Jasmin Latif
Analysis of a Biology Textbook for Instructional Purposes with Respect to the Michigan High School Content Substandard Populations (B3.5)
The biology subject specific textbook used for this analysis is Biology: Principles and Explorations. It was written by G. B. Johnson and P.H. Raven and published by Holt, Rinehart, and Winston in 2001. It is being used as a general reference text for students with ranging ability levels in 9th and 10th grade integrated science classes at Community High (Ann Arbor).
There is a broad learning goal of The Michigan ecological standards: Interdependence of Living Systems and the Environment (B3). I chose to analyze Biology: Principles and Explorations with respect to a smaller learning goal, Populations (B3.5), which falls under B3. In order to properly interpret these standards it was necessary to significantly “unpack” them first. This unpacking was done collaboratively and can be reviewed by accessing the following EDUC 422 website: https://teacherknowledge.wikispaces.com/Biology+-+Unpacking+Ecological+Energy+Flow
Within Biology: Principles and Explorations, there is Chapter 16 entitled Populations. This chapter has only two sections. Section 16-1 is How Populations Grow, whereas Section 16-2 is How Populations Evolve. Section 16-2 has no relevance to the B3.5 standard, so I chose to ignore it. I used Project 2061 criteria III.A (Providing a Variety of Phenomena), III.B (Providing Vivid Experiences), and IV.B (Representing Ideas Effectively), to analyze how well Section 16-1 helps with instruction concerning the B3.5 learning goal. The complete and detailed version of the Project 2061 textbook analysis criteria can be accessed on the following website: http://www.project2061.org/publications/textbook/hsbio/report/crit-used.htm
My analyses are organized into the chart included below. The chart only includes the items which I found to be helpful in reaching the learning goal.
Performance Expectations for B3.5 / Variety of Phenomena / Vivid Experiences / Representing Ideas Effectively1) Graphing population growth / Fig 16-1. The photo is an example of population growth and can be used to support the idea of population growth
RLBA (p.342). Graphs found in the Census can be useful examples.
Fig 16-4. The graph can be explicitly linked to learning how to graph exponential population growth. It can be used to explain time (the independent variable) appears on the x-axis and number of individuals (the dependent variable) appears on the y-axis. The lack of inclusion of unit labels or increments on either axis may be helpful in the beginning when discussion of the graph is simplistic, but something more detailed will have to be used to explain how the points are plotted in order to construct the graph.
Fig 16-5. The graph can be explicitly linked to learning how to graph logistic population growth. This graph is a bit more sophisticated than Fig 16-4. Time appears on the x-axis and number of individuals is replaced by population size on the y-axis. Again, no unit labels or increments appear, but green arrows are used to indicate in which direction time increases and population size increases. This can be helpful when learning how to graph population growth.
HWPPB (p.345). This textbox can be used to show another way scientists can graph population growth. It is explicitly linked to this performance standard in that it discusses how the graph is created with respect to axes and labeling. / Fig 16-1. The photo provides a vicarious sense of population growth by depicting a place densely crowded by people. / Fig 16-1. The densely crowded depiction seems comprehensible to students and is explicitly linked to population growth in real-life.
RLBA (p.342). The Census provides a real-world example of how data is collected and the importance of graphing population growth.
Fig 16-4. Although highly schematic, the graph is accurate and comprehensible. The use of red emphasizes the J-shape.
Fig 16-5. Although highly schematic, the graph is accurate and comprehensible. The use of red emphasizes the S-shape.
HWPPB (p.345). This textbox is explicitly linked to a human real-life application. Students can see the importance of graphing and tracking population graphs over time. Students can see the benefits of population graphs in that they can help to predict future needs of our society.
2) Influences on population growth / Fig 16 -1. Data given in caption can be used to start discussion on what students feel may be influencing this example of population growth
3) Consequences of invading organisms
4) Advantages and disadvantages of reproductive strategies / Fig 16-7. These photos can be used to support, and are explicitly linked to the concept of reproductive strategies. / Fig 16-7. These photos give direct examples of two commonly well-known organisms to students (one for r-strategy and one for k-strategy). However, in the text which references this figure, it is suggested that the characteristics of these strategies are summarized in this figure. This is confusing, because there is no mention of the characteristics; there simply appear the photos and short captions explaining which organism is what type of strategist. I would like to augment these photos with a 2-column summary table with “cockroaches” in the first column and “whale” in the second column. Under each column would be listed the characteristics of the corresponding reproductive strategy for each organism. Construction of this table with students would facilitate comparison of the two types of strategies which is helpful to learn the advantages and disadvantages of each.
