The best examples of introduction examples for biology lab reports

Before talking about theory, let’s look at actual examples of introduction examples for biology lab reports. These are modeled on the kind of writing that earns high marks in U.S. college biology courses in 2024–2025.

Each example is shortened (you’d usually write 1–3 paragraphs), but the structure is realistic: background → specific question → hypothesis → brief rationale.

Example 1: Enzyme activity (catalase and temperature)

This is a classic example of an introduction for a biology lab report on enzymes:

Enzymes are biological catalysts that speed up chemical reactions by lowering activation energy, allowing cells to carry out metabolism efficiently at moderate temperatures. Catalase is a common enzyme in many tissues that converts hydrogen peroxide, a toxic byproduct of cellular respiration, into water and oxygen. Previous studies have shown that enzyme activity is strongly influenced by temperature, with most enzymes exhibiting an optimal temperature range beyond which activity declines due to denaturation (Nelson & Cox, 2021).

In this experiment, we investigated how temperature affects the rate of catalase activity in potato tissue. We predicted that reaction rate would increase with temperature up to approximately 37 °C, then decrease at higher temperatures as the enzyme’s tertiary structure is disrupted. By measuring oxygen production at different temperatures, we aimed to determine the approximate optimal temperature for catalase activity in plant tissue.

Why this works:

• Opens with a clear, concise definition and broad context.
• Narrows to a specific enzyme (catalase) and relevant prior findings.
• States a directional, testable hypothesis.
• Explains how the experiment will test that hypothesis.

This is one of the best examples of introduction examples for biology lab reports because you could swap in amylase, lactase, or pepsin and keep the same backbone.

Example 2: Osmosis and diffusion in plant cells

Another common assignment: osmosis in potato or onion cells.

Diffusion and osmosis are fundamental processes that govern the movement of molecules across cell membranes and are critical for maintaining cellular homeostasis. Osmosis, the passive movement of water across a selectively permeable membrane, occurs in response to differences in solute concentration on either side of the membrane. Plant cells rely on osmosis to regulate turgor pressure, which supports structural rigidity and drives growth. Previous research has used changes in mass or length of plant tissue placed in sucrose solutions of varying molarity to estimate the tissue’s internal solute concentration (Reece et al., 2020).

This experiment examined the effect of external sucrose concentration on water movement in potato cores. We hypothesized that potato pieces placed in hypertonic solutions would lose mass, those in hypotonic solutions would gain mass, and those in an isotonic solution would show no net change. By plotting percent change in mass against sucrose molarity, we aimed to estimate the solute concentration of potato cells and illustrate the relationship between osmotic gradients and water movement.

If you’re searching for examples of introduction examples for biology lab reports that you can adapt for any diffusion or osmosis lab, this one gives you a reusable blueprint.

Example 3: Photosynthesis and light intensity

Here’s a strong lab report introduction example for a photosynthesis experiment using leaf disks or aquatic plants:

Photosynthesis converts light energy into chemical energy, providing the primary source of organic matter for nearly all ecosystems. In plants, light-dependent reactions capture light energy to produce ATP and NADPH, which then power the Calvin cycle. The rate of photosynthesis is influenced by several factors, including light intensity, wavelength, carbon dioxide availability, and temperature. Studies have shown that photosynthetic rate typically increases with light intensity up to a saturation point, beyond which additional light does not increase the rate and may even cause photoinhibition (Taiz et al., 2019).

In this lab, we investigated how light intensity affects the rate of photosynthesis in spinach leaf disks using the floating disk method. We predicted that increasing light intensity would increase the rate at which leaf disks rise, up to a plateau at higher intensities. By quantifying the time required for a set proportion of disks to float at different light levels, we aimed to characterize the relationship between light intensity and photosynthetic rate.

Again, this is one of the best examples of introduction examples for biology lab reports because it ties the classroom setup to real plant physiology and current scientific understanding.

Example 4: Bacterial growth and antibiotic resistance

Microbiology labs have become more relevant than ever post‑COVID, especially as students connect simple plate experiments to real public health issues.

