What anatomical characteristics distinguish marsupial mammals from placental?

Living marsupials and placentals can be distinguished by a number of anatomical features, including structural differences in their ear regions, teeth, postcranial skeletons, reproductive tracts, and brains. Most people think of pouches when they think about marsupials, but not all marsupials have pouches.

When did these two subclasses of mammals separate from their common ancestor? What do we know about that common ancestor?

The lineages that gave rise to living marsupials and placentals are recognizably distinct in the fossil record as far back as the Early Cretaceous (about 125 million years ago), so the most recent common ancestor of these groups must have lived even earlier. How much earlier is controversial, with some estimates suggesting a date of almost 150 million years (in the Late Jurassic). We don’t know anything about that ancestor for certain, but we assume that it was not unlike the earliest known marsupials and placentals: probably a small climbing (arboreal or semiarboreal) mammal, perhaps superficially resembling living opossums or tree shrews. Because the earliest known marsupial and placental fossils are from China, most paleontologists assume that their most recent common ancestor lived somewhere in eastern Asia.

What is convergent evolution and what are some examples of convergent evolution between marsupial and placental mammals?

Convergent evolution is the appearance of similar traits in distantly related lineages. Examples of convergent evolution between placentals and marsupials are the extinct Tasmanian “wolf” (a very wolflike marsupial), marsupial “moles” (living molelike marsupials that burrow in the sandy deserts of Australia), and kangaroo rats (North American rodents that hop on their hind legs like kangaroos).

Why are the majority of current-day marsupials found in Australia? Why are they not more successful elsewhere?

Good question. First, however, it’s important to point out that there are still over 100 species of marsupials alive today in the New World. Most live in South America, although many species also occur in Central America and one (the Virginia opossum) occurs as far north as southern Canada. Before the Panama land bridge connected North America and South America in the Pliocene (about 3 million years ago), South America was an island continent with an even more diverse marsupial fauna than it has today. In fact, the most recent common ancestor of living marsupials probably lived in South America, and its descendants crossed Antarctica (then ice-free) to invade Australia. One line of thinking is that marsupial diversity is greater in Australia than in South America because there were no terrestrial placental mammals to compete with marsupials in ancient Australia.

Kangaroos are the only large mammal to use hopping as their primary form of locomotion. Do we know when this adaptation occurred and why? How does the species benefit from this adaptation? And why are kangaroos the only large mammals to maneuver vast terrains by hopping?

Bipedal hopping, as seen in modern kangaroos, evolved gradually, over millions of years, and resulted from many anatomical adaptations that appear at different times in the fossil record. Some form of primitive hopping locomotion by kangaroo ancestors is probably quite old, perhaps dating back to the Eocene (based on inferences from molecular dates, not fossils). However, fast bipedal hopping is only an effective means of locomotion in deserts, grasslands and other open habitats (free of overhanging woody vegetation), which became widespread in Australia much later, in the last 15 million years or so. The advantages of hopping are still not clear: it’s only energetically efficient at high speeds. Hopping is similar to galloping in that energy is stored in elastic tendons between strides, so these gaits might be energetically equivalent solutions for fast or long-distance locomotion. I don’t know why only kangaroos are the only large mammals that hop, but many smaller mammals (especially rodents) have convergently evolved to do so.

How have marsupials, especially kangaroos and their predecessors, evolved over the years as Australia’s ecosystem changed?

Australian marsupials evolved in many ways to meet the challenges of drier habitats over the last 15 million years. Teeth, for example, reflect adaptive changes from browsing (on woody vegetation in moist climates) to grazing (on grasses in arid climates). Kangaroo ancestors were quadrupedal (walking on four legs most of the time) in forested habitats and became progressively more bipedal as habitats dried out and opened up.

Do you have a favorite marsupial (living or extinct)?

Well, I must confess a fondness for opossums (New World marsupials), so much less charismatic than kangaroos and koalas, but with their own unique adaptations. Several opossum species, for example, eat venomous snakes. Snake-venom resistance is a biochemical, not a morphological adaptation, and it is another example of convergent evolution: besides opossums, mongooses and hedgehogs are also snake-venom resistant.

Though the crocodile’s ancestry dates back 200 million years, the crocodile, as we know it today, first evolved about 80 million years ago. According to the fossil record, their body plan has changed little since, enabling them to outlive the dinosaurs and become the most advanced of all reptiles and the most successful freshwater predator.

