Human Genetics

/in /by

[Type text] [Type text] [Type text]

 

Please answer each question fully and in complete sentences. You may use textbook, or PowerPoint slides, and resources indicated in the questions below; if you use other resources, they must be cited properly in a working bibliography (author, article title, journal or book title, date of publication, page numbers)

 

 

Topic 8: Multifactorial and Acquired Developmental Traits

 

Should a woman be held legally responsible if she drinks alcohol, smokes, or abuses drugs during pregnancy and it harms her child (e.g., fetal alcohol syndrome)? If so, should liability apply to all substances that can harm a fetus, or only to those that are illegal? For example, we know that maternal weight gain in pregnancy is associated with an increased risk for diabetes in their children. What evidence or reasoning leads you to this opinion? State your opinion and then give sound reasoning for it.)

 

 

Topic 9: Multifactorial and Acquired Cancer Traits

 

Many genes contribute to lung cancer risk, especially among people who smoke tobacco. These genes include p53, IL1A, IL1B, CYP1A1, EPHX1, TERT, and CRR9. Search for one of these genes online and describe how mutations in the gene may contribute to causing lung cancer, or how polymorphisms in the gene may be associated with increased risk in combination with smoking. Be sure to choose a trustworthy source and cite the source with your answer.

 

 

Topic 10: Acquired Microbiome Traits

 

Malnutrition is common among children in the African nation of Malawi. Researchers hypothesized that the microbiome may play a role in starvation because in some families, some children are malnourished and their siblings are not, even though they eat the same diet. Even identical twins may differ in nutritional status.

 

Researchers followed 317 sets of twins in Malawi, from birth until age 3. In half of the twin pairs, one or both twins developed kwashiorkor, the type of protein malnutrition that swells bellies. The researchers focused on twin pairs in which only one was starving, including both identical and fraternal pairs. At the first sign that one twin was malnourished, both were placed on a diet of healthy “therapeutic food.” Four weeks later, the pair returned to the nutrient-poor village diet. If the malnourished twin became so again, then the researchers compared his or her microbiome to that of the healthy sibling. The goal was to identify bacterial species that impair the ability of a child to extract nutrients from the native diet. [Smith, et al. (2013) Gut microbiomes of Malawian twin pairs discordant for kwashiorkor. Science 339(6119):548-554.]

 

How might the findings from this study be applied to help prevent or treat malnutrition? Do you think that the study was conducted ethically? Why or why not? Explain how identical twins who follow the same diet can differ in nutritional status.

 

Topic 11: Multifactorial and Acquired Epigenetic Traits

 

The environmental epigenetics hypothesis states that early negative experiences, such as neglect, abuse, and extreme stress, increase the risk of developing depression, anxiety disorder, addictions, and/or obesity later in life through effects on gene expression that persist and can be passed on to the next generation. Suggest an experiment to test this hypothesis.

 

 

Topic 12: Genetics of Human Populations: Hardy-Weinberg Equilibrium

 

Population bottlenecks are evident today in Arab communities, Israel, India, Thailand, Scandinavia, some African nations, and especially among indigenous peoples such as Native Americans. Research an indigenous or isolated population and describe a genetic condition that its members have that is rare among other groups of people, and how the population bottleneck occurred.

 

 

Topic 13: Human Evolution

 

Explain why analyzing mitochondrial DNA or Y chromosome DNA cannot provide a complete picture of an individual’s ancestry. How can a female trace her paternal lineage if she does not have a Y chromosome?

 

 

Topic 14: Biotechnology in Human Genetic Research

 

Go to clinicaltrials.gov and search under “gene therapy.” Describe one of the current research trials for correcting a genetic problem. Include information about the genetic condition if available, including: mode of inheritance, age of onset, symptom severity, variability in expression, existing treatments (standard of care), and how the gene therapy is proposed to correct the problem.

