A free printable natural selection and evolution worksheet for Grade 11 biology.
Students match Darwin’s key ideas, analyse a peppered moth graph, identify stabilizing, directional and disruptive selection, classify genetic drift, gene flow and sexual selection, solve Hardy-Weinberg problems, and sort evidence for evolution. Includes 27 questions (22 marks) and a full answer key.
This free natural selection worksheet covers the core of the Grade 11 Evolution unit. Students match Darwin's key ideas, analyse a peppered moth graph to explain how selection changed direction when pollution rose and fell, and identify stabilizing, directional and disruptive selection from drawn graphs.
It then goes beyond natural selection to genetic drift, gene flow and sexual selection, Hardy-Weinberg calculations and four kinds of evidence for evolution. The Hardy-Weinberg answers in the key were calculated and checked.
It supports the Ontario Grade 11 biology curriculum expectations in the Evolution unit.
How Natural Selection Works
Darwin's theory rests on a few observations. Individuals in a population vary, and much of that variation is inherited. Organisms overproduce offspring, which then compete for limited resources. Individuals with helpful traits, or adaptations, survive and reproduce more, so their alleles become more common over generations. The key point students often miss: populations evolve, individuals don't. For more background, see natural selection on Wikipedia.
The Peppered Moth Case Study
During the Industrial Revolution, soot darkened the trees near Manchester. Dark moths were harder for birds to spot, so they survived and reproduced more, and the dark form rose from about 2% to around 95%. After clean-air laws, the trunks lightened and selection reversed. Part B of the natural selection worksheet asks students to read this model graph and explain both changes.
Natural selection isn't the only way populations change. Genetic drift is random change in allele frequencies, strongest in small populations, as in bottleneck and founder events. Gene flow moves alleles between populations, and sexual selection favours traits that attract mates.
The Hardy-Weinberg equations describe a population that is not evolving: p + q = 1 and p² + 2pq + q² = 1. If 16% of a population is aa, then q = 0.4, p = 0.6 and 48% are heterozygous. The probability skills behind this are practised in the genetics probability worksheet.
Natural Selection Worksheet Practice Questions
These questions match the natural selection worksheet PDF, which has the full-size graphs and ruled answer space.
Part A – Darwin's Key Ideas
Questions 1–6: match each term to its description.
Variation
Overproduction
Competition
Differential survival
Inheritance
Adaptation
Part B – Peppered Moths
Describe how the percentage of dark moths changed between 1850 and 1920.
Factory soot darkened tree trunks during this time. Use natural selection to explain the change. (2 marks)
Explain why the percentage of dark moths fell after clean-air laws were passed.
Part C – Types of Selection
Questions 10–12: name the type of selection in each graph (dashed = before, solid = after).
Graph AGraph BGraph C
Part D – Other Mechanisms
A storm randomly kills 90% of a beetle population. By chance, most survivors are green.
A few birds are blown to a remote island and start a new population with different allele frequencies.
Pollen from a neighbouring cornfield fertilizes plants in another field.
Peahens mate mostly with peacocks that have the largest, brightest tails.
Part E – Hardy-Weinberg
In a population in Hardy-Weinberg equilibrium, 16% of individuals show the recessive phenotype (aa). Find q.
Find p, the frequency of the dominant allele.
What percentage of the population is heterozygous (Aa)?
A population of 500 flowers has 45 white flowers (the recessive phenotype). How many flowers are expected to be heterozygous? (2 marks)
Give two conditions needed for Hardy-Weinberg equilibrium.
Part F – Evidence for Evolution
A human arm, a whale flipper and a bat wing have the same bone pattern.
Bird wings and insect wings both allow flight but are built very differently.
Whales have small pelvis bones that do not support legs.
Humans and chimpanzees share about 98% of their DNA sequence.
Part G – Spot the Mistake
A student writes: “Giraffes stretched their necks to reach high leaves, so their babies were born with longer necks.” Explain the error and correct it.
A student writes: “Antibiotics cause bacteria to mutate so they become resistant.” Explain the error and correct it.
Natural Selection Worksheet Answer Key
Open each part of the natural selection worksheet answers to check your work. The printable key is at the end of the PDF.
Part A answers (Q1–6)
Variation: b
Overproduction: d
Competition: f
Differential survival: a
Inheritance: e
Adaptation: c
Part B answers (Q7–9)
It rose from about 2% to about 95%.
Dark moths were better camouflaged on sooty trunks, so birds ate fewer of them. They survived and reproduced more, passing on the dark allele, so its frequency increased.
Trunks became lighter again, so light moths were now better camouflaged and selection favoured them.
Any two: very large population; random mating; no mutation; no migration (gene flow); no natural selection.
Part F answers (Q22–25)
Homologous structures
Analogous structures
Vestigial structures
Molecular (DNA) evidence
Part G answers (Q26–27)
That is Lamarck’s idea. Traits gained during a lifetime are not inherited. Giraffes that were born with longer necks survived and reproduced more, passing on the genes.
Mutations happen randomly before the antibiotic is used. The antibiotic only selects the bacteria that already carry resistance.
5 Common Natural Selection Misconceptions
"Organisms change because they need to." Variation already exists; selection acts on it.
"Individuals evolve." Individuals survive or don't; populations evolve over generations.
"Acquired traits are inherited." That was Lamarck's idea, and it is wrong for traits gained during life.
"Survival of the fittest means the strongest." Fitness means reproductive success in a particular environment.
"Evolution always moves toward perfection." Selection only fits organisms to current conditions, which can change.
How to Use This Natural Selection Worksheet in Class
Lesson 1: Parts A–C of the natural selection worksheet, ideally after a camouflage "predator" simulation with coloured paper dots.
Lesson 2: Parts D–G on drift, Hardy-Weinberg and evidence.
Extension: Students research a modern example such as antibiotic or pesticide resistance.
Yes. The worksheet and its answer key are free to download and print as a PDF, with no account needed.
What are the main steps of natural selection?
Individuals vary, more offspring are produced than can survive, they compete for resources, the best-adapted survive and reproduce, and their helpful alleles become more common in the population.
What is the difference between natural selection and genetic drift?
Natural selection changes allele frequencies because some traits help survival. Genetic drift changes them by chance, and has the biggest effect in small populations, as in bottleneck and founder events.
Why are peppered moths a classic example of natural selection?
When soot darkened tree trunks, dark moths were better camouflaged from birds and became common. After clean-air laws, light moths had the advantage again, showing selection changing direction with the environment.
What grade is this natural selection worksheet for?
It is written for Grade 11 biology (the Evolution unit) and also works for Grades 9–10 science or Grade 12 review.
Ready to start? Download the free natural selection worksheet PDF (use the Download button above), print it double-sided, and keep the answer key pages for marking.