There is no single secret to the crocodile’s success. With few natural predators, a permanent armor of bony plates covering most of its body and strong jaw muscles capable of crushing anything from bones to cast iron, the croc is an extremely tough and robust creature. A croc can survive even after serious injuries such as a torn off limbs or tail and has a powerful immune system that helps it survive for decades.

But its adaptations go beyond being hardy. One of the keys to its survival is something one might think of as primitive: cold-bloodedness. Like all reptiles, crocs are ectotherms, which means they must gather heat from their environment. Crocodiles have developed behaviors to control their body thermostat: they bask in the sun when cool and seek shade or water when hot. Ectotherms like crocs don’t need to eat regularly to warm their bodies, and so they save an enormous amount of energy that can be put to other use or stored for later. A croc’s metabolism is so evolved that its body uses and stores nearly the entirety of the food it consumes. This is one reason why larger crocodiles can go for over a year without eating a meal. In extreme situations, crocodiles appear to be able to shut down and live off their own tissue for a long period of time.

But most crocs eat much more often than that. In fact, the average croc eats about 50 full meals a year. When they feast, crocodiles are certainly not picky eaters. It’s said that a croc will feed on anything it can outswim or ambush and overpower. These reptiles have extraordinarily adaptable diets. Larger crocodiles will eat larger mammals and birds, but they’ll also eat fish and mollusks like snails. During difficult times, they will even scavenge for carrion. In fact, crocs will consume almost everything they encounter. And that means everything. A croc’s stomach is the most acidic of all vertebrates, allowing it to digest bones, horns, hooves, or shells. Nothing gets left behind in a crocodile’s dinner. In fact these hard objects are used as “gizzard stones” in the croc’s stomach to help grind coarse food.

While the crocodile’s diet may be undiscriminating, its social interactions are a bit more complicated. Crocs are more social than all other reptiles. Though they primarily lead solitary lives, they resort to group behavior for important activities such as hunting or raising hatchlings. Crocs don’t merely recognize one other, they form long-term relationships. They are hierarchical and communicate by means of vocalization, postures, chemical signals, even touch.

A crocodile’s brain is more complex than that of any other reptile. These powerful predators also have an excellent sense of smell and superior sound perception. Noting the crocís ability to learn to avoid dangerous situations, researchers have found that they have to modify their techniques when capturing crocs. It’s very hard to catch a croc twice with the same trick.

Crocodiles have demonstrated behavioral, physiological and structural adaptations that have allowed them to thrive for hundreds of millions of years, but, unfortunately, surviving human encroachment may be their biggest challenge ever. Through habitat enhancement and environmental education, humans may be able to ensure that these once endangered prehistoric reptiles practice their sophisticated survival skills for years to come.

It soars the skies with an effortless elegance. It can catch falling prey mid-flight and even dive-bomb into rivers to snag wriggling salmon. There is no question about it: the American bald eagle is a highly specialized predator. But what is the evolutionary background that allows the bald eagle to pull off these amazing maneuvers?

It may be difficult to believe, but the ancestors of bald eagles have lived on Earth for eons. Evolutionary biologists believe that birds evolved from reptiles. From their skeletal structure to their blood cells, today’s birds share a surprising evolutionary foundation with reptiles. According to biologists, feathers may have evolved from the scales of reptilian skin.

Between 144 million and 66 million years ago, during the Mesozoic era, the first birds began to evolve. Fossil records from this period reveal that the earliest birds had teeth. Eventually, tens of millions of years ago, an ancient group of birds called kites developed. Like today’s bald eagle, early kites are thought to have scavenged and hunted fish.

Finally, about 36 million years ago, the first eagles descended from kites. First to appear were the early sea eagles, which — like kites — continued to prey on fish and whose feet were free of feathers, along with booted eagles, which had feathers below the knee. While no one knows precisely when the bald eagle appeared on the scene, the earliest known fossil remains that closely resemble the bald eagle date back to about a million years ago.

Like the kites, bald eagles have featherless feet, but they also developed a range of other impressive adaptations that help them hunt fish and fowl in a watery environment. Each foot has four powerful toes with sharp talons. Tiny projections on the bottom of their feet called “spicules” help bald eagles grasp their prey. Ospreys, which are also believed to be descendents of kites, have similar projections on their feet. Could these spicules be a remnant of the birds’ shared reptilian ancestry? A bald eagle also has serrations on the roof of its mouth that help it hold slippery fish, and incredibly, the black pigment in its wing feathers has been found to strengthen the feathers against breakage when diving into water.

