Chapter 38: Sense Organs AP Curriculum Alignment Big Idea 1 technically requests that students be able to choose a eukaryotic structure, such as the brain, to provide evidence that organisms continue to evolve. Because the sensory organs send information to the brain for interpretation and initiation of a response, the evolutionary history of the senses is reflected in how the brain has evolved over time. Chapter 38 details sensory perception is simple organisms as well as in the human. ALIGNMENT OF CONTENT TO THE CURRICULUM FRAMEWORK Big Idea 1: The process of evolution drives the diversity and unity of life. Enduring understanding (EU) 1.C: Life continues to evolve within a changing environment. Essential knowledge (EK) 1.C.3: Populations of organisms continue to evolve. b. Scientific evidence supports the idea that evolution continues to occur. To foster student understanding of this concept, instructors can choose an illustrative example such as: Chemical resistance (mutations for resistance to antibiotics, pesticides, herbicides or chemotherapy drugs occur in the absence of the chemical) Emergent diseases Observed directional phenotypic change in a population(grants observations of Darwin s finches in the Galapagos) A eukaryotic example that describes evolution of a structure or process such as heart chambers, limbs, the brain and the immune system Concepts covered in Chapter 38 also align to the learning objectives that provide a foundation for the course, an inquiry-based laboratory experience, class activities, and AP exam questions. Each learning objective (LO) merges required content with one or more of the seven science practices (SP), and one activity or lab can encompass several learning objectives. The learning objectives and science practices from the Curriculum Framework that pertain to sense organs are shown in the table below. Note that other learning objectives may apply as well. LO 1.26 The student is able to evaluate given data sets that illustrate evolution as an ongoing process. LO 3.43 The student is able to construct an explanation, based on scientific theories and models, about how nervous systems detect external and internal signals, transmit and integrate information, and produce responses. LO 3.44 The student is able to describe how nervous systems detect external and internal signals. LO 3.45 The student is able to describe how nervous systems transmit information. LO 3.46 The student is able to describe how the vertebrate brain integrates 536 Mader, Biology, 12 th Edition, Chapter 38
information to produce a response. LO 3.47 The student is able to create a visual representation of complex nervous systems to describe/explain how these systems detect external and internal signals, transmit and integrate information, and produce responses. LO 3.48 The student is able to create a visual representation to describe how nervous systems detect external and internal signals. LO 3.49 The student is able to create a visual representation to describe how nervous systems transmit information. LO 3.50 The student is able to create a visual representation to describe how the vertebrate brain integrates information to produce a response. Key Concepts Summary Evolution of sensory systems Selective pressures have resulted in the evolution of the many different types of sensory receptors, which are specialized cells capable of detecting changes in internal or external conditions, and of communicating that information to the central nervous system. Sensory transduction is the process by which a sensory receptor convers an event or stimulus into a nerve impulse. No difference occurs between the nerve impulses generated by different types of sensory receptors all these impulses are simply the action potentials. The interpretation of these nerve impulses by appropriate areas of the brain brings about a response that is appropriate for the particular type of stimulus. Not all of these sensory impulses are received at the conscious levels of the brain. The extent to which nonhuman animals have perceptions is largely unknown. Chemoreception Chemoreception is found almost universally in animals and is therefore believed to be the most primitive sense. o Chemoreceptors in planarians are concentrated in the auricles located on the sides of the head. o Insects also detect airborne pheromones, which are chemical messages passed between individuals. o In crustaceans, chemoreceptors are widely distributed on their appendages and antennae. o Snakes possess Jacobson s organs, a pair of sensory organs in the roof of the mouth. Humans have five main types of taste receptors on the tongue: sweet, sour, salty, bitter, and umami. In humans, the sense of smell, or olfaction, is dependent on between 10 and 20 million olfactory cells. These structures are located within olfactory epithelium high in the roof of the Mader, Biology, 12 th Edition, Chapter 38 537
