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Crocodiles: A Three Day Lesson Plan


Author(s): Ashish Udhrain, Adam, and William Farris

Date: Spring 2000

 

Summary of Activity
50-100 words

Crocodiles are remarkable reptiles that have survived since the age of the dinosaurs. These voracious predators of land and water, have been able to adapt to their environment over millions of years due to superb design and superior intelligence.

There are 3 crocodilian subspecies: Alligatorinae, Crocodylinae and Gavialinae and all of these contain 23 species, crocodylinae containing 13. These long live reptiles are also widespread throughout the world. Although, they are a very hardy species, many have become endangered due to human activities such as over-hunting, pollution and development.

DAY 1: On this day the students will be introduced to the subject of crocodiles by dividing them into small groups of 2 or 3 and doing prepared research at the school library. Upon returning the completed assignment the teacher will then give them each a "chocodile."

DAY 2: On this day the students will begin by watching "The Ultimate Guide: Crocodiles," a 30 minute video. Afterwards, the teacher will assess the students knowledge of the material presented in the video by engaging in a class discussion. This should take up the rest of the class time.

DAY 3: The lesson plan for the day will be introduced with a short lecture/question review of the information that has already been covered. After the lecture/question review is complete, the students will receive a handout with the outline of a crocodile and the internal organs. They will be required to label, color and know the function of specific organs.

DAY 4: Crocodiles evolved 200 million years ago and have outlived the dinosaurs. when they first evolved they had longer legs and shorter snouts and lived on land. They evolved to have short legs, long snouts and live in water. With changes in environment and human acitivty, what could be next? Today the students will work together, 3-4 to a group, to brainstorm as to why crocodiles are such successful animals. Have them discuss and possibly draw how they think crocodiles will look like in 200 million years from today.

DAY 5: To assess their knowledge of the material taught in the last four days, students will be given a unit quiz. Along with the in class activities, there will be homework assignments and opportunities for extra credit. This lesson plan allows students to learn for themselves through various activities, where crocodiles are found in the world and what their habitats are like, with map and geographical activities. Another activity will help students learn what characteristics have helped them survive while other species have become extinct, through small group brainstorm discussions. Along with that, they can discover their anatomy and specialized structures through lecture, pictures, articles to be read, and videos. These acitvities would involve brainstorming in groups and allow them to express the knowledge they have learned in creative ways.

 

Grade levels

Grade Levels: 6-8th grade The ideal class size for this lesson plan is anywhere from 10-30 students

General description or introduction
The scientific principles that the activity is founded on.

This lesson is aimed at educating young people about animal behavior, archaeology, biology, genetics, evolution, nature, wildlife and conservation of animals and environment. These topics will be taught, discussed and learned through lectures, media and most importantly hands on activities presented in this outline.



Background information

INTRODUCTION: Crocodiles evolved around 200 million years ago (humans evolved about 1 million years ago). They used to be strictly land animals, and had longer legs and shorter snouts than they do today. Around 65 million years ago, at the end of the Mesozoic Era, many land animals became extinct. One species that survived were the crocodilians. Today crocodiles are found in the warm regions of Africa, Asia, Australia and North and South America.

CLASSIFICATION: There are 3 subspecies of crocodles, Alligoritinae, Crocodylinae, and Gavialinae. Each of these contain 23 species. Crocodiles have a large pointy snout with 2 sharp pointy teeth pointing up from the bottom of its mouth. Alligators have a round snout and its 2 prominent teeth are hidden. Members of the subspecies Gavialinae are characterized by their long slender snout. The following discusses 4 of the most common of the species. Saltwater Crocodiles(Crocodylus porosus) is found on the northern coast of Australia through Indonesia to southern India. Primarily found in estuaries but have been seen far out at sea. They can grow to 8 meters in length however most are around 4 meters long. Saltwater crocs are very aggressive and will attack people. Nile Crocodiles live in large numbers in African river basins, lakes and water holes and are also found in Madagascar. They grow to 5 meters and weigh more than 2,000 pounds. Despite their size, they are very agile in the water. Chinese Alligators are found in eastern China in the Yangtze River. They grow to almost 2 meters in length. Chinese alligators hibernate in the winter in holes dug out of the river banks. American Alligators inhabit the southeastern U.S. rivers, lakes and swamps. They can reach lenghts of 6 meters, but more commonly are about 4 meters long.

