Overview

Lesson Procedure

60-70 minutes of class time across 5 phases.

1. Warm-Up5-10 minutes
2. Direct Instruction15-20 minutes
3. Guided Practice15 minutes
4. Independent Practice20 minutes
5. Closure5 minutes

1. Warm-Up5-10 minutes

   Write three sentences on the board and give students two minutes.

   Warm-Up Prompt

   "(1) The base of the lamp is heavy. (2) Add the base to the acid one drop at a time. (3) In DNA, each base pairs with one other base." Write what base means in each sentence. Then underline the words in each sentence that told you.

   Take answers: the bottom part of an object; a substance that neutralizes an acid; one of the four chemical units along a DNA strand. Students should notice that the clue is never the word itself but the words near it ("of the lamp," "to the acid," "in DNA"). Tell them that the standard asks exactly this of science reading: to find the meaning a word, a symbol or a phrase has in this particular text, which may not be the meaning they know.

2. Direct Instruction15-20 minutes

   Part 1: Where science texts put meaning. Keep this table up for the whole lesson. Science writers usually tell the reader what a term or symbol means; the reader's job is to find where.

   Where a science or technical text tells you what a term or symbol means

   Signal in the text	What it gives you	Example from this lesson
   "is termed," "is called," "means"	A formal definition of a key term	"are termed the dominant" (T1, paragraph 1)
   "denoting," "stands for," "where R is"	A key for a symbol or letter	"If A be taken as denoting" (T1, paragraph 5)
   A phrase after a comma, a colon or in parentheses	A short definition set right beside the term	"a grab sample is a single sample" (T2, paragraph 2)
   "not ... but," "does not mean"	A contrast that rules out a wrong meaning	"does not mean the water has no nitrate" (T2, paragraph 5)
   Units, numbers and results around a term	The kind of quantity the term or symbol names	"measured in mg/L" (T2, paragraph 3)

   Part 2: Model with Mendel (T1). Explain that Mendel crossed pea plants that differed in one trait, such as round or wrinkled seeds, and followed their offspring for several generations. His translator kept Mendel's own terms, some of which have changed since. Read the excerpt aloud once, then go back and mark every term and symbol Mendel defines. Diagram 1 sets his symbols beside the modern ones.

   1[...] Henceforth in this paper those characters which are transmitted entire, or almost unchanged in the hybridisation, and therefore in themselves constitute the characters of the hybrid, are termed the dominant, and those which become latent in the process recessive. The expression “recessive” has been chosen because the characters thereby designated withdraw or entirely disappear in the hybrids, but nevertheless reappear unchanged in their progeny, as will be demonstrated later on.

   [...]

   2In this generation there reappear, together with the dominant characters, also the recessive ones with their full peculiarities, and this occurs in the definitely expressed average proportion of three to one, so that among each four plants of this generation three display the dominant character and one the recessive. [...]

   [...]

   3Those forms which in the first generation maintain the recessive character do not further vary in the second generation as regards this character; they remain constant in their offspring.

   4It is otherwise with those which possess the dominant character in the first generation [bred from the hybrids]. Of these two-thirds yield offspring which display the dominant and recessive characters in the proportion of 3 to 1, and thereby show exactly the same ratio as the hybrid forms, while only one-third remains with the dominant character constant.

   [...]

   5If A be taken as denoting one of the two constant characters, for instance the dominant, a, the recessive, and Aa the hybrid form in which both are conjoined, the expression A + 2Aa + a shows the terms in the series for the progeny of the hybrids of two differentiating characters.

   6[...] If an average equality of fertility in all plants in all generations be assumed, and if, furthermore, each hybrid forms seed of which one-half yields hybrids again, while the other half is constant to both characters in equal proportions, the ratio of numbers for the offspring in each generation is seen by the following summary, in which A and a denote again the two parental characters, and Aa the hybrid forms. For brevity’s sake it may be assumed that each plant in each generation furnishes only 4 seeds.

   [...]

   7In the tenth generation, for instance, 2ⁿ-1 = 1023. There result, therefore, in each 2,048 plants which arise in this generation 1,023 with the constant dominant character, 1,023 with the recessive character, and only two hybrids.

