There are four families of marine reptiles: saltwater crocodiles, sea snakes, marine iguanas and sea turtles.

Sea snakes. "Scientific classification: Sea snakes are usually classified in two subfamilies, the Hydrophiinae and the Laticaudinae, both in the family Elapidae. Some taxonomists classify them instead in two families, the Hydrophiidae and Laticaudidae, separate from the family Elapidae. Stokes's sea snake is classified as Astrotia stokesii. The yellow-bellied sea snake is classified as Pelamus platurus

Sea Snake, common name for certain marine members of a family of venomous snakes. Sea snakes inhabit the tropical waters from the Indian to the Pacific oceans; they are particularly abundant in the Persian Gulf and the Bay of Bengal. Most sea snakes are not large, ranging from about 0.5 to 1 m (1.6 to 3.3 ft) in length, although Stokes's sea snake can reach nearly 2 m (6.6 ft). One group of sea snakes, sometimes called the true sea snakes, give birth to live young and lack the enlarged ventral scales typical of most terrestrial snakes. The other group, sometimes referred to as seakraits, lay eggs; because they must leave the water to deposit their eggs, they retain straplike ventral scales, although these may be smaller than those of terrestrial snakes. The paddlelike tail of sea snakes is wide and compressed and makes an effective swimming organ. Unlike eels, sea snakes have no gills and must rise to the surface of the water for air, but they can remain underwater for several hours, obtaining dissolved oxygen from water that they swallow and eject. Many species feed on elongate fishes, such as eels, which they paralyze with their venom. They are generally not aggressive and usually will not bite humans unless handled roughly or forcibly restrained.

The yellow-bellied sea snake, one of the most common sea snakes, ranges along the Pacific coast from southern California to northern South America. It is less than 1 m (3.28 ft) long and is black or dark brown with a bright yellow belly." (The reptile refrence: http://www.iversonsoftware.com/business/reptile.html)

Crocodiles: "Crocodilians first appeared about 200 million years ago and are believed to be remnants of the great age of reptiles. Their ancestors originally lived on land and were lightly built, but they soon diversified into water-dwelling, or aquatic, and amphibious forms. Except for the alligators, crocodilians live in tropical and subtropical areas of the world. Modern crocodilians are amphibious, spending much of their time in water, where they swim with rhythmic strokes of the tail. The tail is sometimes used to capture prey, sweeping it from shallow to deeper water, where it can be devoured more easily.

Crocodilians are well-adapted as predators, with few natural enemies. Bony plates, called osteoderms, form a kind of armor in their thick skin. Their teeth, about 30 to 40 in each jaw, are set into sockets in the jawbones and interlock when the mouth is closed. In crocodiles, the fourth tooth on each side of the lower jaw protrudes when the mouth is closed; in alligators, these teeth are not visible. The jaws of crocodilians are powerful enough in closing to crush the bones of small animals, but so weak in opening that they can be held together by hand. As the crocodilian floats almost completely submerged, its protruding nostrils and eyes and a portion of its back are the only parts visible as it stalks its prey. Crocodilians are the most vocal reptiles, producing sounds from quiet hisses to fearsome roars and bellows, usually during the mating season. On land, crocodilians move quickly in a belly crawl but can also gallop and walk mammal-like on all four legs.

Crocodiles are physiologically the most advanced reptiles; their internal anatomy resembles that of birds. They have a four-chambered heart and well-developed senses. Cold-blooded like all reptilesÑtheir body temperature depends on the environmentÑcrocodilians bury themselves in mud to estivate or hibernate. In warm regions they are dormant during droughts; in colder regions, during winter. Crocodilians are egg-laying, or oviparous, reptiles, reaching reproductive maturity at about the age of ten. The eggs, 20 to 90 in number and about the size of goose eggs, are buried in sand, mud, or vegetable debris, where they are left to hatch by the heat of the sun or of vegetable decomposition. Females of some species remain in the area to protect the nest and care for the newly hatched young, although many of the eggs and young are lost to predators. The parental behavior of crocodilians is unique among reptiles and points to their affinity with birds." (http://www.iversonsoftware.com/business/reptile.html)

Marine Iguana sp[ecies: "Amblyrhynchus cristatusTo be enthusiastic about a Robinson Crusoe life-style is one thing. To actually live more than half a year on a desert island in the middle of the Pacific Ocean is another, especially if you cannot take along fresh fruits (because of the possibility of introducing exotic plants and insects) and there is no electricity, not to mention refrigeration. One also learns how to get by with very little fresh water when one has to carry every single quart and receives supplies only once a month. But when my two Ecuadorian co-workers, Victor Carrillo and William Revelo, and I landed with our gear on the rocky coast of Santa Fe, in the Galapagos archipelago, we didn't think about the hardships ahead.