Obviously, there is much more than their striking white heads that sets these iconic raptors apart from the crowd. Their incredible physiology, built for life near the water, is literally millions of years in the making.

Photo © Laura Johnson

The olm, a troglobite

To see life on another planet, most would suggest a radio telescope or a NASA explorer vehicle. Yet immediately below the earth’s surface there exists an otherworldly ecosystem populated by creatures that never see the light of day. These animals are the troglobites — crustaceans, amphibians, insects and more — built to survive in the dark, limestone labyrinths that form most of the world’s cave systems.

A pseudoscorpion that doesn’t have a stinging tail and instead injects venom with its claws. A Nelson cave spider with claws on two of its super-long legs that measure just shy of six inches. A whitish, almost transparent cave crayfish that can live over 150 years. These are just some of the troglobites, many of which possess similar evolutionary adaptations: blindness, long limbs and spiky feet to better navigate rocky terrain, and lack of pigmentation as there is no need for camouflage in the dark.

Of all the troglobites, it is perhaps the proteus anguinus, or the olm, that is the star. In Slovenia, a tourism industry exists for those who desire a glimpse of the ghostly salamander that’s beguiled humans for hundreds of years. The first written account of the olm dates back to 1689, in which scholar Janez Vajkard Valvasor disputed the belief that olms were baby dragons. Found in the Dinaric Karst of Europe, it’s easy to see why olms could be fodder for myth. They are blind, yet have barely visible, regressed eyes covered by skin. Their serpentine body can grow over a foot in length, and is covered by whitish, translucent skin that’s artfully highlighted by two frilly pink gills at the back of its head. And, unlike other amphibians that metamorphose into an adult form, the olm retains its larval features, a phenomenon known as neotony. Olms spend their whole lives in water, and so there is no need for them to develop terrestrial characteristics.

In keeping with this fairytale-like appearance, olms are said to be able to live up to 100 years and can go without eating for several. Yes, several years. They, like many troglobites, have exceptionally slow metabolism in large part because of the dearth, or erratic availability, of food. Like other troglobites, the olm compensates for lack of vision by using other, specialized senses. Olms’ ears are capable of receiving sound waves in water and vibrations from the ground, their sense of smell is keener than that of most amphibians, and they possess sensors in their heads called “ampullary organs” that enable them to detect weak electric fields.

Despite such specialized capabilities, troglobites are critically connected to what’s going on above earth’s surface. For a nutritious banquet, some troglobites feast on piles of bat guano found on cave grounds. Tree roots that grow through cracks in a cave’s ceiling and leaves that flow in with water can also provide nutrition. But this water can also bring destruction. Human waste — such as sewer leaks, runoffs, and pesticides — can flow into caves disrupting an ecosystem so sensitive it is said that even human dandruff can upset its balance.

Excavations and the building of roads can also threaten cave life directly. It’s important to note that most of the world’s caves have yet to be fully explored or discovered. The limestone labyrinths beneath us are indeed the earth’s last frontier. It’s a fascinating notion –- some of us may be living above an ecosystem populated by strange species, some millions of years old, and not even know it. In 2007, environmental protection officials in Australia halted a multi-billion dollar iron ore mining proposal when 11 species of troglobite were discovered in the area to be mined. Unfortunately, the ruling was overruled several months later. The battle between moneyed interests and our wildlife continues, unfortunately with greater frequency and scope.

Troglobites are at great risk. This includes the beloved olm which is presently listed by the IUCN as threatened, a circumstance that should be taken very seriously, not only because we should be stewards of our planet (above its surface and below) or because the olm is a fascinating, wonderful species, but also because it is the olm’s very sensitivity to such things as pollution that portends what affects humans as well.

Photo © WNET.ORG/Icon Films

GRADE LEVEL: 9-12

TIME ALLOTMENT: Two or three 45-minute class periods

OVERVIEW: Using segments from the PBS program NATURE: “Moment of Impact, Part 2: Jungle,” students will learn about skills and features that help species survive in the jungle. In the Introductory Activity, students will play a game where they are challenged to match species to adaptations which help them survive in the jungle. Students will create a definition for “adaptation” and revise the definition throughout the lesson, based on new information that they learn. In the Learning Activities, students will learn about the panther chameleon and the adaptations that help it survive. In an optional extension activity, students will examine the lyrics to “Karma Chameleon,” using their new knowledge of chameleons and will create a poem or song lyrics about chameleons. Students will also learn about the different layers of the jungle and the species that inhabit them, as well as how species get their prey and defend themselves from predators. In the Culminating Activity, students will create models illustrating the adaptations/skills different species use to survive.

