Animal senses
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Animal Senses. How do animals sense stimuli? Sensory organs perceive stimuli (light, sounds, etc.) with a receptor cell. The receptor cell sends signals to the brain where they are processed and integrated. Animal Senses.

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Animal Senses

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Animal Senses

  • How do animals sense stimuli?

  • Sensory organs perceive stimuli (light, sounds, etc.) with a receptor cell. The receptor cell sends signals to the brain where they are processed and integrated.

Animal Senses

  • Each type of animal is equipped with its own sensory receptors  each animal perceives its environment differently.

Animal Senses

  • Animal senses are more varied and sharper than human senses.

  • Most sensory receptors are found on the head of an animal—in most cases, the “head” is the first part of an animal to enter a new environment

Four Basic Modalities

  • Photoreception – response to light


  • Response to heat!


  • Response to movement.

  • This includes hearing, vibration, touch, balance, etc.


  • Response to chemical energy, including smell and taste

Insect Senses - Vision

  • Compound eyes - made up of 100’s –1000’s of lenses

  • Each individual “eye” is not as accurate as a vertebrate eye, but the compound eyes taken together are better at detecting motion.

  • Respond to minute changes in color and motion—the brain produces 1 detailed image.

Insect – Chemical Receptors

  • For taste and smell

  • Found on mouthparts, antennae and legs.

  • A fly’s foot can tell whether a liquid contains sugar or salt.

Sensory Hairs

  • Found mostly on head and legs

  • Can detect movement in surrounding air or water, and can detect certain chemicals.

Sensory Hairs detect Pheremones

  • These are odor producing molecules that act as chemical messages.

  • They are synthesized by an individual, released into the environment and change the behavior of another individual.

Sensory Hairs detect Pheremones

  • 1000 different insect pheremones known

  • Most are produced by females and are airborne.

  • Species specific sex attractants*.

Animal Senses

  • Specific examples:

  • A homing pigeon senses changes in altitude as minute as four millimeters. Pigeons also see ultraviolet light and hear extremely low-frequency sound.

Animals detect magnetic fields

  • Used for navigation by pigeons and other birds, honeybees, sea turtles, etc.

What happens when an animal that navigates using magnetic fields has a magnet glued to its head?

Pit Vipers – Detect Heat

  • Pits are located on head of pit viper

  • Pits contain receptor cells that can detect infrared radiation (heat)

  • A pit viper is able to “see” a fuzzy image of a warm object –a pit viper can strike at a mouse in complete darkness.

Design an experiment to test if a “pit” is actually sensing heat.

  • Is it possible the snake’s pit is simply sensing the smell of another animal?

  • Hint: Use a light bulb in your experimental set-up!

Elephants Detect Infrasounds

  • Infrasound = sound too low to be heard by the human ear

  • Elephants call to each other with infrasound and stamp their feet which create sound waves that travel through earth.

  • Infrasound can travel exceptionally long distances.

Elephants Detect Infrasounds

  • It is hypothesized that this allows elephants to coordinate movement when they are miles apart.

  • Large elephant ears and feet (vibrations in ground) are the sense organs*

Animals Detect Ultrasounds

  • Ultrasounds = sounds too high to be heard by humans

  • Bats, dolphins, etc.*

Design an experiment to test if bats actually use ultrasounds for navigation

Hint: Use cottonballs as part of your experimental set-up.

Aquatic Predators detect Electric Fields

  • Sharks (and others) can detect electrical activity in the muscles of passing prey.

Sharks and Aquarium

  • What problem might a shark have in a large tank in an aquarium?

Animals detect movement

  • An animal’s ear detects sound by the movement of sound waves through the air or water.

  • Mammals have bones in their middle ear that transmit the information carried in the sound waves to the brain.

Animals detect movement

  • This includes stimulus detected by the lateral line system in fish and other aquatic vertebrates.

  • This system detects movements and pressure changes in the surrounding water.

Animals and vision

  • Some animals can sense parts of the electromagnetic spectrum that are invisible to the human eye.


Human (and most vertebrate) Senses

  • Vertebrate eyes are camera eyes (vs. compound eyes of insects). Focuses incoming light onto a layer of photo-receptor cells on back of retina.

Vertebrate Eyes

  • Iris: The colored diaphragm in the anterior chamber of the eyeball which contracts and expands to adjust for light intensity.

  • Pupil: The opening in the center of the iris through which light passes.

  • Lens: The transparent, dual-convex body which focuses light rays onto the retina. It is normally capable of changing shape to allow the eye to focus on both near and distant images.

Vertebrate Eye

  • Retina – Found on the back of the eye. Sensory cells contain light absorbing pigment (a molecule that absorbs only certain wavelengths of visible light and reflects or transmits other wavelengths)

    • cones = color vision

    • rods = light vision

Vertebrate Eye

  • The optic nerve attaches to retina and there are no photo-receptor cells at that location creating a blind spot.

  • Adaptations, such as the eye, (a characteristic that makes one individual more fit than another) do not have to be perfect.

Experiment with YOUR blind spot

Cat’s Eyes

  • A reflective layer behind the cat's retina called the tapetum reflects incoming light and bounces it back off the cones, making more use of the existing light.

  • The tapetum makes a cat's eyes look like shiny green orbs at night.

Vertebrates and Taste

  • Taste is a chemical sense perceived by specialized receptor cells that make up taste buds.

  • Flavor is a function of both taste and smell.

Vertebrates and Smell

  • Inside the nose is a big area called the “nasal cavity.”

  • On the roof of the nasal cavity are special sensory smell cells called “olfactory receptor cells.”

Vertebrates and Smell

  • Smells are in the form of a gas that is breathed in when animals inhale

  • The scent molecules in the gas pass by the olfactory receptor cells on the roof of the nasal cavity.

  • The smell cells send the signal up a nerve fiber to the brain.

  • This allows vertebrates to react quickly to smells.

Other Senses

  • Nociceptors – Sense pain

  • Thermoreceptors – Detect changes in temperature

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