Nicholas R. Perrone
This unit can be directly applied to learning about one animal in a school - a mascot, for instance, or learning about a series of animals. In my school, each grade is assigned a thematic animal that the students learn about throughout the year. My unit will connect with multiple grade levels to facilitate students to learn more about their thematic animal. In particular, it will present information on the animals listed earlier and will match with the following grade levels: 4
th
(turtle), 5
th
and 6
th
(elephant), and 7
th
(eagle). Each grade level will learn about their respective animal's behaviors, brain anatomy, and its extraordinary senses and then will present this information in the form of a computer slide show, brochure, poster, or concept map. In keeping with 21
st
Century educational technology modalities, students will be encouraged to also go beyond the basic research and retell method. Students should actively seek experts in the field of animal behavior, neuroscience, and anatomy to further immerse their curiosity in this subject matter. They should also be encouraged to create online blogs where anecdotal information can be shared from students and scientists in the field.
The unit is divided into three different chapters that go into detail about each animal in the study. Each chapter will be structured the same way: 1) example anecdote for student engagement, 2) animal behavior data, 3) animal brain anatomy, 4) tying it all together, and 5) activities that compare human and animal abilities. This structure will provide a framework for educators to reuse this information in the most effective way - in parts or as a whole.
Students will not only research their animal, but they will participate in activities that compare their human brain to that of their animal. Activities will include comparing what they can see at a set distance compared to that of a Bald Eagle. In all cases, students will find the comparisons fascinating since the animal's sense exceeds that of a human. By including the student in the study, each child will engage in deeper discussion and will inquire about the animal to a greater extent. Fictional texts will also be recommended for each animal to complement the information the students learn. In this way, fictional reading will provide another academic area that this unit can develop.
The Sea Turtle: Magnetic Detection & Mapping
1. Anecdote - Long Migration
Teacher: "Imagine wandering from your doorstep here in New Haven, CT and traveling all the way to New Orleans, LA, a total distance of 1387 miles. And after a few months of eating at a series of excellent restaurants, you are told to walk home. Could you find your way?
"A group of green turtles feed off the coast of Brazil where they eat for many months, and every two or three years, swim directly to Ascension Island, 1400 miles away in the middle of the Atlantic Ocean, to lay their eggs" (Maier 1970). The turtles do not have any landmarks to guide them, no GPS navigation systems purchased from the local electronics store, and certainly no road signs; so how do they do it?
2. Animal Behavior Data - From Hatchlings to Adults
After sea turtle hatchlings emerge from their shell, they must dig themselves out from approximately 1 meter of sand and then cross a treacherous beach before they enter the sea. In the sea, these turtles begin to tap into their amazing navigational ability. "[Sea turtle]…hatchlings have a magnetic compass sense, which enables them to maintain headings relative to the Earth's field as they migrate offshore" (Lohmann 2007). As soon as they enter the water, this magnetic compass sense engages and leads them to safe areas to feed. "Several laboratory experiments have demonstrated that loggerhead and leatherback hatchlings can orient to the magnet field of the earth" (Lutz and Musick, 1997).
In addition to simple directional compass readings, "…hatchlings can detect magnetic field inclination angle and magnetic field intensity, two geomagnetic features that vary across the surface of the earth and may provide sea turtles with information on their global position" (Lutz and Musick, 1997). These observations point out just how amazing are their abilities.
The precise readings these animals detect are incredible. And as they get older, they develop even further. "Older juveniles learn the magnetic topography of the area where they live and develop 'magnetic maps' which permit navigation toward specific target areas" (Lohmann 2007). These mental maps provide the markers that enable such feats of navigation as these animals perform.
Specifically, "…loggerheads can distinguish between different magnetic inclination angles and perhaps derive from them an approximation of latitude" (Lutz and Musick, 1997). With these latitude approximations, the magnetic maps become detailed navigational coordinates. Eventually, the turtles use these maps to travel over large distances. "An ability to return to a specific nesting beach [where they themselves emerged as hatchlings] from hundreds or thousands of kilometers away, and after years in distant oceanic or coastal habitats, is common among sea turtles" (Lutz and Musick, 1997).
