Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Classification is the process of sorting living organisms into groups based on shared observable features and differences.
A Dichotomous Key is a scientific tool used to identify unknown organisms. The term 'dichotomous' means 'divided into two parts.'
The key consists of a series of numbered steps. Each step offers two contrasting choices (e.g., 'Has feathers' vs. 'Does not have feathers').
By following the choices that match the organism's physical characteristics, the user is led to the organism's name or the next step in the key.
Scientific names are often used in keys following the binomial system, consisting of the Genus and species (e.g., for a lion).
Identification is primarily based on morphology (physical structure), such as leaf shape, number of legs, or presence of a backbone ().
📐Formulae
💡Examples
Problem 1:
Use the following simple dichotomous key to identify an organism that has no wings and has 8 legs:
- a) Has wings... Go to 2 b) No wings... Go to 3
- a) Wings are colorful... b) Wings are transparent...
- a) Has 6 legs... b) Has 8 legs...
Solution:
The organism is an .
Explanation:
Starting at Step 1, the organism has no wings, so we follow choice 1b, which directs us to Step 3. At Step 3, the organism has 8 legs, matching choice 3b, which identifies it as .
Problem 2:
An unknown leaf has a length () of and a width () of . A key asks if the ratio is greater than . Should you follow the path for 'Narrow Leaf' or 'Broad Leaf'?
Solution:
Follow the path for 'Narrow Leaf'.
Explanation:
Calculate the ratio: . Since , the leaf fits the criteria for the ratio being greater than 4, which is typically used to classify 'Narrow' or 'Linear' leaf shapes in botanical keys.