This Document Contains Experiments 38 to 40 Name____________________________________________________Section________________Date___________ Experiment 38: Human Variation Invitation to Inquiry Historically there has been much interest in what are called racial differences. Analyze the concept of race from a purely biological point of view. Do not include differences in culture such as hair styles, speech patterns, types of family units, religious preference, or similar factors. Does race in the human population have meaning from a purely biological point of view? Background Have you ever wondered why people vary so much in appearance, even when they are closely related? These differences exist because all individuals inherit unique combinations of genes from their parents. This variety is possible because there are often many different alleles (alternative forms of a gene) for a specific characteristic within a population and they are mixed in new combinations during sexual reproduction. Each child receives one-half of its genetic information from each parent. More accurately, each parent contributes one allele for each genetic locus (the specific location of a gene on a chromosome). However, because of meiosis even children of the same parents will receive a different set of genes from each parent. (Identical twins are an exception because they are the result of a single fertilization event.) Several different patterns of inheritance have been documented. Because each individual gets one allele for each characteristic from each parent, the two alleles must either be the same or different. When both alleles for a characteristic are identical the individual is said to be homozygous. If the two alleles for a characteristic are different the individual is said to be heterozygous. Many alleles are dominant, which means they mask or hide the expression of recessive alleles. Put another way, dominant alleles are expressed, even when present in just a single dose. Recessive alleles can be expressed only when dominant alleles are absent. In some cases, two alleles may not show dominance or recessiveness and both express themselves, a condition known as incomplete dominance (lack of dominance). Often such heterozygous cases result in phenotypic characteristics that are intermediate between the two homozygous genotypes. Many characteristics have only two alleles available in the population. However, many cases of multiple alleles exist in which there are many alleles for a characteristic within a population although an individual can only have a maximum of two of the alleles, one having been inherited from each parent. Other traits, such as beard growth, are sex-limited, which means their expression is limited to one sex or the other. Other human traits are not determined by a single set of alleles and show a wide variety of phenotypic expressions among the individuals in a population. These traits are thought to be controlled by many sets of alleles (genes) that are located at different loci and these traits are called polygenic characteristics. Some traits are influenced by the action of genes at two or more loci. For example, the alleles that determine hair color or skin color are affected by another set of alleles that determines whether a person can produce pigment or is an albino. This phenomenon, genes at one locus influencing how the genes at another locus are expressed, is what geneticists call epistasis. This laboratory activity provides an opportunity to observe how alleles are passed from one generation to the next and how combinations of alleles determine the phenotype of offspring. This exercise will also illustrate how each of the topics discussed earlier (dominant-recessive, incomplete dominance, multiple alleles, sex-limited, polygenic, and epistasis) influences the pattern of inheritance. In this exercise you will choose a partner of the opposite sex. The two of you will be the parents of an offspring. (If there are unequal numbers of males and females in the class, your instructor may designate you to be a particular sex for the purposes of this laboratory.) “Parents” will be assumed to be heterozygous for characteristics and will flip coins to simulate segregation of alleles during the formation of gametes. Alleles that are on different chromosomes are segregated independently of one another. This independent assortment of chromosomes during the formation of gametes will be simulated by additional flips of coins. We will use facial characteristics in this exercise and you will draw a picture of what the child would look like in his or her teens. The exact manner in which human facial characteristics are determined is often difficult to determine. Some of the characteristics are inherited in exactly the manner suggested and are indicated with a footnote. Others are assumed to be inherited in the manner suggested and are indicated with an asterisk (*). Others are useful for the laboratory exercise and are assumed to be inherited, but the manner of inheritance is not understood; these characteristics will not have a footnote or asterisk. In this lab exercise you will: Flip coins to determine which alleles are passed to your offspring and determine the genotype of your offspring. Record your data on the data sheet on page 335. Make a drawing of your offspring’s phenotype based on the genotype obtained. Share your data with the class and compute the genotypic and phenotypic ratios for certain characteristics using the data from the entire class. Examine different modes of inheritance including simple dominance and recessiveness; incomplete dominance; multiple alleles and sex-limited, polygenic, and epistatic traits. Compute a gene frequency from a set of data. Use chi-square