5) Influence of biotic and abiotic factors on population dynamics
6) Exponential growth and carrying capacity / Fig 16-1. The data given in caption can be used to introduce the possibility of Earth’s carrying capacity for humans.
RLBA (p.342). The Census can be examined for exponential growth curves and possible carrying capacity can be extrapolated.
Fig 16-4. This graph is explicitly linked to exponential growth (self-explanatory)
Fig 16-5. The logistic growth curve is explicitly linked in the text to exponential growth and carrying capacity. It explains that the logistic model is used when exponential growth is limited by density-dependent factors and carrying capacity corresponds to the largest population size an environment can sustain with these limits.
IDA (p.354): This activity is explicitly linked to the key idea. Students need to understand carrying capacity and how to identify and interpret an exponential growth graph. / IDA (p.354). This activity provides a vicarious sense of being a real life scientist that uses an exponential growth graph to estimate carrying capacity. / RLBA (p.342) Examination of the Census provides a real-life link to studies of populations that grow exponentially
Fig 16-4. Although highly simplified, the graph is accurate and comprehensible. The use of red emphasizes the J-shape.
Fig 16-5. Not as simple as fig. 16-4 (see description under “Variety of Phenomena” in this table), the graph is accurate and comprehensible. The use of red emphasizes the S-shape. Leveling-off at carrying capacity is explicitly indicated and pronounced by a blue line extending back to the y-axis from its point on the curve.
IDA (p.354): This activity is explicitly linked to a real-life occurrence. Students are asked to interpret data that actual scientists gathered. Students are given exposure to what an exponential curve may look like made from real-life data. They can see that the graph does not have a perfect S-shape. The graph fluctuates just above and below the carrying capacity, this is more realistic. It is important for students to contrast ideal graphs from real-life graphs.
Key to Helpful Representations and Phenomena (appear in chart)
Fig 16-1: Photo of rush-hour commuters, caption explains there are more people living in greater NYC area than lived on Earth 10,000 yrs. ago.
Real Life Box Activity (RLBA) p.342: Defines U.S. Census and how government collects detailed information on the country’s population, the activity has students use the Internet to learn more about it, why every household should complete a Census form, and what steps have been taken to improve its accuracy.
Fig 16-4: Graph of an exponential growth curve, caption explains that it has a characteristic J-shape.
Fig 16-5: Graph of a logistic growth curve, caption explains that it has a characteristic S-shape.
Fig 16-7: Two photos. First photo shows cockroaches who are given as an example of r-strategists in caption. The second photo shows a Humpback whale who is given as an example of a k-strategist in caption. The figure is titled “Different species have evolved different growth patterns”.
Health Watch on Population Pyramids Box (HWPPB) p. 345: Shows a graphic example of a population pyramid and accompanying text explains it is one way to represent the structure of a large human population. It explains age groups are plotted on the y-axis and the number of individuals is plotted on the x-axis. It discusses why the graph takes on the shape of a pyramid, how dominant age-groups (ex: babies or elderly) can be seen from the graph, and how if these dominant age-groups need certain types of health care (ex: pediatric or geriatric) the graph can be used to predict the health care trends for the population in the future.
Interpreting Data Activity (IDA) p.354: This activity asks students to determine the carrying capacity of an island for a pheasant population that was introduced onto the island in the 1930s. Students are given a population growth graph with ‘Years since introduction’ on the x-axis and ‘Number of individuals’ on the y-axis. They are also asked to describe how they reached their answer.
It is obvious from the table that the ideas of performance standards #3 and #6 were very poorly represented in section 16-1. In fact, I found no appropriate representations or phenomena which addressed invading populations or the physical and chemical influences on population growth. There is hardly any mention of the physical and chemical influences found in the text, but there are no relevant figures to accompany these brief mentions. Invading populations, however, are not mentioned in the text at all. As the teacher, I would look to remedy this first and foremost. Maybe I could turn to another biology textbook written for students of the same age groups to look for more informational readings and representations on invading populations and physical and chemical influences. In order to address influences of invading populations, students must understand how food webs are altered with the new population and what this means for existing populations. If students see that invading populations change the ecosystem and the amount of available resources, they will see how this affects population growth. Beyond simply giving the definition of an invading species, I would hope to provide my students with graphs of population growth that show pronounced shifts in growth rate before and after an invading species. With physical and chemical influences, it is important for students to distinguish between biotic and abiotic factors. I would ask my students to create a list of factors and then go over it as a class and fill in important factors they overlooked.