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| Question | Answer |
| Identify the role of receptors in detecting stimuli. | The roles of receptors are to detect stimuli within the surrounding environment. Once a stimulus has been detected by the organism it will respond. For example if the thermoreceptors on your skin detect cold air you will begin to shiver to maintain your body heat. Receptors are also classified on the basis of their function, they are as follows: Chemoreceptors: detect chemicals. Electromagnetic receptors: change in electromagnetic field, E.G. light receptors in eye. Mechanoreceptors: detect mechanical features such as pressure, touch, stretch. Pain receptors: detect pain. Thermoreceptors: detect change in temperature. |
| Explain that the response to a stimulus involves: - stimulus - receptor - messenger - effector - response | A stimulus is something that produces a response in the organism. For example if you were suddenly exposed to bright light (stimulus) the photo - receptors in the eye (receptor) send a message to the central nervous system (CNS - messenger) which then in turn sends a message to the muscles in the eye (effector) for the muscles to contract which then elicits the response of blinking (response). This process applies to all stimulus/response actions. |
| Explain that the response to a stimulus involves: - stimulus - receptor - messenger - effector - response |
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| Identify data sources, gather and process information from secondary sources to identify the range of senses involved in communication. | There are five main senses which are involved in communication, which are seeing, hearing, touch, taste and smell. Seeing (OCCULAR): or sight involves the use of an eye. An eye contains many structures which allow certain amounts of light as well as different electromagnetic waves to pass in and out of the eye. The organism reacts to these changes by relaying a message via the optic nerve to the brain to either allow more or less light/electromagnetic waves into the eye. Hearing (AUDITORY): involves the use of ears. The ear contains many structures which allow certain frequencies of noise to enter the ear and to be deciphered by the brain. Touch (SOMATOSENSORY SYSTEM): involves the use of mechanoreceptors, pain receptors and thermoreceptors. These receptors are usually found on the skin of the organism and enable the organism to enjoy certain stimulus and to avoid certain stimulus. Taste (GUSTATION): refers to the ability of being able to taste foods and chemicals entering the mouth. Taste involves the use of chemoreceptors which detect chemicals within the food. There is said to be 4 aspects of taste; sweet, sour, salty, bitter. Smell (OLFACTION): smell is the ability of an organism to perceive odours or smells. Chemoreceptors are found in the nose which has the ability of detecting these smells. |
| Describe the anatomy and function of the human eye, including the: - conjunctiva - cornea - sclera - choroid - retina - iris - lens - aqueous and vitreous humor - ciliary body - optic nerve | Conjunctiva - A delicate membrane that covers the surface of the eye and the inside of the eyelids. > Protects the front part of the eye. Cornea - The front part of the eyeball which is transparent and quite thick. > Refracts light rays as they pass through it. Sclera - Continuous with the cornea but not transparent, it forms the tough, white outer back part of the eyeball. > Protects the eye and helps maintain eye shape. Choroid - The choroid lies on the inside of the sclera. It is a thin black layer which contains many blood vessels. > The pigment absorbs stray light preventing stray images. Retina - The innermost layer of the eye. It lines the back of the eyeball with a network of photoreceptors and nerve fibres. > Receives the light images and translates this into electrical impulses which are sent to the brain and deciphered. Iris - The coloured part at the front of the eye containing many fibrous muscles.> Regulates the amount of light entering the eye. Lens - A transparent biconvex protein disc behind the pupil. > Refracts and bends light rays towards the retina. Aqueous and Vitreous Humor - Aqueous humor a vitreous substance fills the front chamber of the eye. Vitreous humor a jelly – like substance fills the back chamber of the eye. > Keeps the eyeball in shape as well as refracts light towards the retina. Ciliary Body - Connects the choroid with the lens. It contains suspensory ligaments as well as ciliary muscles. > Holds the lens in place as well as altering the shape of the lens depending on the distance of an object. Optic Nerve - Connects the eyeball to the brain. Where the optic nerve connects to the brain is known as the blind spot as no image can be made or processed due to the lack of photoreceptors. > Carries nerve impulses to the visual cortex of the brain so images can be translated. |
| Identify the limited range of wavelengths of the electromagnetic spectrum detected by humans and compare this range with those of other vertebrates and invertebrates. | The electromagnetic spectrum is a range of energy forms which all travel at the speed of light. However these energy forms vary in wavelength and frequency. Humans detect visible light which ranges from 400nm to 700nm. This means that humans can only see objects within this wavelength. In comparison snakes use infrared light to detect prey and to avoid predators. Infrared light falls between 750nm to 1mm. Bees use ultraviolet light to detect petals on plants. This leads the bees to a food source (nectar). U.V. light ranges from 10nm to 400nm. |
| Use available evidence to suggest reasons for the differences in range of electromagnetic radiation detected by humans and other animals. | There are many different reasons as to why humans detect a different range of the electromagnetic spectrum in comparison to that of other animals. The reasons are as follows: • Many organisms live in different niches. These niches produce different obstacles for the organism. Each organism needs to detect predator and prey within their environment to survive. This may come in the form of a different electromagnetic field. • For example electric eels emit an electric field within their environment. Any disturbance to this environment such as that by prey is detected by the eel. Subsequently the prey is consumed. Eels use this form of electromagnetic radiation as vision within a water environment is quite poor. • The platypus has electromagnetic receptors in its bill. This helps the platypus to detect prey which produces an electric field. Platypuses use these receptors as vision within a water environment is quite poor. • Snakes use infrared light to detect predators and prey. This is due to the fact that snakes are largely found on the ground and in the underbrush of bushland. Snakes rarely use normal vision due to the lack of periphery on the ground. • Bees use ultraviolet light in detecting the nectar on flowering plants. This form of electromagnetic radiation is an advantage as the bee is able to quickly and efficiently detect a food source. • Humans use two single lens eyes to detect visible light. Humans have many photoreceptor cells of different pigment which detect the various colours of the spectrum. This form of electromagnetic radiation enables humans to produce sharp images of various objects. • It is evident that depending on the organism and its environment organisms have adapted various electromagnetic fields to detect predators and prey. |
| Identify the conditions under which refraction of light occurs. | Light refraction occurs when a light wave travels from a higher density to a lower density or a lower density to a higher density. An example of refraction is light waves travelling from air to water. |
| Identify the cornea, aqueous humor, lens and vitreous humor as refractive media. | Refraction occurs in the eyeball where light waves are bent towards the retina to from an image. This refraction occurs with the use of refractive media. The refractive media in the eye include: - cornea - aqueous humor - lens - vitreous humor |
| Identify accommodation as the focusing on objects at different distances, describe its achievement through the change in curvature of the lens and explain its importance. | Accommodation is the process by which the lens changes shape according to the distance of an object of which it is focusing on. This process is possible due to the lens altering its curvature. If an object is less than six meters away the ciliary body will contract causing the lens to bulge. This in turn will cause the lens to refract the light at a greater angle. The effect of this is a greater sharper image. In contrast if you were to look at an image one hundred meters away the ciliary body relaxes, this cause the lens to elongate, this causes the lens to refract the light at a smaller angle. The effect of this process allows for a sharper image. Therefore accommodation allows humans to focus on objects at varying distances. |
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