analysis to determine if deviation from the expected Mendelian ratios could be due to chance alone. Procedure Pair up with a classmate who will play the role of your spouse. Begin the simulation with the assumption that each of you has one dominant and one recessive allele for each of the facial features illustrated on the following pages. In other words, each of you is heterozygous for each trait. To determine which allele you will pass on to your child, both you and your spouse flip a coin. “Heads” determines that a dominant allele is present in the gamete and is passed on to the offspring. “Tails” determines that a recessive allele is present in the gamete and is passed on to the offspring. Thus, if your partner flips heads and you flip tails, the child’s genotype for that trait would be heterozygous (Aa). If you both flip heads, the child’s genotype would be AA, and if you both flip tails, the child’s genotype would be aa. First we should determine the sex of the child. Females have two X chromosomes and males have an X and a Y chromosome. Which parent determines the sex of the child? All egg cells have X chromosomes, but half of the sperm have Y chromosomes and half have X chromosomes. If a sperm cell bearing a Y chromosome fertilizes an egg, a male (XY child) will result; if a sperm bearing an X chromosome fertilizes an egg, a female (XX child) will result. Therefore, in this simulation, only the father needs to flip the coin to determine the sex of the child. If heads is flipped, your child is a boy (Y-bearing sperm) and if tails is flipped, your child is a girl (X-bearing sperm). Give your child a name and record this information on the data sheet. Both you and your partner should flip a coin for each facial feature. Record (a) the alleles contributed by each parent, (b) the genotype of the offspring, and (c) the phenotype of the offspring on the data sheet. Facial Traits Face shape: RR or Rr = round face; rr = square face. Round face (RR, Rr) Square face (rr) Chin size: PP or Pp = very prominent chin; pp = less prominent chin. Very prominent chin (PP, Pp) Less prominent chin (pp) Chin shape: Only flip coins for this trait if chin size genotype is PP Pp. The genotype pp prevents the expression of chin shape. CC or Cc = round chin; cc = square chin. Round chin (CC, Cc) Square chin (cc) Cleft chin: 11900 AA, or Aa = cleft chin; aa = no cleft chin. Present (AA, Aa) Absent (aa) Skin Color Skin color*: To determine skin color, assume there are three sets of alleles, located at three different loci, that contribute to the amount of pigment produced. Both you and your partner should flip coins to determine the genotype of the first pair of alleles (AA, Aa, aa). Then flip again to determine the genotype of the second pair of alleles (BB, Bb, bb). Flip for the last time to determine the third pair of alleles (CC, Cc, cc). Determine the phenotype of your offspring based on the following polygenic model: Six dominant alleles—very dark black Five dominant alleles—very dark brown Four dominant alleles—dark brown Three dominant alleles—medium brown Two dominant alleles—light brown One dominant allele—light tan Zero dominant alleles—fair skin Example: If you flipped heads for the first two sets of alleles and tails for the third set of alleles, and your partner flipped tails for the first set of alleles and heads for the second and third sets of alleles, your offspring’s genotype would be AaBBCc and your offspring’s phenotype would be dark brown. Hair Traits–Next Four Flips White forelock*: A tuft of hair over the forehead is white.FF, or Ff = white forelock; ff = no white forelock Widow’s peak*: The hairline comes to a point in the center of the forehead.WW, or Ww = widow’s peak present; ww = widow’s peak absent Present (WW, Ww) Absent (ww) Hair type and hair color*: Hair type and hair color are determined by multiple alleles. To determine which alleles you have and are able to contribute to your offspring your instructor will have designated each individual in class as belonging to one of five groups. From the “Special Characteristics Chart” determine your genotype and which alleles you may pass to your offspring. The alleles for hair type are SK = kinky, SC = curly, SW = wavy, and SST = straight. They exhibit dominance and recessiveness in the order given. Kinky is dominant to all other alleles, straight is recessive to all other alleles. Curly is recessive to kinky but dominant to wavy. Wavy is recessive to kinky and curly and dominant to straight. The alleles for hair color are CBK = black, CBR = brown, CBD = blond, and CR = red. They exhibit dominance and recessiveness in the order given. Determine the hair type and hair color of your offspring by flipping coins. Special Characteristics Chart Group Assigned by Instructor Hair Type Genotype Hair Color Genotype Albinism Genotype Group 1 K S SC BK BR C C aa Group 2 S SK ST C CBK R AA Group 3 C W S S BR BD C C AA Group 4 C ST S S BR R C C Aa Group 5 S SW ST BD R C C Aa Once you have determined your genotype for hair type and color, complete the following chart. Trait My Genetic Information My Partner’s Genetic Information Genotype Phenotype Genotype Phenotype 8a. Hair Type 8b. Hair Color Now flip your coins to determine which hair type and hair color alleles each of you will pass on to your offspring. Albinism: Albinos are not able to produce pigment. Therefore none of the skin color, hair color, or eye color genes can express themselves if an individual is an albino. The recessive gene for albinism is rare in the population. To determine your genotype for the ability to produce pigment, refer to the Special Characteristics Chart. Once you have determined your genotype and phenotype, complete the following chart. Trait My