   Mendel's summary table, which follows paragraph 6 in the source (4 seeds per plant)

   Generation	A	Aa	a	Ratio A : Aa : a
   1	1	2	1	1 : 2 : 1
   2	6	4	6	3 : 2 : 3
   3	28	8	28	7 : 2 : 7
   4	120	16	120	15 : 2 : 15
   5	496	32	496	31 : 2 : 31
   n				2ⁿ-1 : 2 : 2ⁿ-1

   Work the three examples aloud. For each one, point to the words in the passage that fix the meaning, and say which signal from the table they are.

   • A symbol defined in the text: Mendel's A, Aa and a

     In paragraph 5, what does the symbol A stand for? Is it the same as the A in a modern Punnett square?

     Result: Paragraph 5 gives the key: "If A be taken as denoting one of the two constant characters, for instance the dominant." So Mendel's A names a kind of plant, one that is constant for the dominant character, Aa is "the hybrid form in which both are conjoined," and a is the constant recessive form. In a modern textbook, A is one copy of a gene (an allele), and Mendel's A plant would be written AA. Read with Mendel's key, A + 2Aa + a is the modern 1 AA : 2 Aa : 1 aa.

   • A key term with a science meaning: constant

     Paragraph 3 says the recessive forms "remain constant in their offspring." What does constant mean here?

     Result: The same sentence explains it: these forms "do not further vary in the second generation as regards this character." Constant therefore means breeding true: the offspring show the same character as the parent, generation after generation. It is not the math sense (a fixed number) or the everyday sense (never stopping). Paragraph 4 uses the same meaning when "only one-third remains with the dominant character constant." Note that character, too, means a trait such as seed shape, not a person in a story.

   • One word, two meanings in the same text: expression

     The word expression appears in paragraph 1 and in paragraph 5. Does it mean the same thing both times?

     Result: No. In paragraph 1, "The expression “recessive” has been chosen" means a word or term: Mendel is explaining why he picked that name, because recessive characters "withdraw or entirely disappear in the hybrids" and then reappear. In paragraph 5, "the expression A + 2Aa + a" means a mathematical expression, a combination of symbols. The clue each time is what follows the word: a term in quotation marks, then a line of symbols.

3. Guided Practice15 minutes

   Pairs read the stream report (T2) with two highlighters: one color for every symbol or abbreviation, the other for every term the report defines. Then check as a class: the report defines outfall, discharge, grab sample, DO, turbidity, suspended particles and detection limit, and gives a key for n, ±, NTU, < and ≥. Work the two examples together, one step at a time. Diagram 2 shows the DO results with the meter's uncertainty.

   1Purpose. Volunteers from a high school environmental science class sampled Alder Creek above and below the outfall of a small wastewater treatment plant. An outfall is the end of the pipe where treated water flows into the creek. The question was whether the discharge, the treated water the plant releases, changes the quality of the creek water. All values in this report are invented for teaching.

   2Sites and sampling. Site 1 is 200 m upstream of the outfall, so its water has not yet met the discharge. Site 2 is 150 m downstream. At each site we took three grab samples (n = 3) between 9:00 and 10:00 a.m. on May 14. A grab sample is a single sample of water collected at one place and one moment, here from mid-depth in the main flow.

   3Measurements. T is the water temperature in °C. DO is dissolved oxygen: oxygen gas dissolved in the water, which fish and insects take in through their gills, measured in mg/L (milligrams per liter). The DO meter was calibrated that morning, and its uncertainty is ± 0.2 mg/L: a reading of 8.0 mg/L means the true value lies between 7.8 and 8.2 mg/L. Turbidity is the cloudiness of water caused by suspended particles, bits of soil, algae or other matter carried along in the water instead of settling out. It is reported in NTU (nephelometric turbidity units); a higher number means cloudier water. Nitrate (NO₃⁻), a nutrient that feeds algae, was measured with a test kit whose detection limit, the smallest amount it can reliably measure, is 0.2 mg/L. A result below that limit is written "<0.2."

   4Results. Each value is the mean of the three samples at that site. Site 1: T = 14.2 °C, pH 7.8, DO = 9.6 mg/L, turbidity 4 NTU, nitrate <0.2 mg/L. Site 2: T = 15.8 °C, pH 7.5, DO = 7.1 mg/L, turbidity 11 NTU, nitrate 2.6 mg/L. The pH scale runs from 0 to 14: 7 is neutral, values below 7 are acidic and values above 7 are basic.