The rapid emergence of antibiotic-resistant bacteria is a major public health concern, leading to infections that are increasingly difficult to treat. Bacteria can acquire resistance through spontaneous mutations or horizontal gene transfer, and exposure to sublethal antibiotic concentrations can select for resistant strains. Surveillance data from the U.S. Centers for Disease Control and Prevention (CDC) show rising rates of resistance in several clinically important pathogens, including Escherichia coli and Staphylococcus aureus (CDC, 2024).

In this experiment, we examined the effect of different concentrations of ampicillin on the growth of non-pathogenic E. coli cultured on nutrient agar plates. We hypothesized that increasing antibiotic concentration would reduce bacterial colony formation, with a minimum inhibitory concentration above which no visible colonies would appear. By quantifying colony counts across a dilution series, we aimed to model how antibiotic concentration shapes bacterial survival and to connect lab findings with broader concerns about antibiotic resistance.

When students ask for real examples of introduction examples for biology lab reports that feel timely, this style—linking simple plate counts to CDC data—is exactly what instructors like to see.

Example 5: Human physiology – heart rate and exercise

Physiology labs often ask you to connect your own body’s responses to published research.

During exercise, the cardiovascular system adjusts to meet increased metabolic demands by elevating heart rate, stroke volume, and cardiac output. These changes help deliver more oxygen and nutrients to active muscles and remove metabolic waste products such as carbon dioxide and lactate. The American Heart Association and related organizations have documented typical heart rate responses to graded exercise in healthy adults, with heart rate increasing approximately linearly with workload until near maximal effort (NIH, 2023).

This lab investigated the acute effect of moderate and vigorous exercise on heart rate in college-aged students. We hypothesized that heart rate would increase with exercise intensity and return toward baseline within five minutes of recovery. By comparing pre‑exercise, immediate post‑exercise, and recovery heart rates across different intensity levels, we aimed to evaluate how closely student responses matched expected physiological patterns described in the literature.

If you’re looking for an example of an introduction that balances textbook concepts with real human data, this is a solid model.

Example 6: Genetics – Drosophila inheritance patterns

Genetics labs are notorious for confusing students. A clear introduction can save you from a messy discussion section later.

Mendelian genetics describes how traits are inherited through discrete units known as genes, with alleles segregating and assorting independently during gamete formation. Model organisms such as Drosophila melanogaster have been widely used to study inheritance patterns because of their short generation time, large number of offspring, and easily observable phenotypes. Classic experiments have demonstrated predictable phenotypic ratios for monohybrid and dihybrid crosses, providing a framework for testing genetic hypotheses (Griffiths et al., 2022).

In this experiment, we analyzed the phenotypic ratios of offspring from crosses involving wild-type and mutant Drosophila strains differing in eye color and wing shape. We hypothesized that the observed offspring ratios would not differ significantly from the expected Mendelian ratios for autosomal, independently assorting genes. By comparing observed and expected counts using chi-square analysis, we aimed to determine whether the data supported a simple Mendelian inheritance model.

This is one of those examples of introduction examples for biology lab reports that you can tweak for peas, fast plants, or any other genetics system.

Example 7: Ecology – Species diversity in local habitats

More biology courses now include field-based ecology labs, often with a conservation angle.

Biodiversity, often quantified as species richness and evenness, is a key indicator of ecosystem health and resilience. Urbanization, habitat fragmentation, and pollution can alter local species composition and reduce diversity, with consequences for ecosystem services such as pollination and nutrient cycling. Recent studies have highlighted the importance of small urban green spaces in supporting biodiversity and providing habitat corridors for wildlife (USGS, 2024).

This study compared plant species diversity in a managed campus lawn and an adjacent unmowed meadow. We hypothesized that the meadow would exhibit higher species richness and diversity than the lawn due to reduced mowing and lower human disturbance. By recording species presence along transects and calculating diversity indices, we aimed to assess how land management practices influence local plant communities.

If your assignment focuses on quadrats, transects, or diversity indices, this is a clean example of an introduction you can adapt.

Breaking down the structure behind these examples

Seeing these real examples of introduction examples for biology lab reports is helpful, but you also need to recognize the pattern they share. Most strong biology lab introductions include:

1. A broad opening that sets the biological context
One or two sentences that remind the reader why this topic matters biologically or socially.

2. A focused background paragraph
This is where you briefly summarize key concepts, define important terms, and mention 1–2 relevant findings or accepted ideas. Citing an introductory textbook or a reputable site like NIH, CDC, or a university resource (for example, Harvard’s biology guides) can strengthen this section.