SUBJECT MATTER: Science

Learning Objectives:
Students will be able to:
o Provide a definition for an “adaptation” and describe different adaptations that help species capture prey and protect themselves from predators.
o Describe a panther chameleon and list at least 3 adaptations that help it survive in the jungle.
o Discuss the different layers of the jungle, species that reside in each and adaptations that help them survive.
o Create a diagram and/or 3D model to explain an adaptation that helps a species survive.
o Describe one jungle species in detail and explain the features/ skills that help it survive.

STANDARDS
National Science Education Standards

Grades 9-12:
Content Standard C: Life Science
Fundamental concepts and principles that underlie this standard include:
• The Interdependence of Organisms
o Organisms both cooperate and compete in ecosystems. The interrelationships and interdependencies of these organisms may generate ecosystems that are stable for hundreds or thousands of years.
• The Behavior Of Organisms
o Multicellular animals have nervous systems that generate behavior. Nervous systems are formed from specialized cells that conduct signals rapidly through the long cell extensions that make up nerves. The nerve cells communicate with each other by secreting specific excitatory and inhibitory molecules. In sense organs, specialized cells detect light, sound, and specific chemicals and enable animals to monitor what is going on in the world around them.
o Organisms have behavioral responses to internal changes and to external stimuli. Responses to external stimuli can result from interactions with the organism’s own species and others, as well as environmental changes; these responses either can be innate or learned. The broad patterns of behavior exhibited by animals have evolved to ensure reproductive success. Animals often live in unpredictable environments, and so their behavior must be flexible enough to deal with uncertainty and change. Plants also respond to stimuli.
o Like other aspects of an organism’s biology, behaviors have evolved through natural selection. Behaviors often have an adaptive logic when viewed in terms of evolutionary principles.
o Behavioral biology has implications for humans, as it provides links to psychology, sociology, and anthropology.

MEDIA COMPONENTS
NATURE: “Moment of Impact, Part 2: Jungle,” selected segments
Note: Clip 1 is used in Learning Activity 1. The other clips can be used by students, as they create their culminating projects.

Clip 1: “Panther Chameleon”
An overview of what skills/features help the colorful panther chameleon survive in the jungle.

Clip 2: “Amazonian Boa”
An overview of the features that help the Amazonian boa capture prey and survive the jungle.

Clip 3: “Antsy on the Forest Floor”
A close look at the leafcutter and carnivorous trap-jaw ants.

Clip 4: “Bats”
A close look at bats and how they use sound to locate prey.

Clip 5: “Cuban Crocodile”
A look at the bioengineering of the Cuban crocodile and how it navigates in water and on land.

Clip 6: “The Lizard and the Butterfly”
A close look at a basilisk lizard’s surprise attack on an unsuspecting blue morpho butterfly.

Clip 7: “Monkey Business”
An overview of the spider monkey and how it moves through the jungle.

Clip 8: “Osprey”
A brief look at the osprey and how its body design is well-suited for spotting and capturing fish.

Clip 9: “Paradise Tree Snake”
A look at how the paradise tree snake escapes danger by “snaking” through the air.

Clip 10: “Red Eyed Tree Frog”
A look at how the paradise tree snake escapes danger by “snaking” through the air.

Clip 11: “Tiger”
A look at what makes the tiger a successful hunter.

Access the streaming and downloadable video segments for this lesson at the Video Segments Page.

Websites:
o Supporting Resources for the Lesson
The following sites are resources which can be helpful for students to use when conducting research during the following portions of the lesson:
Introductory Activity
• The BBC Virtual Jungle website
This website features a variety of information about the structure of the jungle and the plants and animals living there.
• Rainforest Alliance
This website contains a variety of information about rainforests, including a section about rainforest species (http://www.rainforest-alliance.org/resources.cfm?id=species_profiles) which could be helpful to students in this lesson.
Note: Both of these websites can also be used by students as resources throughout the lesson.

Learning Activity 2:
• Jungle Journey
In this section of the Nature website, students can explore the different layers of the jungle and the wildlife that inhabits each.

