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

Real shells

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.

Shell anatomy diagrams

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: ________________________

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 changeThe scientic name is the basis of all

other ecological studies