The phrase dichotomous key might not be instantly familiar, but we’re betting as a parent, you’ve seen them before.A dichotomous key is an important tool used by biologists to identify a given species or organism, and crop up in the GCSE biology syllabus. Dichotomous keys look like flow charts, and feature a series of images and text with two choices branching off at each step: you choose the one that fits the organism you want to identify.At each stage, you’re presented with a choice of characteristics, and answer ‘yes’ or ’no’, until you make an identification of an organism, or species.The word ‘dichotomous’ means two; they’re sometimes also called a ‘branching tree’. A dichotomous key is used to order information, and as a classification key, plus they’re a tool for teaching younger nature-lovers about similar species.When out exploring nature in a field, take a dichotomous key, to identify and learn characteristics of any organisms you discover.What Is An Example of A Dichotomous Key?Dichotomous keys help you identify characteristics and features, and order information. As you can see below, you ask specific questions where the answer is ‘yes’ or ’no’.Image © Wikihow under a creative commons licence.Vertebrates Dichotomous KeyBelow are the classifications of vertebrates you can use your dichotomous key to discover.Mammals: You might ask ‘Does it have fur?’. If the answer is ‘yes’, it leads to ‘mammal’.Birds: If you said ’no’, next maybe ‘Does it have feathers’? If you say ‘yes,’ you’ve identified a bird.Reptiles: If you choose ’no’, you may ask if your organism has dry or moist skin. If you say ‘dry’, you’ve identified a reptile.Fish: If you say ‘moist’, you might ask if your organism has scales or smooth skin. If ‘scales’, you’ve identified a fish.Amphibians: If your organism has smooth, moist skin, it’s an amphibian, like a frog.InvertebratesA similar biological key can be used to help you identify invertebrates (animals without backbones), which divide into one of various examples.Worms: If your organism has no legs, or shell, but is segmented, it may be a worm.Molluscs: If it has no legs, but a shell, it might be a mollusc.Arachnids: If your specimen has eight legs, it’s probably a spider (but could be a tick or mite).If if it has six legs, you might ask, ‘does it have wings’?Lepidoptera: If the species has wings, it could be a moth or butterfly.Insects: If it has no wings, it could be an insect or crustacean. If the body has three sections, it might be an insect-like an ant. Crustacean: If two sections, it might be a crustacean, like a crayfish.There’s a vast number of invertebrates, but based on the set of examples and features you’ve seen, a dichotomous key can help you make choices to simplify and discover which species it might be, and help you name it.PlantsDichotomous keys are an important tool for budding botanists. A dichotomous key can be useful in helping you name species, and recognise organisms’ characteristics. You can use a dichotomous key during any field trip.Typical Dichotomous Keys Ask:Does your plant grow seeds? If ‘yes’, you might ask if it has flowers.Dicot: If ‘yes’, (it grows seeds and flowers) and it has leaves with net-like veins, it’s a dicot, like a sunflower.Monocot: If ‘yes’, (it has seeds and flowers) and it has leaves with long veins, it’s a monocot, like a grass.Conifer: If it has seeds, but no flowers, does it have needle-like leaves? If ‘yes’, it’s a conifer.Fern: If your plant has no seeds, but ‘does have stems and leaves, it’s a fern.Moss: If it has no seeds, stems or leaves, it’s moss or algae.
The phrase dichotomous key might not be instantly familiar, but we’re betting as a parent, you’ve seen them before.