• The Layers of the Rainforest

This page contains info about the 4 rainforest layers, which can be used in Learning Activity #2. (This page is within the rainforest section of the California Institute of Technology’s Space Radiation Lab website)

• Mongabay.com
This website features a variety of information about wild lands and wildlife, including information about rainforests: http://rainforests.mongabay.com.

The following sections can be used to help students explore the layers of the rainforest in Learning Activity 2:
o The Canopy
o The Forest Floor

Optional Extension Activity:
• Karma Chameleon Lyrics
These lyrics to Boy George’s “Karma Chameleon” can be used in the optional activity.

Culminating Activity:
• Additional Resources Page
This page on the Nature website includes links to resources about blue morpho butterflies, tigers, trap-jaw ants, spider monkeys, snakes, Cuban crocodiles, tigers and other species, which could be used by students in the culminating activity.
• Animals of the Rainforest
This page provides details about different rainforest species including the blue morpho butterfly and spider monkey. (This page is within the rainforest section of the California Institue of Technology’s Space Radiation Lab website: http://www.srl.caltech.edu/personnel/krubal/rainforest/serve_home.html)
• Rainforest Connection
This Montclair State University website includes information about various species of mammals that live in the rainforest, including bats and spider monkeys, which students can use in the culminating activity. To directly access this information, students can go to the mammal index.

o Optional related website:
• Jungle Survival Game
This Discovery Channel Game challenges visitors to make decisions to help them survive in the jungle.

MATERIALS
For the class:
o Computers with internet access.
o Computer, projection screen and speakers (for class viewing of online/downloaded “Panther Chameleon” video segment).
o 1 copy of the “Adaptations Game” answer key.” (download here)

For each group of 5-10 students:
o 1 copy of the “Adaptations Game” (download here).

PREP FOR TEACHERS
Prior to teaching this lesson, you will need to:

Preview all of the video segments and websites used in the lesson.

Download the video clips used in the lesson to your classroom computer(s) or prepare to watch them using your classroom’s Internet connection.
Bookmark any websites that you plan to use in the lesson on each computer in your classroom. Using a social bookmarking tool such as del.icio.us or diigo (or an online bookmarking utility such as portaportal) will allow you to organize all the links in a central location.
Print out one copy of the “Adaptations Game” for each group of 5-10 students.

Print out one copy of the “Adaptations Game Answer Key.”

In the “Adaptations Game,” cut out each species card along the dotted lines and paper clip each set of 10 species cards to the corresponding box in the adaptations sheet.

Next: Proceed to Lesson Activities

Excerpts from the NATURE episode, “Moment of Impact: Part 2, Jungle”
Panther Chameleon
An overview of what skills/features help the colorful panther chameleon survive in the jungle.
(View full post to see video)
Amazonian Boa
An overview of the features that help the Amazonian boa capture prey and survive in the jungle.
(View full post to see video)
Antsy on the Forest Floor
A close look at the leafcutter and carnivorous trap-jaw ants.
(View full post to see video)
Bats
A close look at bats and how they use sound to locate prey.
(View full post to see video)
Cuban Crocodile
A look at the bioengineering of the Cuban crocodile and how it navigates in water and on land.
(View full post to see video)
The Lizard and the Butterfly
A close look at a basilisk lizard’s surprise attack on an unsuspecting blue morpho butterfly.
(View full post to see video)
Monkey Business
An overview of the spider monkey and how it moves through the jungle.
(View full post to see video)
Osprey
A brief look at the osprey and how its body design is well-suited for spotting and capturing fish.
(View full post to see video)
Paradise Tree Snake
A look at how the paradise tree snake escapes danger by “snaking” through the air.
(View full post to see video)
Red-eyed Tree Frog
A look at how the red-eyed tree frog changes its appearance to avoid danger.
(View full post to see video)
Tiger
A look at what makes the tiger a successful hunter.
(View full post to see video)

Downloadable QuickTime versions of the video segments:
(Note: To download a video, right click on the video title and click “Save Link As…’ or “Save Target As…”. On a Mac, press the CTRL key and simultaneously click the mouse, then save the link.)

Video Clips
1. Panther Chameleon
An overview of what skills/features help the colorful panther chameleon survive in the jungle.

