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Research Title
The use of a dichotomous key in the development of scientific classification skills in Grade 7 learners.
What is a dichotomous key?
Example of a simple dichotomous key to distinguish between 4 learners.
1. Are you a girl? ………………………….Go to 2
Are you a boy? …………………………Go to 3
2. Do you have long brown hair? ………...Sally
Do you have short brown hair?..............Lucy
3. Are you between 1.0m and 1.2m tall?....Leon
Are you between 1.3m and 1.4m tall? …Paul
What is classification?
Why do humans like to classify things?How do scientists classify all life on
Earth?Five-kingdom system of classification:
PlantaeAnimaliaFungiMonera (Bacteria)Protoctista
Linnaean taxonomic system of binomial nomenclature.
Kingdom
Phylum 1 Phylum 2 Phylum 3
Class 1 Class 2 Class 3
Order 1 Order 2 Order 3
Family 1 Family 2 Family 3 Family 4
Genus1 Genus 2 Genus 3
Species 1 Species 2 Species 3 Species 4
Let’s classify humans scientifically?
Kingdom: Anamalia Phylum: Chordata Class: Mammalia Order: Primates (nails, large brains, vision) Family: Hominidae (humans, chimpanzees,
gorillas) Genus: Homo (Human being) Species: sapiens (Wise man)
Instrument used
Learners required to classify 6 shells to species level using the following tools:
• Real shells
• Glossary
• Shell anatomy diagrams
• Dichotomous key
• Worksheet
Extract from the Glossary
Glossary of terms Aperture: the opening at the front end of a
gastropod shell. Apex: the starting point of growth, the highest
point of the shell. Bivalve: a mollusk with a shell formed of two
pieces / valves. Dichotomous: regularly forking into pairs of
branches. Gastropod: a mollusk with a single / one –
piece shell.
Extract from the Dichotomous Key
Dichotomous key for the identification of selected members from the phylum Mollusca.
1. Consists of a hinged bivalve shell. Class: Bivalvia (Go to No 2) Consists of a single spiral or cap shaped shell. Class: Gastropoda (Go to No 5)
2. Valves are triangular shaped. (Go to No 3) Valves are paddle shaped. (Go to number 4)
3. Smooth valves with brown rays, radial ribs absent: Scissodesma splengeri
Bumpy valves with deep mottled -brown radial ribs. Trachycardium flavum
Extract from the Worksheet
Shell 1:
Kingdom: _______________________
Phylum: ________________________
Class: _________________________
Order: Veneroida
Family: Mactridae
Genus: _________________________
Species: ________________________
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