3. Animal Brain Anatomy - The Presence of Magnetite Crystals
In particular, "…a significant part of a turtle's navigational skill involves magnetoreception - the ability to detect the Earth's magnetic field" (Lohmann 2007). Magnetoreceptors in the sea turtle's brain function similar to magnets and detect minuscule variations in the earth's magnetic field.
In one study, the heads of three hatchling loggerhead turtles were dissected; the author of the article found organic magnetite crystals, a comparable substance found in honey bees and homing pigeons - 10
5
more amounts as compared to an extremely sensitive compass, suggesting their sensitivity can notice slight changes in the earth's magnetic field and intensity (Kirschvink 1980).
An expert on loggerheads, named Jack Rudloe, demonstrated the magnetic properties on an Olive Ridley hatchling that was found dead on a Costa Rican beach. He brought the hatchling to the lab, placed it on a small sponge in a large pan of water, and began pulling it and spinning it around with an ordinary magnet near its head. Placing the magnet at its tail made the hatchling slowly spin around until its head faced the magnet again (Spotila, 2004).
4. Tying It All Together - Life Finds A Way
The magnetite crystals in their brains help sea turtles detect magnetic information like the inclination of the earth's magnetic field, which is the angle the magnetic field intersects at the surface of the earth. The equator has a zero degrees inclination while the poles are 90 degrees. Sea turtles can also detect slight changes in the field's intensity. Using these skills, the turtles can create a virtual magnetic map of the oceans allowing them to navigate precisely toward a particular area - nesting beach, feeding sea, etc. Although, what makes sea turtles amazing is that even if their magnetic sense is disrupted, they use other senses like sight and smell to assist them in migration (Spotila, 2004). A study of a group of green turtles demonstrated that even when their magnetic field was disrupted, the turtles still navigated back to Ascension Island, more than 2,000 km away. Scientists attached six static magnets to each turtle with the purpose of creating artificial fields around them. The trip the turtles made back to Ascension Island was similar to the same trip made by eight turtles the previous year. Magnetic navigation is therefore not the only migratory mechanism turtles rely upon (Papi et al, 2000).
Furthermore, "…when magnetic cues are disrupted, the turtles can fall back on other sources of information such as celestial compasses, wave direction, or olfactory cues, in much the same way that blind and blindfolded people are often able to use non-visual cues to guide themselves" (Lohmann 2007). In other words, as amazing as their ability to read and follow the earth's magnetic field, the truth is that sea turtles do not rely solely upon one sense for survival. Life tends to find a way no matter what.
5. Classroom Activities - Testing Student Navigational Skills
See the lesson plan #1, "Can you navigate as well as a sea turtle?" in the Appendix.
The Elephant: Infrasonic Hearing
1. Anecdote - Disney's Happy Ending
An elephant filmed in the Disney movie, Earth, was able to find her way back to her herd amidst separation of many miles and a fierce sand storm. The Kalahari Desert herd was traveling to a yearly flood area at the inland delta, Okavango, when a storm hit. The elephant was disoriented and dehydrated; she fell back from the herd and began going the wrong direction. Eventually she made her way back to the herd (Fothergill 2009). How did she do it?
2. Animal Behavior Data - From Foot to Ear
An elephant's sense of hearing is remarkable and is in part due to the size of its ears. He can produce infrasonic (very low) sounds allowing communication over long distances. These very low frequencies are not detectable by humans; humans can hear between 29-19,000Hz whereas elephants can hear frequencies as low as 17Hz, but only as high as 12,000Hz (Fowler and Mikota, 2006). Low-frequency sounds travel further distances as compared to higher frequencies; especially since low frequency sounds can travel through the ground like seismic waves in earthquakes (Davies 2008). This is why thumping bass is all that can be heard from a passing car that is playing music loudly; the actual tune cannot be heard since the other sounds are of a higher frequency and do not travel as far.