To cope with the high salt content of their diets, marine iguanas have the most efficient salt-excreting glands of all reptiles. The glands are located just above the nostrils. By sneezing frequently, the lizards expel the salt in small white geysers, which often give these black lizards a whitewashed look. After eating, a marine iguana must reset its body temperature and heart rate (from 30 to 100 beats per minute), because the digestive system works best at a constant, relatively high temperature. By flattening their dark bodies against the warm lava rocks, the lizards expose as much skin surface as possible to the sun and the rock surface. The flow of heat from the rocks is controlled by vessels in the marine iguanas' chest, which close and open to regulate body temperature. To prevent overheating, the lizards elevate their torsos and face the sun, thereby diminishing the amount of body area exposed and allowing the cooling coastal breezes to convect heat away. Unable to sweat, most marine iguanas pant when the temperature approaches 104 degrees. Not so the hatchlings; they sometimes enter the intertidal flats with body temperatures of 108 degrees and, in general, have higher body temperatures than all the other marine iguanas. This allows them to digest their food in half the time adults require and supplies the energy needed for fast growth." (Maritn Wikeski: http://www.life.uiuc.edu/wikelski/iguana2.html)

sea turtle species: Caretta caretta: Loggerhead Sea Turtle

According to the Website - Turtle Trax, a 1990 study showed that the S.E. of the US recorded 50-70,000 nests which they estimate is 30-40% of the world population of loggerehads.
Decline in Australian rookeries (Limpus and Reimer 1994)
Florida populations stable.
South African doubled since early 1960s (Hughes 1989)(Euro Turtle: http://www.exeter.ac.uk/telematics/EuroTurtle/dleath.htm)

Chelonia agassizi: Black Sea Turtle
Inhabits coastal waters of the eastern tropical Pacific ocean.
Not commonly observed in the opean ocean. :
http://www.exeter.ac.uk/telematics/EuroTurtle/dleath.htm)

Chelonia mydas: Green Sea Turtle; (2,000) waters.
Rarely nest in waters below 25 degrees C.
Near continental coasts and around islands.
Rare in temperate waters.
Along with hawksbill, the most tropical of turtles.
Population: (FAO)
Some estimated population figures shown above.
Many populations on the decline, mainly in Australasian region.
Here, 100,000 green turtles per annum harvested for meat.
Near total egg harvesting in Indonesia and Malaysia. (Sarawak Turtle Islands)
Strong conservation in Sabah, Hawaii and Florida have seen some recovery" (Euro Turtle: http://www.exeter.ac.uk/telematics/EuroTurtle/dleath.htm ).

Eretmochelys imbricata: Hawksbill Sea Turtle;
Wide spread nesting patterns with few very large nesting places.
Nesting confined to 25 degrees N and 35.5 degrees S.
Population: According to the Website Turtle Trax, 38 out of 65 population areas are on the decline.
Population difficult to assess but under pressure from commercialization for its shell.
According to Agardy (BBC Wildlife) 1992 approx: (Limpus 1995)(Euro Turtle: http://www.exeter.ac.uk/telematics/EuroTurtle/dleath.htm)".

Lepidochelys kempii: Kemp's Ridley Sea Turtle; are still being added up. Since each female is thought to lay an average of 2.3 clutches, it is likely that about 1671 turtles laid these clutches. Only a portion of adult Kemp's ridley females nest every year." (Euro Turtle: http://www.exeter.ac.uk/telematics/EuroTurtle/dleath.htm).

Lepidochelys olivacea: Olive Ridley Sea Turtle; " (Euro Turtle: http://www.exeter.ac.uk/telematics/EuroTurtle/dleath.htm)."