DIET: Crocodiles are carnivores. Their diet depends on their size and what is available around them. Hatchlings and young animals eat insects, snails, small fish and crustaceans. They grow fast and must eat often. As they grow larger, their prey and time between meals does also. They go from eating large fish and reptiles to mammals of all size, monkeys and buffalo to zebras and snakes. They generally eat the larger mammals as they come to the water to drink or cross rivers, during the dry season or migration. Since this is seasonal, crocodiles eat large amounts and can go for a year between meals. The crocs teeth are big and sharp, but are not used to chew. Instead they use them for snatching and grasping prey, which is then taken under and drowned. Chunks of flesh are twisted off and swallowed whole.

REPRODUCTION: Mating takes place in the water and the mother then lays between 20 and 80 eggs on a hard nesting area on the shore. Incubation takes up to 3 months and the nest is guarded fiercely by the female. The hatchlings are oviporous, meaning they are perfectly formed, but stay with their mother for 3 years before they are weened. Sexual maturity is reached at a certain length anywhere from 5 to 15 years of age.

HABITS: Crocodiles are cold blooded, and spend a lot of time in the water, which helps them to maintain a constant body temperature. Generally, they will spend the night in the water and the day basking in the sun. Crocs cannot sweat and during hotter months can be seen with their mouths open, panting like dogs, to stay cool. Crocodiles are usually found in large groups that are controlled by a dominat male who is very territorial. Crocs make a variety of sounds, from grunts and hisses to chirps and growels. This helps them to communicate messages to each other. Crocs can walk and even gallop on land but are more adept to the water. They propel themselves using their large, powerful tails.

PROBLEMS: Although crocodiles,date back some 200 million years, many species of crocodiles have become endangered in the last century. Once revered and even worshipped by such groups as the Egyptians, Phillipinos, and Australian Aborigines, crocodiles are now hunted primarily for their skins. In 1929, 190,000 alligator skins were sold in America. It is estimated that if the government, in 1944, had not stepped in, they would be extinct. The Nile Crocodile has also been hunted, and has disappeared from many of its northern habitats. The Indian gharial may already be extinct in the wild; In 1973 only 6 were found along 5000 km of waterway, where they were once overcome with animals. In South America an estimated 1 million caimans are killed each year. These are sad trends in population decline, showing the desparate need of conservation of the species.

INTERESTING FACTS: Crocodiles are the largest, most intelligent reptiles in the world. They can live for up to a century and can wait a year between meals. Crocodiles have many specialized structures that have helped them to evolve to what they are today. Crocodile's jaws are capable of producing 16 tons of crushing force! Another interesting feature on the jaws,is a unique structure on young hatchlings jaws, an "egg tooth", which is located on the tip of their snout. It is used to penetrate the membrane of the egg during hatching. The "egg tooth" is then gradually enveloped and disappears in an adult crocodile. They also have a unique feature to keep water from going down their throat while submerged underwater, a Palatal Valve. Since their mouths allow water in even when closed, the Palatal Valve covers the opening to the trachea and esophagus. Crocodiles also have a very complicated heart. It can actually bypass the lungs and pump oxygenated blood to the brain and other organs while underwater. This allows them to stay submerged for long periods of time, voluntarily up to 30 min, when pressed though they have been known to stay submerged for 2 hours or more! Crocodiles also have some sensory cells, ISO cells, which help them to detect vibrations under water. This helps them to locate prey in murky conditions. They are also thought to be chemoreceptors, which help them sense changes in salinity of the water. Crocodiles are amazing creatures which have survived since the dinosaurs and should be preserved for another 200 million years.



Credit for the activity
.

This is our original activity. The credit for this activity goes to Ashish Udhrain, Adam, and William Farris.


Estimated time to do the activity

This unit involves 5 class periods. Day one of the lesson plan will take nearly 45-50 minutes. Day two of the lesson plan will conclude after 50 minutes. Day three will also take up to 50 minutes. Day four - 50 minutes Day five - 50 minutes



Goals of Activity:

Goal A
To introduce the students to wildlife animals.



Goal B
To distinguish between crocodiles and alligators.



Goal C
To help the students understand Darwin's theory of evolution.