Elephants are social animals and, therefore, use vocal communication as a part of their society and survival. However, these levels of communication go far beyond the animal's ability to hear through the air. Elephants have the ability to produce low-frequency vocalizations at high amplitudes that actually travel into the ground and along its surface (O'Connell-Rodwell, 2007). They use their foreheads as huge sounding boards and transfer these infrasonic rumbles over large distances allowing distant herds to reunite and lone males to locate females (Downer, 1999). There are vibration sensors in the elephant's trunk, feet, and even toenails that react to vibrations and transmit nerve signals to the brain (Davies 2008). Therefore, it is possible that the Disney happy ending mentioned in the previous section was a result of infrasonic communication through the ground.
3. Animal Brain Anatomy - Massive Brain, Massive Ability
The average weight of an African elephant brain is between 3.6-6.5 Kg (7.9-14 lbs.). It is the largest brain of any land animal. In comparison, the human brain weighs between 1.3-1.4 Kg (2.8-3 lbs.). The elephant has the largest proportion of brain weight to body size of any other animal; even though the blue whale has a larger brain, its brain weight to body weight ratio is much smaller than an elephant (Davies 2008).
Elephants have the largest cerebral cortex of all land animals; this allows the animal to process subtle signals from noise including being able to use multimodal cues available to them, such as listening to the sound vibrations they feel through the ground (O'Connell-Rodwell, 2007). And since these sounds compete with very little other seismic noise, elephants can communicate with ease. A large portion of the elephant's brain is devoted to hearing: the temporal lobe; and it is far greater in proportion size than that of dolphins or humans (Davies 2008).
4. Tying It All Together - Herd Survival & Communication
When elephants are threatened they thump the ground in mock charges. The vibrations from these charges carry upwards to 30 miles through the surface of the ground. Other elephants "hear" them as the vibrations travel through their feet and into their ears. Coupled with the infrasound, these vibrations communicate levels of danger and caution for other herds (Downer, 1999).
The elephant uses these seismic stimuli to avoid or threaten predators, assess and navigate within the environment, and communicate. "This has important ramifications for a herd's ability to maintain contact with other herds, while minimizing conflict over resources, and also the distance over which a warning of danger can be detected from another herd" (O'Connell-Rodwell, 2007). Therefore, an elephant's purpose for effective communication is in part for survival, but also to promote a peaceful balance of resources and interaction.
Furthermore, elephants have an interesting succorant behavior with other elephants. In an observational study, two elephants were found supporting a third elephant that was wounded (Maier 1970). This act of giving support is a clear measure of the elephant's intelligence and compassion, and can be attributed to the animal's large temporal lobes - an area associated with memory and learning (Fowler and Mikota, 2006). It is also important to consider the emotional factor behind this observation. Like humans, elephants have the ability to cry tears from their eyes; this fact is usually appreciated by younger students. Therefore, the fact that these elephants were helping out a wounded friend may be due to their emotional attachment to that member.
5. Classroom Activities - Testing Student Hearing Skills
See the lesson plan #2, "Do you listen like an elephant?" in the Appendix.
The Eagle: Acute Eyesight
1. Anecdote - An Eagle's Unfair Advantage
Imagine you are a salmon swimming peacefully up an Alaskan river. You struggle up waterfalls, dodge the heavy footsteps of grizzly bears, and even manage to slip through the nets set out by local fishermen. Just when you think your worries are over, you are grabbed right out of the water and pulled high up into the air. As you gasp for your last few breaths you wonder where this thing came from; after all, you were looking out for all your predators, right?
Wrong; no matter how alert you are as a fish, you are no match for the keen abilities of one of the most efficient predators around: the eagle.
