Cambridge O Level Biology · Syllabus 5090 · Classification
Observable Feature
What is Observable Feature?
An observable feature is a characteristic of an organism that can be seen or measured directly on the specimen, such as the number of legs, the presence of wings or the pattern of leaf veins. Dichotomous keys must be built from observable features, because a user with only the specimen in front of them cannot check habitat, behaviour or anything that requires outside information.
This definition is part of the Classification chapter in Cambridge O Level Biology.
Observable Feature in context
Classification is the placing of living organisms into groups on the basis of the features they share, so that organisms with many features in common sit in the same group. Cambridge O Level Biology (5090) Chapter 2 covers four things: the definition of a species and the binomial naming system, dichotomous keys, the five kingdoms (animal, plant, fungus, prokaryote and protoctist), and the observable features that separate the vertebrate groups, the arthropod groups, ferns from flowering plants and monocotyledons from dicotyledons. Viruses sit apart from all five kingdoms because they have no cellular structure.
Questions students ask about Observable Feature
How should I answer a question that asks me to classify an unfamiliar organism?
State the observable features you used and match each one to the defining feature of the group. Write "feathers, a beak and hard-shelled eggs, so it is a bird", not "it flies, so it is a bird", because bats and many insects fly and penguins do not. Keep the syllabus qualifiers — mammals usually give birth to live young, dicotyledons often have a main tap root — and classify on the whole set of evidence rather than on one feature.