Genetic Information My Partner’s Genetic Information Genotype Phenotype Genotype Phenotype Pigment production Determine if your child is an albino by flipping coins based on the genotype you were assigned. If you are homozygous you do not need to flip a coin because you can only pass on one type of allele. If your child is an albino, all color characteristics will be altered: eyes will be pink because there is no pigment in the iris, the skin will be very pale white/pink because there is no pigment, and all hair (on head, eyebrows, eyelashes, etc.) will be white regardless of the other color alleles he/she may have inherited. Also, white forelock will not show because all hair will be white and freckles will not show because no pigment is produced in the skin. Albinism is inherited in the following manner: AA or Aa = normal pigment; aa = no pigment (albino) Eyebrow Traits—Next Two Flips Eyebrow thickness: BB = very bushy; Bb = intermediate; bb = very thin. Bushy (BB) Intermediate (Bb) Very thin (bb) Eyebrow placement: NN or Nn = not connected; nn = connected Not connected (NN, Nn) Connected (nn) Eye Traits Eye color: Dark brown eyes are produced by the presence of a layer of brown pigment that covers the entire surface of the iris. Lighter eyes (hazel) are caused by patches of brown pigment on the iris. Blue eyes are caused by the absence of pigment on the iris. In this situation, the dominant allele S is for solid pigment and the recessive allele s is for patchy pigment. The dominant allele B is for the presence of brown pigment and the recessive allele b is for the absence of brown pigment. To determine eye color, both you and your partner will need to flip twice. Determine the genotype of the first pair of alleles (SS, Ss, ss) and then the second pair of alleles (BB, Bb, bb). Determine the phenotype of your offspring according to the following guidelines: SSBB, SSBb, SsBB, or SsBb brown ssBb or ssBB hazel SSbb, Ssbb or ssbb blue 6. Close together (EE) Average distance (Ee) Far apart (ee) Eye distance: EE = close together; Ee = intermediate; ee = far apart. Eye shape: AA or Aa = almond shaped; aa = round. Almond (AA, Aa) Round (aa) Eyelashes: LL or Ll = long; ll = short. Long (LL, Ll) Short (ll) Mouth and Lip Traits Determine the phenotype with respect to all three characteristics before drawing the mouth. Mouth size: MM = wide; Mm = intermediate; mm = narrow. Wide (MM) Intermediate (Mm) Narrow (mm) 17. Lip thickness: TT or Tt = Thick; tt = thin. Thick (TT, Tt) Thin (tt) Dimples on side of mouth: DD or Dd = dimples; dd = no dimples. Present (DD, Dd) Absent (dd) Nose Traits Nose thickness: BB or Bb = broad nose; bb = narrow nose. Narrow (bb) Nose shape: RR or Rr = tip rounded; rr = tip pointed. Rounded (RR, Rr) Ear Traits Earlobe attachment: FF or Ff = free earlobes; ff = attached earlobes. Attached (ff) Free (FF, Ff) Darwin’s earpoint: DD or Dd = point present; dd = point absent. Present (DD, Dd) Absent (dd) Ear pits: 12870 PP or Pp = pits present; pp = pits absent. Present (PP, Pp) Absent (pp) Hairy ears: Hairy ears is a recessive allele located on the Y chromosome so it is only contributed by the male and only males can display the characteristic. If your child is female it cannot show the characteristic so you do not need to do anything. If your child is a male, the father must flip a coin to decide if the child will have hairy ears. Tails denotes hairy ears. Absent Present Freckles Freckles on cheeks: CC or Cc = freckles present; cc = freckles absent. Present (CC, Cc) Absent (cc) Freckles on forehead: FF or Ff = freckles present; ff = freckles absent. Present (FF, Ff) Absent (ff) Data Sheet Parents’ Names ____________________________________ and _______________________________ Child’s Name _________________________________________________________ Child’s Sex ___________________________________________________________ Name _______________________________ Lab section __________________________ Your instructor may collect these end-of-exercise questions. If so, please fill in your name and lab section. End-of-Exercise Questions Compare your child with the child of another couple. List five traits that both of the children have. The children are concordant for these traits. Answers will vary Using the same children for comparison, list five traits that are different. The children are disconcordant for these traits. Answers will vary For most of the characteristics in this exercise both parents are heterozygous. What is the probability that both parents will contribute a recessive allele for any given trait? One out of four Refer to your child’s data sheet and complete Table 38.1. Place an X in the dominant column inTable 38.1 if your child received at least one copy of the dominant allele. Place an X in the recessive column if your child received two copies of the recessive allele. Total the number of dominant and recessive phenotypes for these traits. What is the ratio of dominant-to-recessive traits? What ratio would you expect? Why? Answers will vary, but they should approximate 3 to 1 since each parent is heterozygous for each characteristic. There are three characteristics that demonstrate incomplete dominance in this exercise. What are they? Eyebrow thickness Eye distance Mouth size If the genes for earlobe shape and dimples were located close to one another on the same chromosome, how would their location influence how these two genes are passed to the next generation? If genes were located on the same chromosome, they would not assort independently and would tend to be inherited together. List two examples of epistasis described in this exercise. Eye color, hair color, skin color in combination with albinism; Eye color with solid and patchy distribution of pigment are