Population Ecology

/in /by

Population Ecology Hands-On Labs, Inc. Version 42-0281-00-02 Review the safety materials and wear goggles when working with chemicals. Read the entire exercise before you begin. Take time to organize the materials you will need and set aside a safe work space in which to complete the exercise. Experiment Summary: You will explore the field of population ecology and survey factors involved in the decline, expansion, and maintenance of a population. Simulated growth of a population will be modeled, graphed, and analyzed. You will use quantitative data from a cemetery population to study demographics. www.HOLscience.com 1 © Hands-On Labs, Inc. EXPERIMENT Learning Objectives Upon completion of this laboratory, you will be able to: ● Define species, population, and metapopulation. ● Differentiate between density-dependent and density-independent factors and describe how each can influence population size. ● Outline factors that influence carrying capacity and describe the potential consequences of overpopulation. ● Illustrate graphs of linear and exponential population growth. ● Describe how demography data may be used to calculate probability of mortality. ● Model population growth and determine if the growth was linear, exponential, or had no observable pattern. ● Determine constraints placed on a modeled population and draw conclusions about carrying capacity. ● Use birth and mortality data of a cemetery to investigate demography. ● Determine probability of death within a cohort. Time Allocation: 3.5 hours Note: This experiment suggests a field trip to a local cemetery for data collection. Please plan your time accordingly. www.HOLscience.com 2 ©Hands-On Labs, Inc. Experiment Population Ecology Materials Student Supplied Materials Quantity Item Description 3 Sheets of paper (optional) 1 Pen or pencil 1 Access to a cemetery (optional) 1 Access to a printer (optional) HOL Supplied Materials Quantity Item Description 1 Packs of dice, mini (100 pcs) 1 Cup, plastic, 9 oz., short 1 HOL Supplied Cemetery Data Supplemental Document Note: To fully and accurately complete all lab exercises, you will need access to: 1. A computer to upload digital camera images. 2. Basic photo editing software such as Microsoft Word® or PowerPoint®, to add labels, leader lines, or text to digital photos. 3. Subject-specific textbook or appropriate reference resources from lecture content or other suggested resources. Note: The packaging and/or materials in this LabPaq kit may differ slightly from that which is listed above. For an exact listing of materials, refer to the Contents List included in your LabPaq kit. www.HOLscience.com 3 ©Hands-On Labs, Inc. Experiment Population Ecology Background Species and Populations A species is a group of organisms that share many common characteristics and breed among themselves to produce fertile offspring. Individuals of a species that occupy a defined area at the same time are called a population. The habitat area of a population is often naturally enclosed within geographical boundaries, such as rivers or mountains. See Figure 1. In research studies about populations, scientists often define artificial boundaries. For example, scientists may investigate the population within a county or state boundary. Figure 1. Small population of water lilies (family Nymphaeaceae) inhabiting a pond. © yuriy kulik When suitable habitat is patchy or fragmented, populations can be spatially isolated, but members of the population can have some level of interaction with one another. When this occurs, the interacting populations are referred to as a metapopulation. An example of a species that is often found as a metapopulation is the desert bighorn sheep (Ovis canadensis). See Figure 2. The bighorn sheep occupies steep slopes of mountains that are separated by flat lowlands. Although the lowlands are an unsuitable long-term habitat for the sheep, individuals and groups of sheep are able to travel through the lowlands to adjacent mountains, resulting in interaction among individuals of different but connected populations. www.HOLscience.com 4 ©Hands-On Labs, Inc. Experiment Population Ecology Figure 2. Bighorn sheep. © Shane W. Thompson Population Density Biologists who study population ecology often investigate population size and factors involved in the decline, expansion, and maintenance of a population. Data about populations include the following: ● Mortality (death) and birth rates ● Movement of members into and out of the population (immigration and emigration) ● Number of individuals in a group, or cohort (for this experiment cohorts are the age classes of deceased individuals) ● Spatial distribution of species ● Population density (the number of individuals per unit area) Factors related to the density of a population, called density-dependent factors, affect population growth by reducing or increasing the population size. For example, the ability to acquire a mate is a density-dependent factor. When population density is great, competition for mates increases. Members of the population may spend more energy competing for mates than actually mating, and the population size can subsequently decrease due to reduced births. On the other hand, when population density is optimal, competition may be relatively low and mating opportunities may be high, resulting in growth of the population. Other density-dependent factors include resource availability, predation rates, and disease transmission. Density-independent factors influence population growth but are not dependent on population density. Consider how the population density of trees may be affected by weather patterns and wildfires. Growth rates can follow various patterns, as shown in Figure 3. When resources are unlimited, a population’s growth rate can be exponential. Although the graph of exponential growth illustrates a potentially great increase in population size, no population can grow indefinitely. In nature, members of the population will eventually consume available resources, and the population size will ultimately plateau or decline due to density-dependent factors. www.HOLscience.com 5 ©Hands-On Labs, Inc. Experiment Population Ecology Figure 3. Population growth patterns. A. Linear. B. Exponential. Every natural area has a carrying capacity, a decided number of individuals that can be supported given the area’s limited resources. Carrying capacity is influenced not only by the number of members of a single population, but also members of competing populations. Furthermore, a given population may act as a resource for another population; for example, voles are a food resource for owls. Carrying capacities are in constant flux, as they are affected by both densitydependent and density-independent factors. In the event that overpopulation occurs and the carrying capacity is exceeded, a population collapse can occur; whereby the population size decreases dramatically. When a population completely collapses and no members remain, the population is locally extinct, or extirpated. Human Populations A subset of population ecology, demography, is the study of human populations. Cemeteries are an excellent place to study demography as they provide data on both the birth and death dates of individuals of a local population. This information can be used in turn to determine the probability of death and survival at different ages in a population. Table 1 is an example analysis of mortality. To generate the table, the number of individuals that died in each cohort (based on age class) must be determined. For example, the first cohort listed in Table 1 includes individuals that died from age one to nine. From this information, probability of mortality can be calculated. According to Table 1 there is a 15% probability of death in this specific population, between ages one and nine. Closely study the table descriptions provided below. www.HOLscience.com 6 ©Hands-On Labs, Inc. Experiment Population Ecology Table 1. Cemetery Demography Data. Cohort (X) Number of deaths (D) Frequency of population in cohort (d) Frequency of survivorship entering the cohort (l) Probability of death within a cohort (Q) 1-9 24 0.15 1.00 0.15 10-19 20 0.13 0.85 0.15 20-29 5 0.03 0.73 0.04 30-39 10 0.06 0.69 0.09 40-49 16 0.10 0.63 0.16 50-59 40 0.25 0.53 0.47 60-69 35 0.22 0.28 0.78 70+ 10 0.06 0.06 1.00 Table Description: ● Cohort (X) – The age intervals of deceased individuals ● Number of deaths (D) – The number of individuals that died in each cohort ● Frequency of population in cohort (d) – The portion of the population that died in each cohort, d = D / Total Population Size ● Frequency of survivorship entering the cohort (l) – The portion of the population that enters the cohort, l cohort2 = lcohort1 – dcohort1 ● Probability of death within a cohort (Q) – The probability that any given individual will die within a cohort, Q = d / l www.HOLscience.com 7 ©Hands-On Labs, Inc. Experiment Population Ecology Exercise 1: Modeling Population Growth In this exercise, you will use dice to model population growth. Each die will represent an individual; new individuals will be born, and individuals will also die. You will track the entire population until the population density (number of individuals) reaches 100. 1. Before you begin to model population growth, examine the rules listed below and shown in Figure 4. Rules ● Each die represents 1 individual of the population. ● You will start with 4 individuals. ● You will roll the dice to investigate births and deaths of the population. ● The number of dots on each die will represent a birth, a death, or neither birth nor death. ● Birth = 1, 4 ● Death = 6 ● Neither = 2, 3, 5 Figure 4. Rules of population growth activity. 2. Select 4 dice and place them in the cup. These dice represent the 4 individuals comprising generation 1, the initial population. Note: The color of the dice does not matter. 3. In Data Table 1 of your Lab Report Assistant, record the “Initial population size (N)” (for the first generation, the initial population size is 4). www.HOLscience.com 8 ©Hands-On Labs, Inc. Experiment Population Ecology 4. Cover the cup with your hand and shake the dice. Gently pour the dice onto a table or work surface. Important Note: Pouring the dice out too quickly or too high from the work surface may result in lost dice. Take care not to inadvertently lose individuals. 5. Determine the number of individuals that were born (any dice displaying numbers 1 and 4). Determine the number of individuals that died (any dice displaying number 6). See Figure 5. Figure 5. Example first generation: 2 individuals gave birth, and 1 individual died. 6. Record the “Number of births (B)” and the “Number of deaths (D)” in Data Table 1. 7. Remove any dead individuals. For example, in Figure 5 above, the dead individual should be removed from the population and returned to the bag. 8. Add a die for each birth. For example, in Figure 5 above, 2 dice should be added to the population. 9. Calculate the final population size and record the value in Data Table 1. Use the following equation: Final population size = N + B – D 10. Count the number of dice in your population to ensure that it equals the value recorded for “final population size” and return the dice to the cup. 11. To obtain data for generation 2, repeat steps 3-10. Note: Because you will be starting with a very small population, extinction is a possibility, but the odds are against it. If your population does go extinct, start again. 12. Continue rolling the dice and recording data until your population size reaches a minimum of 100. www.HOLscience.com 9 ©Hands-On Labs, Inc. Experiment Population Ecology 13. Once you have reached a population size of 100, calculate the change in population size for each generation. Record each value in Data Table 1. Use the following equation: Change in population size = Final population size – Initial population size 14. Graph the initial population size for each generation. To do this, create a scatter plot with the generations on the independent axis (x-axis) and the initial population size on the dependent axis (y-axis). Consider whether the population growth you modeled showed a linear pattern, exponential pattern, or no pattern. 15. Resize the graph and insert it into Data Table 2 of your Lab Report Assistant. Refer to the appendix entitled, “Resizing an Image” for guidance with resizing an image. 16. Graph the change in population size for each generation. To do this, create a bar graph with the generations on the independent axis (x-axis) and the change in population size on the dependent axis (y-axis). Consider whether changes in population size were greatest when the population was smaller or larger. 17. Resize the graph and insert it into Data Table 3 of your Lab Report Assistant. Questions A. How many generations did it take to reach a population size of 100? B. Consider the mode of reproduction modeled in your population. Would sexual reproduction or asexual reproduction likely be the cause of a birth? Are individuals of the species likely or unlikely to have separate male and female sexes? C. Did the modeled population exhibit linear growth, exponential growth, or no pattern? Use Data Table 2 to support your answer. D. Were changes in population size greatest when the population was smaller or larger? Which generation exhibited the greatest change in size? Use Data Table 3 to support your answer. E. What resource constraints were placed on the modeled population? F. Could the modeled population exhibit indefinite growth? If so, how? Is indefinite growth observed in nature? Explain why or why not. www.HOLscience.com 10 ©Hands-On Labs, Inc. Experiment Population Ecology Exercise 2: Investigating a Human Population In this exercise, you will investigate demography of a human population. You will collect birth and death information from a cemetery and analyze trends in the population. 1. Research your local area to find a cemetery that you may visit for this exercise. Note: If you are unable to access a cemetery, you may use the data provided in the “HOL Supplied Cemetery Data” Supplemental Document. If you choose to do this, skip to step 8. 2. Print a copy of Data Table 4 from your Lab Report Assistant, to bring with you to the cemetery. Travel to a cemetery during the day, ensure that conditions are safe and public access is permitted. 3. In Data Table 4, record the name, birth date and date of death for 80 deceased individuals. As you collect data, be sure to spread out within the full sampling area. Individuals of the same family or who died in shared years will often be grouped together, and the goal is to take a representative sample of all individuals in the population. 4. Record the cemetery name and location in Data Table 4. 5. Determine how old each person was when they died, and record your data in Data Table 4. Use the following equation: Age at death = Birth year – Death year 6. Investigate the first names of each individual and record the sex (M for male; F for female) in Data Table 4. If the name is gender-neutral, such as Jean, Lynn, or Pat, you may leave the area blank. Ensure that any data you recorded by hand is present in the Lab Report Assistant document that you report to your instructor. Note: This concludes the outdoor portion of this exercise; the rest of Exercise 2 may be performed from home. 7. Record a summary of the population. Address each of the following questions, and record data in Data Table 5 of your Lab Report Assistant. ● What were the first and last birth years? ● What were the first and last death years? ● How many individuals died before 1950? How many died after 1950? ● How many individuals are male and female? www.HOLscience.com 11 ©Hands-On Labs, Inc. Experiment Population Ecology 8. In the next steps, you will calculate the probability of dying within a given cohort. As shown in Data Table 6 of your Lab Report Assistant, cohorts are age classes. For example, cohort 1 includes individuals that died between the ages of 1 and 9; cohort 2 includes individuals who died between the ages of 10 and 19. Examine Data Table 6 and study the following descriptions for each column heading: ● Cohort (X) – The age intervals of deceased individuals. ● Number of Deaths (D) – The number of individuals that died in each cohort. ● Frequency of Population in Cohort (d) – The portion of the population that died in each cohort. ● Frequency of Survivorship Entering the Cohort (l) – The portion of the population that enters the cohort. ● Probability of Death within a Cohort (Q ) – The probability that any given individual will die within a cohort. 9. Count the number of people who died in each cohort (age interval). Record your data under “Number of deaths (D)” in Data Table 6. 10. Calculate the “Frequency of population in cohort (d).” Record each value as a number with two decimal places. Use the following equation: d = D / Total Population Size Note: “Frequency of survivorship of cohort (l)” is based on entry into the cohort. Thus, the first cohort listed will always have a value of 1.00 because 100% of the population was born, entering into the cohort. A value of 1.00 has been entered for cohort # 1 in Data Table 6. With each subsequent cohort, values of “l” will decrease. 11. Calculate the “Frequency of survivorship of cohort (l)” for cohort # 2. Record each value as a number with 2 decimal places. Use the following equation: I cohort2 = Icohort1 – dcohort1 12. Calculate the “Frequency of survivorship of cohort (l)” for each of the remaining cohorts. For example, “Frequency of survivorship of cohort (l)” for cohort 3 will be calculated as: I cohort3 = Icohort2 – dcohort2 Note: The final recorded “l” in Data Table 6 should be equivalent or very close to the final recorded “d.” 13. Calculate the “Probability of death (Q).” Record each value as a number with 2 decimal places. Use the following equation: Q = d / l www.HOLscience.com 12 ©Hands-On Labs, Inc. Experiment Population Ecology Note: The probability of death is a frequency and may be interpreted as a percentage. For example, if Q=0.30 for cohort # 1, then there is a 30% probability that a given individual will die between the ages of 1 to 9. Note: To find Q, use data within a single cohort: Qcohort1 = dcohort1 / lcohort1 14. Create a bar graph of the probability of death within each cohort. Plot the cohort age interval (1-9, 10-19, etc.) on the independent axis (x-axis), and plot the probability of death on the dependent axis (y-axis). 15. Resize the graph and insert it into Data Table 7 of your Lab Report Assistant. 16. When you are finished uploading photos and data into your Lab Report Assistant, save your file correctly and zip the file so you can send it to your instructor as a smaller file. Refer to the appendix entitled “Saving Correctly” and the appendix entitled “Zipping Files” for guidance with saving the Lab Report Assistant correctly and zipping the file. Questions A. Which cohort had the greatest probability of death? Which had the least probability? Use the graph in Data Table 7 to support your answer. B. Overall, does human mortality tend to be greatest at young ages or older ages? C. How many individuals were male, and how many were female? How many individuals were you unable to assign a gender to? D. Using the raw data in Data Table 4, calculate the average age at death for males and for females. What inferences can you make about male versus female age at death? E. If the government made significant cuts in social services, such as prenatal and infant care, how might your data be affected? www.HOLscience.com 13 ©Hands-On Labs, Inc. Experiment Population Ecology Population Ecology Hands-On Labs, Inc. Version 42-0281-00-02 Lab Report Assistant This document is not meant to be a substitute for a formal laboratory report. The Lab Report Assistant is simply a summary of the experiment’s questions, diagrams if needed, and data tables that should be addressed in a formal lab report. The intent is to facilitate students’ writing of lab reports by providing this information in an editable file which can be sent to an instructor. Exercise 1: Modeling Population Growth See next page www.HOLscience.com 14 ©Hands-On Labs, Inc. Experiment Population Ecology Data Table 1. Population Growth Model. Generation Initial Population Size (N) Number of Births (B) Number of Deaths (D) Final Population Size (N + B – D) Change in Population Size (Final – Initial) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 www.HOLscience.com 15 ©Hands-On Labs, Inc. Experiment Population Ecology Data Table 2. Population Size and Generations: Scatter Plot. Population Size Data Table 3. Population Size and Generations: Bar Graph. Population Size www.HOLscience.com 16 ©Hands-On Labs, Inc. Experiment Population Ecology Questions A. How many generations did it take to reach a population size of 100? B. Consider the mode of reproduction modeled in your population. Would sexual reproduction or asexual reproduction likely be the cause of a birth? Are individuals of the species likely or unlikely to have separate male and female sexes? C. Did the modeled population exhibit linear growth, exponential growth, or no pattern? Use Data Table 2 to support your answer. D. Were changes in population size greatest when the population was smaller or larger? Which generation exhibited the greatest change in size? Use Data Table 3 to support your answer. E. What resource constraints were placed on the modeled population? F. Could the modeled population exhibit indefinite growth? If so, how? Is indefinite growth observed in nature? Explain why or why not. www.HOLscience.com 17 ©Hands-On Labs, Inc. Experiment Population Ecology Exercise 2: Investigating a Human Population Data Table 4. Raw Data for Deceased Individuals. Cemetery Name and Location: Individual First Name Last Name Birth Year Death Year Age at Death Sex (M/F) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 www.HOLscience.com 18 ©Hands-On Labs, Inc. Experiment Population Ecology 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 www.HOLscience.com 19 ©Hands-On Labs, Inc. Experiment Population Ecology 69 70 71 72 73 74 75 76 77 78 79 80 Data Table 5. Summary of Deceased Individuals. Observations Data First birth year Last birth year First death year Last death year Number of individuals who died before 1950 Number of individuals who died after 1950 Number of males Number of females www.HOLscience.com 20 ©Hands-On Labs, Inc. Experiment Population Ecology Data Table 6. Demography Data. # Cohort (X) Number of Deaths (D) Frequency of Population in Cohort (d) Frequency of Survivorship Entering the Cohort (l) Probability of Death within a Cohort (Q) 1 1-9 1.00 2 10-19 3 20-29 4 30-39 5 40-49 6 50-59 7 60-69 8 70+ Total 80 1.00 Data Table 7. Probability of Death within Each Cohort. Probability of Death www.HOLscience.com 21 ©Hands-On Labs, Inc. Experiment Population Ecology Questions A. Which cohort had the greatest probability of death? Which had the least probability? Use the graph in Data Table 7 to support your answer. B. Overall, does human mortality tend to be greatest at young ages or older ages? C. How many individuals were male, and how many were female? How many individuals were you unable to assign a gender to? D. Using the raw data in Data Table 4, calculate the average age at death for males and for females. What inferences can you make about male versus female age at death? E. If the government made significant cuts in social services, such as prenatal and infant care, how might your data be affected? www.HOLscience.com 22 ©Hands-On Labs, Inc. Experiment Population Ecology

