A study into the development of scientific classification skills

1. Research Title
The use of a dichotomous key
in the development of
scientific classification skills
in Grade 7 learners.

2. 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

3. What is classification?
Why do humans like to classify things?
How do scientists classify all life on
Earth?
Five-kingdom system of classification:
 Plantae
 Animalia
 Fungi
 Monera (Bacteria)
 Protoctista

4. 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

5. 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)

6. Instrument used
Learners required to classify 6 shells to
species level using the following tools:
• Real shells
• Glossary
• Shell anatomy diagrams
• Dichotomous key
• Worksheet

7. Real shells

8. 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.

9. Shell anatomy diagrams

10. 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

11. Extract from the Worksheet
Shell 1:
Kingdom: _______________________
Phylum: ________________________
Class: _________________________
Order: Veneroida
Family: Mactridae
Genus: _________________________
Species: ________________________

12. Why do we need to know the
scientific name?
Common names differ from place to
place
Common names differ from language to
language
Latin words tend not to change
The scientic name is the basis of all
other ecological studies