Lesson Exemplar — Science 8

Term 1 · Week 4 · Day 1 · Domain: Life Science

This is one day. For the whole of Week 4 in the format DepEd prescribes for filing, see lesson-plan-ilaw.md.

I. CURRICULUM CONTENT, STANDARDS, AND LESSON COMPETENCIES

A. Content Standards

Quoted from the curriculum guide (DepEd, August 2023, p. 51), Grade 8 Quarter 1, content standard 2:

Inherited traits passed from parents to offspring are governed by the rules on the patterns of inheritance.

B. Performance Standards

By the end of the Quarter, learners represent patterns of inheritance and predict simple ratios of offspring.

C. Learning Competency

CG Quarter 1, competency 5:

predict simple ratios of offspring genotypes and phenotypes in crosses involving dominant/recessive gene pairs.

By the end of the session, learners can:

1. complete a 2 × 2 Punnett square from two parent genotypes;
2. state the genotype ratio and the phenotype ratio separately, and say why they differ;
3. explain that a ratio gives a chance for each offspring, not a share of a family; and
4. explain how two parents showing a dominant trait can produce offspring showing the recessive one.

D. Key Vocabulary

The class sentence, said in §D and printed on the wall chart: "Each offspring is a fresh throw of the same dice."

E. Integration Across Learning Areas

II. MATERIALS

Needed — no cost. Two coins per pair of learners — the whole lesson runs on them. Paper and pencil. Chalk and a board.

If coins are short, cut squares of card with T on one side and t on the other, or use bottle caps marked with chalk. Anything with two equally likely faces will do.

Not used: a genetics kit, coloured beads, or anything bought. Coins model independent random assortment exactly, and every learner already knows how a coin behaves — which removes one thing to learn.

In addition. slides.html slides 1–12 · worksheet.html · game.html Rounds 1–2 · wall-chart.html

III. TEACHING AND LEARNING PROCEDURE

A. Activating Prior Knowledge · 6 minutes

Slide 2. Tell the rice story, briefly and as fact:

"Before the 1960s, rice in this country grew tall. Tall rice falls over in wind and rain, and the grain is lost. At IRRI in Los Baños, a shorter, stiffer variety was bred — IR8 — and it stayed standing. That is genetics, done here, and it changed how much rice the Philippines could grow."

Slide 3. Say: "Call tall T and semi-dwarf t. Tall is dominant. How many different pairs of letters can one plant have?"

Take answers. Establish TT, Tt and tt on the board.

Slide 4. Ask the question that does the work: "Which two of those three look the same?"

TT and Tt. Both tall. "So you cannot tell them apart by looking, and that is going to matter."

B. Establishing Lesson Purpose · 3 minutes

Say: "Today you will learn to fill a box that predicts what the offspring might be. Filling it takes about a minute. Reading it correctly is what the rest of this week is for — and it is the part that most adults get wrong."

C. Developing and Deepening Understanding · 26 minutes

C1 · Filling the square · 7 minutes

Slide 5. Build Tt × Tt on the board, slowly, narrating each cell:

One parent's letters across the top. The other's down the side. Each box takes the letter above it and the letter beside it.

Result: TT · Tt · Tt · tt.

Slide 6. Ask for both ratios, separately:

• Genotype ratio — 1 TT : 2 Tt : 1 tt
• Phenotype ratio — 3 tall : 1 semi-dwarf

Ask: "Why does the second one have two numbers when the first has three?" Because TT and Tt look the same. That is §A's question, arriving where it is needed.

Do two more on the board — Tt × tt and TT × tt — quickly, with the class calling out the cells.

C2 · The question the square does not answer · 8 minutes

Slide 7. Say: "A farmer plants four seeds from a Tt × Tt cross. How many will be semi-dwarf?"

Take the vote. Write the counts on the board. Most classes say one, confidently.

Slide 8. Say: "Nobody knows. Each seed has a one in four chance, on its own. All four could be semi-dwarf. None of them could be."

Expect resistance. Do not argue — go to the coins.

Slide 9. Say: "Heads is T. Tails is t. Flip twice — once for each parent — and write down what you get. Do that ten times."

Give them five minutes. Then collect the class totals on the board: how many TT, how many Tt, how many tt, across everybody.

C3 · What the data says · 7 minutes

Slide 10. Put two numbers side by side:

Ask: "So is the square wrong for the farmer with four seeds?"

The honest answer: "No. It is right about the chance and silent about the outcome. With four hundred seeds it is a good prediction. With four, it is not a prediction at all — it is a probability."

This is the eight minutes the lesson exists for. The square is arithmetic; this is the science. A class that does the coin work and sees its own scatter will not later write exactly one in four.

C4 · Two tall parents, one short offspring · 4 minutes

Slide 12. Ask: "Two tall plants are crossed. One offspring is semi-dwarf. What were the parents' genotypes?"

Work it back: a tt offspring needs a t from each parent, and both parents look tall — so both were Tt.

Say: "In a Tt plant, the t is not damaged, weakened or overwritten. It is simply not the one you can see. That is how a trait can pass through a generation without appearing."

D. Making Generalisations · 6 minutes

Slides 13 and 14. Count the class for one visible trait — tongue rolling is quickest. Put the numbers up.

Ask: "Does the dominant trait have more people?" Sometimes it does; sometimes it does not.

Say: "Extra fingers is dominant and very rare. Blood type O is recessive and it is the most common type in this country. Dominance tells you what happens inside one individual. It tells you nothing about how many people there are."

Say the class sentence together, twice: "Each offspring is a fresh throw of the same dice."

Hand out worksheet.html.

IV. EVALUATING LEARNING

A. Assessment · 4 minutes

Exit ticket, three lines:

1. Tt × Tt. Give the genotype ratio and the phenotype ratio.
2. A Tt × Tt couple has three tall children. What is the chance the fourth shows the recessive trait?
3. Two tall parents have a semi-dwarf offspring. What were their genotypes, and how do you know?

Item 2 is the one that reads. Item 1 is mechanical and item 3 is on the wall chart by Friday.

B. Teacher Reflection

1. What did the class vote in §C2 before the coins, and what did the coin data show? Record both. The gap between them is the lesson, and it is measurable.
2. Did anybody argue that the square was wrong after seeing their own ten flips? That is a good objection, not a misunderstanding — it deserves a real answer, and the answer is that the square describes a chance rather than an outcome.
3. How many exit tickets said the fourth child was more likely? Plan Day 3 around that number.

C. Enrichment and Remediation

Anticipated Misconceptions

If There Is No Electricity

Nothing here needs it. Two coins, paper and a board are the whole apparatus, and §III carries everything on the slides.

If there are no coins: cut card squares with T on one face and t on the other, or use bottle caps marked in chalk. What matters is two equally likely faces, which is the same assumption the square makes.

Part of the E-turo MATATAG artifact set. Companion files: syllabus.md · lesson-plan-ilaw.md · assessment.md · offline-activities.md