Population Ecology Hands-On Labs, Inc. Version 42-0281-00-02

Review the safety materials and wear goggles when working with chemicals. Read the entire exercise before you begin. Take time to organize the materials you will need and set aside a safe work space in which to complete the exercise.

Experiment Summary:

You will explore the field of population ecology and survey factors involved in the decline, expansion, and maintenance of a population. Simulated growth of a population will be modeled, graphed, and analyzed. You will use quantitative data from a cemetery population to study demographics.

© Hands-On Labs, Inc. www.HOLscience.com 1

EXPERIMENT

 

 

Learning Objectives Upon completion of this laboratory, you will be able to:

● Define species, population, and metapopulation.

● Differentiate between density-dependent and density-independent factors and describe how each can influence population size.

● Outline factors that influence carrying capacity and describe the potential consequences of overpopulation.

● Illustrate graphs of linear and exponential population growth.

● Describe how demography data may be used to calculate probability of mortality.

● Model population growth and determine if the growth was linear, exponential, or had no observable pattern.

● Determine constraints placed on a modeled population and draw conclusions about carrying capacity.

● Use birth and mortality data of a cemetery to investigate demography.

● Determine probability of death within a cohort.

Time Allocation: 3.5 hours

Note: This experiment suggests a field trip to a local cemetery for data collection. Please plan your time accordingly.

www.HOLscience.com 2 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

Materials Student Supplied Materials

Quantity Item Description 3 Sheets of paper (optional) 1 Pen or pencil 1 Access to a cemetery (optional) 1 Access to a printer (optional)

HOL Supplied Materials

Quantity Item Description 1 Packs of dice, mini (100 pcs) 1 Cup, plastic, 9 oz., short 1 HOL Supplied Cemetery Data Supplemental Document

Note: To fully and accurately complete all lab exercises, you will need access to:

1. A computer to upload digital camera images.

2. Basic photo editing software such as Microsoft Word® or PowerPoint®, to add labels, leader lines, or text to digital photos.

3. Subject-specific textbook or appropriate reference resources from lecture content or other suggested resources.

Note: The packaging and/or materials in this LabPaq kit may differ slightly from that which is listed above. For an exact listing of materials, refer to the Contents List included in your LabPaq kit.

www.HOLscience.com 3 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

Background Species and Populations

A species is a group of organisms that share many common characteristics and breed among themselves to produce fertile offspring. Individuals of a species that occupy a defined area at the same time are called a population. The habitat area of a population is often naturally enclosed within geographical boundaries, such as rivers or mountains. See Figure 1. In research studies about populations, scientists often define artificial boundaries. For example, scientists may investigate the population within a county or state boundary.