2. Animal Behavior Data - Seeing is for the Birds
Birds have better vision than all other vertebrates and no bird species compares to that of the eagle. Generally, birds can see two or three times more sharply than humans; in comparison, eagles can see better than eight times that of a human. In comparison to their heads, birds' eyes are so large that they leave little room for the brain or for eye muscles. This explains why birds must turn their entire head and neck to align their field of vision (Early, 2003). Many times birds even have to alter their preferred angle depending on how far away they are from an object. For example, raptors spend more time looking straight at objects closer than 8m away. At 21m, they spend more time looking at it sideways. At distances of 40m or greater, raptors look at the object sideways 80% or more of the time; they do this because of the structure of their eye anatomy. Sideways views provide higher acuity vision for the birds whereas front views provide stereoscopic binocular perception (Tucker, 2000).
Birds also see into the ultraviolet range, allowing them to detect subtle differences in plumage as well as slight movements of small animals that are far away (Early, 2003). For example, an eagle can identify and track a rabbit moving almost a mile away. Therefore, an eagle flying at an altitude of 1000 feet over an open space can spot prey over an area of almost 3 square miles. And when one spots prey, it can follow it continuously from 1000 feet down to 0 feet.
3. Animal Brain Anatomy - Retinas, Cones, and Rods…Oh My!
Birds do not rely on their sense of smell, as a result the "smell" area of the brain, the olfactory lobes, are very small. However, large areas of a bird's brain receive and process visual information (Freedman Morriss 1972). In addition, the visual cortex area of a bird's brain is larger than the other areas.
Humans and eagles share many similarities with their eye anatomy. Both have a cornea, iris, lens, retina, and optic nerve. Although the structure of the eye is similar between human and eagle, three distinct differences are clear: eagles have a different ratio of rods to cones, a deep pit of concentrated cells in their retina, and a greater total number of cells in the retina (Barth, 2001).
Rods and cones are specialized cells in the retina; their relative ratio is important in determining quality of vision in different situations. Rods are sensitive in situations with poor light and are best utilized by nocturnal animals. Cones detect colors and are used primarily during the day with the presence of plenty of light. As compared to humans, eagles have a greater concentration of cones as compared to rods, thus giving them finer vision and a greater ability to focus on objects at a distance. The only trade-off is that eagles have a difficult time seeing in the dark (Barth, 2001).
The retina pit, or fovea, increases the spatial resolution set by the relative size of the eye and thus turns the eye into a telephoto lens, giving the bird the ability to closely zoom in on its prey. The pit also contains a greater amount of cones and a high density of nerves that carry information directly to the brain. Humans do not have this pronounced pit on the retina (Barth, 2001).
The eagle's retina is covered with four to five times as many light-sensitive cells per square millimeter as humans. In this case, quantity definitely matters. The more light-sensitive cells in a retina, the greater the resolve power (Discovery, 2008).
With the presence of these three adaptations, eagles have a resolving power that is 8 times sharper than that of the human; one could say that an average eagle can see 8 times better than an average human. Because of this resolve power, eagles also boast the widest field of vision compared to all other animals; giving them the ability to see danger well before danger sees them.
4. Tying It All Together - My, What Big Eyes You Have
Another reason why eagles have such amazing sight is the size of its eyes, which are enormous in comparison to its skull. Generally speaking, the larger the eyes, the more light is let in, the better the vision (Discovery, 2008). If a human's eye was proportional in size to that of an eagle's eye, it would be approximately twice as large. This means it would require a contact lens four times as large as a normal one - about one inch in diameter. Glasses would cover more than half of a person's face.
To emphasize the clear difference between what a human can see versus an eagle, the following is a prime example. If a human with excellent eyesight can resolve a 1 inch object from 100 feet away, an eagle could resolve the same object from 800 feet away. Taking that same formula for a 12 inch object, the approximate size of an edible salmon, would put an eagle's maximum distance to spot this fish at 9600 feet, or 1.8 miles. This is truly a natural marvel!
5. Classroom Activities - Can You See It?
See the lesson plan #3, "Can you see as well as a bald eagle?" in the Appendix.