2. Amazonian Boa
An overview of the features that help the Amazonian boa capture prey and survive in the jungle.

3. Antsy on the Forest Floor
A close look at the leafcutter and carnivorous trap-jaw ants.

4. Bats
A close look at bats and how they use sound to locate prey.

5. Cuban Crocodile
A look at the bioengineering of the Cuban crocodile and how it navigates in water and on land.

6. The Lizard and the Butterfly
A close look at a basilisk lizard’s surprise attack on an unsuspecting blue morpho butterfly.

7. Monkey Business
An overview of the spider monkey and how it moves through the jungle.

8. Osprey
A brief look at the osprey and how its body design is well-suited for spotting and capturing fish.

9. Paradise Tree Snake
A look at how the paradise tree snake escapes danger by “snaking” through the air.

10. Red-eyed Tree Frog
A look at how the red-eyed tree frog changes its appearance to avoid danger.

11. Tiger
A look at what makes the tiger a successful hunter.

2. Explain that today you are going to explore species living in the jungle and the adaptations and skills that help them survive. Ask students to brainstorm what they think an “adaptation” is. Write down all answers. (Possible points to raise during the discussion: An adaptation is a physical feature, behavior or skill, developed over the course of many generations, which helps a species survive. Adaptation also refers to the evolutionary process by which a species becomes better suited to its habitat.)

3. Ask students to list some animal adaptations. Write down their responses. (Answers might include camouflage, long necks to grab food in high places, etc.)

4. Let students know they will be playing a game where they will learn about various adaptations that help species survive in the jungle. Divide the class into groups of 5-10 students each. Give each group an “Adaptations Game.” (download here)

5. Challenge each group to match each species to an adaptation that helps it survive. Encourage students to use print and/or online resources to help them complete this task.
Note: Some of the featured adaptations are used by more than one of the species listed on the “Species Cards” and some of the species have more than one of the adaptations listed on the “Adaptations Sheet.” For this activity, challenge students to place only one species on each adaptation.

6. Once each group has successfully matched a species to an adaptation, encourage students to work alone or in pairs to gather information about each adaptation and how it helps the species survive. Each student or pair of students should select one adaptation to research. Encourage students to use a variety of print and/or online sources, including the BBC’s Virtual Jungle website . Give students about 15 minutes to conduct their research.

7. After the groups have collected their information, ask them to share their findings with the rest of the class. Lead a discussion about the adaptations featured in the game. Refer to the “Adaptations Game Answer Key,” as needed. During the discussion, talk about how each adaptation helps the species survive in the jungle. Refer to the table below for possible items to include in the discussion.

8. Review your description and examples of an “adaptation” that the class brainstormed earlier. Work with the class to revise the description. Encourage students to add more details to the definition of the adaptation. (For example: An adaptation is a physical feature or a skill, developed over the course of many generations which helps a species to find, capture and kill prey and to defend itself.)

9. Add additional examples of adaptations to the list, based on information gathered in the first activity. Create a three-column list, like the one shown below, to record student responses. (Leave room in the chart for students to add more information later in the lesson.

LEARNING ACTIVITY 1
1. Summarize that there are a variety of adaptations that help species defend themselves and find food in the jungle. FRAME clip #1, “Panther Chameleon,” by explaining that students will now learn more about a species called the panther chameleon and the adaptations that help it survive in the jungle.

2. Ask students to share information they know about chameleons. Write down the students’ responses. (Possible answers might include that they change color.) If students mention chameleons change color, ask them to brainstorm why they think this happens.

3. Explain that you are now going to show a video segment from the PBS program NATURE: “Moment of Impact, Part 2: Jungle.” Provide a FOCUS for the clip, asking students to list 3 different skills that help the panther chameleon survive and describe how each skill helps them in the jungle.

4. PLAY Video Segment #1, “Panther Chameleon.” After playing the clip, FOLLOW UP by asking students to list some adaptations (including special skills and physical features) the panther chameleon uses to survive and describe how each of those adaptations helps it. Access the video segments for this lesson at the Video Segments Page.
The discussion can include the following:
o How and why its color changes.
• How its color changes: The color change takes place below transparent outer skin. Chromatophores (stretchable pigment cells) are ringed with muscle fibers. When the fibers contract, they pull on the chromatophores, quickly spreading their color. The upper layer handles red and yellow tints. Another layer of cells below reflects blue light.
• Why its color changes: Panther chameleons don’t change color to camouflage their presence from surroundings. They change color to communicate. Coloring reflects their mood when sparring with other males or when attracting attention of females.

o Special skills/ features:
• Tongue: When extended, the panther chameleon’s tongue is longer than its body. The tongue enables the chameleon to quickly catch a prey. The sticky tip grabs the prey and its skin flaps keep it in place.
• Eyes: Each eye can rotate and focus separately. With a pinhole in the center, each eye has a full 360 degree view.
• Hunting Strategy: The chameleon edges toward the prey, but doesn’t chase it.

