Gr.
11 SUMMARY NOTES: CLASSIFICATION
There are a great variety of organisms that co-inhabit the earth. These organisms occur in many different
forms and sizes. Some of them are invisible to the naked eye. These different species can live in a variety of
different habitats.
Classification refers to the grouping and sorting of things according to similarities and differences.
Life forms are put into groups as a result of classification. This makes it easier for the scientist to study these
life forms.
Taxonomy refers to the science of naming and classifying a wide range of living things.
Living things were classified into two groups: plants and animals.
This became known as the two-kingdom system.
The following characteristics are used to classify organisms as plants or animals:
Are able to make own food
Kingdom
Plantae Have a cell wall
All living Sedentary/sessile
organisms Can't make own food
Kingdom
No cell wall
Animalia
Motile
The more scientists came to know about life the more advanced the classification systems became:
Currently, 3 systems are used:
• Two-kingdom system
• Five-kingdom system
• Three domain system (which we do not use at school level)
The Five Kingdom system
Developed by Robert H. Whittaker in 1969.
All living organisms were placed into 5 kingdoms based on certain characteristics.
Terminology:
Eukaryotes: A true nucleus is a nucleus that is surrounded by a nuclear membrane. Organisms that possess
true nuclei are called eukaryotes. The organelles in eukaryotes are all bound by membranes.
Prokaryotes: All organisms with nuclear material not enclosed by membranes are called prokaryotes. All the
organelles found in prokaryotes do not have membranes.
Autotrophic organisms: are those that can manufacture their own food by photosynthesis.
Heterotrophic organisms: are those organisms that are unable to manufacture their own food.
Saprophytes: organisms that feed on dead and decaying matter.
Unicellular: Organisms that are made up of one cell only.
Multicellular: Organisms that are made up of many cells.
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The Five Kingdom
classification system
Monera Protista Fungi Plantae Animalia
There are certain characteristics or criteria that are used to develop the five-kingdom classification system:
Kingdom Monera:
o Made up of bacteria and blue-green algae.
o Bacteria are unicellular and microscopic. microscope
o Some bacteria are colonial, meaning that while they occur in groups each bacteria function on its own.
THEY COME TOGETHER BUT DO NOT WORK TOGETHER
o Bacteria are prokaryotes: All organisms with nuclear material not enclosed by membranes are called
prokaryotes. All the organelles found in prokaryotes do not have membranes
o Some bacteria are autotrophic: are those that can manufacture their own food by photosynthesis
o Most bacteria are heterotrophic: are those organisms that are unable to manufacture their own food.
o Some of the heterotrophic bacteria are parasitic or saprotrophic.
Kingdom Protista
o Most are unicellular but some are multicellular.
Unicellular: Organisms that are made up of one cell only.
Multicellular: Organisms that are made up of many cells.
o Therefore, they may be microscopic or macroscopic. SOME CAN BE SEEN WITH AN NAKED EYE WHILE SOME
YOU REQUIRE A MICROSCPE TO SEE THEM
o Some of the unicellular protists can be colonial (live in colonies).
LIVE TOGETHER BUT DO NOT FUNCTION TOGETHER
o They are all eukaryotes. Protists are not identical in appearance.
o They also differ in the way in which they obtain their food differently
o Therefore, they are divided into 3 groups based on nutrition and appearance.
o These 3 groups are: algae, protozoan and slime moulds.
o The algae are plant-like and autotrophic.
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o The protozoans are animal-like, and they obtain their food from other plants or animals or dead organic
matter.
o Slime moulds are almost like fungi.
Kingdom Fungi
o Mushrooms, yeast, and mould found on bread and jam etc. are found in this kingdom.
o Some have plant-like features, and some are different from plants.
o They are heterotrophic, but they obtain food by secreting enzymes into the food and then absorbing the
digested food. Many of the organisms found in this kingdom are decomposers.
o Some are parasitic while others are saprotrophic.
o Fungi may be unicellular or multicellular. SOME CAN BE SEEN WITH AN NAKED EYE WHILE SOME YOU
REQUIRE A MICROSCPE TO SEE THEM
o They all produce spores.
o Some produce spores in sporangia.
o Some produce spores in club shaped structures. These structures are usually found within the cap-like fruiting
bodies: mushrooms. Others produce the spores in sac like structures like Penicillium.
