In biology, accurate classification is crucial for identifying new species, and dichotomous keys are indispensable tools in this process. This guide explains what a dichotomous key is and provides step-by-step instructions on how to create one. You’ll also find a variety of editable templates in the examples section, available for immediate use. Download these templates in PNG, JPEG, SVG, or PDF formats for easy publishing, printing, and sharing.
What is the Purpose of a Dichotomous Key
A dichotomous key is a tool used in biology and other scientific fields to help identify and classify organisms, objects, or other items based on their characteristics. Simply put, it is a method used to identify a species by answering a series of questions based on contrasting features (eg: physical characteristics) that have two possible outcomes.
“Dichotomous” means divided into two parts, hence the dichotomous keys always present two choices based on the key characteristics of the organism in each step. By correctly selecting the right choice at each stage, the user will be able to identify the name of the organism at the end. The further you divide the key, the more you learn about the specimen you are trying to identify.
Students and professionals use the dichotomous key to identify and classify objects (i.e. people, animals, plants, bacteria, etc.) into specific categories based on their characteristics. It’s the most commonly used form of classification or type of identification key used in biology as it simplifies identifying unknown organisms.
Simply put, it is a method used to identify a species by answering a series of questions based on contrasting features (eg: physical characteristics) that have two possible outcomes.
When creating a dichotomous key, both qualitative (i.e. physical attributes such as how the organism looks, what color it is, etc.) and quantitative (i.e. the number of legs, weight, height, etc.) factors are considered.
It can be done in both a graphical as a branching flowchart or written format - series of paired statements organized sequentially. Most often, they are used to identify plant and animal species, although it can be used to classify any object that can be identified by a set of observable characteristics.
In addition to dichotomous keys, researchers often employ phylogenetic trees and cladograms to explore evolutionary relationships. Phylogenetic trees visually represent the evolutionary pathways and connections among species, illustrating how they diverged over time. Cladograms emphasize the branching patterns of evolutionary descent, grouping organisms based on shared traits. Explore our detailed guide on cladograms vs phylogenetic trees to understand their unique roles in depicting evolutionary relationships and how they complement dichotomous keys.
Cladogram Template
Phlylogenetic Tree Template
What is the Dichotomous Key Used For?
A dichotomous key simplifies complex classification tasks by guiding users through a series of binary decisions. Here are its main uses, expanded with additional points:
- Identifying and Categorizing Organisms: It directs users through a series of paired comparisons to accurately determine the identity of organisms, making it an essential tool in taxonomy and biological research.
- Helping Students Easily Understand Harder Scientific Concepts: By breaking down classification into simple yes/no questions or paired statements, it turns complex taxonomic concepts into an interactive learning experience, improving comprehension and critical thinking skills.
- Organizing Large Amounts of Information: The key systematically narrows down numerous observable characteristics, streamlining the identification process and reducing the risk of errors during analysis.
- Facilitating Biodiversity Assessments: It aids researchers in efficiently cataloging species in various ecosystems, which is crucial for conducting biodiversity surveys and monitoring ecological changes over time.
- Supporting Field Research and Ecological Surveys: Portable and easy to use, dichotomous keys are invaluable during fieldwork, allowing researchers to quickly identify species on-site and document findings accurately.
- Enhancing Conservation Efforts: By providing a reliable method for species identification, dichotomous keys help conservationists track and manage biodiversity, essential for protecting endangered species and maintaining ecosystem health.
- Streamlining Comparative Analysis: The structured approach of a dichotomous key enables clear comparisons between similar species, facilitating studies on evolutionary relationships and morphological differences.
- Standardizing Classification in Scientific Communication: The consistent format of dichotomous keys promotes uniformity in species identification, making it easier for scientists across different regions and disciplines to share and compare data.
These expanded points highlight the multifaceted utility of dichotomous keys, from education to advanced research and conservation initiatives.
How to Make a Dichotomous Key: Step by Step Guide
Below we have listed the steps you need to follow when creating a dichotomous key.
Step 1: List down the characteristics
Pay attention to the specimens you are trying to identify with your dichotomous key. List down the characteristics that you can notice. For example, say you are trying to classify a group of animals. You may notice that some have feathers whereas others have legs, or some have long tails and others don’t.
Step 2: Organize the characteristics in order
When creating your dichotomous key, you need to start with the most general characteristics first, before moving to the more specific ones. So it helps to have identified the more obvious and less obvious contrasting characteristics among the specimen before creating your dichotomous key.
Step 3: Divide the specimens
You can use statements (i.e. has feathers and no feathers) or questions (does it have feathers?) to divide your specimens into two groups. The first differentiation should be made on the most general characteristic.
Step 4: Divide the specimen even further
Based on the next contrasting characteristic, divide the specimen further. For example, first, you may have grouped your animals as having feathers and have no feathers, in which case the ones with feathers can be categorized as birds while you can further subdivide the ones that have no feathers as having fur and having no fur. Continue to subdivide your specimen by asking enough questions until you have identified and named all of them.
Step 5: Draw a dichotomous key diagram
You can either create a text-based dichotomous key or a graphical one where you can even use images of the specimen you are trying to identify. Here you can use a tree diagram or a flowchart as in the examples below.