Figure 1. Small population of water lilies (family Nymphaeaceae) inhabiting a pond. © yuriy kulik

When suitable habitat is patchy or fragmented, populations can be

spatially isolated, but members of the population can have some level of interaction

with one another. When this occurs, the interacting populations are referred to as a metapopulation. An example of a species that is often found as a metapopulation is the desert bighorn sheep (Ovis

canadensis). See Figure 2. The bighorn sheep occupies steep slopes of mountains that are separated by flat lowlands. Although the lowlands are an unsuitable long-term habitat for the sheep, individuals and groups of sheep are able to travel through the lowlands to adjacent mountains, resulting in interaction among individuals of different

but connected populations.

www.HOLscience.com 4 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

Figure 2. Bighorn sheep. © Shane W. Thompson

Population Density

Biologists who study population ecology often investigate population size and factors involved in the decline, expansion, and maintenance of a population. Data about populations include the following:

● Mortality (death) and birth rates

● Movement of members into and out of the population (immigration and emigration)

● Number of individuals in a group, or cohort (for this experiment cohorts are the age classes of deceased individuals)

● Spatial distribution of species

● Population density (the number of individuals per unit area)

Factors related to the density of a population, called density-dependent factors, affect population growth by reducing or increasing the population size. For example, the ability to acquire a mate is a density-dependent factor. When population density is great, competition for mates increases. Members of the population may spend more energy competing for mates than actually mating, and the population size can subsequently decrease due to reduced births. On the other hand, when population density is optimal, competition may be relatively low and mating opportunities may be high, resulting in growth of the population. Other density-dependent factors include resource availability, predation rates, and disease transmission. Density-independent factors influence population growth but are not dependent on population density. Consider how the population density of trees may be affected by weather patterns and wildfires.

Growth rates can follow various patterns, as shown in Figure 3. When resources are unlimited, a population’s growth rate can be exponential. Although the graph of exponential growth illustrates a potentially great increase in population size, no population can grow indefinitely. In nature, members of the population will eventually consume available resources, and the population size will ultimately plateau or decline due to density-dependent factors.

www.HOLscience.com 5 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

Figure 3. Population growth patterns. A. Linear. B. Exponential.

Every natural area has a carrying capacity, a decided number of individuals that can be supported given the area’s limited resources. Carrying capacity is influenced not only by the number of members of a single population, but also members of competing populations. Furthermore, a given population may act as a resource for another population; for example, voles are a food resource for owls. Carrying capacities are in constant flux, as they are affected by both density- dependent and density-independent factors. In the event that overpopulation occurs and the carrying capacity is exceeded, a population collapse can occur; whereby the population size decreases dramatically. When a population completely collapses and no members remain, the population is locally extinct, or extirpated.

Human Populations

A subset of population ecology, demography, is the study of human populations. Cemeteries are an excellent place to study demography as they provide data on both the birth and death dates of individuals of a local population. This information can be used in turn to determine the probability of death and survival at different ages in a population. Table 1 is an example analysis of mortality. To generate the table, the number of individuals that died in each cohort (based on age class) must be determined. For example, the first cohort listed in Table 1 includes individuals that died from age one to nine. From this information, probability of mortality can be calculated. According to Table 1 there is a 15% probability of death in this specific population, between ages one and nine. Closely study the table descriptions provided below.

www.HOLscience.com 6 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

Table 1. Cemetery Demography Data.

Cohort (X)

Number of deaths

(D)

Frequency of population in

cohort (d)

Frequency of survivorship

entering the cohort (l)

Probability of death within a

cohort (Q)

1-9 24 0.15 1.00 0.15 10-19 20 0.13 0.85 0.15 20-29 5 0.03 0.73 0.04 30-39 10 0.06 0.69 0.09 40-49 16 0.10 0.63 0.16 50-59 40 0.25 0.53 0.47 60-69 35 0.22 0.28 0.78 70+ 10 0.06 0.06 1.00

Table Description:

● Cohort (X) – The age intervals of deceased individuals

● Number of deaths (D) – The number of individuals that died in each cohort

● Frequency of population in cohort (d) – The portion of the population that died in each cohort, d = D / Total Population Size

● Frequency of survivorship entering the cohort (l) – The portion of the population that enters the cohort, lcohort2 = lcohort1 – dcohort1

● Probability of death within a cohort (Q) – The probability that any given individual will die within a cohort, Q = d / l

www.HOLscience.com 7 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

Exercise 1: Modeling Population Growth In this exercise, you will use dice to model population growth. Each die will represent an individual; new individuals will be born, and individuals will also die. You will track the entire population until the population density (number of individuals) reaches 100.

1. Before you begin to model population growth, examine the rules listed below and shown in Figure 4.

Rules

● Each die represents 1 individual of the population.

● You will start with 4 individuals.

● You will roll the dice to investigate births and deaths of the population.

● The number of dots on each die will represent a birth, a death, or neither birth nor death.

● Birth = 1, 4

● Death = 6

● Neither = 2, 3, 5

Figure 4. Rules of population growth activity.

2. Select 4 dice and place them in the cup. These dice represent the 4 individuals comprising generation 1, the initial population.

Note: The color of the dice does not matter.

3. In Data Table 1 of your Lab Report Assistant, record the “Initial population size (N)” (for the first generation, the initial population size is 4).

www.HOLscience.com 8 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

4. Cover the cup with your hand and shake the dice. Gently pour the dice onto a table or work surface.

Important Note: Pouring the dice out too quickly or too high from the work surface may result in lost dice. Take care not to inadvertently lose individuals.

5. Determine the number of individuals that were born (any dice displaying numbers 1 and 4). Determine the number of individuals that died (any dice displaying number 6). See Figure 5.

Figure 5. Example first generation: 2 individuals gave birth, and 1 individual died.

6. Record the “Number of births (B)” and the “Number of deaths (D)” in Data Table 1.

7. Remove any dead individuals. For example, in Figure 5 above, the dead individual should be removed from the population and returned to the bag.

8. Add a die for each birth. For example, in Figure 5 above, 2 dice should be added to the population.

9. Calculate the final population size and record the value in Data Table 1. Use the following equation:

Final population size = N + B – D

10. Count the number of dice in your population to ensure that it equals the value recorded for “final population size” and return the dice to the cup.

11. To obtain data for generation 2, repeat steps 3-10.

Note: Because you will be starting with a very small population, extinction is a possibility, but the odds are against it. If your population does go extinct, start again.

12. Continue rolling the dice and recording data until your population size reaches a minimum of 100.

www.HOLscience.com 9 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

13. Once you have reached a population size of 100, calculate the change in population size for each generation. Record each value in Data Table 1. Use the following equation:

Change in population size = Final population size – Initial population size

14. Graph the initial population size for each generation. To do this, create a scatter plot with the generations on the independent axis (x-axis) and the initial population size on the dependent axis (y-axis). Consider whether the population growth you modeled showed a linear pattern, exponential pattern, or no pattern.

15. Resize the graph and insert it into Data Table 2 of your Lab Report Assistant. Refer to the appendix entitled, “Resizing an Image” for guidance with resizing an image.

16. Graph the change in population size for each generation. To do this, create a bar graph with the generations on the independent axis (x-axis) and the change in population size on the dependent axis (y-axis). Consider whether changes in population size were greatest when the population was smaller or larger.

17. Resize the graph and insert it into Data Table 3 of your Lab Report Assistant.

Questions A. How many generations did it take to reach a population size of 100?

B. Consider the mode of reproduction modeled in your population. Would sexual reproduction or asexual reproduction likely be the cause of a birth? Are individuals of the species likely or unlikely to have separate male and female sexes?

C. Did the modeled population exhibit linear growth, exponential growth, or no pattern? Use Data Table 2 to support your answer.

D. Were changes in population size greatest when the population was smaller or larger? Which generation exhibited the greatest change in size? Use Data Table 3 to support your answer.

E. What resource constraints were placed on the modeled population?

F. Could the modeled population exhibit indefinite growth? If so, how? Is indefinite growth observed in nature? Explain why or why not.

www.HOLscience.com 10 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

Exercise 2: Investigating a Human Population In this exercise, you will investigate demography of a human population. You will collect birth and death information from a cemetery and analyze trends in the population.

1. Research your local area to find a cemetery that you may visit for this exercise.

Note: If you are unable to access a cemetery, you may use the data provided in the “HOL Supplied Cemetery Data” Supplemental Document. If you choose to do this, skip to step 8.

2. Print a copy of Data Table 4 from your Lab Report Assistant, to bring with you to the cemetery. Travel to a cemetery during the day, ensure that conditions are safe and public access is permitted.

3. In Data Table 4, record the name, birth date and date of death for 80 deceased individuals. As you collect data, be sure to spread out within the full sampling area. Individuals of the same family or who died in shared years will often be grouped together, and the goal is to take a representative sample of all individuals in the population.

4. Record the cemetery name and location in Data Table 4.

5. Determine how old each person was when they died, and record your data in Data Table 4. Use the following equation:

Age at death = Birth year – Death year

6. Investigate the first names of each individual and record the sex (M for male; F for female) in Data Table 4. If the name is gender-neutral, such as Jean, Lynn, or Pat, you may leave the area blank. Ensure that any data you recorded by hand is present in the Lab Report Assistant document that you report to your instructor.

Note: This concludes the outdoor portion of this exercise; the rest of Exercise 2 may be performed from home.

7. Record a summary of the population. Address each of the following questions, and record data in Data Table 5 of your Lab Report Assistant.

● What were the first and last birth years?

● What were the first and last death years?

● How many individuals died before 1950? How many died after 1950?