all examples. What type of inheritance pattern best describes how skin color is determined? Ignore the cases of albinism. Polygenic inheritance Analyze the number of dominant versus recessive phenotypes recorded in Table 38.1. Do your results agree with a Mendelian mode of inheritance? Use a chi-square test to determine if the deviation from the expected results could be attributed to chance. Make up your own chi-square table. Answers will vary, but they should approach a 3 to 1 ratio. What impact do cases of multiple alleles have on the number of kinds of phenotypes displayed in the population? The number of possible phenotypes is increased. Name____________________________________________________Section________________Date___________ Experiment 39: Sensory Abilities Invitation to Inquiry There are many kinds of eye-glasses used for special purposes. People who fish like to wear polarizing sunglasses. People who shoot guns competitively, typically wear amber colored glasses. Conduct some research to determine why each prefers a particular kind of eye-wear. Background This laboratory exercise gives you an opportunity to study how we sense changes in our surroundings. Your ability to sense changes in your surroundings involves (1) the specific ability of sense organs to respond to stimuli (detection), (2) the transportation of information from the sense organ to the brain by way of the nervous system (transmission), and (3) the decoding and interpretation of the information by the brain (perception). In order for us to sense something, all three of these links must be functioning properly. For example, a deaf person might be unable to detect sound because (1) there is something wrong with the ear itself, (2) the nerves that carry information from the ear to the brain are damaged, or (3) the portion of the brain that interprets information about sound is not functioning properly. While this laboratory activity focuses on the function of sense organs, it is important to keep in mind that the peripheral and central nervous systems are also important in determining your sensory ability. All sense organs contain specialized cells that are altered in some way by changes in their environment (stimuli). The sensory cells depolarize and since they are connected to nerve cells, they cause the nerve cells to which they are attached to depolarize as well, and information is sent to the brain for interpretation by way of nerve pathways. In this lab exercise you will: 1. Make a map of the location of different kinds of taste buds on your tongue. 2. Determine several characteristics of the sense of “touch.” Locate different kinds of temperature sensors in the skin. Study several aspects of visual acuity. Study several aspects of the sense of hearing. Procedure Taste Taste involves several different kinds of sensory cells located on the tongue and pharynx. Each kind of sensory cell responds to specific kinds of chemicals. So there is not just one sense of taste; there are several. We recognize at least five different kinds of taste senses: sweet, sour, salty, bitter, and umami (meaty). Mapping the Sense of Taste on the Tongue Work with a lab partner. Obtain a cotton swab and dip it into one of the solutions. The solutions are labeled sweet, sour, salt, bitter, and umami (meaty). Have your lab partner touch the swab to the tongue at the following five locations: a. the tip, b. right side, c. left side, d. center, and e. back. Place an X on the following drawings of the tongue to indicate where you detected each chemical. Sweet Sour Salt Bitter Umami 20% sugar vinegar 5% NaCl 0.5% quinine 20% monosodium glutamate Test the other four solutions in the same manner, but be sure to rinse your mouth with water after each solution. When you have tested each of five chemicals, switch positions with your partner. Results Can you detect each chemical at all places on the tongue? No Compare your results to your partner and other people in class. Do they detect the same chemicals in the same place? Probably not, there is a great deal of individual variation. What does this tell you about the sense of taste? Taste is not a single sense, but a combination of several. The Role of Solubility in Detecting Taste Dry off the tip of your tongue with a clean paper towel. Place a few grains of table salt (NaCl) on the tip of your tongue. Record the time interval from the time you place salt on the tip of your tongue until you first taste the salt. __________ Dissolve a few grains of salt in a small amount of water. Place this on the tip of your tongue. Record the time interval from the time you place the salt solution on the tip of your tongue until you first taste the salt. __________ Were the two time intervals different? What does this tell you about the ability to taste salty materials? It should take longer to taste the salt with a dry tongue because the salt needs to be in solution before the sense organs can perceive it. Touch The sense of touch is made up of a number of different types of receptor organs. Pressure, pain, heat, and cold are all aspects of the sense of touch. We will experiment with some of them here. Localization of Touch You need a partner for this exercise. The subject should keep his or her eyes closed throughout the exercise. Touch the skin on the back of the hand of the subject lightly with the pointed end of a soft lead pencil. Be sure to leave a mark. Then ask the subject (with eyes still closed) to use a blunt probe to locate the place on the skin where the stimulus was received. Use a ruler to measure as closely as possible the error in locating where the stimulus was applied. Measure the error in millimeters. Repeat five times at different locations on the back of the hand. Change