Optional Extension Activity
1. Share “Karma Chameleon” lyrics with students and play the song for the class to hear.

2. Ask students to reflect upon and discuss the lyrics in relation to what they know about chameleons. Ask students to look at the bolded words and phrases below. Ask students to conduct additional research about chameleons to see how accurately the bolded words and phrases (such as “cling” or “come and go”) describe chameleons:

When we cling our love is strong
When you go you’re gone forever
You string along, you string along

Karma karma karma karma, karma chameleon
You come and go, you come and go
Loving would be easy if your colors were like my dream
Red gold and green, red gold and green
Every day is like survival
You’re my lover, not my rival
Every day is like survival
You’re my lover, not my rival

3. Challenge students to write their own poem or song lyrics to the tune of “Karma Chameleon,” another existing song or an original composition, with words that accurately describe the panther chameleon’s adaptations. Here are two sample verses (to the tune of the last two “Karma Chameleon” verses listed above):
Panther, panther, panther, panther, panther chameleon
You move so slow, you move so slow
Your eyes keep movin’ & turnin’ around and around
You’re on the hunt, but don’t make a sound

Your hue is ever changing
Where you are we do not know
Your hue is ever changing
Where you are we do not know

4. After students have written their poems/verses, ask them to present and discuss them with the group.

LEARNING ACTIVITY 2
1. Divide students into four groups. Assign each group to one of the four layers of the jungle:
1) forest floor, 2) understory, 3) canopy and 4) emergent layer.

2. Give each group 15-20 minutes to research their assigned section of the jungle. Specifically, ask students to find out the following:
o Names of species living in the layer.
o Adaptations that help the species protect themselves and find food.
Encourage students to use online and print resources to gather the information. Here are some websites that could be helpful:
• The PBS Jungle Journey website
• The BBC Virtual Jungle website
• Mongabay.com’s rainforest information: http://rainforests.mongabay.com/:
•The Canopy
•The Forest Floor
• Layers of a Rainforest

3. Ask each group to present information about the layer it studied, the species that inhabit it and the adaptations that help them survive.

4. Lead a discussion with the group about the challenges of living in each of the layers of the jungle. Here are some possible items to include in the discussion:

5. Review the class’ 3-column chart of adaptations and add additional adaptations to the list.

CULMINATING ACTIVITY
1. Explain to students that, working in pairs or small groups, they will select a species that lives in the jungle, find out information about that species and create a 3-dimensional model or computer-animated model to illustrate how it seeks prey and/or defends itself in the jungle.

2. Ask students to review a few of the “Moment of Impact, Part 2: Jungle” video segments listed for this lesson in order to select the species they would like to research. (Access the video segments for this lesson at the Video Segments Page.) Ask each group to select one of the following species:
o Amazonian boa
o basilisk lizard
o bat
o Cuban crocodile
o leafcutter ant
o blue morpho butterfly
o osprey
o panther chameleon
o paradise tree snake
o red-eyed tree frog
o spider monkey
o tiger
o trap-jaw ant

3. Once students have selected their species, ask them to watch the corresponding segment again and record information about the highlighted adaptations. Encourage students to conduct additional research to find out more about their species.

4. Ask students to pick one or more adaptations to highlight in their project and to brainstorm the best ways to illustrate how that adaptation works. For example, if they have selected the panther chameleon, they could create a 3-d model of a panther chameleon that includes a “tongue” that extends to a length larger than the chameleon’s body, a body that changes color and/or eyes that each rotate 360 degrees.

5. The completed project could include a diagram, 3-d model and/or computer-generated animation and must include the following:
o Information about adaptations/features that help the species get food and/or defend itself against predators.
o A diagram, 3-d model or computer-generated video, created by the students, which demonstrates one or more skills/adaptations that help the species to survive. Here are some examples of adaptations that can be highlighted for each species:

6. Ask each group to present its work to the class and to lead a discussion about what it discovered about the species and its adaptations during the process.

