Dichotomous Keys USE

Summary

This video teaches how to use dichotomous keys to identify species, specifically fish. The process involves examining anatomical features such as body shape, fins, and tails, and using a step-by-step approach to narrow down the species. The key offers two options at each step, and users must choose the one that best matches the organism. The video provides practical examples with two fish species, demonstrating how to follow the key to identify them. It also emphasizes the importance of working through the key methodically, one organism at a time, and starting from step one each time.

Takeaways

• 😀 Dichotomous keys are used to identify species based on their anatomical features, focusing on the organism's appearance.
• 😀 A dichotomous key involves reading two choices at each step and selecting the one that best describes the species you are identifying.
• 😀 When using a dichotomous key, always key out one organism at a time. If you have multiple organisms, handle them one by one.
• 😀 Always start at step one of the dichotomous key. Skipping ahead or relying on pictures might cause you to miss important details.
• 😀 Each dichotomous key has one fewer step than the number of species it identifies. For example, eight steps for nine species.
• 😀 Follow the steps of the key in order, as skipping or mismatching steps can lead to incorrect identifications.
• 😀 The dichotomous key will often provide scientific names alongside common names to help with species identification.
• 😀 Some organisms may be identified quickly, while others may require going all the way to the final step in the key.
• 😀 The example fish in the video, the spotted eagle ray, was identified by following specific features like its eye placement and tail type.
• 😀 After practicing with the key, students are encouraged to try identifying two more fish species for practice before the next class.

Q & A

What is the purpose of using a dichotomous key?

A dichotomous key is used to identify species based on their anatomical features, which means looking at the organism's physical characteristics to determine what species it belongs to.

How does a dichotomous key work?

A dichotomous key works by presenting two choices at each step. The user reads the two options and decides which one best describes the species they're trying to identify. Following this, they move to the next step based on their choice.

What is the first step to follow when using a dichotomous key?

Always start at step one of the dichotomous key. Never skip ahead, as each step is important for accurately identifying the species.

Can you use pictures to help identify species in a dichotomous key?

While pictures may be provided with the key, it's important not to rely solely on them. The pictures might mislead you, so it's essential to follow the steps carefully and consider all features described in the text.

How many steps will a dichotomous key have if there are nine organisms to identify?

A dichotomous key will have one fewer step than the number of organisms to be identified. So for nine organisms, there will be eight steps.

What should you do if you have multiple organisms to identify using a dichotomous key?

You should key out one organism at a time. After identifying one species, go back to start the process again for the next organism.

What happens if the choices at each step of the dichotomous key are ambiguous or unclear?

If you're unsure about the choices, take your time to carefully analyze the organism's features again. It may be helpful to check any reference materials or clarify the physical traits before making a decision.

In the example shown in the video, how do you identify a spotted eagle ray using the dichotomous key?

To identify a spotted eagle ray, you start at step one, where the fish shape is not long and skinny. Then, you follow through the steps, noting that it has both eyes on top of the head and a long whip-like tail, ultimately leading to the spotted eagle ray identification.

How does the dichotomous key handle different fish species with different features?

The dichotomous key uses distinct anatomical features, like the shape of the fish, the position of the eyes, and the shape of the tail, to guide you through each step until a unique species is identified.

How do you use a dichotomous key when you have to identify a fish with a long and skinny shape?

If the fish has a long and skinny shape, you proceed to step two. In this case, the next decision point involves determining if the fish has pointed or smooth fins, which further narrows down the species identification.