Comparative Anatomy and Physiology of Animals
Lecture 26 Vertebrate Sensory Systems 16/02/21
Introduction
- Animals are constantly bombarded with sensory information.
- They only extract and process the tiny proportion of this information that is
ecologically relevant.
- They have a limited sensitivity, a limited detection range, to detect changes.
Vision
- All vertebrates do or did have eyes.
- Eyes vary in their acuity, the range of wavelengths they can
detect, their sensitivity in low light levels, their ability to detect
motion, and whether they can discriminate colours (and which
ones).
- Eye morphology is highly conserved from fish to higher
vertebrates. This includes a transparent cornea in front of a lens
and an iris.
- The major difference between terrestrial and aquatic
species is the degree of accommodation to change in
the focus of images at varying distances.
Bird eyes
- They can perceive a wider range of light
wavelengths, such as ultraviolet.
- They also have a blood-rich pectan that can protrude
from the retina and is considered as a means of
maximising nutrition to the eye.
Field of vision
- Prey: wide possible view.
- Predators: stereopsis and depth perception.
- Where the monocular fields overlap, the brain can develop binocular vision
within the shared area.
- Predators and those that need for precise focusing tend to have more
binocular vision. Many species also have a ‘blind-spot’ where the eyes do
not see. This tends to be associated with predatory species with large angles
of binocular vision.
- The hare and woodcock have binocular vision in front and back of the head
– allows ease of vision for potential problems.
Colour vision
- The light receptors are in the retina that lines the
inside surface of the eyeball. There are two types of
receptor cell – rods are larger, more numerous, and
are sensitive to monochromatic low light, but cones
need brighter light and different in wavelength that
they are sensitive to.
- The cells contain photosensitive rhodopsin and
chromophore that respond to light.
- Different classes of cones with different spectral
sensitivities underpin colour vision.
Lecture 26 Vertebrate Sensory Systems 16/02/21
Introduction
- Animals are constantly bombarded with sensory information.
- They only extract and process the tiny proportion of this information that is
ecologically relevant.
- They have a limited sensitivity, a limited detection range, to detect changes.
Vision
- All vertebrates do or did have eyes.
- Eyes vary in their acuity, the range of wavelengths they can
detect, their sensitivity in low light levels, their ability to detect
motion, and whether they can discriminate colours (and which
ones).
- Eye morphology is highly conserved from fish to higher
vertebrates. This includes a transparent cornea in front of a lens
and an iris.
- The major difference between terrestrial and aquatic
species is the degree of accommodation to change in
the focus of images at varying distances.
Bird eyes
- They can perceive a wider range of light
wavelengths, such as ultraviolet.
- They also have a blood-rich pectan that can protrude
from the retina and is considered as a means of
maximising nutrition to the eye.
Field of vision
- Prey: wide possible view.
- Predators: stereopsis and depth perception.
- Where the monocular fields overlap, the brain can develop binocular vision
within the shared area.
- Predators and those that need for precise focusing tend to have more
binocular vision. Many species also have a ‘blind-spot’ where the eyes do
not see. This tends to be associated with predatory species with large angles
of binocular vision.
- The hare and woodcock have binocular vision in front and back of the head
– allows ease of vision for potential problems.
Colour vision
- The light receptors are in the retina that lines the
inside surface of the eyeball. There are two types of
receptor cell – rods are larger, more numerous, and
are sensitive to monochromatic low light, but cones
need brighter light and different in wavelength that
they are sensitive to.
- The cells contain photosensitive rhodopsin and
chromophore that respond to light.
- Different classes of cones with different spectral
sensitivities underpin colour vision.
