HSC Option

Communication

1. Humans and other animals, are able to detect a range of stimuli from the external

environment, some of which are useful for communication

• Identify the role of receptors in detecting stimuli

•A stimulus is a change in the external or internal environment of an organism. Organisms detect these changes using receptors. There are many different types of receptors that are used to detect different types of stimuli. Receptors are commonly associated with sense organs.

The Senses

• Humans have 5 senses. Sight, hearing, taste, touch, smell. Each sense has a different role in communication. The role of some senses is more significant than others in effective communication.

• Some species utilise senses that humans often under utilise. The sense of smell for example, is very important to dogs and other animals. A dog has a much better sense of smell than humans. It has recently been discovered that humans use their sense of smell extensively to attract members of the opposite sex by releasing pheromones. Other animals also produce pheromones for different purposes.

Stimulus Sense Organ Receptors Function Sense

Light Eye PhotoreceptorRods and

Cones on retina

Detect Light and colour

Sight

Sound Ear Mechanoreceptor

Hairs in organ of Corti

Detect sound waves

Hearing

Pressure Skin Mechanoreceptor

In skinDetect pressure

on skinTouch

Chemical Tongue Chemoreceptors

in taste budsDetect dissolved

moleculesTaste

Chemical Nose Chemoreceptors

in nasal passages

Detect chemicals in the

air

Smell

•Explain that the response to a stimulus involves:

- stimulus, receptor, messenger, effector, response

• When a stimulus occurs it is detected by a receptor. The receptor sends a message to the CNS. The CNS sends a message to the effector which in turn creates a response.

2. Visual communication involves the eye registering changes in the

immediate environment

• Identify the limited range of wavelengths of the electromagnetic spectrum detected by humans and compare this with range with those of other vertebrates and invertebrates.

•The electromagnetic spectrum is a range of energy forms that all travel in waves at the speed of light. They all have different frequencies and wavelengths. Visible light is one type of electromagnetic radiation.

The Electromagnetic Spectrum

• The energy in the electromagnetic spectrum is able to produce changes in electric and magnetic fields. It includes things such as radio waves, TV waves, microwaves, visible light, infrared and x-rays.

• Visible light (380 – 780nm) is the only part of the spectrum that is able to be detected by humans. It is only at these wavelengths that the rods and cones of the eye are activated.

• The waves of the electromagnetic spectrum can travel through a vacuum (no other particles present) unlike sound waves that require a medium in which to travel.

• The speed at which visible light travels may be altered as it moves in and out of different substances. This property was used by Isaac Newton to demonstrate that white light is made of all colours in the spectrum of visible light. (ROY G BIV) Red, Orange, Yellow, Green, Blue, Indigo, Violet. Most humans can see all colours of the spectrum but studies have demonstrated the greatest sensitivity to light in humans is to colours in the green range of the spectrum.

Range of Wavelengths Detected in Vertebrates

• Humans are said to be trichromatic. This means that we are able to detect wavelengths in three main regions of the spectrum. Red, green and blue. Many other mammals do not possess good colour vision.

• Birds have been found to be tetrachromatic. Some may be pentachromatic. Birds are able to detect light in the UV range as well as the blue, green and red regions.

• Some reptiles and rodents are also able to detect light in the UV range.

Range of Wavelengths detected in Invertebrates

• Many studies have been conducted with bees. It has been found that bees are able to detect light in the UV spectrum but not the red region of the visible spectrum of colour.

• Butterflies have up to 5 colour receptors in the eye indicating that they are able to see a greater range of colours than humans including the UV light range.

• Ants and other insects are able to see in the UV light region of the electromagnetic spectrum.