● How many individuals are male and female?

www.HOLscience.com 11 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

8. In the next steps, you will calculate the probability of dying within a given cohort. As shown in Data Table 6 of your Lab Report Assistant, cohorts are age classes. For example, cohort 1 includes individuals that died between the ages of 1 and 9; cohort 2 includes individuals who died between the ages of 10 and 19. Examine Data Table 6 and study the following descriptions for each column heading:

● Cohort (X) – The age intervals of deceased individuals.

● Number of Deaths (D) – The number of individuals that died in each cohort.

● Frequency of Population in Cohort (d) – The portion of the population that died in each cohort.

● Frequency of Survivorship Entering the Cohort (l) – The portion of the population that enters the cohort.

● Probability of Death within a Cohort (Q ) – The probability that any given individual will die within a cohort.

9. Count the number of people who died in each cohort (age interval). Record your data under “Number of deaths (D)” in Data Table 6.

10. Calculate the “Frequency of population in cohort (d).” Record each value as a number with two decimal places. Use the following equation:

d = D / Total Population Size

Note: “Frequency of survivorship of cohort (l)” is based on entry into the cohort. Thus, the first cohort listed will always have a value of 1.00 because 100% of the population was born, entering into the cohort. A value of 1.00 has been entered for cohort # 1 in Data Table 6. With each subsequent cohort, values of “l” will decrease.

11. Calculate the “Frequency of survivorship of cohort (l)” for cohort # 2. Record each value as a number with 2 decimal places. Use the following equation:

Icohort2 = Icohort1 – dcohort1 12. Calculate the “Frequency of survivorship of cohort (l)” for each of the remaining cohorts. For

example, “Frequency of survivorship of cohort (l)” for cohort 3 will be calculated as:

Icohort3 = Icohort2 – dcohort2 Note: The final recorded “l” in Data Table 6 should be equivalent or very close to the final recorded “d.”

13. Calculate the “Probability of death (Q).” Record each value as a number with 2 decimal places. Use the following equation:

Q = d / l

www.HOLscience.com 12 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

Note: The probability of death is a frequency and may be interpreted as a percentage. For example, if Q=0.30 for cohort # 1, then there is a 30% probability that a given individual will die between the ages of 1 to 9.

Note: To find Q, use data within a single cohort: Qcohort1 = dcohort1 / lcohort1

14. Create a bar graph of the probability of death within each cohort. Plot the cohort age interval (1-9, 10-19, etc.) on the independent axis (x-axis), and plot the probability of death on the dependent axis (y-axis).

15. Resize the graph and insert it into Data Table 7 of your Lab Report Assistant.

16. When you are finished uploading photos and data into your Lab Report Assistant, save your file correctly and zip the file so you can send it to your instructor as a smaller file. Refer to the appendix entitled “Saving Correctly” and the appendix entitled “Zipping Files” for guidance with saving the Lab Report Assistant correctly and zipping the file.

Questions A. Which cohort had the greatest probability of death? Which had the least probability? Use the

graph in Data Table 7 to support your answer.

B. Overall, does human mortality tend to be greatest at young ages or older ages?

C. How many individuals were male, and how many were female? How many individuals were you unable to assign a gender to?

D. Using the raw data in Data Table 4, calculate the average age at death for males and for females. What inferences can you make about male versus female age at death?

E. If the government made significant cuts in social services, such as prenatal and infant care, how might your data be affected?

www.HOLscience.com 13 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

Population Ecology Hands-On Labs, Inc. Version 42-0281-00-02

Lab Report Assistant This document is not meant to be a substitute for a formal laboratory report. The Lab Report Assistant is simply a summary of the experiment’s questions, diagrams if needed, and data tables that should be addressed in a formal lab report. The intent is to facilitate students’ writing of lab reports by providing this information in an editable file which can be sent to an instructor.

Exercise 1: Modeling Population Growth

See next page

www.HOLscience.com 14 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

Data Table 1. Population Growth Model.

Generation Initial Population

Size (N)

Number of Births

(B)

Number of Deaths

(D)

Final Population Size

(N + B – D)

Change in Population Size (Final – Initial)

1 2 3 4 5 6 7 8 9

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

www.HOLscience.com 15 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

Data Table 2. Population Size and Generations: Scatter Plot.

Population Size

Data Table 3. Population Size and Generations: Bar Graph.

Population Size

www.HOLscience.com 16 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

Questions A. How many generations did it take to reach a population size of 100?

 

B. Consider the mode of reproduction modeled in your population. Would sexual reproduction or asexual reproduction likely be the cause of a birth? Are individuals of the species likely or unlikely to have separate male and female sexes?

 

C. Did the modeled population exhibit linear growth, exponential growth, or no pattern? Use Data Table 2 to support your answer.

 

D. Were changes in population size greatest when the population was smaller or larger? Which generation exhibited the greatest change in size? Use Data Table 3 to support your answer.

 

 

E. What resource constraints were placed on the modeled population?

 

F. Could the modeled population exhibit indefinite growth? If so, how? Is indefinite growth observed in nature? Explain why or why not.

www.HOLscience.com 17 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

Exercise 2: Investigating a Human Population Data Table 4. Raw Data for Deceased Individuals.

Cemetery Name and Location:

Individual First Name Last Name Birth Year Death Year Age at Death

Sex (M/F)

1 2 3 4 5 6 7 8 9

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

www.HOLscience.com 18 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68

www.HOLscience.com 19 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

69 70 71 72 73 74 75 76 77 78 79 80

Data Table 5. Summary of Deceased Individuals.

Observations Data First birth year Last birth year

First death year Last death year

Number of individuals who died before 1950 Number of individuals who died after 1950

Number of males Number of females

www.HOLscience.com 20 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

Data Table 6. Demography Data.

# Cohort (X)

Number of Deaths

(D)

Frequency of Population in

Cohort (d)

Frequency of Survivorship

Entering the Cohort (l)

Probability of Death within a

Cohort (Q)

1 1-9 1.00 2 10-19 3 20-29 4 30-39 5 40-49 6 50-59 7 60-69 8 70+

Total 80 1.00

Data Table 7. Probability of Death within Each Cohort.

Probability of Death

www.HOLscience.com 21 ©Hands-On Labs, Inc.

Experiment Population Ecology

 

 

Questions A. Which cohort had the greatest probability of death? Which had the least probability? Use the

graph in Data Table 7 to support your answer.

 

B. Overall, does human mortality tend to be greatest at young ages or older ages?

 

C. How many individuals were male, and how many were female? How many individuals were you unable to assign a gender to?

 

D. Using the raw data in Data Table 4, calculate the average age at death for males and for females. What inferences can you make about male versus female age at death?

 

E. If the government made significant cuts in social services, such as prenatal and infant care, how might your data be affected?

www.HOLscience.com 22 ©Hands-On Labs, Inc.

Experiment Population Ecology

Survey Of Life Science BIO

/in /by

Chapter 1: Learning about Life

Copyright © 2019 Pearson Education, Inc. 1

Name ________________________ Period _________

Chapter 1: Learning about Life

Guided Reading Activities

Chapter Content: The Scientific Study of Life

Complete the following questions as you read the first chapter content—The Scientific Study of Life:

1. is the study of life.

2. Jane Goodall is famous for her research on chimpanzees. Dr. Goodall observed the chimpan- zees for long periods of time and made numerous observations of them that she recorded very carefully. Which stage of scientific inquiry is this considered?

A) Exploration

B) Testing

C) Making a hypothesis

D) Drawing a conclusion

3. Use the following figure to answer this question. Assume your results reject your initial hypothesis as indicated. Briefly explain why you would not return to the exploration portion of the process to change the question instead of revising the hypothesis.

Hypothesis

The remote’s batteries are dead.

TESTING • Forming hypotheses • Making predictions • Running experiments • Gathering data • Interpreting data • Drawing conclusions

Prediction

If I replace the batteries, the

remote will work.

Experiment

I replace the batteries with

new ones.

Experiment does not support

hypothesis; revise hypothesis or

pose new one.

Experiment supports hypothesis;

make additional predictions

and test them.

Revise

EXPLORATION

SIMO0333_06_ARG_SE_C01_PRF.indd 1 5/14/18 7:23 PM

 

 

Chapter 1: Learning about Life

2 Copyright © 2019 Pearson Education, Inc.

4. Match the following terms with the best definition: data, science, hypothesis, experiments, and peer review

Scientific tests where conditions can be controlled:

A tentative explanation for a set of observations:

A thorough review of scientific results prior to publication:

Inquiry into how the natural world functions:

Recorded observations:

5. The following figure indicates that the testing and communication components of science connect to each other. Briefly explain how these two components interact to strengthen each other. Hint—think back to peer review

6. An often misunderstood concept is the difference between a scientific theory and a hypothesis. Briefly explain what you would tell a student who believes a scientific theory and a hypothesis are the same.