Goal D
{Goal D}



 

National Science Education Standards. (NSES)

Two content standards that this lesson plan covers:

Standard 1
Student knows about the diversity and unity that characterize life: Through this lesson plan, students will observe ways in which living things can be classified (e.g., taxonomic groups of various crocodile; groups based on the details of an organism's internal and external features). The activity will reveal to the students that crocodiles have a great variety of body plans and internal structures that serve specific functions for survival (e.g., digestive structures, reproductive structures, etc.).



Standard 2
Student understands how species depend on one another and on the environment for survival: The activity will illustrate how the crocodile's ability to regulate its internal environment enables it to obtain and use resources, grow, reproduce, and maintain stable internal conditions while living in a constantly changing external environment. Students will observe ways in which these species interact and depend on one another in an ecosystem (e.g., predator/prey interactions, competitive as well as mutualistic interactions).



 

Materials Needed

DAY 1:
Pre-quiz, as many copies as needed and hand out for web resources.

DAY 2:
Video "The Ultimate Guide: Crocodiles," index cards, pushpins and world maps.

DAY 3: Ditto with outline of crocodile and internal organs, coloring devices (crayons, coloring pencils, markers, etc).

DAY 4: Piece of paper, writing utensils and thinking cap.

DAY 5:
Prepared quiz and appropriate number of copies.



Preparation

Engage: The engagement activity is the first activity of the first day of this unit. It is designed to elicit prior knowledge that students have regarding crocodiles, as well as capture the students interest of crocodiles. In order to assess the students previous knowledge, a pre-quiz will be given (the questions in the pre-quiz are mentioned in the section below titled "Step-by-Step Procedure for the Activity"). The students will not know most answers but the questions will be worded in a way as to grab their interest. Following the quiz, they will work in small groups doing research to further their knowledge of crocodiles by answering the questions they answered incorrectly on the pre-quiz. This will take place in the school library through periodicals and the internet, if accessible. Upon completion of the assignment the students will be rewarded with a "chocodile."

Preparation:
DAY 1: Prepare the pre-quiz. Reserve library.
DAY 2: Have video ready. May take a week or so to order. Reserve VCR and TV.
DAY 3: Prepare ditto with the crocodile outline and internal organs and have appropriate number of copies.
DAY 4: Make sure to understand the concepts of evolution.
DAY 5: Prepare quiz in advance and make sure to have appropriate number of copies. Bring in drinks, cups, napkins, plates, etc. for the party.



Step-by-Step Procedure for the Activity

DAY 1: See "Engagement Acitivty."

Questions for the pre-quiz:

  1. What type of animal is a crocodile?
  2. What is the general habitat in which crocodiles live?
  3. What are the two distinguishing factors between crocodiles and alligators?
  4. How many species of crocodiles are there?
  5. Give the names of two species.
  6. What must crocodiles do in order to digest their food?
  7. Crocodiles spend a lot of time under water, what specific organkeeps them from drowning?
  8. What is special about the crocodile heart?
  9. What special feature helps crocodiles hatch from their eggs?
  10. How does the mother crocodile protect her young before and after they have hatched?

Answers to pre-quiz:

  1. Reptile
  2. Marine: River, Swamps, Lakes (Saltwater Crocodiles are often times found in oceanic waters.
  3. Crocodiles have a long pointy snout and two prominent bottom teeth can be seen protruding from their mouths; whereas, alligators have a shorter more round snout and non protuding teeth.
  4. (14)
  5. acutus, cataphractus, intermedius, johnstoni, mindornsis, moretelli, niloticus, novaeguineae, palustris, porosus, rhombifer, slamensis, tetraspis, schlegelii
  6. Swallow a stone or wood
  7. Palatal Valve
  8. .It can bypass the lungs and send blood directly to the brain and other vital organs while the crocodile is underwater.
  9. Egg-tooth
  10. She protects the nest before they hatch and after they hatch she carries them in her mouth to the water. She then continues to protect them until they are three years old.

After the students complete the pre-quiz, collect them from the students so the teacher can evaluate how much prior knowledge the students have of crocodiles. After collection, break the students up into small groups of 2-3 (depending upon number of computers and other resources available). Each group will be given another copy of the pre-quiz to take with them and to be filled out at the library. Make sure to tell the students which resources are appropriate to search for the answers.