7. Lead a discussion with the class, encouraging students to share facts they learned about the jungle, its species and their adaptations. Review the class’ definition of an “adaptation” and revise, as needed. Ask students to look at the class’ 3-column chart of adaptations and add new information learned during the lesson.

GRADE LEVEL: 5-8

TOPIC/SUBJECT MATTER: Life Science

TIME ALLOTMENT: Two 45-minute class periods

OVERVIEW:

During this video-enhanced lesson, students will learn that all dogs came from one ancestor- the wolf. Students will watch and discuss video segments from the NATURE film “Dogs that Changed the World,” and explore different theories about how this transformation happened. Students will learn about different breeds of dogs and create a book with pictures and information about a variety of dog breeds. In the culminating activity, students will interview a dog owner and create a poster and/or a presentation about his/her dog.

MEDIA RESOURCES

Video

Access the streaming and downloadable video segments for this lesson at the Video Segments Page.

Clip 1: From Wolf to Dog

Reflections about the transformation from wolf to dog

Clip 2: The Speed of Change

Exploring the speed of evolution

Clip 3: Today’s Dog

A quick look at the dogs of today

Websites

American Kennel Club

This Web site includes information about the internationally-recognized breeds.

National Geographic Web sites’ Animal Section
This Web site features many photos of animals including photos of dogs and wolves, which can be used in this lesson.

Standards:

National Science Education Standards, Grades 5-8

LIFE SCIENCE: Content Standard C

As a result of their activities in grades 5-8, all students should develop understanding of

• Regulation and behavior

o       An organism’s behavior evolves through adaptation to its environment. How a species moves, obtains food, reproduces, and responds to danger are based in the species’ evolutionary history.

• Diversity and adaptations of organisms

o       Millions of species of animals, plants, and microorganisms are alive today. Although different species might look dissimilar, the unity among organisms becomes apparent from an analysis of internal structures, the similarity of their chemical processes, and the evidence of common ancestry.

o       Biological evolution accounts for the diversity of species developed through gradual processes over many generations. Species acquire many of their unique characteristics through biological adaptation, which involves the selection of naturally occurring variations in populations. Biological adaptations include changes in structures, behaviors, or physiology that enhance survival and reproductive success in a particular environment.

MATERIALS

For each student:

• “Dog Breed” Student Organizer (PDF) (RTF)
• “Dog Interview” Student Organizer (PDF) (RTF)

For the class:

• Photographs of a few very different looking dogs, such as a Chihuahua, a Saint Bernard and a Greyhound. (A good source for these photos is the American Kennel Club Web site.)
• Two photographs of a wolf (full-body and close-up of head)

OBJECTIVES

Students will be able to:

• Explain that all dogs evolved from wolves;
• Discuss theories about how the wolf evolved into the dog;
• Explain how quickly the transformation from wolf to dog might have happened;
• Understand how breeding animals for specific traits can result in the altered look and behavior of the descendents of those animals;
• Describe different breeds of dogs;
• Discuss the behaviors, skills, appearance and personality of one particular dog and explain whether the dog “fits in” with the general description of the breed.

Prep for Teachers

Prior to teaching this lesson, you will need to:

Preview all of the video segments and Web sites used in the lesson.

Download the video clips used in the lesson to your classroom computer, or prepare to watch them using your classroom’s Internet connection.

Bookmark the Web sites used in the lesson on each computer in your classroom. Using a social bookmarking tool such as del.icio.us or diigo (or an online bookmarking utility such as portaportal) will allow you to organize all the links in a central location.

Print out a copy of the “Dog Breed” and “Dog Interview” Student Organizers for each student.

Print out photographs of a few (3-4) very different looking dogs, such as a Chihuahua, a Saint Bernard and a Greyhound. (A good source for these photos is the American Kennel Club Web site.)

Print out two photos of a wolf – a full body shot and a close-up of its head. (One good place to look for wolf photos is the Animal Section of the National Geographic Web site.)

Proceed to Activities

Excerpts from the NATURE episode, “From Wolf to Dog”

Downloadable QuickTime versions of the video segments:
(Note: To download a video, right click on the video title and click “Save Link As…’ or “Save Target As…”. On a Mac, press the CTRL key and simultaneously click the mouse, then save the link.)
Clip 1: From Wolf to Dog

Clip 2: The Speed of Change

Clip 3: Today\’s Dog