Pages 5-51 to 5-53

26. 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.
Crustaceans – Underwater Arthropods
Chapter 5 Pages 5-53 to 5-55

27. 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 close to chordates.
The adult is radially symmetrical.
The larvae are bilaterally symmetrical. Bilateral symmetry, along a vertical axis, is what mammals, fish, etc. have.
Echinoderms – Stars of the Sea
Chapter 5 Pages 5-57 & 5-58

28. 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 carried into 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.
Echinoderms – Stars of the Sea
Chapter 5 Page 5-58

29. 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 proportionately longer and thinner than those on sea stars.
Brittle stars feed on detritus and small animals.
They use arms and tube feet for locomotion.
Echinoderms – Stars of the Sea
Chapter 5 Page 5-59

30. 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 sand to 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.
Echinoderms – Stars of the Sea
Chapter 5 Pages 5-60 & 5-61

31. Characteristics of Chordates
Phylum Chordata are characterized by having a notochord and 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, colonial drifting 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.
Invertebrate Chordates
Chapter 5 Pages 5-62 & 5-63

32. Characteristics of Subphylum Vertebrata
A notochord that has developed into a spinal cord protected by vertebrae and a head with a brain characterize organisms in this 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 may represent 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.
Vertebrates – Top of the Food Web
Chapter 5 Pages 5-64 & 5-65

33. 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 incredibly diluted substances.
Sharks have a “conveyor belt” of multiple rows of teeth.
They swing into place as old teeth wear out and fall away.
Sharks and Rays – Teeth and Wings
Chapter 5 Pages 5-65 to 5-67

34. 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.
Sharks and Rays – Teeth and Wings
Chapter 5 Page 5-69

35. 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.
Sharks and Rays – Teeth and Wings
Chapter 5 Page 5-69

36. Special Attributes of Rays
Superorder Batidoidimorpha of subclass Elasmobranchii consists of the rays, 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.
Sharks and Rays – Teeth and Wings
Chapter 5 Page 5-71

37. 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.
Bony Fish – Half the World’s Vertebrates
Chapter 5 Page 5-73

38. Characteristics of Bony Fish (continued)
Bony fish have characteristics for life on the reef and for life in the open 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 use survival strategies more diverse and include concealment and armor instead of swimming.
For this reason, you see far more diversity in color, shape, and size among reef and bottom fish.
Bony Fish – Half the World’s Vertebrates
Chapter 5 Pages 5-74 & 5-75

39. Special Attributes of Orders Clupeiformes and Gadiformes
Two orders in class Osteichthyes have an important place 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 the world’s fish catch.
Alaskan pollack, the haddock and whitings have become important fisheries.
Historically, worldwide fisheries have influenced politics and caused wars.
Bony Fish – Half the World’s Vertebrates
Chapter 5 Pages 5-75 & 5-76

40. 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 in freshwater. 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.
Marine Reptiles – Cold Blood and Warm Water
Chapter 5 Pages 5-77 to 5-80

41. 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.
Seabirds – At Flight Over and In the Ocean
Chapter 5 Page 5-81

42. 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 massive marine 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 waters surrounding the Galapagos Islands near the equator,
They cannot fly, but they’re as at home underwater 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.
Seabirds – At Flight Over and In the Ocean
Chapter 5 Page 5-82

43. 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 challenges to 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 for long periods.
They use myoglobin, a protein, to bind reversibly with oxygen to make it available for use in 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.
Marine Mammals – Warm Blood in Cold Water
Chapter 5 Pages 5-83 & 5-84

44. 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 cannot rotate 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.
Marine Mammals – Warm Blood in Cold Water
Chapter 5 Pages 5-84 to 5-86

45. Special Attributes of Dolphins, Whales and Porpoises
Whales, porpoises, and dolphins come from different families organized under 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.
Marine Mammals – Warm Blood in Cold Water
Chapter 5 Pages 5-86 & 5-87

46. 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 not seem 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 environments to survive.
Marine Mammals – Warm Blood in Cold Water
Chapter 5 Pages 5-88 & 5-89