Also mention the names of the websites which are appropriate if access to the internet is available: http://school.discovery.com http://www.cnnect.freeserve.co.uk http://flmnh.ufl.edu/natsci/herpetology/brittoncrocs/csp_cpor.htm#imag

While the students are performing their research make sure to grade their pre-quizes. When the students complete their research and turn in the completed forms reward each child with a "chocodile."

DAY 2:When the students arrive in class review the information from the previous day. Answer any question the students may have on the information discussed so far. View video. Discuss the information provided in the video and ask if the students have any further questions. Homework Assignment:(Due by Friday) Divide the students into groups of three. Have each group research one of the species of Crocodylidae to locate where each species lives. On an index card they should record the name, habitat, diet, size and notable fact of each species and post a picture (if available). Use a world map and pushpins to then identify the area in which each species lives: you can use pins of different colors for each species. Post the index card around the map connecting each card to a pushpin with thin pieces of ribbon or coordinating numbers.

DAY 3:When students arrive in class, review the information which has been discussed up to date. Students will then be given a handout containing a diagram with the outline of a crocodile and the internal organs. Hand out crayons to the students and then instruct them to color each organ a specific color, eg. the stomach can be colored red. Tell them to also make a key off to the side. So "red" will match up with "stomach." Then after the coloring is complete, break them up into groups of three and assign each group an organ. Have each group then brainstorm as to what the function of their assigned organ is. Give them roughly 10-15 minutes. At the end of this time period have each group come up to the front of the room and present the function of the organs to the class. Make sure to tell the students that when they are not up in front of the class that they should be taking notes on the other organs. Homework Assignment: (Due Friday) Have the students go home and create the outside and interns of the crocodile, which they learned that day in class, completely out of food. Usually candy and cakes work well for this activity; however, most "fun" foods will work. Tell the students to try to use different food items that they believe to be appropriate for each organ. For instance, licorice for the esophogus, it is long narrow and hollow. Tell the students that this will be do on Friday and that they will explain their designs and reason for each food item after the quiz and then when they have all explained their designs they will then be able to eat each others edible crocodiles during the party.

DAY 4:Discuss how crocodiles evolved 200 million years ago and have outlived the dinosaurs. When they first evolved they had longer legs and shorter snouts and lived on land. They evolved to have short legs, long snouts and live in water. With changes in environment and human acitivty, what could be next? Today the students will work together, 3-4 to a group, to brainstorm as to why crocodiles are such successful animals. Have them discuss and possibly draw what they think crocodiles may look like in 200 million years from today. Homework Assignment: Complete the crocodile food sculpture, the group geopgraphy/information cards and also remind them to study for the quiz tomorrow.

DAY 5: Upon arriving have the students hand in their geography/information card assignments and place their food sculptures on a table off to the side of the room. Then have them get in their seats for the quiz. After the quiz the students will then explain their food crocodile sculptures and the class will party. Homework Assignment: NONE! Have a great weekend. :)



Images, work sheets, additional web pages

{none}

Items for discussion or conclusion

1st question

What are the two main distinctions between crocodiles and alligators?


2nd question
What special features help to protect crocodiles when they dive underwater?



3rd question
Why is a crocodile's heart considered so specialized?



4th question
How long ago did crocodiles evolve?



 

Conclusion
Mainly the students will be assessed on the difference in their performance from the pre-quiz to their performance on the final quiz given on DAY 5. The students will also be evaluated by their participation in class activities, their in-class as well as homework assignments.



Beyond the Activity
Further activities which relate to and extend the complexity of the experiment.

To get the students thinking about conservation biology, homework can be assigned requiring students to write a one page (hand-written) essay in which they would answer the following questions: How would the extinction of crocodiles affect us? What can we do to help prevent the extinction of crocodiles? Have students contact the education department of a local zoo or animal conservation organization to find out what activities are most harmful to crocodiles within the U.S. as well as around the world. Have them find out what actions are being taken to help preserve and restore crocodile populations. Two internet sources are as follows: "Crocodile Specialists Groups" "Crocodiles: Natural History and Conservation"



Web Resources
A web address with information on the topic of the activity.

Web Address
http://www.flmnh.ufl.edu/natsci/herpetology/brittoncrocs/csl.html



 
Additional References

Reference
Video: Discovery Channel Presents...