BIO-Animal Behavior Midterm #2

Camera lens eye

A lens at the front that focuses light

onto the retina (Best for a sharp, bright image)

Compound eye

Made of many tiny lenses (ommatidia), but the image is blocky and lower quality. Many insects (Best for a wide field of view and detecting movement)

Pigment cup eye

only senses light direction and moving shadows/ simplest eye (Worst for forming an image)

Pinhole eye

Makes an actual image (strength), but it is dim and blurry because only a little light gets in (weakness)

Filled cup eye

Clear material protects the photoreceptors and bends light slightly (strength), but gives a poor image that only works over short distances (weakness)

Eye types: simplest to best image

Pigment cup → pinhole → filled cup → camera lens (compound eyes are a separate design built for wide view and movement)

Rods

Photoreceptors for sensitivity (dim-light/night vision); 1 photon can trigger a nerve impulse

Cones

Photoreceptors for color vision; need more light than rods

Diurnal vs. nocturnal camera eye

Diurnal: small flat lens, large image

Nocturnal: large round lens, small but intense (bright) image.

Speed of sound formula and values

Wavelength λ = speed (c) ÷ frequency (f).

Ampullae of Lorenzini

Pick up electric fields from OTHER animals (passive electroreception), like the weak fields prey give off. Found in sharks, rays, lungfish, coelacanths.

Passive vs. active electroreception

Passive: only listens for other animals' electric fields (ampullae of Lorenzini). Active: makes its own electric field and senses distortions (weakly electric fish, tuberous receptors).

Homing

Returning home after being moved away (type of navigation)

Piloting

Finding your way using landmarks you already know (type of navigation)

True navigation

Finding your way in totally unfamiliar places with no past experience (type of navigation)

Compasses animals use (types)

Sun compass, polarized light, celestial (star) compass, magnetic compass

Sun compass

Using the sun for direction, corrected for its movement (15°/hour) by the body clock. If the clock is shifted (jet-lagged bees), they fly the wrong way.

Polarized light compass

The pattern of polarized light in the sky changes with the sun's position, so some animals use it for direction (even when the sun is hidden)

Celestial compass

Using the rotation of the night sky around a fixed point (like the North Star). Emlen's indigo bunting experiment tested this.

Magnetic compass

Using Earth's magnetic field: polarity (direction), inclination (angle = latitude), and intensity (strength)

Basic model of the internal clock

Environmental cue → receptors/detection → internal clock (pacemaker) → rhythms (behavior, hormones, movement)

Zeitgeber

A "time giver" that resets the clock; it must be highly predictable (sunrise/sunset, tides, seasons, moon)

Spring tides

Sun and moon line up (new and full moon), their pulls add together, and tides are biggest

Neap tides

Sun and moon at right angles (1st and 3rd quarter moon), their pulls cancel, and tides are smallest

Honest communication

A signal exchange between sender and receiver that benefits BOTH: senders send signals that help the sender, and receivers respond in ways that help the receiver

Honest communication (altruism)

Not altruistic. Both sides may benefit, but only because they share interests or are at a stalemate (equilibrium).

Reasons signals stay honest

1) Indices can't be faked

2) Costly signals (only high-quality animals can afford them)

3) Punishment for fakers

4) Shared interests mean no reason to cheat.

Index (honest signal)

A signal that can't be faked because it's physically tied to the animal (a deep croak requires a big body)

Dishonesty in signaling

Exists but is rare

Deceit / manipulation

Dishonest signal that helps the sender and hurts the receiver. Still communication, just not honest. Receivers evolve resistance.

Receiver benefit grid: communication

Sender + and receiver +: honest communication. Sender + and receiver −: manipulation/deceit (still communication, broad definition).

Receiver benefit grid: not communication

Sender 0 or − and receiver +: NOT communication (it's a cue)

Cue

A trait or action that gives information but did NOT evolve to change the receiver's behavior (often an incidental side effect, like walking or metabolism)

Signal

A trait that evolved (was selected) to change the receiver's behavior

Signal vs. cue (quick rule)

Signal: evolved to change the receiver's behavior

Cue: a side effect the receiver happens to use.

CHEMICAL (environmental properties of different sensory modalities)

speed = slowest

effect of temperature = strong effect

effect of solid barriers = no effect

effect of ambient light = no effect

ELECTRICAL (environmental properties of different sensory modalities)

speed= fastest

effect of temperature= no effect

effect of solid barriers = strong effect

effect of ambient light = strong effect

MECHANICAL (environmental properties of different sensory modalities)

Speed = fast, but slower than electrical

effect of temperature = minor effect

effect of solid barriers = minor effect

effect of ambient light = no effect

biological timekeeping

activities and behavior patterns are linked to environmental features with regular frequencies (tides, days, seasons)

Biological clocks

internal mechanisms that keep time

Biological rhythms

• are temperature compensated

• rhythms are set by external factors but are approximately self-sustaining even in the absence of the feature

Orientation

how an animal position itself positions itself in relation external cues. No positional information about where the goal actually is

Navigation

an animal uses various cues to determine its position in reference to a goal (requires both a compass to provide directional

dispersal

a relatively shoer distance, one way movement to settle in a new area or habitat

• Natal dispersal (one time movement away from place of birth, early in life)

• Adult dispersal (dispersal as an adult, can happen more than once)

Site fidelity vs. win-stay lose-shift strategy vs public information

• site fidelity = when adults stay at (or return to) the same site to breed again

• Win-stay lose-shift strategy = when animal base their decision on their own previous reproductive success

• public information = when individuals use information about the reproductive success of other individuals at a site to decide whether to bread there in the future

Sensory Systems:

1. CHEMORECEPTION = detect chemicals—> gustation(mouth) and faction(nose)

2. PHOTORECEPTION = detect light (electromagnetic waves) —> vision

3. MECHANORECEPTION = detect changes in pressure/vibration —> audition (sound waves) and touch (vibration)

4. ELECTRORECEPTION = detect bioelectric fields generated by other animals

5. MAGNETORECEPTION = detect large scale magnetic field of the Earth