EXPLORATION • Making observations • sking uestions • eeking information

TESTING • Forming hypotheses • Making predictions • Running experiments • Gathering data • Interpreting data • Drawing conclusions

COMMUNICATION • haring data • btaining feedback • ublishing papers • Replicating findings • uilding consensus

OUTCOMES • uilding knowledge • olving problems • Developing new technologies • enefiting society

SIMO0333_06_ARG_SE_C01_PRF.indd 2 5/14/18 7:23 PM

 

 

Chapter 1: Learning about Life

Copyright © 2019 Pearson Education, Inc. 3

7. Use the following table to compare a control group to an experimental group.

Control group Experimental group Description

8. On page 8 of your textbook the authors describe an experiment in which the amount of butter is changed between two cookie recipes. Imagine a scenario in which a person also changes the type of flour used (whole wheat flour versus regular bleached flour). Is this still an effective controlled experiment? Briefly explain your answer either way.

9. Use the following figure to answer this question. By day 8 how far have the baby turtles traveled?

10. How many factors does a scientist want to differ between the experimental and control groups?

A) 2

B) 0

C) 1

D) 3

250

200

150

100

50

0

Days after release

D is

ta nc

e tr

av el

ed (k

m )

0 14128 10642

Key

Average of 24 green sea turtles verage of oating buckets

SIMO0333_06_ARG_SE_C01_PRF.indd 3 5/14/18 7:23 PM

 

 

Chapter 1: Learning about Life

4 Copyright © 2019 Pearson Education, Inc.

11. You are a research scientist for the National Institutes of Health (NIH) interested in perform- ing a controlled experiment to determine the effects of caffeine on human blood pressure. One group of people will get caffeinated coffee and one will get decaffeinated coffee. Briefly explain why you would want that to be the only variable that differs between the two groups.

12. A is a fake treatment given to patients in the control group.

13. A friend tells you her grandfather’s pancakes are superior to all other pancakes because he puts only hand-churned butter from llamas into the batter. This is an example of what kind of evidence?

Chapter Content: The Properties of Life

Complete the following questions as you read the first chapter content—The Properties of Life:

1. A giant sequoia tree is very different from a human. List two properties these two organisms would exhibit despite all of their obvious differences.

2. A smart phone is not alive. List three characteristics of life that the phone does not exhibit.

3. List the properties of life.

Chapter Content: Major Themes in Biology

Complete the following questions as you read the first chapter content—Major Themes in Biology:

1. The branched structure of human lungs significantly increases the surface area for gas exchange. This greatly increases the efficiency of gas exchange within the lungs. Which of the following unifying themes of biology does this example illustrate?

A) Evolution

B) Relationship to structure and function

C) Interaction within biological systems

D) Information flow

SIMO0333_06_ARG_SE_C01_PRF.indd 4 5/14/18 7:23 PM

 

 

Chapter 1: Learning about Life

Copyright © 2019 Pearson Education, Inc. 5

2. Human growth hormone (HGH) is necessary for growth during human adolescence. Pituitary dwarfism is a condition that results from the inability of a person to produce HGH. Luckily, the human gene for HGH can be inserted into E. coli bacteria, which are able to make our HGH. The resulting HGH is used by people who are unable to make their own. What prop- erty about hereditary information makes this possible?

3. Energy and chemicals move through ecosystems in different ways. Energy flows an ecosystem, while nutrients are constantly through the ecosystem.

4. What level of biological organization is represented by Figure 1.14 on page 12 of your textbook?

C ol

or iz

ed S

EM 5

,4 00

*

SIMO0333_06_ARG_SE_C01_PRF.indd 5 5/14/18 7:23 PM

 

 

Chapter 1: Learning about Life

6 Copyright © 2019 Pearson Education, Inc.

5. What about Figure 1.13 on page 12 of your textbook?

6. Even though they have several differences, a bacterium and a human cell will both contain DNA. With respect to evolution, what does this fact suggest?

7. True or false: If false, please make it a correct statement. A rancher uses a particular chicken for breeding purposes because, on average, she observed that the chicken laid more eggs than other chickens. The rancher selecting the desirable trait would be considered an example of natural selection.

Major Theme Connection:

1. As a general rule, viruses are not considered to be alive based on several reasons. One such reason is that some viruses use RNA as their genetic material instead of DNA. Which of the five biological themes does this violate? Briefly explain why.

SIMO0333_06_ARG_SE_C01_PRF.indd 6 5/14/18 7:23 PM

 

 

Chapter 1: Learning about Life

Copyright © 2019 Pearson Education, Inc. 7

Common Thread Connection:

1. A scientist at the University of Iowa uses a microscope to observe cells in the brain known as microglia. He makes observations about their structure, location, and activity. The scientist eventually observes the cells undergo a sudden and radical shift in their structure/shape and their motility (ability to move). He asks himself questions about what is causing this shift in behaviors and begins to design an experiment to determine the answer. Briefly describe how the scientist practiced both the exploration and testing aspects of scientific inquiry.

SIMO0333_06_ARG_SE_C01_PRF.indd 7 5/14/18 7:23 PM

Lab Osmosis And Diffusion

/in /by

0/1/13 10:29 AMBIO156 – Lab 4

Page 1 of 11https://www.riolearn.org/content/bio/BIO156/BIO156_INTER_0000_v…b04.shtml?encrypted-sectionid=Z0RiRVE3bkZMRnd4WmZJc2doQjNnZz09

Lab 4 Cell Structure, Osmosis, and Diffusion

Introduction: Connecting Your Learning

The basic building block of life is the cell. Each cell contains several structures, some of which are common to both eukaryotic and prokaryotic cells and some that are unique to specific cell types. This lab will discuss cell structures and how materials are moved in and out of the cell. Specifically, the principles of diffusion and osmosis will be demonstrated by performing a scientific investigation that studies the effect of salt concentration on potato cells.

Focusing Your Learning

Background Information

In 1662, Robert Hooke investigated the properties of cork when he discovered cells. He named them after small rooms in a monastery because they reminded him of them. Years later, in 1837, Schleiden and Schwann were attributed with developing the cell theory. While their original theory was modified, the fundamental ideas be- hind the theory held true. Three general postulates are included in the cell theory: 1) All organisms are composed of cells. 2) The cell is the unit of life. 3) All cells arise from pre-existing cells.

Because a cell is the basic building block of living things, it is important to become familiar with its characteristics. Several structures comprise a cell. Many of these structures are visible with the use of a standard compound microscope. Below are pictures of idealized plant and animal cells, illustrating the important structures.

The cell membrane encloses all cells and is responsible for separating the internal en- vironment from the extracellular space (the space between cells). Because other struc- tures within the cell are also surrounded by a membrane, the outer membrane is of- ten called the plasma membrane.

 

 

10/1/13 10:29 AMBIO156 – Lab 4

Page 2 of 11https://www.riolearn.org/content/bio/BIO156/BIO156_INTER_0000_v…b04.shtml?encrypted-sectionid=Z0RiRVE3bkZMRnd4WmZJc2doQjNnZz09

The cell membrane is semi-permeable, allowing cer- tain molecules to enter into the cell freely, while oth- ers are prohibited from entering the cell. It is com- posed of phospholipids, which have a head consist- ing of a phosphate group and a tail of two fatty acid chains. The phosphate group is attracted to water

(hydrophilic) while the fatty acid chains are repulsed by water (hydrophobic). When in water, the properties of the phospholipids cause them to form two layers: The hy- drophobic tails face the inside of the double layer (away from the water), and the hy- drophilic heads face out (toward the water). Because two layers are formed, the mem- brane is made up of a phospholipid bilayer, as seen in the image.

The cell wall surrounds the cell membrane in plant cells, bacteria, and some fungi. In plant cells, the cell wall is composed of cellulose. In bacteria, the wall is made mostly of polypeptides (protein) or polysaccharides (carbohydrates). The cell wall provides support and protection and is responsible for giving plant cells their shape.

Another important structure found only in eukaryotic cells is the nucleus. This struc- ture contains the genetic information and is the control center of the cell. Protecting the nucleus is a double-membrane called the nuclear envelope, which, like the plasma membrane, is semi-permeable. It is important to note that although prokaryotes lack a nucleus, they still contain genetic information.

Within the nucleus is the nucleolus. This is the site where ribosomes are formed. Ri- bosomes function to assemble proteins. Many cells have multiple nucleoli, which con- tain concentrated areas of DNA and RNA.

Flagella (singular is flagellum) is Latin for whip. Flagella are whip-like projections of- ten found in prokaryotes, eukaryotic single-celled organisms, and some specific cells (like human sperm). These structures extend beyond the cell membrane and cell wall and are used for locomotion (movement). Although flagella are found in both eukary- otes and prokaryotes, the structure of the flagella is different for each cell type.

Cilia (singular is cilium) are structurally similar to eukaryotic flagella but are smaller and more hair-like. Cilia are found in some eukaryotic organisms. Some cilia are used for locomotion, as in the single-celled paramecium. In other organisms, the cilia act as

 

 

10/1/13 10:29 AMBIO156 – Lab 4

Page 3 of 11https://www.riolearn.org/content/bio/BIO156/BIO156_INTER_0000_v…b04.shtml?encrypted-sectionid=Z0RiRVE3bkZMRnd4WmZJc2doQjNnZz09

a filter. Sometimes, cilia are used not to move the cell itself, but to move objects through a cell (akin to a conveyer belt).

