Lecture 14 Flashcards
Some birds have learnt to successfully mimic the alarm calls of multiple species. What is the benefit of this?
These alarm calls are given to
convince a potential predator
that a larger predator is near
(a threat to both species)
All organisms can generate visual images passively. How?
Light reflects off their bodies.
How can organisms increase their visibility?
increasing contrast
between themselves and their background, moving, or generating
one’s own light signal
__________ _______ from the visible range of the spectrum of EM radiation.
radiant energy
What are some sources of light?
Sun/moon
Burning objects
Biolumenescent
Light travels in ________.
waves
Light obeys the inverse square law. What is that?
(intensity decreases with distance from a point source as the inverse function of the distance squared)
• Decreases in intensity equal the square of the distance from the source to the perceiver
Light travels best in a _________.
vacuum
Define diffraction.
– light waves bend
and spread out as they travel
through a narrow aperture
When would diffraction effects be pronounced?
when the
propagating wavelength is
similar in size to the
diffracting object
Define refraction?
change in direction of a wave due to a change in its speed, most commonly observed when a wave passes fro one medium to another
Define reflection.
the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated.
Define absorption?
optical energy is
lost (absorbed) as it travels
through the medium
Define brightness?
refers to a signal’s overall intensity
Function of both the range of wavelengths reflected and the surface
structure of the object or signaling organism
_______ surface will produce higher intensity signal
Smooth
Brightness of self generated signals depends on the…?
amount of energy used to produce the signal.
Define spectral composition?
the color of a light signal Hue (dominant wavelength) • Chroma (saturation or purity of dominant frequency)
Reflected and self-generated
light signals may be
characterized by their _______.
color
Describe spatial characteristics?
Visual acuity of the receiver
impact the details and
localizability of the sender
Define temporal variability?
timing changes in intensity, color, and
spatial characteristics
• Used to generate a wide variety of signals
What are some typical components of visual displays?
Complex patterns of changes
in size, shape, color, flashing,
and limb movements
__________ between an object
of interest and the object’s
background determines the
conspicuousness of the object
contrast
How can contrast be achieved?
Contrast can be achieved with
any one or more of these light
signal characteristics
What is camouflage?
color or shape of an animal is similar to the background.
What is mimesis?
mimics another plant or animal for camouflage.
What is an aposematic signal?
warning signals associated with the
unpalatability of a prey animal to potential predators
What is batesian mimicry?
one species has evolved to mimic the warning
signals of another species directed at a common predator; mimic
is palatable while model is poisonous or noxious
• E.g., Moarch and Viceroy butterflies
•
What is mullerian mimicry?
convergence between two or more species
to warn predators of their unpalatability; both species are
poisonous or noxious
• E.g., cuckoo bee and yellow jacket
What is an example of batesian mimicry?
The filefish mimics the coloring of the unpalatable puffer fish
What is an example of mullerian mimicry?
Unpalatable caterpillars mimic stinging wasps and coral snakes.
Optical communication relies on?
Specializations of the sender
• Body structures modified to generate or reflect light for the purpose of communication
• Specializations of the receiver
• Visual system is designed to pick up electromagnetic radiation
• Adaptation to the channel • Properties of the signal are selected to maximize the likelihood of
unambiguous reception
For a reflecting surface to appear colored it must selectively…?
reflect certain wavelengths of light more than others
• Reflecting all wavelengths equally = white
• Absorbing all wavelengths equally = black
Curves with _____ peak over a _______ wavelength range are highly saturated.
high, narrow
broader curves are less saturated
Area under the curve is a measure of what?
brightness
_______ animals generally perceive a wider range of colors.
Diurnal
Color is produced through 3 different mechanisms:
- Pigments
- Thin-layer interference
- Scattering
What are pigments?
chemical compounds whose molecules absorb certain
wavelengths of light and transmit the remaining wavelengths
Long-pass filters allow only _______ wavelengths to pass
longer
How is the color red produced? Yellow?