roles with your partner and repeat the experiment. Results and Conclusions In the space provided, write a short paragraph that states your findings and conclusions. Students will not always be able to localize the source of the stimulus. This implies that the receptors are not evenly distributed and that there are spaces not served directly by sensory receptors. Density of Sense Organs You need to work in pairs. Have the subject keep his or her eyes closed. Use a pair of forceps or calipers to gently touch the subject’s skin so that the two points of the instrument touch with the same light pressure and at the same time. Test the palm of the hand and two other regions of the body. Other regions that may be tested are the back of the hand, the tip of the index finger, the forearm, the tip of the nose, the forehead, and the back of the neck. Not all of these need to be tried, but a selection should be made. Ask the subject to state whether one or two points of the instrument are felt. Repeat this procedure five times for each area of the body chosen. (To keep the subject from guessing, the experimenter should occasionally touch the skin with only one point. However, do not record the result of the response in your data). Record your data in the following manner: Record a minus sign (–) whenever two points were felt as one and a plus sign (+) whenever the two points were actually felt as two. Begin with the points 20 millimeters apart and systematically decrease the distance between the points from 20 mm to 15 mm to 10 mm to 5 mm. Find the smallest distance at which the subject can still distinguish two points for each portion of the body tested. Change roles. Record the data made on yourself as the subject. From the data, estimate the comparative densities of touch receptors of the different parts of the body. Area I: _____________________ distance between points of forceps in mm Area II: _____________________ distance between points of forceps in mm Area III: _____________________ distance between points of forceps in mm Results and Conclusions What is the smallest distance the subject can still recognize two points for each of the three areas tested? Are they the same? Explain. Answers will vary. Some areas have a higher density of touch receptors, allowing better discrimination. Place a sketch of your “two-point device” on the drawing to indicate why two points are sometimes felt as one. The sketch should show both points touching the skin but only one of the points directly over a sensory cell. Which of the regions of the skin that you tested is represented by the left side of the drawing and which is represented by the right side of the drawing? Explain your answer. The left side represents areas like the arm or back of the neck. The right side represents areas like the palm of the hand or finger tip. Temperature Sense–Detecting Hot and Cold Work with a partner. With a pen, draw a square with 20 mm sides on the back of the subject’s hand, then subdivide thissquare into 16 smaller squares by dividing each of the sides into 5 mm segments. Have the subject keep eyes closed and place his or her hand flat on the table. Obtain a nail that has been in ice-cold water. Dry it off with a paper towel. Lightly touch each of the squares of the grid on the hand at random. The subject should respond by saying “cold” if such a sensation is actually felt; otherwise the subject remains silent. It is important for the subject to ignore the sense of touch and concentrate on the sensation of cold. For every positive response, the experimenter marks a plus sign (+) on the following grid at a point corresponding to the point tested on the skin. Be sure that the nail is really cold when you make each test. Repeat this exercise with a very warm nail and record your results on the second grid. Cold Warm Switch roles with your partner and repeat the exercise. Answer the following questions. Do you detect hot in every square? No Do you detect cold in every square? No Are hot and cold receptors always located in the same squares? No Do the same receptors respond to hot and cold? Explain how you know. There are a variety of different receptors, but the student should be able to recognize that some areas sense cold but not hot. This means that there must be two different kinds of receptors. Temperature Sense—Detecting Changes in Temperature Dip one finger into a beaker of hot water and at the same time put a finger from the other hand intocold water. After 30 seconds, transfer both fingers into a third beaker of warm water. Results and Conclusions Describe the sensations of both fingers in the beaker of warm water and explain why there is a difference in sensation. The lukewarm water will feel hot to the hand previously located in ice water, and the hand previously in hot water will feel cold. This means that there is a relative temperature sense that sends information to the brain about whether the skin surface is getting warmer or colder, regardless of the specific temperature. Vision The eye is a complex structure that focuses light on cells of the retina that respond to changes in light. There are two kinds of light receptors; rods and cones. Rods are very sensitive to light and only respond to differences in light intensity. The cones are less sensitive to light. There are at least three kinds of cones, each of which responds to specific colors of light. The rods and cones are located in different places in the retina of the eye. In this part of the lab activity you will make a number of observations about the eyes and their response to various stimuli. Light Intensity and Color Vision Work with a partner. 