nasal cavity The olfactory bulbs have direct connections with the limbic system and its centers for emotions and memory. The sense of taste and the sense of smell work together to create a combined effect when interpreted by the cerebral cortex. Vision Some animals lack photoreceptors, sensory receptors that are sensitive to light, and instead depend on senses such as smell and hearing. o Arthropods have compound eyes composed of many independent visual units that are each capable of photoreception. o Many insects can see some ultraviolet rays which enables them to locate the particular parts of flowers, such as nectar guides, that have ultraviolet patterns. o Animals whose eyes face forward have stereoscopic vision. o Animals with their eyes on the side of their head have panoramic vision which is an advantage for prey animals as it allows early detection of predators. In the human eye, focusing starts at the cornea and continues as the rays pass through the lens. o The lens provides additional focusing power as the shape of the lens is changed by the ciliary muscle. o Sensory transduction occurs once light has been focused on the photoreceptors in the retina. o The optic nerves carry nerve impulses from the eyes to the optic chiasma, a point of crossover. o The image arriving at the thalamus in the visual area has been split because the left optic tract carries information about the right portion of the visual field and the right optic tract carries information about the left portion of the visual field. o The right and left visual areas must communicate with each other for us to see the entire visual field. o The image is inverted and reversed onto the retina so it must be righted in the brain for us to correctly perceive the visual field. Common disorders of vision include diseases of the retina, glaucoma and cataracts, and problems with visual focus. Hearing The evolutionary advantage of hearing is that it allows animals to receive information at a distance, as well as from any direction. Hearing plays an important role in avoiding danger, detecting prey, finding mates, and communication. Hearing is caused by the vibration in a surrounding medium that resonates in some part of an animal s body. o Fish have a lateral line system with special cells that sense vibrations in the water. 538 Mader, Biology, 12 th Edition, Chapter 38
o Bats, dolphins, and whales are capable of echolocation, meaning they can produce very high frequency sounds, and then learn about objects in their environment by listening for echoes. The human ear has two sensory functions: hearing and balance (equilibrium). o The process of hearing begins when sound waves enter the auditory canal. And strikes the tympanic membrane causing it to vibrate. o The malleus passes the vibration by means of the incus to the stapes in such a way that the pressure is multiplied about 20 times as it moves. o The stapes strikes the membrane of the oval window, causing it to vibrate, and in this way, the pressure is passed to the fluid within the cochlea. o When the stapes strikes the membrane of the oval window, pressure waves move hair cells that synapse with nerve fibers of the auditory nerve and are carried to the b rain. o The three semicircular canals of the inner ear provide sensory input for balance. o The brain uses information from the semicircular canals to maintain equilibrium through appropriate motor output to various skeletal muscles that can right our position in space as need be. Most cases of hearing loss can be attributed to the effect of years of frequent (and preventable) exposure to loud noise. Some types of deafness can be present at birth. Several genetic disorders can interfere with the ability to hear, Key Terms blind spot camera-type eye cataracts chemoreceptors choroid ciliary muscle cochlea compound eyes cone cells conjunctiva cornea cutaneous receptors electromagnetic receptors farsighted (hyperopic) glaucoma gravitational equilibrium inner ear iris lateral line lens macular degeneration mechanoreceptors middle ear nearsighted (myopic) olfactory cells ossicles otoliths outer ear panoramic vision photoreceptors pupil retina retinal detachment rhodopsin rod cells rotational equilibrium saccule sclera semicircular canals sensory receptors sensory transduction stereoscopic vision taste buds thermoreceptors tympanic membrane utricle vertigo vestibule Mader, Biology, 12 th Edition, Chapter 38 539
Teaching Strategies Class time: Two 45-minute class periods Day 1: Lecture on sensory organs 20 minutes Activity 1, eye anatomy and function 25 minutes Day 2: Activity 2, evolution of sensory organs 45 minutes Suggested Approaches All of the sensory organs and their evolution and function are illustrative examples. Allow students to choose one sensory organ to concentrate on and learn how it functions and how it has changes from the most ancient animals to humans. Student Misconceptions and Pitfalls Some students still believe that each sensory organ is capable of receiving sensory input, interpreting that information, and providing the proper response to the information that was obtained through that organ. Students do not tend to perceive that the brain must interpret these sensory signals and provide the stimulus for appropriate action. 540 Mader, Biology, 12 th Edition, Chapter 38
Suggested Activities Activity 1: Eye Anatomy and Function Have students go the following website to learn how the eye functions: http://www.lensshopper.com/eye-anatomy.asp Activity 2: The Evolution of Sensory Organs Have students pick one sensory organ and explain how this organ originated in its simplest form, trace it through several animals, and explain how that organ functions in humans. Mader, Biology, 12 th Edition, Chapter 38 541