Red is produced by allowing all wavelengths above 600 nm to pass
• Yellow is produced by allowing all wavelengths above 500 nm to pass
_______ ______ filters allow only short wavelengths to pass.
Short pass
_________ only allow wavelengths below 450 nm to pass.
Violet
What does color combination result in? Give an example.
additive color mixing
• Purple is not a spectral color but results form filters that block mid-range wavelengths (green) and allow red (long) and blue (short) wavelengths to pass
What are the 3 types of pigments?
Carotenoids – produced by plants and acquired by eating plants or by eating
something that has eaten plants
• Typically produce red, orange, yellow
• Porphyrins – modified amino acids all fluoresce under ultraviolet light
• Typically produce pink, browns, reds, and greens
• Melanin – tiny granules of color found in feathers and skin; provide
structural support as well as coloring
• Typically produce darkest black, reddish browns, pale yellow
What are conjugated double bonds?
Pigments are organic compounds that contain long chains of conjugated double bonds. They are carbon atoms joined by alternating single and double bonds.
What is carotene?
18-carbon chain that absorbs longer wavelength and transmits green, yellow,
and red to appear yellow or orange
Carotenoids bound to proteins absorb green but
transmit violet and red – appear purple
What are Pterins?
nitrogenous rings that
produce white, yellow and red
colors often found in butterfly
wings
What is a Quinone?
Represent a class of organic compounds that are formally “derived from aromatic compounds
What is a Verdins?
produce blue-green
color often found in bird’s eggs
What are porphyrins?
verdin molecule with
the ends connected into a ring around
a central metal ion; color is
dependent on the type of metal
Most animals place _____ in the center.
iron.
Hemoglobin: red (chicken comb)
Plants place _________ in the center.
magnesium
chlorophyll: green
Turacos place _______ in the center
copper
Describe melanin?
dark-colored pigments found in a wide
variety of vertebrates, invertebrates, and
plants
• Large protein molecule that absorbs most
or all visible wavelengths to produce
brown or black
Define guanine?
forms microcrystalline deposits (platelets) that reflect
all wavelengths
• Dense packing of guanine crystals causes specular reflectance
• Silvery appearance of fish scales
What must pigments be coupled with?
Reflective structures
Where are pigments located.
outer epidermal or derman llayers of skin.
What are chromatosomes?
small granules or packets that contain
pigments; found in chromatophores
What are chromatophores?
pigment-containing and light-reflecting cells, or groups of cells, found in a wide range of animals including amphibians
What happens to light when it travels through pigment?
undergoes the first round of absorption/reflection
• Light waves that are reflected back out will undergo a second
round of absorption/reflection through the pigments
What are Iridosomes?
contain guanine platelets that reflect all wavelengths of light (act like a mirror)
___________ is responsible for producing iridescent coloring.
Interference
• White light hits the surface at an angle and is partially _______
reflected
Some light enters the wax/covering and is _______, then
_______ by the boundary at the bottom wax layer, and _________
again as it exits the layer
refracted, reflected, refracted
In birds, why do some appear to be very shimmery and color changing?
Primary and secondary reflections will be in phase for certain colors and out of phase for others resulting in the appearance of very shimmery changing colors
What are iridescent feathers?
– iridescent coloring is produced by the structure of the feathers (Interference) • … • Damage to feather structure results in decrease of iridescence
• Small particles with a different________ ______ from the general
medium can cause some wavelengths to scatter
refractive index
What causes light scattering in animals.?
Animal’s surface is coated with transparent material that contains
a matrix of tiny dense particles considerably smaller than 300 nm
in diameter
• Underneath this surface is a layer of melanin
Tiny air pockets in the bards of feathers causes what?
scattering of incoming light, resulting in a specific non iridescent color.
Blue is always produced in this manner.
Placing a thin yellow carotenoid layer above this
arrangement, violet and blue wavelengths are
absorbed and _______ is the only wavelength
scattered
green
How is white coloring made?
produced by scattering particles that
are larger than wavelengths of light
(resulting in multiple wavelengths
being reflected = white)
T/F: Pigment, scattering and interference produced coloring cannot be changed quickly
True
What is the purpose of badges?
used to communicate
information and are very noticeable
Define badges.
morphological specializations used as visual signals • Bright patches of skin, fur, feathers • Horns, casques, or crests
