Sensing Energy
Sensing Light Energy
In some animals, the organ used to detect light is the
eye. Although most large animals (humans, fish,
birds, and reptiles) have similar eyes, not all eyes are
the same. Some eyes are very complex, while others
are simple in their function. With our human eyes, we
can see a variety of colors, shades, and sharp details of
shapes by collecting the light reflected off of objects.
Life as seen through the eyes of an insect would look very different. Insect eyes come in two
varieties-simple and complex. Simple insect eyes, called ocelli, detect little detail but can tell
different shades of light and dark. Compound eyes are more complex. These organs function
similarly to many human eyes bundled together and working as one.
Some critters have eyes that swivel on short stalks which help them to see in all directions
without turning their heads. Ever tried to swat a fly? They have compound eyes that help them
see behind them. They see behind them but can’t detect shapes very well. Plants can also detect
light. In fact, if they couldn’t, we could not exist, as we know it. Special organs in plants, called
chloroplasts, collect light energy and use it to convert carbon dioxide and water into sugar for
us.
Sensing Sound Energy
Even though we can tell many types of vibrations
with our hands, feet or other body parts, we
understand sounds by using our ear. Human ears,
and the ears of other large animals, are generally
made of an air chamber covered by a thin piece of
skin-like material (your eardrum). Some animals
like dogs have specialized hearing that allow them
to hear high pitch sounds that humans can’t hear
with their auditory system.
Insect ears, like human ears collect and transform
sound vibrations. But, insect’s ears are called
tympanal organs. Any idea why they have this name? It is because the membrane vibrates like
a drum.
Fish have what is called a lateral line system to help detect sound vibrations in water. This
helps them detect when predators and other objects are near. The lateral line looks like dashed or
dotted lines on the sides and around the head of fish, reptiles, and amphibians. This system also
helps these animals sense movement of water past their bodies, and the temperature of the water.
The lateral line system is made up of epithelial cells which act like tiny hair cells that sense
movement and heat in their surroundings.
Sensing Heat Energy and Electrical Energy
Have you ever burned your hand on the stove? How does your brain actually know that your
hand is getting warm? We, like other animals, have certain nerve endings that are sensitive to
heat. These are often called thermoreceptors.
For some animals, such as amphibians, fish, and reptiles these receptors are part of the lateral
line system. Insects also have thermoreceptors located on all sorts of different body parts.
Many animals have a variety of sense organs that
allow them to detect different forces of energy. For
example, some animals can actually sense changes in
electrical fields. Fish are the most common electrical
detectors. Some, such as certain sharks, can detect the
presence of external electrical fields (such as metal in
trash dumped in the ocean by humans). Others create
their own electrical field and sense external electrical
fields by detecting changes in their own electrical
fields.
Devices Used to Perceive Energy
Eyeglasses/Contact Lenses
Have you ever wondered why many people need glasses? Well, first you will need to know the
journey of light rays through the eye into the brain. So hold on to your myopia; here we go. As
the light passes through the cornea, the shape of the eyeball will determine the focus of the
image. Throw a ball to a friend. Notice the change of focus your eye automatically makes. That
is because the light, after going through the cornea, will pass through a lens that changes shape
according to the distance from the object as it increases or decreases. Then, the lens refracts the
light projecting an inverted (upside down) image on the retina. The last part of the light’s
journey takes us to the retina. The retina is a complex layer of cells on the back of the eyeball.
The retina has little objects called cones and rods. The rods are used to detect light and the cones
are used to interpret color. These generate small nerve signals when they are hit by light. These
signals are carried to the brain by the optic nerve.
Some people’s eyes become misshaped and are to long
or to short. Individuals with slightly longer eyeballs
have problems with the image forming on the retina and
need corrective lenses. The type of lens needed would
be concave lens. This condition is known as myopia,
which is commonly referred to as near-sightedness. If
eyeballs are slightly too short individuals need convex
lenses. This condition is known as hyperopic or farsightedness. The strength of these lenses are
determined by the lens material and the angle of the
curve of the lens.
Telescopes
A telescope is an instrument that collects visible light, a small fraction of the electromagnetic
spectrum. It forms enlarged images of distant objects and concentrates them through an eyepiece for better observation. The simplest optical telescope is made of two lenses. One lens,
called the objective lens, collects light and forms an image at the back of the telescope. The
bigger the objective lens, the more light the telescope can gather. The second lens is located in
the eyepiece of the telescope. This lens magnifies the image produced by the objective lens.
Different eyepieces can be selected depending on the magnification of light that is desired.
Hearing Aids
Ears are extraordinary organs. Ears pick up all the sound around you and then translate this
information into an electrical impulse your brain can understand. For some people hearing loss
is a problem. A hearing aid is a small electronic device that amplifies sound waves that enter the
ear canal. It can fit nicely in the canal of the ear, or some can be placed behind the ear and
vibrate the bones that are inside the ear when they detect noise.
All hearing aids have the same components: a microphone, an amplifier, a receiver and a battery.
The parts of the hearing aid work together to amplify sound energy. The microphone changes
sound waves into electrical signals. These signals pass through the amplifier of the hearing aid
and are made louder. The amplified electrical signals are changed back into sound waves by the
receiver and are channeled into the ear.
Seismograph Equipment
Most earthquakes take place along cracks in the surface
of the Earth. These waves produced from an earthquake
are called seismic waves. A seismograph is able to
sense and measure seismic waves. Seismographs use an
ink pen to record movements of the Earth’s surface.
The resulting record is called a seismogram. We even
use seismographs to detect moon quakes.
Additional Questions to Consider
1. What is energy?
2. What types of energy do you know of?
3. In what other ways can organisms including humans detect different types of energy?
4. What other devices (not including glasses, hearing aids, telescopes, seismographs) do you
know of that help humans detect energy?
5. How do humans use energy? What forms of energy do we use and how?
6. How do other organisms use energy?