1a. Take three pieces of different but similarly colored paper that are about 100 × 100 cm into a nearly dark room. Show only one square at a time and ask your partner to identify the color of the paper. Determine the distance at which your partner can tell the color of the squares of paper. It is not necessary to measure the distance exactly. Simply count the number of paces between you and your partner. 1b. Change roles and have your partner show you the papers. 2. Return to a well-lighted area and determine the distance at which your partner can still identify the colors. Explain your results by discussing the function of the rods and cones in the retina. Cones require high amounts of light to function. In dim light, only the black and white rods function. Determining the Location of Rods and Cones Rods and cones are not located in the same place on the retina of the eye. When you look at things from directly in front of the eye, the cornea and lens of the eye focus the light on a region known as the fovea centralis. When you look at things with your peripheral vision, the light is focused on regions of the eye other than the fovea centralis. Work with a partner. Choose three similarly colored squares of paper about 100 × 100 cm. Have your partner stare at a distant object directly in front of him or her. Start behind your partner (out of the field of vision) and slowly move the piece of paper forward at eye level about 30 cm to the side of the head. Ask your partner to tell you when the piece of paper is first seen and when the color of the paper can be detected. Use the information about the location of rods and cones and the results you just obtained to answer the following questions. Which sense organs (rods or cones) are most common in regions outside the fovea centralis? Rods Which sense organs (rods or cones) are most common within the region of the fovea centralis? Cones Explain how this experiment allows you to answer these questions. The student will not be able to identify the color of an object in his peripheral vision because the light does not fall on the fovea centralis. Areas outside the fovea centralis are dominated by rods which do not respond to differences in color. As the object is moved toward the center of the field of view more of the light falls on the fovea centralis and the cones in the fovea detect different colors of light. Detecting the Blind Spot Use the + and dot below in the following manner. Close your left eye. Place the page close to your face. Stare at the + with your right eye. Slowly move the page away from you. What happens to the dot? + • In order to detect the presence of an object, light must fall on the retina of the eye and stimulate either rods or cones. There are no rods or cones at the point where the optic nerve goes out of the back of the eye. Use this information to explain what you observed when looking at the + and • above. The dot will disappear when it is at the specific distance from the eye that causes the image of the dot to fall on the blind spot, here the optic nerve exits the back of the retina. Hearing The sense of hearing involves the detection of sound vibrations. Airborne sounds cause the eardrum to vibrate. The eardrum is attached to a series of three small bones: the malleus, incus, and stapes. The stapes is attached to a membrane over a small opening in the cochlea. The cochlea is fluid filled. Thus, the vibrations of the air are transferred to the fluid of the cochlea. When the fluid in the cochlea vibrates, cells in the cochlea are stimulated. When these cells depolarize, they send a signal by way of the auditory nerve to the brain. In this part of the lab activity we will explore some aspects of hearing. Work with a partner. Strike a low frequency tuning fork (100 cps) and hold it near one ear. Determine how far from theear the subject can hear the tuning fork. Repeat with the other ear. Are both ears the same? Often students will have better hearing in one ear. Strike the tuning fork and touch the base of the vibrating tuning fork to the skull just in front of the ear. Does the volume change? Generally the student will perceive bone conduction as being louder. How is this sensation of hearing different from when the base of the turning fork touches the skull near the ear? The student will “hear” the sound because it is being conducted through the bone to the inner ear. 3a. Have the subject sit with closed eyes. Strike the tuning fork. Have the subject point to the position of the tuning fork. Repeat three times from different positions. Can the subject correctly identify the position of the tuning fork? Yes 3b. Now have the subject keep eyes closed and plug one ear with a finger. Have the subject point to the tuning fork as it is struck at different positions. Was the subject able to locate the position of the tuning fork accurately? No Why was there a difference between the two different trials? Localization of the source of sound on the different times that the sound reaches the two ears. If one of the ears is plugged, it is more difficult to locate the source of the sound. Sensory Abilities Name ___________________________________________ Lab Section____________________ Your instructor may collect these end-of-exercise questions. If so, please fill in your name and lab section. End-of-Exercise Questions Describe the regions of your tongue that are most sensitive to sweet, sour, salt, bitter, and umami. There is a great deal of individual variation but students should recognize that there are distinct regions of the tongue that are more sensitive to specific tastes and that these will vary from individual to individual. How is solubility important to the sense of taste? The greater the solubility, the greater the sensation of taste. Substances need to be in solution before the sense organs