Step 6: Test it out
Once you have completed your dichotomous key, test it out to see if it works. Focus on the specimen you are trying to identify and go through the questions in your dichotomous tree to see if you get it identified at the end. If you think the questions in your dichotomous key need to be rearranged, make the necessary adjustments.
Check out our video on how to create a dichotomous key. In this step-by-step guide, we break down the process of building an effective dichotomous key to help you classify and identify objects with ease.
Helpful Resources
Visually organize large amounts of information to quickly identify, categorize, and analyze organisms.
Effectively visualize and identify the evolutionary relationships among various biological species.
Effectively visualize and identify the phylogenetic relationships among various biological species with cladograms.
Creately for Making Dichotomous Keys
Creately is an intuitive online diagramming tool designed to simplify the creation of dichotomous keys. For an interactive experience, try our dichotomous key maker to start building your key today. Whether you’re an educator, researcher, or student, Creately provides a seamless experience for designing clear and effective classification diagrams.
Key Features of Creately for Dichotomous Keys:
- User-Friendly Interface: Easily drag and drop elements to build logical flows for species classification or any binary decision-making process.
- Customizable Templates: Choose from a variety of pre-designed templates and shapes to create professional-looking dichotomous keys quickly.
- Real-Time Collaboration: Work together with peers and colleagues simultaneously, making group projects and classroom activities more interactive.
- Flexible Export Options: Save your work in multiple formats such as PNG, JPEG, SVG, and PDF for hassle-free sharing, printing, and publishing.
- Versatile Applications: Ideal for both basic educational purposes and advanced scientific research, Creately helps streamline the process of identifying and categorizing organisms.
- Evolutionary Connection Tools: To draw connections between species and better establish evolutionary relationships, use our Phylogenetic Tree Maker or Online Cladogram Maker.
Creately streamlines the process of creating and sharing dichotomous keys while also offering powerful tools for exploring evolutionary relationships. Get started today to elevate your classification projects.
Essential Best Practices for Crafting an Effective Dichotomous Key
- Consider only one characteristic at a time
- Use morphological or observable characteristics as much as you can
- Use major characteristics when dividing the organisms in the beginning and use lesser or less obvious characteristics to divide them into smaller groups
- When writing contrasting statements, rely on similar word formats (i.e. have feathers and don’t have feathers)
- Be specific in your statements and avoid repeating the same characteristics
- Use questions that lead to yes or no answers rather than statements
Benefits of Dichotomous Key
Dichotomous keys offer several benefits in various scientific and educational contexts:
- Accurate Identification: Dichotomous keys provide a systematic and accurate method for identifying organisms or objects by focusing on their key characteristics. This reduces the likelihood of misidentifications.
- Easy to use: The keys are designed to be user-friendly, so they can be used by everyone from students to experts.
- Consistency: Dichotomous keys follow a standardized format, using specific terminology and criteria, so that different users can consistently get to the same identification for the same item.
- Great for learning: Dichotomous keys help students learn to observe, compare, and understand the characteristics of different organisms, so they can better understand the natural world.
- Useful in research: In scientific research, these keys are useful for cataloging and documenting biodiversity, which is important for understanding species relationships and ecological dynamics.
- Helps with field work: Dichotomous keys are portable and can be used in the field, which makes them ideal for on-site surveys, ecological studies, and biodiversity assessments.
Mastering Dichotomous Keys: Advanced Tips and Strategies for Success
We hope this guide lays a strong foundation for understanding dichotomous keys. Here’s a concise summary of advanced tips to refine your key-making process:
- Plan and Organize: List all observable traits and arrange them from general to specific to ensure clarity and avoid overlapping decision points.
- Maintain Consistency: Use uniform language and formatting—such as clear yes/no questions or paired statements—to make your key easy to follow.
- Leverage Visual Aids: Incorporate images, diagrams, or icons to support textual descriptions, making the key more accessible, especially for visual learners.
- Test and Refine: Validate your key with known specimens, gather feedback, and iteratively improve any ambiguous or confusing sections.
- Document Your Process: Keep detailed notes on why traits were chosen and how each branch was determined, which aids both current refinement and future projects.
- Utilize Digital Tools: Consider using specialized software or online platforms that support real-time collaboration and offer multiple export formats for easy sharing and printing.
- Encourage Collaboration: Invite peers or colleagues to review and edit your key online, fostering diverse perspectives and innovative improvements.
- Stay Open to Innovation: Continually explore new methods and digital resources to enhance your dichotomous key’s usability as the field of classification evolves.
Feel free to share your own tips and experiences in the comments, and let’s continue the conversation on mastering this essential identification tool.
Resources:
LibreTexts Website LibreTexts. (n.d.) Introduction to Dichotomous Keys. In: Red Seal Landscape Horticulturist: Identify Plants and Plant Requirements I (Nakano). Available at: https://bio.libretexts.org/Bookshelves/Agriculture_and_Horticulture
PDF from Texas A&M Texas A&M University. (n.d.) Dichotomous Key Activity [PDF]. Available at: https://tfsweb.tamu.edu/uploadedFiles/TFSMain/Learn_and_Explore/Conservation_Education_Resources