   5Interpretation. The state benchmark for trout streams, the level used to judge whether the water is healthy for trout, is DO ≥ 7.0 mg/L, read as "at least 7.0 mg/L." Site 2 is only 0.1 mg/L above the benchmark, which is less than the meter's uncertainty, so we cannot say for certain that Site 2 meets it. The nitrate result at Site 1 does not mean the water has no nitrate: it means that any nitrate present was below what the kit can detect. Downstream, the water was warmer, cloudier and lower in oxygen, and it carried more nitrate. One morning of samples cannot show that the discharge caused these differences; the class plans to sample again in July.

   • Symbols in a data report: ± and ≥

     Site 2 has DO = 7.1 mg/L, and the benchmark is DO ≥ 7.0 mg/L. Use paragraphs 3 and 5 to explain what ± 0.2 mg/L and ≥ mean here, and whether the report can say that Site 2 meets the benchmark.

     Result: Paragraph 5 reads ≥ aloud: "at least 7.0 mg/L." Paragraph 3 defines ± by an example: a reading of 8.0 means the true value is between 7.8 and 8.2. So Site 2's 7.1 means a true value between 7.1 - 0.2 = 6.9 and 7.1 + 0.2 = 7.3 mg/L. Part of that range, from 6.9 up to 7.0, is below the benchmark, which is why the report says "we cannot say for certain." Site 1 (9.6, so 9.4 to 9.8 mg/L) clearly meets it.

   • A symbol with a limit: <0.2

     Nitrate at Site 1 is reported as "<0.2." A classmate writes, "Site 1 has no nitrate." Is that what the symbol means?

     Result: No. The symbol < means "less than," and paragraph 3 defines 0.2 mg/L as the kit's detection limit, "the smallest amount it can reliably measure." So <0.2 means there was too little nitrate for the kit to measure: somewhere from none up to 0.2 mg/L. Paragraph 5 rules out the classmate's reading directly: the result "does not mean the water has no nitrate."

   Debrief with one question: Which terms in T2 did the report define, and which did it expect you to know already? (It defines DO, turbidity and detection limit but not pH until the end of paragraph 4, and it never defines benchmark in a separate sentence: the phrase after the comma in paragraph 5 does that work.) Students should see that a definition can be a whole sentence, a phrase after a comma or an example with numbers.

4. Independent Practice20 minutes

   Students read the flashlight circuit guide below on their own and answer quiz questions 1-20 with the text open. Remind them to find the words in the guide that set each meaning before they choose an answer, and to cite paragraphs in their short answers.

   1About this guide. The kit flashlight runs on three 1.5 V AA cells and has a slide switch, a 100 Ω resistor and a white LED. This guide explains the symbols on the circuit diagram printed inside the lid of the box and the terms you need to build and test the circuit.

   2Symbols. On the diagram, each cell is drawn as a long thin line beside a short thick line. The long line is the positive terminal (+) and the short line is the negative terminal (-). Strictly, a single AA is a cell; two or more cells joined together make a battery, so the three cells in the kit form a 4.5 V battery. A zigzag line is a resistor, a part that limits the current. A triangle pointing at a bar, with two small arrows leaving it, is the LED (light-emitting diode). The two arrows stand for the light it gives off, not for the direction in which you connect it.

   3Units and quantities. V stands for volts, the unit of voltage, the electrical push that a battery gives. A stands for amperes, or amps, the unit of current, which is the rate at which electric charge flows past a point. The kit meter shows milliamperes, written mA, where 1 mA = 0.001 A. Ω, the Greek capital letter omega, stands for ohms, the unit of resistance. In the formula in paragraph 6, the letters stand for quantities, not units: I is current, R is resistance and each V is a voltage.

   4Series and parallel. Parts are in series when they are joined one after another in a single loop, so the same current passes through each of them. Parts are in parallel when each sits on its own branch between the same two points. In the kit, the cells, switch, resistor and LED are all in series.

   5Direction. An LED is polarized: it lets current through in one direction only. Its longer leg, the anode, must be connected toward the positive terminal of the battery; its shorter leg, the cathode, goes toward the negative terminal. On the diagram, the triangle points in the direction of the current. Current in this guide means conventional current, which is described as flowing out of the positive terminal, around the circuit and back into the negative terminal.

   6Checking the current. To measure the current, connect the meter in series with the LED, so that the current has to pass through the meter. Set the meter's dial to the 200 mA range; the range is the largest current the meter can show on that setting. You can predict the current with I = (Vb - VL) ÷ R, where Vb is the battery voltage, VL is the voltage across the LED (about 2.9 V for a white LED) and R is the resistance. With I in amperes, multiply by 1,000 to compare it with the meter reading in mA.

