34.12 Sensing Sounds: Hearing

• A lateral line system supplements the fish’s sense of hearing provides a sense of “distant touch” is a

pressure wave in water.• Vibrations produce movements in the capula that

causes hair cells to bend

is not present in terrestrial vertebrates

Figure 34.30 The lateral line system

34.12 Sensing Sounds: Hearing

• Some mammals perceive distance by means of sonar using echolocation, they emit sounds and

then determine the time it takes these sounds to reach an object and return

mammals that use sonar are bats, shrews, whales and dolphins

Figure 34.31 Using ultrasound to locate a moth

34.13 Sensing Light: Vision

• Vision, the perception of light, is carried out by a special sensory apparatus called an eye eyes contain sensory receptors, called

photoreceptors, that capture light energy

• Many invertebrates have simple visual systems with photoreceptors clustered in an eyespot can perceive the direction of light but cannot form a

visual image

Figure 34.32 Simple eyespots in the flatworm

34.13 Sensing Light: Vision

• Well-developed, image-forming eyes have evolved independently in four animal phyla annelids mollusks arthropods vertebrates

• These eyes are examples of convergent evolution

34.13 Sensing Light: Vision

• Human eyes works like a camera light first passes through a transparent covering called

the cornea a lens helps to focus the light from the cornea to the

rear of the eye• the shape of the lens can be adjusted by ciliary muscles

the iris is a muscle that acts as a shutter to control the amount of light entering the lens

• the pupil is the transparent zone in the middle of the iris the retina is an array of photoreceptors in the back of

the eye

Figure 34.34 The structure of the human eye

34.13 Sensing Light: Vision

• The retina is the light-sensing portion of the eye w/ two kinds of photoreceptors Rods -sensitive to light intensity but do not

detect color or sharp images cones -detect color and produce sharpest

images• the center of the retina, the fovea, is densely

packed with cones and produces the sharpest image. The lens focuses light here.

Figure 34.35 Rods and cones

34.13 Sensing Light: Vision

• photoreceptors work because of pigments (molecules that capture light) within them

• Pigments capture light that initiates a chain of events that lead to a nerve impulse out of the photoreceptor.

34.13 Sensing Light: Vision

• Three kinds of cone cells provide us with the ability to see color.

• Each allows us to detect either blue, green, or red. Other colors are from different intensities of blue, green, and red.

• Rods detect only the intensity of light.

Color blindness occurs when individuals are not able to perceive all three colors

Figure 34.38 Test for color

blindness

34.13 Sensing Light: Vision

• The rods and cones are at the rear of the retina so nerve impulses are transmitted in the opposite direction of the light

Figure 34.39 Structure of the retina

34.13 Sensing Light: Vision

• Primates and most predators have two eyes, one located on each side of the face the image each eye sees is slightly different

because each eye views the object from a different angle

this slight displacement permits binocular vision, the ability to perceive 3-D images and to sense depth or the distance to an object

Figure 34.40 Binocular vision