Dermochelys coriacea: Leatherback Sea Turtle; "Range: Widely distributed and can be found in colder waters due to ability to thermo-regulate.
Highly pelagic species
Population: In 1980, the population was estimated (Ripple) at between 70,000 and 115,000 but since then it has declined at an alarming rate to its present estimate (Spotila) of about 34,500. Most important rookeries are northern coast of South America, especially French Guiana. Also good populations in Mexico. Serious declines are being observed in Malaysian nesting sites (Terengganu - Limpus/Bjorndal).
Some recent articles and papers are: Hell for Leatheries - an article by Tom Langton in the BBC Wildlife Magazine (March 1999, Vol.17, no.3)
Worldwide Population Decline of Dermochelys coriacea: Are Leatherback Turtles Going Extinct? (1996?)"(Euro Turtle: http://www.exeter.ac.uk/telematics/EuroTurtle/dleath.htm).

This activity will need the following materials:

• A live reptile will be needed for examining reptilian characteristics. (I recommend seeing if one is available through a classroom at school, or borrowing one from someone if this activity will not be performed regularly. The best reptile for this part of the activity is either a rosy boa or a bearded dragon; they are extremely docile. If you have to buy a reptile, buy a captive bred specimen from a local pet shop. The pet shop will provide information for proper care of the animal.)
• Pictures of all four types of marine reptiles will be needed.
• Obtain as many types of preserved marine reptile specimens as possible. Check with a university if possible, they may have something available through a teaching collection. If you cannot get preserved specimens, use a model. This model can be plastic, clay, or rubber. If a model is not obtainable, then an extra picture will suffice.

1. To elicit prior knowledge, ask what characteristics define a reptile (pass a live reptile around to the students). -Ectothermic
-Scales
-Leathery eggs, or live birth (oviparous and ovoviviparous)
-Some are venomous (what is the difference between venomous and poisonous and what is the venom used for?)

2. Observational investigation. Divide students into groups of 4-5 and have them answer the following questions about the specimens (each group should have either a crocodile and a marine iguana or a sea snake and a sea turtle). Each group should develop an answer the following questions by considering physical features (give hints if absolutely necessary).
-What do you think they eat? (Students should be looking at the mouth of each animal; crocodiles are meat eaters, sea snakes primarily eat fish, marine iguanas eat algae, and sea turtles can eat sea grass, jelly fish, and fish.
-What part of the ocean do you think they live in? (Marine iguanas spend most of their time in the intertidal zone, corcodiles live near land as well, and turtles and sea snakes live in the open ocean, rarely or never going to land). To answer this queation students should be encouraged to look at such features as claws/fins and body shape.
-Are they venomous? (sea snakes are the only venomous sea reptile).
-How do they move about? (Look at body structure).

3. Have each group report their observations.

4. Now pass out cards to each group with pictures of the animals on them and the correct answers to the questions on the back. The cards should also have some additional information for the students to discover such as:
-Which reptiles have live birth versus lay eggs and why?
-Are any of these reptiles endangered? Why?
-How do crocodiles eat larger prey?
-What sea turtle is an omnivore?

Here are some further activities which relate to and extend the complexity of the experiment.

What can students do about thretend and endangered species? This is a list of some activities that students can do to get involved. This is from the web site http://www.bagheera.com/inthewild/class_activities.htm#CS1-4

Develop a code of ethics for a recreational activity that can injure or harass wildlife. Investigate the problems that recreational activities cause for threatened and endangered species. For example, determine what problems boat traffic causes for endangered marine or freshwater species such as whales, manatees, giant otters, and corals.

Develop a Boating Code of Ethics that will help prevent or minimize harassment and injury to these species. Other activities to examine include birdwatching, wildlife photography, sport hunting, sport fishing, and SCUBA diving and snorkeling. Can you think of others?

Develop a Code of Ethics for any of the activities, send your proposed Code of Ethics to an organization involved with the activity, and ask for the group's comments.

G1-2. Support the recovery process for an endangered species in the United States by using the media. Contact the federal and state agencies in charge of recovery of endangered species. (For most species, the federal agency is the Fish and Wildlife Service and the state agency is the Department of Wildlife or the Department of Game. For marine species, the federal agency is the National Marine Fisheries Service. The federal agencies, and some state agencies, have web sites on the Internet.)

a) Find out what threatened or endangered species live in your state and select one of these species.
b) Ask for a copy of the recovery plan for the species. If there is no recovery plan, ask why. (Not all listed species have a plan, even though the Endangered Species Act requires one for every listed species.)
c) Find out what programs the agency has initiated to help the species recover and what the status of these programs is.
d) Make a list of ways citizens can support recovery efforts for this species.
e) Try to get your list published in a local newspaper.