Vacuoles are specialized organelles that are responsible for storing starch, water, and pigments. They also act as a repository for metabolic wastes. Some plant cells contain a large, central vacuole, which occupies almost the entire cell. Central vacuoles are re- sponsible for providing support, which is based on the amount of water or pressure against the cell wall. If too much water is lost in the central vacuole, a plant will lose its support and appear to droop.

Centrioles are found in all animal cells and some plant cells. These structures, which occur in pairs, are responsible for the cytoskeleton. The cytoskeleton is composed of microtubules, microfilaments, and intermediate filaments. It is with these long struc- tures that the cytoskeleton provides support, maintains the cell shape, and anchors the organelles. The cytoskeleton is also used for moving structures or products.

Within eukaryotes is an endomembrane system. In this system, the endoplasmic retic- ulum, which consists of a membrane that forms folds and pockets, connects the nu- clear envelope, the Golgi apparatus (or Golgi complex), and cell membranes. This system is often called the factory of the cell because each of the individual organelles contributes to the production and delivery of proteins, lipids, and other molecules.

The nucleus contains the blueprints for proteins. These plans are then passed to the rough endoplasmic reticulum (RER). This structure is composed of several folds of a membrane and is covered with ribosomes (these bumps are why it is called rough en- doplasmic reticulum). Once the ribosomes receive the plans, the protein is built. Some proteins will move to the Golgi complex. Other proteins will move to the smooth en- doplasmic reticulum (it is called smooth because it lacks ribosomes). These proteins instruct the organelle to build other molecules, such as lipids and carbohydrates. Like some proteins from the RER, some of these molecules will move to the Golgi com- plex.

The Golgi apparatus is the central post office area of the cell. It receives the products of the rough endoplasmic reticulum and smooth endoplasmic reticulum, packages them, and ships them to their intended destination.

Another structure found only in photosynthetic cells is the chloroplast. This special- ized structure belongs to a class of membrane-lined sacs called plastids (like the vac-

 

 

10/1/13 10:29 AMBIO156 – Lab 4

Page 4 of 11https://www.riolearn.org/content/bio/BIO156/BIO156_INTER_0000_v…b04.shtml?encrypted-sectionid=Z0RiRVE3bkZMRnd4WmZJc2doQjNnZz09

uole). The chloroplast contains pigments and is responsible for creating food through photosynthesis.

Eukaryotic cells contain an organelle called the mitochondria, which is the site of en- ergy production. This structure is often referred to as the powerhouse of the cell. Cel- lular energy is stored in the form of adenosine triphosphate (ATP).

The ability of a cell to absorb water and nutrients is an important aspect of its sur- vival. Diffusion is the movement of solutes (dissolved molecules) in a solution or ma- trix from an area of high concentration to an area of lower concentration. Molecules move down the concentration gradient: from an area of high concentration to an area of low concentration. The greater the concentration differential, the faster the rate of diffusion. The size, shape, and composition of the solute also affect the ability of a substance to diffuse. These factors become increasingly important when considering the diffusion of substances across the cell membrane. Diffusion, being a passive process, is quite efficient across small distances. However, as distances become longer, the efficiency of diffusion decreases.

Osmosis is the movement of water across a selectively permeable membrane from an area of lower concentration (of solute) to an area of higher concentration (of solute). Remember that everything in the universe is constantly moving toward a state of equilibrium. Living cells contain a small amount of salt. For example, human cells contain 0.85% NaCl. If the solution outside the cell has this same concentration, the solution is said to be isotonic. Because there is no net difference in solutes between the inside and outside of the cell, there is no net movement of water. Higher concen- trations of solutes outside of the cell are termed hypertonic, while lower concentra- tions are termed hypotonic.

An important concept that affects how well a cell can absorb and pass material through the membrane is the surface-to-volume ratio. This formula for calculating this ratio is:

Surface area ÷ Volume

Because cells constantly interact with their external environments to obtain nutrients and remove wastes, it is critical that they maintain a proper surface-to-volume ratio.

As objects of the same shape increase in size, the surface-to-volume ratio decreases.

 

 

10/1/13 10:29 AMBIO156 – Lab 4

Page 5 of 11https://www.riolearn.org/content/bio/BIO156/BIO156_INTER_0000_v…b04.shtml?encrypted-sectionid=Z0RiRVE3bkZMRnd4WmZJc2doQjNnZz09

For example, suppose there are two cubes. Cube 1 is 1 cm x 1 cm x 1 cm, and Cube 2 is 10 cm x 10 cm x 10 cm. To calculate the surface-to-volume ratio, the formula for de- termining the surface area (SA) of a cube (length x width x number of sides) and the formula for the volume (V) of a cube (length x width x height) must be known. Once the formulas for calculating surface area and volume of a cube are known, the surface area to volume ratios can be calculated, as seen below.

CUBE 1 CUBE 2

Surface Area: 1cm x 1cm x 6 sides = 6cm2 10cm x 10cm x 6 sides = 600cm2

Volume: 1cm x 1cm x 1cm = 1cm3 10cm x 10cm x 10cm = 1000cm3

SA/V: 6cm2/1cm3 = 6.0 cm2/cm3 600cm2/1000cm3 = .6cm2/cm3

As shown in the calculations above, the ratio for Cube 2 is significantly smaller than the ratio for Cube 1. The same trend holds true for cells. As a cell gets larger, the SA/V ratio decreases, meaning that it is not as efficient in moving material in and out of the cell. In other words, the size of the cell membrane relative to the contents of the cell decreases as the cell size increases.

An illustration of the importance in maintaining a high surface-to-volume ratio can be found in the human digestive system. Cells in the human digestive system contain villi, which are finger-like projections. Because of their shape, they have a large sur- face area for a small volume.

Procedures

1. Cell Structure and Function a. Label the following idealized plant and animal cells.

 

 

b. Observing Cell Structures Under a Microscope i. Utilize the Virtual Microscope to view several cell structures. When

using the virtual microscope, complete the following steps in the order provided below. Failure to properly perform the steps in the correct order will result in failure to complete subsequent steps. Click to view

 

 

10/1/13 10:29 AMBIO156 – Lab 4

Page 6 of 11https://www.riolearn.org/content/bio/BIO156/BIO156_INTER_0000_v…b04.shtml?encrypted-sectionid=Z0RiRVE3bkZMRnd4WmZJc2doQjNnZz09

optional detailed instructions. ii. Drag and drop the desired slide onto the microscope.

iii. Click on the stage clip knob on the left of the microscope stage. iv. Adjust the interpupillary distance. First click on the title interpupillary

distance. Next, place the pointer on the images and adjust them until the two images are observed as one image.

v. Adjust the slide position. Place the pointer on the positioner and ad- just the slide so there is a clear view of the specimen.

vi. Adjust the iris diaphragm until a comfortable light is obtained. vii. Adjust the diopter until a clear image is obtained. Use the line on the

slide and move it up or down. viii. Adjust the coarse focus. Use the line and move it up or down until a

clear image is obtained. ix. Adjust the fine focus. Use the line and move it up or down until a

clear image is obtained. x. Adjust the magnification by clicking on the objective numbers on the

microscope. xi. Using the virtual microscope, view Spirogyra. Identify and draw an

image of the chloroplasts. xii. Using the virtual microscope, view the slide of a paramecium. Identify

and draw an image showing the cilia. xiii. Using the virtual microscope, view the slide of the Euglena. Identify

and draw an image of the flagella. 2. Demonstration of Osmosis in a Potato

a. Learn to use the caliper. 1. Take the Vernier caliper out of the lab kit. Examine the scale on the

tool and try to measure the length of an object. Look closely at the scale. The metric scale will be used for measurements in this lab.

2. Read the scale by measuring exactly 2 cm (20 mm). Next, measure 4.5 cm (45 mm).

3. This caliper is accurate enough to measure to the nearest tenth of a millimeter (measured by the small, scored lines in the window). With the caliper in hand, go to this instructional Web site, which describes how to use a Vernier caliper.

Watch the scale move as in an actual measurement.

 

https://www.riolearn.org/content/bio/BIO156/BIO156_INTER_0000_v8/pdf/Additional%20Instructions%20for%20the%20Virtual%20Microscope.pdf
http://www.physics.smu.edu/~scalise/apparatus/caliper/
http://www.physics.smu.edu/~scalise/apparatus/caliper/tutorial/

 

10/1/13 10:29 AMBIO156 – Lab 4

Page 7 of 11https://www.riolearn.org/content/bio/BIO156/BIO156_INTER_0000_v…b04.shtml?encrypted-sectionid=Z0RiRVE3bkZMRnd4WmZJc2doQjNnZz09

b. Set up the experiment 1. Get four 8 oz. cups from the lab kit. Place a piece of tape on each cup

or glass. Using a pen or marker, label the tape on each cup with one of the following percentages: 0%, 1.75%, 3.5%, and 7%.