Kingdom Plantae
o Organisms belonging to this kingdom all have cell walls, they are all multi-cellular and have chloroplasts.
o They are autotrophic.
o Some plants are vascular: they have xylem and phloem which is used for transport of nutrients, mineral salts
and water.
o Such plants have true roots, stems and leaves because they have vascular tissue.
o Vascular plants may be divided into seed producing plants and non-seed producing plants.
o Some plants do not have vascular tissue.
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Kingdom Animalia
o These organisms occupy a variety of habitats.
o They are multi-cellular.
o They do not have cell walls around their cells.
o They do not have chlorophyll, herefore, they are heterotrophic.
o There are huge differences in appearances. They do not look alike
o They can be sub divided into vertebrates and invertebrates.
Taxonomy
Taxonomy is the branch of biology that classifies all living things. It was developed by the Swedish botanist
Carolus Linnaeus, who lived during the 18th Century, and his system of classification is still used today.
Linnaeus and other scientists used Latin because it was a dead language- meaning nobody spoke it anymore.
Hence, it is a neutral language, and the scientific name can be used to avoid confusion with common
names.Linnaeus invented binomial nomenclature, the system of giving each type of organism a genus and
species name.
He also developed a classification system called the taxonomic hierarchy, which has seven ranks from general to
specific: kingdom, phylum, class, order, family, genus, and species.
Genus and species are always typed in italics and underlined when it is handwritten.
The Genus name will be written with a capital letter while the species name is written with a small letter.
Example of taxonomic classification of a red fox:
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Another example of classification of humans and ostriches:
Remember this sentence: “King Philip Came Over For Good Spaghetti”.
The two types of taxonomic keys:
1. Pictorial
o These keys have illustrations.
o These illustrations maybe in the form of pictures, photographs or a combination of these.
o Organisms are identified by comparing them to the illustrations.
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2. Verbal
o Clues are in the form of statements or questions of characteristics.
o By answering the questions or following the statements and looking at the specimen the correct taxon can
be identified to which the specimen belongs.
For example:
Key to the five kingdoms of living organisms
1. Do the organisms have a definite nucleus?
YES. Go to question 2. If NO then its Kingdom Monera.
2. Is the organism multicellular or unicellular?
If it is unicellular then Kingdom Protista. If it is multicellula then go to question 3.
ACTIVITY CLASSIFICATION
Question 1: Biological keys
We use a biological key to name and identify unknown plants and animals.
Look at the following invertebrates
Read the first pair of statements in the key below
Which statement is true?
Follow the instructions at the end of each statement until you arrive at a name for the animal.
Invertebrate key
1.The animal has six legs Go to 3
The animal have more than six legs Go to 2
2. The animal have eight legs Spider
The animal have more than eight legs Go to 4
3. The animal has wings Locust
The animal has no wings Ant
4. The animals has a rounded body Millipede
The animal has a flattened body Centipede
Question 2: Using a key to classify leaves
You will now classify the following South African plants, using their leaf characteristics.
The diagram below shows different leaves of plants like Agapanthus, Clivia, Ziziphus cordatum, Syzigium,
Erythrina, Dombeya
A B C D E F
What you do:
Use the following key to identify the leaves
Plant key
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1.Veins on the leaves are parallel Go to 2
Veins on leaves are not parallel Go to 3
2. Tip of head is pointed Agapanthus
Tip of head is rounded Clivia
3. Has one main vein Syzigium cordatum
Has more than one vein Go to 4
4. Edge of leave is serrated Ziziphus mucronata
Edge of leave is smooth Go to 5
5. Leaf divided into three leaflets Erythrina
Leafs is not devided Dombeya
Answers:
1. A= Insect
B = Spider
C= Locust
D= millipede
E= centipede
2. A= Agapanthus
B= Dombeya
C= Erythrina
D= Ziziphus mucronata
E= Syzigium cordatum
F = Clivia