can perceive them. Determine the average distance between points on the palm of the hand at which persons in the class correctly identified that they were being touched by two points. On the average, individuals could discriminate between two points that were 5 mm apart. Using the data you collected for different parts of the skin, rank them according to which had the greatest density of touch receptors and which had the lowest density. Answers will vary, depending on areas tested, however, the density of touch receptors is generally greater on the hands and face than on other parts of the body. Write a paragraph describing what you learned about the receptors that respond to temperature. How many kinds of receptors are there? Explain how you know there are different kinds of receptors. Some areas were sensitive to cold and hot, while others were sensitive to only one or the other. This suggests that there are two different kinds of temperature receptors that send information to the brain about whether the skin surface is getting warmer or colder, regardless of the specific temperature. There are some kinds of people who can see well in bright light but are not able to see in dim light.This condition is called “night blindness.” What kinds of sensory cells do not function to capacity in individuals who have night blindness? The rods do not function to capacity in an individual with night blindness. Name____________________________________________________Section________________Date___________ Experiment 40: Daily Energy Balance Invitation to Inquiry Many kinds of foods are marketed to those who participate in various kinds of sports. The implication is that these foods have additional nutrients or higher quantities of nutrients need by the athlete. Go to a store and read the ingredient label on one of these products. Compare it to an equivalent product that is not marketed in such a manner. For example, you could compare a sports drink to a soft drink or orange juice. You could compare a “nutrient bar” to an equivalent candy bar or snack food. Look specifically at quantities of calories, fats, proteins, sodium, and potassium. How are they different? What other foods could you eat that would provide the same calories and nutrients? Background The theoretical biological sciences of biochemistry, anatomy, cell biology, and physiology are brought together in the practical biological field of nutrition. The science of nutrition is the study of the processes involved in taking in, assimilating, and utilizing nutrients. The amount of food and drink consumed by a person from day to day is a person’s diet. There has been an increased interest in diet and personal nutrition as more information concerning these subjects becomes available through the popular press, scientific publications, health clubs, and schools. Not only are people “counting calories” and concerned with the grams of fat they consume, but they are becoming scientifically literate enough to ask significant questions to their physicians, teachers, food manufacturers, and government officials. With a minimal amount of nutrition information, it is possible to get a better handle on your own nutritional status. In this exercise, you determine your daily basal metabolic rate, voluntary muscular activity, and specific dynamic action per day. These are used to estimate your total energy requirements per day in kilocalories (kcal). You then calculate your total daily kcal intake. By comparing these two figures, you can determine whether or not your present diet should result in your maintaining, losing, or gaining weight. You will determine your: basal metabolic rate; voluntary muscular activity level; specific dynamic action; kilocalorie intake per day by adding your BMR, activity level, and SDA;5. total energy requirements and compare to your energy kcal intake per day; and 6. energy balance. Procedure Determining Your Basal Metabolic Rate Your BMR (basal metabolic rate) is the rate at which kcals are used for maintenance activities and can be measured on a daily basis. This is also the total amount of energy per kilogram per hour expended after a 12-hour fast. Energy is measured in kilocalories, the amount of energy needed to raise the temperature of 1 kg of water 1˚C. BMR can be estimated by using a short formula that is based on 1.0 kcal per kilogram of body weight per hour for men, or 0.9 kcal per kilogram of body weight for women. Even though this is a crude method, it does give some idea of the BMR. Body weight × BMR factor = Estimated BMR (kcal/kg/hour) For example: If a male weighs 150 lbs, his mass in kilograms will be 68 kg. Therefore, the estimated BMR is 68 kg × 1.0 kcal/kg/hr = 68 kcal/kg/hr 24 hours/day × Estimated BMR/hour = Estimated energy expenditure/day 68 kcal/kg/hr × 24 hours = 1632 kcal/kg/day If a female weighs 120 lbs, her mass in kilograms will be 55 kg. Therefore, the estimated BMR is 55 kg × 0.9 kcal/kg/hr = 49 kcal/kg/hr 24 hours/day × Estimated BMR/hour = Estimated energy expenditure/day 49 kcal/kg/hr × 24 hours = 1176 kcal/kg/day These are estimated basal metabolic rates for these two people. Using this method, calculate your own BMR: Body weight in kg × BMR factor in kcal/kg/hr = Estimated energy expenditure in kcal/kg/hr kcal/day 24 hours/day × Your estimated energy expenditure/hour = (your estimated energy expenditure/day or kcal/day used while at rest) For a more accurate determination of your BMR, use standard tables from your text and calculate your skin surface area from your height and weight. A table of kilocalories per day per square meter of skin lists the kilocalories expended by a female or male by age group. This kilocalorie figure should be multiplied by your skin surface area to