G1-3. Investigate the role of development banks in the decline of biodiversity, and develop a set of guidelines for funding projects that affect biodiversity. Find out what development banks are and how they work. Do they require the projects they fund to be environmentally safe? Can you find some examples of projects funded by development banks that have contributed to species endangerment?

Investigate what development banks can do to help conserve wildlife while still funding projects to help the people of developing countries. Write a set of guidelines for funding development projects that will help conserve biodiversity.

Send your list to a development bank, such as the World Bank in New York, and ask the bank if it uses similar guidelines in evaluating projects for funding.

G1-4. Get involved in the Democratic process. Find out if your state has its own Endangered Species Act. (The Federal ESA applies in all states, but many states have their own law, too.) Investigate current bills related to endangered species or the environment in your state. (This information is available on the Internet.)

Find out who your state senators and representatives are and how they have voted on similar bills in the past. Call their offices and find out their current opinions on these issues.

Investigate the likely impact of one of these bills on biological diversity and on your community. Research the issues, form your own opinion, and write your legislators to influence their vote on the bill.

G1-5. Encourage your state government to help prevent animals and plants from becoming endangered. As you have learned in this study unit, it is more effective and less costly to conserve species before their populations get so low that they are endangered. Contact the agency in your state that is in charge of conserving biodiversity. (The agency usually is called the Department of Fish and Wildlife, the Department of Wildlife, or the Department of Game.) Find out if your state has an Endangered Species Act of its own and how the law works.

Next, find out if the agency keeps track of "species of concern" or "sensitive species," those that are not yet formally listed as threatened or endangered under state or federal law but whose populations appear to be declining.

Ask what measures the agency takes to prevent declining species from getting to the point where they are threatened or endangered. If there is no program to prevent endangerment, write to the agency and tell them why you think there should be such a program.

INQUIRE, ANALYZE & COMPARE
G2-1. Design a database and find patterns of endangerment or extinction. a) Design a database of the endangered and extinct species in this curriculum that includes the following categories of information: species; scientific name; classification (e.g., mammal, reptile, bird, amphibian); location (e.g., Brazilian rain forests); habitat (e.g., forest, ocean, grassland); population decline over time (see ActivityG2-2); causes of endangerment (or causes of extinction, if extinct). Include at least 20 species. b) What patterns or trends can you find?

G2-2. Graph the population decline of several species. a) Choose several species and make a graph for each, showing population decline over time. Use either spreadsheet software or paper to create line graphs or bar graphs. Plot dates (years) on the X axis and population on the Y axis. b) Compare your graphs. Can you draw some conclusions? Use these graphs as a visual in a written or oral presentation on species decline.

G2-3. Choose an endangered or extinct species and create a series of diagrams showing species relationships in that ecosystem and what happens when one species is removed. a) Draw a diagram showing what the animal eats, what other animals compete for the same food, and what animals eat the animal, its young, or its eggs. Other relationships you can portray in your diagram include where the animal nests (in a certain kind of tree, for example), what other animals compete with it for nest sites, and what pollinators (e.g., bees, bats) are needed to pollinate its food plants. Can you think of other relationships that are important? b) Remove one of the species in the diagram and analyze what is likely to happen to the entire web of relationships. Draw a new diagram representing the new relationships.

G2-4. Investigate the effects of war and political instability on wildlife. Include the Persian Gulf war, the war in Bosnia, and other wars of your choosing. What are the main causes of injury or death to wildlife from war? What are the positive impacts of war on wildlife?

G2-5. Visit a local habitat with a guide and find out what lives there. Contact a national, state, or local park agency or a group like the Audubon Society and find out if they have naturalist programs for students. Go to a local habitat (like a wetland, forest, or meadow) with a professional or volunteer naturalist. Find out what plants and animals form the ecosystem and how they interact with each other. Ask questions like: Have there been surveys of the area to inventory the species? (For example, for a wetland area, do they know what amphibians live there and how abundant they are?) Are there any threatened or endangered species in the area? What are the main threats to the area? What is being done to conserve the ecosystem? (http://www.bagheera.com/inthewild/class_activities.htm#CS1-4)