The Natural Selection
October 30, 2026
Did you notice the addition of the red text in the Content Specificity column on the Biology TEKS Specificity Chart?
The red text indicates content that is included in a Boundary statement in the TEA TEKS Guide. In order for students to earn either Meets or Masters on the Biology EOC, students must be exposed to the information in the red text, as items beyond TEA's identified boundaries can appear on the Biology EOC exam.
Please ensure your students receive instruction over ALL content on the TEKS Specificity Chart.
- On the first page of the IPC, you will find ELPS and Language Objectives listed for each lesson.
- Biology, Chemistry, & Physics teachers - Below the daily lesson links, you will find links to short, student-centered activities for select lessons. Biology teachers will also find short activities that spiral other standards into select lessons.
WHAT - Genetics & Inheritance Patterns: Predict possible outcomes of various genetic combinations using monohybrid and dihybrid crosses, including non-Mendelian inheritance patterns such as incomplete dominance, codominance, sex-linked traits, and multiple alleles. Students must calculate expected genotype and phenotype ratios using Punnett squares and analyze pedigree charts to trace genetic patterns across generations.
WATCH OUT FOR - Students frequently confuse incomplete dominance (where alleles blend, e.g., red + white = pink) with codominance (where both alleles express simultaneously, e.g., red + white = speckled/spotted). Additionally, students often forget to attach sex-linked traits directly to X/Y chromosomes during Punnett square setups, leading to inaccurate male vs. female probability calculations. In dihybrid crosses, students routinely struggle with setting up parent gamete combinations using the FOIL method before filling in the 16-box grid.
HOW TO TEACH - Guide students through setting up color-coded 2x2 and 4x4 Punnett squares. Use step-by-step gamete determination (FOIL method) for dihybrid crosses. For non-Mendelian traits, use real-world blood typing examples (ABO system for multiple alleles and codominance) and human X-linked traits like colorblindness or hemophilia to make non-Mendelian ratios tangible.
STUDENT ENGAGEMENT - "Genetic Predictor Challenge" Prompt: Present a complex parent cross scenario on the board (e.g., a sex-linked carrier mother crossed with an affected father, or a blood type cross involving I^A and I^B alleles). Have students work on individual whiteboards to determine gametes, construct the Punnett square, and write out both genotypic and phenotypic ratios for offspring.
HANDS-ON ACTIVITIES -
- Virtual Lab: Monohybrid Plant Cross
- Virtual Lab: Dihybrid Plant Cross
- Quick Lab: Investigate Human Pedigrees
- BioLab: What are the chances?
- BioLab: Investigate Inherited Characteristics
WHAT - Chemical Reactions & Balancing Equations: Interpret, write, and balance chemical equations, including synthesis, decomposition, single replacement, double replacement, and combustion reactions using the law of conservation of mass. Students must identify reactants and products, translate word equations into balanced chemical equations, classify reaction types, and verify that the number of atoms for each element is conserved on both sides of the reaction.
WATCH OUT FOR -Students often alter chemical subscripts rather than adding coefficients when attempting to balance equations, which changes the identity of the chemical compounds. They may also misidentify reaction types or neglect diatomic elements (such as H2, O2, N2, Cl2) when writing chemical formulas from word equations.
HOW TO TEACH - Use T-charts and physical or digital atom manipulatives (such as colored counting chips or molecular model kits) to model the Law of Conservation of Mass visually. Emphasize that coefficients act as multipliers for the entire compound and practice classifying reactions by identifying patterns (e.g., a single product for synthesis, hydrocarbon + oxygen producing CO2 + H2O for combustion).
STUDENT ENGAGEMENT - "Reaction Balancer & Classifier" Prompt: Display word equations on the board representing various reaction types (e.g., combustion of propane or single replacement of copper by zinc). Have students write the unbalanced formula equation on mini-whiteboards, construct a T-chart to tally atoms in the reactants and products, insert correct coefficients to balance it, and label the specific reaction type.