   7Faults. An open circuit is a break anywhere in the loop, such as a loose wire or a switch that is off: no current flows, and the LED stays dark. A short circuit is a path with almost no resistance that lets current bypass the resistor and the LED, for example a bare wire touching both ends of the battery. In this term, short means that the current takes a shortcut, not that the wire is short. A short circuit makes the cells hot and can damage them. If any part feels warm, open the switch at once and take out the cells.

5. Closure5 minutes

   Exit ticket: "Choose one term or symbol from today's texts whose science meaning is different from its everyday meaning. Give both meanings and quote the words in the text that set the science one." Sort the tickets into "both meanings and the clue," "both meanings, no clue" and "everyday meaning only" to plan the next lesson.

   Teacher note on Mendel's language. The Mendel excerpt uses the spelling and style of a 1902 British translation ("colour," "hybridisation," "conjoined"), and several of its terms have changed meaning. Mendel wrote before the words gene, allele, genotype and phenotype existed. His "hybrid" is any cross-bred plant (a modern heterozygote); his A and a name kinds of plants, not gene copies; and "character" means a trait. His "first generation [bred] from the hybrids" is the generation a modern textbook calls F2, and the table's generation 1 is that same F2. His table rests on the assumptions he states in paragraph 6: equal fertility in all plants and, for brevity, 4 seeds per plant. Students should read his terms by his definitions, then translate them, not the reverse.

   Homework passage. The homework uses the weather station key below. It packs symbols, key terms and everyday words with weather meanings into one short text.

   1Purpose. The school weather station posts one line of data every hour. This key explains the symbols and terms in that line. A typical line reads: 14:00 T 18.4 Td 11.2 RH 63 P 1009.6 ↓1.8 W SW 14 G 31 PCP T. All sample lines are invented for teaching.

   2Time and temperature. Times use the 24-hour clock, so 14:00 is 2 p.m. T is the air temperature in °C, measured in the shade 1.5 m above the ground. Td is the dew point in °C: the temperature to which the air would have to cool, with no change in the amount of water vapor it holds, for dew to start to form. The dew point is never higher than the air temperature. When the two are equal, the air is saturated, holding all the water vapor it can at that temperature, and fog or dew is likely.

   3Humidity. RH is the relative humidity, in percent: how much water vapor the air holds compared with the most it could hold at its present temperature. RH is not the chance of rain. Because it depends on temperature, RH usually falls during the afternoon as the air warms, even when the amount of water vapor stays the same.

   4Pressure. P is the air pressure in hPa (hectopascals), adjusted to sea level so that stations at different heights can be compared; 1 hPa = 100 Pa. The arrow and the number after it give the pressure tendency, the change over the last 3 hours: ↓1.8 means the pressure has fallen by 1.8 hPa since three hours earlier, and ↑ means it has risen. A fall of more than 1.0 hPa in 3 hours often means that a low-pressure system or a front, the boundary between two air masses, is approaching.

   5Wind. W gives the direction the wind is blowing from, not the direction it is blowing toward, followed by the average speed in km/h over the last 10 minutes. G is a gust, the highest 3-second speed in those 10 minutes. If no gust is at least 10 km/h faster than the average, G is left off the line. The word "calm" in place of a direction and speed means an average speed under 2 km/h.

   6Precipitation. PCP is the rain, or melted snow, that fell in the last hour, in mm. A number is the depth measured by the gauge, and 0.0 means none fell. The letter T in this column means a trace: some precipitation fell, but less than the 0.2 mm the gauge can measure. Do not confuse this T with the T for temperature near the start of the line; its place in the line tells you which one it is.

Differentiation Strategies

Assessment Guidance

1. Question 1 of 20 · Multiple Choice

   In the circuit diagram, a cell is drawn as two lines side by side. What does the long thin line stand for?

   AThe negative terminal (-) BA wire joining two cells CThe positive terminal (+) DThe metal case of the cell

2. Question 2 of 20 · Multiple Choice

   According to paragraph 3, what is current?

   AThe rate at which electric charge flows past a point BThe electrical push that a battery gives CThe brightness of the light the LED gives off DThe amount of charge stored inside the battery when it is new

3. Question 3 of 20 · Multiple Choice

   On the LED symbol, what do the two small arrows stand for?