3. A clear experimental question or objective
State what your experiment is trying to find out: “This experiment investigated…” or “This study examined…”

4. A specific, testable hypothesis
Use directional language: increase, decrease, no difference, optimal range, plateau, etc. Avoid vague phrases like “We think something will happen.”

5. A brief rationale or prediction
Explain why you expect that result, linking back to the background theory or prior research.

When you look back at the best examples of introduction examples for biology lab reports above, you’ll see every single one hits all five of these elements.

How to adapt these examples to your own biology lab

You should never copy these paragraphs word‑for‑word. Instructors and plagiarism tools will catch that. Instead, treat these as templates:

• Swap in your organism (yeast, bacteria, plants, human subjects).
• Replace the variable (temperature, pH, concentration, light intensity, time, treatment type).
• Adjust the context to match your course level and reading. If your professor gave you a specific article or dataset, reference that instead of generic textbooks.
• Update the hypothesis so it matches your actual design and predictions.

For example, if you’re doing a membrane transport lab with dialysis tubing and starch, you could adapt the osmosis example like this:

Membranes regulate the movement of molecules into and out of cells, allowing some substances to pass while restricting others. In this experiment, we used dialysis tubing as a model for a selectively permeable membrane to investigate how molecular size and concentration gradients influence diffusion. We hypothesized that iodine and glucose would diffuse across the membrane, while starch would remain inside the tubing due to its larger molecular size.

Same structure, different details. That’s exactly how to use these examples of introduction examples for biology lab reports without getting into academic integrity trouble.

Common mistakes that weaken lab report introductions

Even when students have good examples in front of them, the same problems show up over and over:

Too much textbook summary
If your introduction reads like a copy‑paste from your biology book, it’s too long and too generic. Your goal is not to rewrite the chapter; it’s to highlight the specific pieces of theory that connect directly to your experiment.

No actual research question
Sentences like “In this lab we learned about enzymes” are not enough. Your reader should be able to underline a specific question or goal: “We investigated how X affects Y.”

Vague or missing hypothesis
“We think the enzyme will react” is not a hypothesis. A strong hypothesis is directional and measurable: “We predicted that increasing temperature from 10 °C to 40 °C would increase reaction rate, with a decrease at 60 °C.”

No logical link between theory and prediction
If you say enzymes denature at high temperature but then predict they’ll work better at 80 °C, your instructor will notice. Good introductions make the reasoning transparent.

Use the real examples of introduction examples for biology lab reports earlier in this article as a checklist. If your draft doesn’t look structurally similar, it probably needs another pass.

FAQ: Short answers about writing biology lab introductions

How long should a biology lab report introduction be?
For most college‑level labs, one to three paragraphs (about half a page to a full page, double‑spaced) is typical. Honors or upper‑division courses may expect more background and citations.

Can I use first person (I/we) in my introduction?
Many biology instructors now accept first person, especially in the hypothesis and purpose statements (for example, “We hypothesized that…”). Check your course guidelines or ask your instructor. If in doubt, use neutral phrasing like “This experiment investigated…”.

Do I have to include citations in a lab introduction?
In most 2024–2025 syllabi, yes. Even one or two citations—to your textbook, a review article, or a reputable site like NIH or CDC—show that you’re grounding your experiment in real science.

Where can I find more examples of introduction examples for biology lab reports?
Look at sample lab reports posted by your department, writing center, or university library. Many schools publish open lab-writing guides. For instance, large universities often host PDF lab manuals or writing tutorials on their .edu sites that include at least one example of a strong introduction.

What is one quick example of a weak vs. strong hypothesis?
Weak: “We thought temperature might affect enzyme activity.”
Strong: “We hypothesized that catalase activity would increase from 10 °C to 37 °C and then decrease at 60 °C due to thermal denaturation.”

Use that difference as a mental model when you revise your own hypothesis.

The bottom line: if you study several high‑quality examples of introduction examples for biology lab reports and then reverse‑engineer their structure, writing your own stops feeling intimidating. You’re not trying to be a professional scientist; you’re trying to show that you understand the biology well enough to make a clear, logical prediction. The examples above give you a realistic starting point for almost any biology lab you’ll meet this year.