HANDS-ON ACTIVITIES -
WHAT - Conservation of Energy & Work-Energy Theorem: Apply the concept of conservation of energy using the work-energy theorem, energy diagrams, and energy transformation equations, including transformations between kinetic, potential, and thermal energy. Students must calculate work (W = Fd), kinetic energy (KE = 1/2 mv^2), gravitational potential energy (PE = mgh), and analyze how mechanical energy is conserved or transformed into thermal energy due to non-conservative forces like friction.
WATCH OUT FOR -Students often treat total mechanical energy as conserved even when external forces like friction or air resistance do work, neglecting the transformation of mechanical energy into thermal energy. They may also assume that potential energy exists without establishing a defined zero-reference level (h = 0).
HOW TO TEACH -Use pie charts and bar graphs alongside everyday classroom setups (such as toy cars, ramps made from cardboard or textbooks, pendulums made with string and washers, or sliding blocks on different surfaces) to track energy distribution continuously throughout a system. Explicitly show how the Work-Energy Theorem bridges forces and energy change, and demonstrate how frictional work dissipates mechanical energy into non-recoverable thermal energy
STUDENT ENGAGEMENT - "Energy Tracker" Prompt: Show a diagram or simulation of a roller coaster car moving along a track with friction. Have students create energy bar charts at three distinct points on mini-whiteboards, construct the energy transformation equation for each stage, and calculate the amount of mechanical energy converted to thermal energy.
HANDS-ON ACTIVITIES
- PhysicsLAB: Stair Climbing and Power
WHAT - Population Growth Dynamics: Compare exponential and logistic population growth using graphical representations. Students must analyze population growth curves (J-curves vs. S-curves), identify key parameters such as carrying capacity (K), intrinsic growth rate (r), and environmental resistance, and interpret how density-dependent and density-independent factors limit population sizes.
WATCH OUT FOR - Students often confuse carrying capacity (K) as a hard, permanent limit rather than a dynamic baseline around which real-world populations fluctuate. They also frequently assume exponential growth can continue indefinitely in nature or struggle to distinguish between density-dependent factors (e.g., disease, competition) and density-independent factors (e.g., natural disasters, temperature changes) on growth graphs.
HOW TO TEACH - Contrast J-curves and S-curves side-by-side using real-world organism case studies (e.g., invasive species or bacteria for exponential growth vs. reintroduced wolves or yeast cultures for logistic growth). Explicitly highlight the horizontal asymptote (K) on logistic graphs to illustrate where environmental resistance counteracts growth rate.
STUDENT ENGAGEMENT - "Curve Sketch & Predict" Prompt: Display two population graphs on the board (one J-curve, one S-curve). Have students use mini-whiteboards to label carrying capacity ($K$), identify where growth rate is highest, and write a 2-sentence explanation predicting what environmental factor caused the growth rate to level off or crash.
HANDS-ON ACTIVITIES -
"Carrying Capacity & Resource Limit" Modeling Challenge (10–15 mins):
Setup: Divide students into small groups representing an animal population (e.g., deer). Scatter 30 paper tokens (representing food resources) across the center of the room. Provide each group with a mini-whiteboard to record population size.
The Task:
Round 1 (Unlimited Resources / J-Curve - 3 mins): Start with 2 deer. Allow the population to double each generation while restocking food tokens without limit to model unrestricted exponential growth. Have students plot the steep J-curve on their whiteboards.
Round 2 (Limited Resources / S-Curve - 5 mins): Reset the setup, but cap the maximum food tokens in the room at 15 to establish a fixed carrying capacity (K). Run multiple generations where deer must collect at least 1 token to survive and reproduce. Have students record how competition causes population growth to level off into an S-curve.
Debrief (3–5 mins): Students write a 1-sentence takeaway on their mini-whiteboards explaining how resource availability transforms an exponential J-curve into a logistic S-curve at carrying capacity.
Ready to Help Your Lessons Evolve?
My door is always open for office hours! Think of me as your partner in the field. I'm here to help you explore our online curriculum resources, cultivate engaging new student activities, or offer targeted content support whenever you need a boost.
Please contact me directly at cycurtis@dallasisd.org to set up a time to collaborate. Whether in-person or virtual, I’m here to support your growth and help your teaching flourish this year!