Animal Senses

1
Animal Senses

• How do animals detect environmental stimuli?

2
Remember!

• Sensory stimulation is the starting point of
  behaviour.
• Animals senses are not necessarily the same as
  ours.

3
Photoreceptors

• In animals light is detected by?
• The eyes
• The structure of the eye varies for different
  organisms.

4
(No Transcript)
5
Structure of Eyes

• Snails
• Have simple eyes which detect light in the same
  way as we detect heat.
• Insects and Crustaceans
• Have compound eyes made up of many separate
  ommatidia. These give a mosaic vision, very good
  for detecting movement.

6
Compound Eyes
7
Structure of Eyes

• Vertebrates
• Have lenses that help to form clear images.
• If two eyes face forwards they have overlapping
  fields (Binocular vision) enabling good judgement
  of distance

8
Vertebrate Eyes
9
Vertebrate Eyes
10
Structure of Eyes

• Night Vision
• This involves a structure called the tapetum,
  this is a layer of silvery crystals that acts as
  a reflector allowing animals like cats to pick up
  50 more light at night than humans can detect.
• This is why cats eyes glow in the dark.

11
Night Vision
12
Vision

• Animals also use their vision to detect movement,
  speed of movement, shapes etc.

13
Colour Vision

• We, as humans see violet, indigo, blue, green,
  yellow, orange and red parts of the light
  spectrum.
• Bees see ultraviolet light but are less sensitive
  to red. This is why most red flowers have some
  blue or a strong scent.

14
How bees see
15
Colour Vision cont

• Goldfish can see far red light.
• Sea birds are particularly sensitive to red
  light.

16
Sea Birds Vision
17
Thermoreceptors

• Infra-red light is a form of heat.
• No animal can see infra-red with eyes, but
  certain animals can detect warm objects as if
  they can see them.
• E.g. snakes

18
Snakes Heat Sensors

• Snakes have 2 heat sensing pits in front of and
  slightly below their eyes these are so accurate
  the snakes can strike prey in pitch dark.

19
Thermoreceptors

• Humans can detect heat with their skin.
• Other animals e.g. mosquitoes home in on their
  prey using thermoreceptors.

20
Mechanoreceptors

• These sense gravity, touch, pressure, stretch and
  movement.
• These let the animal know which way is up.
• They help recognition of the position of one part
  of the body in relation to another. This is
  important for coordinated movement.

21
Mechanoreceptors Cont

• Touch, pressure and the texture of objects in the
  environment, plus the tension in internal organs
  such as the stomach or bladder, are the functions
  of these receptors.

22
Mechanoreceptors cont

• The skin of humans has tactile receptors.
• Sometimes animals have hairs with receptors at
  the base, like whiskers in cats

23
Cats whiskers
24
Mechanoreceptors cont

• Some animals have special sense organs called
  statocysts that serve as gravity receptors.

25
Mechanoreceptors cont

• Fish have a lateral line organ that runs the
  length of the body. This consists of hairs with
  their tips enclosed in a jelly-like substance.
  These respond to waves, currents or disturbances
  in the water.

26
Lateral Line
27
Mechanoreceptors cont

• Proprioreceptors are sense organs that respond to
  tension in the muscles or joints.

28
Chemoreceptors

• Olfaction (smell)
• this is the detection of chemicals in the air or
  water that diffuse towards or are swept towards
  the animal
• Used for the preliminary examination of things at
  a distance.

29
Chemoreceptors

• Gustation (taste)
• the detection of chemicals in the liquid or solid
  state.
• For the examination of objects that have been
  touched.
• Four basic tastes sweet, sour, salty and bitter

30
Human Tongue
31
Gustation Cont

• These are located in different areas of the
  tongue.

32
Chemoreceptors

• The distinction between smell and taste becomes
  blurred in simpler animals.
• Humans use their noses and tongues.

33
Chemoreceptors

• Flies have taste hairs on their feet.
• Many insects smell using antennae.

34
Chemoreceptors

• Reptiles have a small opening in the head, this
  opens into the roof of the mouth.
• This is called the Jacobsons organ.

35
Jacobsons Organ
36
Chemoreceptors

• A snake flicking out its forked tongue is
  collecting chemical samples and bringing them
  back to the Jacobsons organ for analysis.

37
Pheromones

• These are chemicals used to communicate between
  members of the same species.
• Members of the same species have receptors to
  pick up these pheromones, other species ignore
  them.

38
(No Transcript)
39
Auditory Receptors

• In humans sound waves cause the eardrum to
  vibrate, these vibrations are transmitted across
  the middle ear by 3 small bones
• This sets up vibrations in the fluid-filled
  cochlea.
• This initiates impulses in the auditory nerve and
  we finally hear with our brain.

40
Human Ear
41
Auditory Receptors

• Humans can hear from 20 Hz to 20 000 Hz. Sound
  above that is ultrasonic.
• Bats use ultrasonic bleeps as a form of sonar.
• Dogs and many insects hear in the ultrasonic
  range.

42
Auditory Receptors

• Whales use a complicated communication system
  involving ultrasonic sounds, echo-location and
  very low sounds called infrasounds (travel for
  long distances)

43
(No Transcript)
44
Auditory Receptors

• Elephants and Hippos use infrasound waves to
  communicate over long distances.

45
Detection of Electric Fields.

• Certain species stun their prey with an
  electric shock e.g. eels
• Certain fish create an electric field around
  themselves, allowing them to pick up any
  disturbances in the field.

46
(No Transcript)
47
Detection of Magnetic Fields.

• Homing pigeons can detect the magnetic field
  lines of the earth, they use this to navigate
  during migration or homing.

48
Questions

• Name the colours of light we can see.
• Which cells see colour and which see black and
  white?
• Two eyes facing forward . Vision which is good
  for judging
• Insects have .. Eyes made up of many . Which
  give vision.
• Snakes can see .. With small pits set
  under their ..

49
Questions Cont

• A gravity-detecting organ in invertebrates is
  called a It consists of a round cavity with
  small .., and placed on these is a small, hard,
  pebble-like object called a ..
• In fish the ... .. Organ detects disturbances
  in the water.
• Name 5 ways that animals use chemicals.

50
Questions Cont

• Sounds above those that humans can hear are
  called .., and those below are called.
• Some fish living in muddy conditions use .
  to test the world around them.