Student Edition Chapter Review Answers Answers to Assess Questions 1. c; 2. c; 3. b; 4. c; 5. b; 6. a; 7. d; 8. c; 9._a. retina contains photoreceptors; b. choroid absorbs stray light; c. sclera protects and supports eye; d. optic nerve transmits impulses to brain; e. fovea centralis makes acute vision possible; f. muscle in ciliary body holds lens in place, also accommodation; g. lens refracts and focuses light rays; h. iris regulates light entrance; i. pupil admits light; j. cornea refracts light rays; 10. b; 11. d; 12. b; 13. c; 14. c; 15. a; 16. c; 17. c; 18. c Answers to Applying the Big Ideas Questions 1. A rare species of bat lives in two discreet populations in neighboring countries. Karst landscape evidence suggests that the two populations were at one time connected but are now isolated from one another. While the two species look similar, they each have developed their own echolocation call which influences communication within each population. (a) Describe which data could be used as evidence for the two bat populations diverging into two species. (b) Explain how the data about these small bats would provide a direct answer to the question, how do scientists know that an organism is currently experiencing the process of evolution? Essential Knowledge Science Practice Learning Objective 1.C.3: Populations of organisms continue to evolve. 5.3: The student can evaluate the evidence provided by data sets in relation to a particular scientific question. 1.26: The student is able to evaluate given data sets that illustrate evolution as an ongoing process. (5.3) 542 Mader, Biology, 12 th Edition, Chapter 38
3 points maximum. Explanations for how the data supports the idea of evolution as an ongoing process may include: Description of data as evidence for speciation (1 point each) Scientists are able to know the history of a species by looking at the history of its habitat through geographic and geologic data, and are able to gain understanding of past behaviors. One example of this is seen in the karst landscape between the two bat populations. Scientists can then compare the geologic and geographic history to what is observed presently. If the organisms within the original larger population were no longer able to communicate with echolocation, this could be a mating and reproductive barrier. The biological species concept would say that the two populations could become separate species if they are no longer able to reproduce. Explanation of evidence for evolution as ongoing process (1 point each) Scientists may not know whether it was the geographic isolation or the divergence in their sensory systems that was the original barrier to gene flow, but either way, the two populations no longer experience gene flow, which is a contributor to evolution. Scientists are able to observe and document current competition and mating behaviors within and between populations, as well as analyzing genotypes, in order to determine discreet species or they can evaluate the similarities and differences between populations. This could be done with the bat populations with intensive trapping, sampling and acoustic recording of their echolocation calls. Answers to Applying the Science Practices Questions Think Critically 1. Males respond more to polarized light from female wings than they do to nonpolarized light. 2. Possible answer: Forest-dwelling butterflies have iridescent wings to reflect any light that filters through the tree leaves. Meadowdwelling butterflies are exposed to large amounts of light and iridescent wings are not useful. Mader, Biology, 12 th Edition, Chapter 38 543
Additional Questions for AP Practice 1. Describe the sensory reception of smells. 2. Describe one disease of that can interfere with sight. 3. Give a detailed description of the movement of sound to the brain. 4. The ability of the eye to adjust the amount of light entering the eye is A) a reflex. B) a learned response. C) consciously controlled. D) accommodation. 544 Mader, Biology, 12 th Edition, Chapter 38
Answers to Additional Questions for AP Practice 1. Olfactory cells end in cilia that bear receptor proteins for specific odor molecules. The cilia of each olfactory cell can bind to only one type of odor molecule and stimulate that odor molecule to be stimulated. Neurons designated for that odor molecule in the olfactory bulb are activated. The primary olfactory area of the cerebral cortex interprets the pattern of stimulation to produce a certain perception of odor. 2. Answers will vary, and may include glaucoma, macular degeneration, retinal detachment or cataracts. 3. The process of hearing begins when sound waves enter the auditory canal and strikes the tympanic membrane causing it to vibrate. The malleus passes the vibration by means of the incus to the stapes in such a way that the pressure is multiplied about 20 times as it moves. The stapes strikes the membrane of the oval window, causing it to vibrate, and in this way, the pressure is passed to the fluid within the cochlea. When the stapes strikes the membrane of the oval window, pressure waves move hair cells that synapse with nerve fibers of the auditory nerve and are carried to the b rain. 4. The correct answer is A. Mader, Biology, 12 th Edition, Chapter 38 545