Alien Bodies Lesson 11
What We Know from Our Experiences
On this topic, it makes sense to start with what we know.
On earth, we see a number of useful senses. They include
Sight: Eyes have evolved independently for a number of different organisms.
Insects have compound eyes with many facets. Some can see in the ultraviolet part of the light spectrum as well as at the wave lengths visible to us.
Shellfish have a row of eyes along their bodies close to where their shells open.
Squid and octopi have large, sensitive eyes.
Vertebrates, including humans, have eyes: some have color vision.
Worms, etc, have eye spots that can tell light from dark but do not "see" objects.
Hearing: Being able to detect vibration in the environment helps animals to detect the presence of others of their own species, predators and/or prey. Ears detect vibration in air and/or water. Sometimes sound vibrations are felt through the sense of touch.
Smell: This is the dominant sense for many animals, including dogs. It can give a lot of information about the environment, including the presence or absence of predators or prey, the location of food sources, whether members of the same species are juveniles or adults, and whether adults of the same species are ready to reproduce.
Touch and temperature: The sense of touch provides useful information about temperature, pressure, vibration, and injury. Is this information useful to all organisms? Do fish feel the temperature of the water? Is pain useful? Some organisms also have structures that just detect heat, like the pits on the heads of pit vipers, a kind of snake.
Taste: This sense tells an organism if an object can safely be eaten. It warns us if food has spoiled or is unripe.
Magnetism: It is believed that some birds use a sense of the earth's magnetic field to guide them in their migrations. Detecting a magnetic field would require some sort of sensor with iron molecules in it.
Movement: We have built robots with motion sensors, and some animals have vision systems that notice movement in their environments but probably do not "see" identifiable objects that merely stand still.
Echo-location: Bats use echo-location to detect insects and solid objects: dolphins use echo-location to detect objects in water. Dolphins can tell the difference between a copper disk and an iron disk with this sense. These animals emit a sound and sense it when it bounces back at them.
Are There Other Possible Senses?
Here is a chance to use imagination. What else is there to sense? Air pressure, perhaps? Humidity? We have instruments that measure these. Radioactivity?
How to Describe Your Aliens' Senses
Think about the environment and look at the body sketch that you have made. What senses would be most useful to your aliens? How can they find food? Avoid enemies? List the senses that they have.
For example, the snorvep has hearing organs on the blue structures on its head. The green sensor antennae have hearing structures on the blue tips, and detectors for smell, taste, and light and dark on the green parts. The sensor antennae are rigid, but can be swivelled at the base to help find the direction of the stimuli.
The tentacles have a delicate sense of touch, and also taste buds on the undersides of the tips. The body is sensitive to touch and pressure, and somewhat sensitive to pain.
The snorvep lives in a rather gloomy, dim world, where it is often foggy, so vision is not the most useful sense. Hearing is the snorvep's dominant sense, and the tiny, cone-shaped hearing organs are attached to the blue structures near the front of the body.
The organs of hearing are small cones, clustered together on the rigid blue plates and the tips of the green sensor antennae. You see the cones in this small picture, with red lines leading down to the supporting plates. These red lines represent nerve fibers and blood vessels, which form a mat that underlies the layer of cones. Each cone is closed by a small membrane that vibrates rather like our ear drums. These structures are small, and look a bit like the compound eyes of insects. They are often wet, and small drops of water on the open tops of the cones function as additional membranes that vibrate in response to sound.
The grey part in the picture represents a spongy substance that protects the cones and holds them steady. It also makes it easier for the snorvep to locate the direction of sounds because the vibration is not moving from cone to cone.
Assignment: Describe the senses that your aliens have. Explain how these senses are useful in their environmens. Give details about the dominant sense.