Grade 8 · Science · 35 minutes
Unit 1 · Systems, Evidence and Variation · Lesson 2 of 2
Compare Two Ways of Passing on Information
Use chromosome-card models to contrast inheritance in sexual and asexual reproduction.
Mr. S Teaches · Original starter mini-lesson · MS8-SCI-02Learning objective
Construct two inheritance diagrams and explain why the modeled offspring differ in variation.
Before you begin
- Understand an allele as a gene version and one-parent versus two-parent reproduction.
Gather your materials
- Paper or notebook
- Pencil and the passage, model directions or data printed in this lesson
Language to know
- asexual reproduction
- Reproduction from one parent without combining two parents’ genetic contributions.
- sexual reproduction
- Reproduction combining genetic contributions from two parents.
- variation
- Differences among individuals in a population.
Understand the concept
Model account: An asexual parent has cards A and B; three modeled offspring each receive copied A and B cards. In a sexual model, Parent 1 can contribute A or B, while Parent 2 can contribute C or D. Offspring combinations include AC, AD, BC and BD. This is a simplified information model rather than a full chromosome diagram. Asexual offspring can still differ through mutation and environment, and sexual reproduction does not guarantee that every visible trait will differ.
Teach it step by step
- Read the account and draw the copied-card pathway from one parent to three offspring.
- Make a two-parent combination table and label which contribution comes from each parent.
- Compare the number of distinct modeled combinations and connect that difference to the text.
- Revise “asexual offspring can never differ” using the account’s limitation statement.
Make the thinking visible
Worked example or model response
The one-parent copying model gives AB, AB and AB. The two-parent model allows AC, AD, BC and BD. This demonstrates one source of variation through combining inherited information, not a rule that copied offspring are identical in every possible characteristic.
Guided practice
Together show why AC and CA in this model contain the same selected contributions even when the writing order changes.
Independent practice
Draw both models. Write a paragraph comparing inheritance and identifying two processes the card model leaves out, such as mutation or environmental effects.
Quick assessment
Can the card model predict every visible feature of a real offspring? Explain.
Answer key & assessment criteria
Answers and teaching guidance
- Guided: AC and CA each include A from Parent 1 and C from Parent 2; order alone does not create a new inherited combination.
- Independent: Models should preserve the stated contributions. Explanations should contrast copying with combining and identify omitted mutation, environmental effects or the many genes of real organisms.
- Quick check: No. The model includes only selected information and omits interactions among many genes and the environment.
Look for: Look for a claim that answers this lesson’s question, accurate use of the supplied evidence and an explanation of a limit or alternative. Ask the learner to point to the detail supporting each inference.
Make it work for your learner
More support
Use colored cards showing parent origin and a comparison sentence frame with “both” and “whereas.”
Extension challenge
Combine the model with a one-gene Punnett square and explain how the two representations emphasize different aspects of inheritance.
Selected contributions · Official sources
Standards connections
Selected NGSS band contribution; not complete performance expectation coverage.
Contributes to NGSS performance expectation
MS-LS3-2NGSS · Grades 6–8 band
Model how reproduction affects inherited similarities and differences.
Read the official performance expectation ↗The paired models address copying versus combining information. They intentionally omit detailed chromosome mechanisms and do not establish predictions for all real traits.
Source and mapping checked 2026-11-04. This mini-lesson contributes selected skills; it does not claim full attainment.
Supporting Common Core literacy connection
RST.6-8.7Common Core · Grades 6–8
Connect scientific prose with a diagram, model or table.
Read the official standard ↗The provided scientific passage/model is explicitly analyzed in the activity. This selected literacy practice does not establish subject-content alignment or complete coverage of the standard.
Source and mapping checked 2026-11-04. This mini-lesson contributes selected skills; it does not claim full attainment.