Genetic drift and allele frequency worksheets for Grade 10 Science help students examine how random events change the genetic makeup of populations over generations. The reading passage explains why genetic drift has a stronger effect in small populations, how alleles can become more or less common by chance, and why genetic diversity may decline even when no particular allele affects reproductive success.

How populations change through chance

Students explore two important examples of genetic drift: the founder effect and the population bottleneck. They consider how a small group of individuals establishing a new population may carry only part of the original gene pool, while a sudden decline caused by drought or habitat loss can leave survivors with a different mix of alleles. The lesson also introduces allele fixation, when one version of a gene becomes the only version present in a population.

A central focus is distinguishing genetic drift from natural selection. Students examine the difference between random changes in allele frequencies and changes associated with differences in reproductive success. They also consider how migration introduces existing alleles from other populations and how mutation creates new genetic variants. These processes can interact over generations, influencing genetic variation and the divergence of isolated populations.

What students practise

The activities ask students to apply genetic drift concepts to population scenarios rather than rely only on definitions. They identify the process behind an island population established by a few insects, consider the genetic consequences of a drought-related population decline, and explain how isolated populations may develop different allele frequencies over time.

Students work through multiple-choice and true-or-false questions, short-response explanations, matching, a cloze passage, and an extended written response. The writing tasks give them opportunities to explain why bottlenecks reduce diversity, compare drift with natural selection, and evaluate how migration and mutation may affect populations after genetic variation has been lost.

Files included

• Student worksheet: Reading passage and activities covering genetic drift, small populations, founder effects, bottlenecks, allele fixation, genetic diversity, migration, mutation, and natural selection.
• Separate answer key PDF: Answers for checking student work and reviewing the concepts.
• Student Notes & Lesson Summary: A companion supplement for recording and revisiting the main ideas and vocabulary.
• Separate Teacher Guide: Learning objectives, teaching tips, discussion questions, and common mistakes to address during instruction.

Classroom use

Use this Grade 10 evolution worksheet during a lesson on changes in allele frequencies, as guided practice after introducing population genetics, or as independent review. The population scenarios provide starting points for class discussion about why chance can have lasting effects, particularly in small or isolated groups. The extended response can also help students connect genetic drift with mutation, migration, and natural selection instead of treating each evolutionary process in isolation.

Written for the TEKS Science curriculum, this resource addresses TEKS §112.34(b)(10)(A). It gives students focused practice explaining how random events influence genetic variation and how several evolutionary processes contribute to population change.