determine your BMR more accurately. Skin surface area × Kilocalories per day per square meter of skin = BMR kcal/day Your skin surface area × Kilocalories per day per square meter of your skin = Estimating Your Energy Output per Day Energy output per day is an estimate of your voluntary muscular activity per day. For a person who engages in only sedentary activities such as desk work, the estimated energy output is approximately 50% of his or her already determined BMR. For example, if the male in the previous example were a typist, his voluntary muscular activity level for the day would be: 0.50 × 1632 kcal/day = 816 kcal/day For a person who engages in light activities such as standing, talking, and minor amounts of walking, the estimated energy output is approximately 60% of his or her already determined BMR. For example, if the female in the previous example were a teacher, her voluntary muscular activity level for the day would be: 0.60 × 1176 kcal/day = 706 kcal/day For a person who engages in moderate activities that exceed those described as light, the estimated energy output is approximately 70% of his or her already determined BMR. For example, if the male described were a nurse, his voluntary muscular activity level for the day would be: 0.70 × 1632 kcal/day = 800 kcal/day Those participating in heavy activities are estimated to use an equivalent of their BMR per day. For a person engaged in heavy lifting and moving or a daily workout of an hour or more: 1.00 × 1632 kcal/day = 1,632 kcal/day Estimate your voluntary muscular energy expenditure per day: kcal/day Percent of BMR based on activity level × BMR = (your voluntary muscular energy expenditure) Estimating Your Specific Dynamic Action (SDA) The specific dynamic action (SDA) is the amount of energy needed to metabolize food for the day. This is approximately 10% of a person’s total daily basal expenditure and total daily voluntary muscular activity. For example, the male nurse had a voluntary muscular activity level for the day of 800 kcal, and his daily expenditure was 1,632 kcal. Therefore, his SDA for the day would be an estimated 243 kcal. kcal/day (Your basal energy expenditure + Your voluntary daily physical activity) × 0.10 = kcal/day (your SDA) Add together your BMR and your voluntary muscular energy expenditure. BMR + voluntary muscular activity = Total Daily Energy Requirements kcal/day Your total daily energy requirements are the sum of your BMR + voluntary muscular activity + SDA = Determining Your Daily Caloric Intake Before you can draw any conclusions about your daily energy balance, you must determine your total energy intake. This can be estimated by recording your total consumption of nutrients and determining their kcal values. Fill in Table 40.1 beginning with the first meal of your day and ending with the last snack you consume. The estimate of your kcal intake can be determined by using the tables found in many supermarkets, bookstores, and libraries. Such tables are usually referred to as pocket calorie counters. Compare your total daily energy requirement with your actual kilocalorie intake per day: Total daily energy requirement – Actual kilocalorie intake = Gain/maintenance/loss If these two figures are the same, you are meeting your energy requirements and maintaining your weight. If your total daily caloric intake is greater than your caloric requirement, you are exceeding your energy requirements and, therefore, gaining weight. The opposite is true if you are not meeting your caloric requirement. Therefore, you are losing weight. Table 40.1 Total Energy Intake Food Food Serving Size Energy kcal Breakfast Lunch Dinner Other Total = ________________ Determining Your Daily Energy Balance Name ___________________________________________ Lab section____________________ Your instructor may collect these end-of-exercise questions. If so, please fill in your name and lab section. End-of-Exercise Questions What is basal metabolic rate? BMR is the amount of energy (kcal) a person needs to maintain basic body functions while at rest. Do basal metabolic rates differ between males and females? On what evidence can you base your answer? Yes, the amount of food (kcal) men can take in while maintaining their weight is greater than the amount woman can take in. The charts all demonstrate that BMR is higher in males than females. What factors are involved in accurately determining your BMR? One would need to know, at least, total body surface area and age. Amount of daily activity also influences BMR in addition to its direct effect on caloric output. What is specific dynamic action? The amount of energy required to digest and assimilate food is called specific dynamic action. SDA is equal to approximately 10 percent of your total daily kilocalorie intake. If your total kilocalorie intake per day is higher than your total kilocalorie requirements, what happens to your weight? It will increase. What can you do to bring about an energy balance? Try to match total kilocalorie intake with total kilocalorie output. This may include increasing exercise and decreasing food intake, especially as one ages. Other than kilocalories, what information is important in determining whether or not you are consuming a healthy diet? Amount of fat, protein, fiber, vitamins, and minerals are all important components to a well-balanced diet. What resources are available to help you develop a balanced diet? FDA guidelines and literature, nutrition books, nutritional specialists, Weight Watchers, and several popular magazines offer dietary recommendations. Solution Manual Experiment for Integrated Science Bill W. Tillery, Eldon D. Enger , Frederick C. Ross 9780073512259
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