Echolocation

Question 1

Barn owls

Answer 1

Asymmetrical ears
Left ear above midpoint of eyes and directed downwards
Right ear below midpoint of eyes and directed upwards
allows the owl to obtain information about both the horizontal position of prey as well as its orientation

Question 2

Bats

Answer 2

Use ultrasound for echolocation - navigation and hunting
Frequencies around 50kHz
50kHz has small wavelengths, prey of similar size give an audible echo - target discrimination
Produce ultrasound in their larynx
Emit calls either through their mouth (most species) or though a complicated nose leaf structure (horseshoe bats)

Question 3

The Human Ear

Answer 3

The human ear, which is located in the skull, is divided into three sections:

(1) The outer ear collects and directs sound
(2) The middle ear filters and amplifies the acoustic energy to the inner ear
(3) The inner ear transforms the acoustic energy to electrical signals (neural impulses) that are processed by the brain.

Question 4

The Outer Ear

Answer 4

The outer ear includes the ear flap (pinna) and outer ear canal (external auditory meatus).
The pinna funnels sound into the outer ear canal.
The canal ends in the eardrum

Question 5

The Middle Ear

Answer 5

The middle ear in land mammals is an air-filled space that contains a series of three small bones or ossicles called the incus (anvil), malleus (hammer), and stapes (stirrup).
These bones connect the tympanic membrane and the oval window.

Question 6

The Inner Ear

Answer 6

The function of the inner ear is to change the sound intensity into electrical signals that the brain processes.

Question 7

Bat Ears

Answer 7

Extended pinna and tragus
tragus important in vertical localisation of objects - Lawrence and Simmons (1982)
Pinna important in lateral localisation of objects

Question 8

Organ of Corti

Answer 8

contains mechano-receptors
Hair cells project into the cochlea duct
When sound waves cause the basilar membrane to vibrate, the stereocilia are bent outwards
results in the depolarization of the hair cells
increases neurotransmitter release and the frequency of action potentials in the sensory neurons

Question 9

Outer Hair Cells

Answer 9

only found in mammals
3x as many as inner hair cells
can change length
oscillate at same frequency as incoming sound
act as cochlear amplifier

Question 10

Inner Hair Cells

Answer 10

main auditory receptors

communicate with 95% of ganglion neurons

Question 11

Amplitude

Answer 11

detected by the extent to which hairs are deflected

Question 12

Frequency

Answer 12

where in the cochlea the vibrations occur

Question 13

Microchiroptera

Answer 13

Only bats that use echolocation
Constant frequency (CF) bats usually emit sounds through a nose leaf structure
Frequency modulated (FM) bats emit sounds from their mouth

Question 14

Feeding buzz

Answer 14

increase the rate of calling to enable more frequent updates about prey location

Question 15

Doppler Effect

Answer 15

Horseshoe bats use CF calls and use the Doppler effect to determine whether objects are stationary or moving in a particular direction

Question 16

Moths

Answer 16

ability to detect approaching bats
sensitive acoustic neuron
A1 response then A2 response 
between 20-120ft moth flies away from sound
less than 20ft moth flies erratically

Question 17

Barbastrelle Bat

Answer 17

moth specialist - eared moths

developed stealth echolocation to catch moths