2. Using the graduated cylinder, measure out 100 mL of distilled water. Pour the water into the fifth, unlabeled cup.

3. Measure out 1.5 level teaspoons of salt and add it to the unlabeled cup containing 100 mL of distilled water. Mix completely. This is the 7% salt solution.

4. Using the graduated cylinder, measure out 50 mL of this mixture and pour it from the graduated cylinder into the cup labeled 7%.

5. Add distilled water up to the 100 mL mark of the graduated cylinder to make the next dilution. Adding 50 mL distilled water to 50 mL of a 7% solution will result in 100 mL of a 3.5% solution.

6. Using the graduated cylinder, measure out 50 mL of the 3.5% solution and pour it from the graduated cylinder into the cup labeled 3.5%.

7. Add distilled water up to the 100 mL mark of the solution in the grad- uated cylinder to make the next dilution. Adding 50 mL of distilled water to the 50 mL of the 3.5% solution will result in 100 mL of a 1.75% solution.

8. Using the graduated cylinder, measure out 50 mL of the 1.75% solu- tion and pour it from the graduated cylinder into the cup labeled 1.75%.

9. Empty the remaining 1.75% solution down the drain of the sink and rinse out the graduated cylinder with tap water.

10. Using a sharp steak or kitchen knife, slice eight pieces of potato exact- ly 10 mm x 10 mm x 40 mm (1 cm x 1 cm x 4 cm). It is critically impor- tant that these potato core pieces are cut as precisely as possible; they need to all start out having the same volume. A single- edge razor blade may work better than a knife.

11. Determine the volume of the potato cores. The volume, is calculated by multiplying the width x height x length. Therefore, each core starts out with a volume of 4,000 cubic millimeters or 4 cubic centimeters. Measure the cores with both the mm ruler and the calipers. Measuring with the calipers to the nearest millimeter will be good enough for this lab. Create a data table like the one below to record the beginning and

 

 

10/1/13 10:29 AMBIO156 – Lab 4

Page 8 of 11https://www.riolearn.org/content/bio/BIO156/BIO156_INTER_0000_v…b04.shtml?encrypted-sectionid=Z0RiRVE3bkZMRnd4WmZJc2doQjNnZz09

ending volumes.

Table 1. Potato core measurements

0% saltsolution 1.75% salt solution

3.5% salt solution

7% salt solution

Beginning average volume (cu mm)

Ending average volume (cu mm)

Percent difference

12. Place two measured cores into each solution overnight, or for at least 8 hours. That time period is not critical to the results; it can be longer.

13. Remove the cores from one of the cups and pat them dry with a paper towel. The solution may now be discarded down the drain of a sink.

14. Using the caliper, measure the height, width, and length of the cores, and then determine the volume of each core. Average the measure- ments for the two cores and record in the data table above. The cores can now be discarded.

15. Repeat Steps 11 – 14 three more times: one time for each cup. 3. Illustration of the Importance of Surface-to-Volume Ratios

a. Calculate the surface-to-volume ratio of the following potato cubes: 1. CUBE 1: Length, width, and height are all 5 mm 2. CUBE 2: Length, width, and height are all 3 mm

b. Effect of cell size on diffusion rate 1. With clean hands, cutting board, and knife, cut the skin off of the pota-

to. 2. Using the knife, cut two cubes of potato with dimensions of 1 cm x 1

cm x 1 cm. 3. Using the knife, cut two cubes of potato with dimensions 1.5 cm x 1.5

cm x 1.5 cm. 4. Using the knife, cut two cubes of potato with dimension of 2 cm x 2

cm x 2 cm. 5. Place distilled water into a cup or glass. Add the vial of food coloring

to the water until a dark color is achieved.

 

 

10/1/13 10:29 AMBIO156 – Lab 4

Page 9 of 11https://www.riolearn.org/content/bio/BIO156/BIO156_INTER_0000_v…b04.shtml?encrypted-sectionid=Z0RiRVE3bkZMRnd4WmZJc2doQjNnZz09

6. Carefully place the potato cubes in the solution. The cubes must be completely submerged in the water. Let them stand in the solution for 2 to 4 hours.

7. After 2 to 4 hours, remove the cubes. Using the knife, cut each cube in half.

8. Using the ruler, measure how far the solution has diffused into each potato cube.

9. Record the results. A sample data table is included below that may be used to organize and record the results.

10. Complete the following calculations to determine the rate of diffusion and record the results.

Rate of Diffusion (cm/min)= Distance of diffusion ÷ time.

Cube Distance of Diffusion Rate of Diffusion

1 cm cubed

1 cm cubed

1.5 cm cubed

1.5 cm cubed

2 cm cubed

2 cm cubed

Average Rate of Diff.

Assessing Your Learning

Compose answers to the questions below in Microsoft Word and save the file as a backup copy in the event that a technical problem is encountered while attempting to submit the assignment. Make sure to run a spell check. Copy the answer for the first question from Microsoft Word by simultaneously holding down the Ctrl and A keys to select the text, and then simultaneously holding down the Ctrl and C keys to copy it. Then, click the link on the Lab Preview Page to open up the online submit form for the laboratory. Paste the answer for the first question into the online dialog boxes by inserting the cursor in the dialog box and simultaneously holding down the Ctrl and V keys. The answer should now appear in the box. Repeat for each question. Review all work to make sure that all of the questions have been completely answered and then click on the Submit button at the bottom of the page.

 

 

10/1/13 10:29 AMBIO156 – Lab 4

Page 10 of 11https://www.riolearn.org/content/bio/BIO156/BIO156_INTER_0000_…b04.shtml?encrypted-sectionid=Z0RiRVE3bkZMRnd4WmZJc2doQjNnZz09

LAB 4

1. Answer the following questions: a. List four cell structures that are common to both plant and animal cells. (4

points) b. What structures are unique to plant cells? (2 points) c. What structures are unique to animal cells? (2 points)

2. List five structures observed in the cell images and provide the function of each structure. (5 points)

a. Structure 1 and function b. Structure 2 and function c. Structure 3 and function d. Structure 4 and function e. Structure 5 and function

3. William is observing a single-celled organism under a microscope and notices that it has a nucleus and is covered in small, hair-like structures.

a. Provide a probable name for this organism (1 point) b. Explain why William came to this conclusion. (2 points)

4. Where in the cell are the chloroplasts located? (5 points) 5. In the Spirogyra cells observed on the virtual microscope, about how many cir-

cular green chloroplasts were seen in a single cell? (2 points) 6. What were the percent differences between the volumes of the potatoes in the

osmosis experiment for each salt solution? (8 points) a. 0% b. 1.75% c. 3.5% d. 7%

7. What extraneous variables might have affected how the results came out in the osmosis experiment? Describe three. (6 points)

a. b. c.

8. In osmosis, which direction does water move with respect to solute concentra- tion? (2 points)

9. Answer the following questions: a. Explain what would happen to a freshwater unicellular organism if it were

suddenly released into a saltwater environment. Use the terms isotonic,

 

 

10/1/13 10:29 AMBIO156 – Lab 4

Page 11 of 11https://www.riolearn.org/content/bio/BIO156/BIO156_INTER_0000_…b04.shtml?encrypted-sectionid=Z0RiRVE3bkZMRnd4WmZJc2doQjNnZz09

hypotonic and hypertonic in the answer. (3 points) b. What would happen if a marine organism were placed in freshwater? (3

points) 10. A student purchases and weighs 5 pounds of carrots from a local grocery store.

She notices that the grocery store constantly sprays its produce with distilled water. After returning home, she weighs the carrots again and discovers that they weigh only 4.2 lbs. They also no longer seem as crisp and taut. Provide a possible explanation for why the carrots weighed more at the store, based on the information learned in this lab. (5 points)

11. People always say that leeches can be removed from the body by pouring salt on them. Based on what the student learned about osmosis, provide an explanation that supports or refutes this information. (5 points)

12. What is the rate of diffusion for the potato cubes from the surface-to-volume ex- periment (procedure 3b)? (6 points)

a. Cube 1 b. Cube 2 c. Cube 3

13. Assume the potato cubes are cells. Which cube would be most efficient at mov- ing materials into and out of the cube? Briefly explain the answer. (4 points)

14. From what was observed in the potato procedure, how do the rate of diffusion and surface-to-volume ratio limit cell size? (5 points)

15. One night, Hans decides to cook a hamburger and spaghetti with meatballs. To test ideas of surface-to-volume ratios, he makes a quarter pound hamburger and a quarter pound meatball and cooks them at the same temperature. Which food item will cook the fastest and why? (5 points)

16. While watching a special on animals, Brianna discovers that hares tend to lose heat through their ears. Based on this and what is known about surface-to-vol- ume ratios, propose an explanation as to why hares that live in hot climates (such as the desert) have large, extended ears. (5 points)

17. (Application) How might the information gained from this lab pertaining to cell structures and diffusion be useful to a student employed in a healthcare related profession? (20 points)