   AThe direction in which to connect the LED BThe flow of current through the LED CThe two legs of the LED DThe light the LED gives off

4. Question 4 of 20 · Multiple Choice

   What does the symbol Ω stand for in "a 100 Ω resistor"?

   AWatts, the unit of power BOhms, the unit of resistance CThe resistor itself, drawn as a letter DOmega, the name of the resistor's maker

5. Question 5 of 20 · Multiple Choice

   The kit meter shows 27 mA. What is this current in amperes?

   A0.027 A B27,000 A C0.27 A D0.0027 A

6. Question 6 of 20 · Multiple Choice

   What does it mean that the parts of the kit are "in series"?

   AEach part sits on its own branch between the same two points BThe parts are sold together as one set CThey are joined one after another in a single loop DThe parts must be connected in the order they are listed

7. Question 7 of 20 · Multiple Choice

   Paragraph 5 says an LED is polarized. What does polarized mean here?

   AIt gives off light of only one color, like a colored filter BIt lets current through in one direction only CIt needs a resistor in order to work DIt can be used only in a parallel branch

8. Question 8 of 20 · Multiple Choice

   Which leg of the LED is the anode, and where does it connect?

   AThe shorter leg, toward the negative terminal BThe shorter leg, toward the positive terminal CEither leg, because the LED works both ways DThe longer leg, toward the positive terminal

9. Question 9 of 20 · Multiple Choice

   In paragraph 7, what is an open circuit?

   AA break in the loop, so no current flows and the LED stays dark BA circuit with the switch on, so current can flow CA circuit with no case around it DA circuit whose parts are joined in parallel branches instead of in one series loop

10. Question 10 of 20 · Multiple Choice

    Paragraph 7 says a short circuit "lets current bypass the resistor and the LED." What does bypass mean here?

    APass through them more quickly than usual BBe stopped by them completely CGo around them instead of through them DFlow through them in the wrong direction

11. Question 11 of 20 · Multiple Choice

    In the formula I = (Vb - VL) ÷ R, what does VL stand for?

    AThe voltage of one cell, 1.5 V BThe voltage across the LED, about 2.9 V CThe unit volts, written for the LED DThe largest voltage the kit meter can show on its dial

12. Question 12 of 20 · Multiple Choice

    Use the formula in paragraph 6 with the kit's battery and resistor. What current should the meter show?

    A45 mA B29 mA C0.016 mA D16 mA

13. Question 13 of 20 · Multiple Choice

    As the guide uses the term, in which direction does conventional current flow?

    AOut of the positive terminal, around the circuit and into the negative terminal BOut of the negative terminal, around the circuit and into the positive terminal CBack and forth between the two terminals DFrom the LED toward the cells

14. Question 14 of 20 · Multiple Choice

    Paragraph 6 says to set the meter's dial to "the 200 mA range." What does this phrase mean?

    AThe meter must show exactly 200 mA BThe circuit should draw about 200 mA CThe meter can show currents up to 200 mA on that setting DThe meter must be kept within 200 mm of the LED during the test

15. Question 15 of 20 · Short Answer

    In paragraph 2 the guide says, "Strictly, a single AA is a cell." People often call one AA "a battery." Explain the difference the guide makes, and why a technical guide cares about it.

    Show model answer

16. Question 16 of 20 · Short Answer

    A classmate reads "open the switch at once" in paragraph 7 and thinks it means switching the flashlight on. Use paragraph 7 to explain what open means in this guide, and why the mistake would matter.

    Show model answer

17. Question 17 of 20 · Short Answer

    A student replaces the 100 Ω resistor with a 68 Ω resistor and keeps the same battery and LED. Use the formula in paragraph 6 to predict the current in mA, and say what each symbol stands for.

    Show model answer

18. Question 18 of 20 · Short Answer

    The letter V appears in "1.5 V" and in "Vb." Explain the different job the letter does in each, citing paragraph 3.

    Show model answer

19. Question 19 of 20 · Short Answer

    Which part of the LED symbol shows which way round to connect the LED, and how does it fit with the rule for the anode? Cite paragraphs 2 and 5.

    Show model answer

20. Question 20 of 20 · Short Answer

    In the term short circuit, what does short mean, and what does it not mean? Explain, citing paragraph 7, and say why the term matters for safety.

    Show model answer

These standards connect to RST.9-10.4: prerequisites to review first, parallel standards at the same level, and next steps that build on it.

Standard text: Common Core State Standards for English Language Arts & Literacy. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.