Lecture 16 Flashcards
Are dogs color blind?
Dogs have the ability to detect
color in a limited scope
compared to humans. They can see more than black/white.
What study did Kasparson do with dogs?
Researchers trained dogs to associate dark yellow paper with food reward
The dogs were tested with either a dark blue box or a light yellow box
Dogs reliably selected the color matched box in ______ of test trials
70%
Visual systems have evolved to detect light. How?
Light sensitive organs have developed at least three separate
times in convergent evolution (for ‘camera’ eyes) This process triggers an electrical response in the receptor neuron
Vision provides a means of detecting objects in an animal’s
surroundings. What are these?
Luminance (intensity differences; brightness) – Reflectance (spectral composition; color)
Vertebrate visual systems contain two types of receptors:
Rods: low light conditions
Cones: light sensitive photoreceptors to perceive color.
Properties of color?
Brightness (intensity) ■ Hue ■ Chroma (degree of saturation or purity of the dominant frequency)
■ Cone cells in the retina contain a pigment called ______
opsin
Opsin
group of light-sensitive proteins found in photoreceptor cells of the retina
Opsin absorbs light energy which…?
activates retinal neurons and results
in action potentials in the optic nerve
Two different wavelengths of light
can produce the same ______ ____ _______ in a cone cell
pattern of activation
Outputs of ____ _____ are combined
and compared in the visual
nervous system
cone cells
Tetrachromatic color vision
based on four types of cone cells – Birds, lizards, turtles, and many fish
Trichromatic color vision
based on three types of cone cells – Old world primates, humans
Dichromatic color vision
– based on two types of cone cells – Most other mammals (dogs, cats, etc.)
Progenitors of mammals lost ____ of the four types of cones during a
period in evolutionary history when they were primarily _______.
two, nocturnal
Human color vision depends on interactions of three types of cones:
red, green, blue
Most other mammals are ________
dichromats
Dichromacy occurs in humans when one of the cone pigments is missing. What are the types?
Protanopia: no red receptor
Deutanopia: no green receptor
Tritanopia: no blue receptor
Several groups of
animals (birds,
reptiles, fish) have
_______ distinct types of cones
four
Bees are technically __________
trichromatic
Appears to be a trade in
sensitivity between _____ and
________ wavelengths
red, ultraviolet
Bees lack sensitivity to what?
red end of the electromagnetic spectrum
What are the properties of light used in animal communication?
Spatial characteristics
Temporal characteristics
What are spatial characteristics?
Variations in shape, size, surface features and color pattern.
What are temporal characteristics?
changes in pattern of color, surface, color change and apparent size/shape over time.
_______ ________ is very common for increasing visibility.
Brightness contrast
Forests have 4 major light habitats…?
Forest Shade: Yellow-green
– Woodland Shade: Blue-gray
– Small Gaps: Reddish
– Large Gaps: “White
Due to natural differences in these light spectra an animal my appear…?
very different in each light environment
What are some factors influencing the evolution of signals?
Properties of the physical environment where the signal is
generated
– Perceptual systems of individuals (potential mates, predators,
prey) receiving the signal
– The nature of the information signaled
What are the characteristics of warblers?
8 species, all small and green No color patches – Two wing-bars Two wing-bars plus a crown-stripe – All of the above plus white outer tail feathers
The distribution of patches across species is nested…?
Species with more complex patterns contain all patches of
simpler patterns
Species can be ranked from _____ to _______
duller, brighter
The ability to perceive visual signals is linked to what?
ambient light in the environment ( should have a direct impact on the evolution of coloring and
behavior signals)
Warblers that breed in the dark, dense habitats have what?
have a
greater number of color patches than those that breed in lighter, open habitats
Strong negative correlation between…?
between wing-bars (brightness) and light
levels in the natural habitat
Habitats of warblers?
Bright species have the most stripes; may serve as camouflage to predators
– If color patterns are used for intraspecies communication and the
visibility of these patterns depends on the background, then species in dark habitats should have the brightest coloring
Variation in display is associated with location of color patches. What are some of those locations?
Species with crown-strips bow their heads in display – Species with rump patches turn and flash their rumps
Display movements enhance visibility of the patches. What is an example?
Temporary effect due to specific movements
Since different species use different display patterns for intraspecies, how is communication linked?
the effects may be linked primarily to the differing
displays
What should provide evidence of the effect of
coloring
Altering the level of conspicuousness during display by eliminating or
enlarging color patches should provide evidence of the effect of
coloring
Males of the species inornatus were manipulated in 1 of 3 ways?
Control group: …
– Reduced: wing-bars were
painted with green paint – Enlarged: wing-bars were
painted with yellow paint
Signals were manipulated while males were establishing territories
and ______ to females arriving at the breeding grounds
prior
Males from the control group had ___________ sized territories
intermerdiate
Males in the reduced group had the __________ territories
smallest
Territory shifts were immediate with the ______ ________ male
taking over portions of the less conspicuous males
more conspicuous
Songs aren’t used in territorial displays suggesting what?
conspicuousness is a primary form of communication between individuals
Increased territory size was correlated with increased levels of conspicuousness
Some minimal level of ___________ is necessary to maintain a
territory and reproduce
conspicuousness
What is sensory drive?
Conspicuousness is context-dependent thus the properties of the environment will bias the direction in which signaling characters
evolve
Color patterns, habitat choice, and courtship/display patterns
appear
evolve together
Properties of the environment can lead to what?
species divergence
whether or not perceptual systems vary
Properties of the environment appear to influence what?
the evolution of
conspicuous coloring
Coloring can vary across what?
body structures to take
advantage of the different levels of illumination
What is reverse countershading?
A form of conspicuous coloring that serves
to increase visibility of the animal that is illuminated from above
What is countershading?
protective coloration of some animals in which parts normally in shadow are light and those exposed to the sky are dark.
If ambient light is strongly colored, animals can use…?
Contrasting color patches – Color patch that matches the ambient light peak and surround it
with colors that reflect poorly
Define disruptive coloration?
uses patterning to
interfere with the perception of the true outline of the animal – …
– Disrupt a receiver’s eye from the animal’s outline
(like zebras)
Define movement contrast?
terrestrial and shallow water environments present a moving background – Wind, wave action
Animals attempting to stand out against this type of background use
_______, ________ accelerating movement
jerky, rapidly
_________ and striped color patterns often work together in creating
crypticity or conspicuousness
Movement
Stripes ___________ to the direction of motion conceal motion.
parallel
