Classification I - Biology Form 1
Classification of Organisms
Classification refers to placing of organisms into their respective groups which are known as taxa (one is a taxon), in relation to features or characteristics of the specific organism.
There are millions of living organisms on earth. Traditionally man classified organisms depending on their characteristics, habitat as well as the use to which the organisms could be put. Scientists classify them basing on their physical and physiological characteristics.
Classification also allows for easy identification, easy naming and study of the organisms. It is also easy to establish ancestral relationships between organisms using a classification system.
Organisms are grouped into five major kingdoms namely;
The seven taxonomic units of a Kingdom, in descending order are:
7. SpeciesBinomial nomenclature is a system of naming organisms by
assigning them a generic and specific name e.g., the lion belongs to the genus Panthera and species leo. The scientific name of the lion, therefore is "Panthera leo".
In Primary Science study, you grouped living organisms as shown below:
By the end of the lesson you should be able to state the necessity and significance of classifying organisms.
Necessity and Significance of Classification
Organisms are classified according to similarities and differences. This is based on external and sometimes internal features of the organisms. The illustrations below indicate organisms with varying characteristics that can be used in classification.
Place the following animals into their respective groups by dragging and dropping method.
- Man - Lizard - Crab - Elephant
- Cockroach - Octopus - Warthog - roundworm
Drag and drop the following plants into the group of monocotyledons or dicotyledons.
Flow chart of classification of plants into monocots and dicots.
Onion bulb with leaves
Monocots- sisal, onion, sugarcane
Dicots- Rose flower, banana and pawpawThe placing of organisms into various groups based on their structural and physiological differences and similarities is called classification.
Necessity for Classifying Organisms
You have already learnt that Classification is important for:1.) Easy identification of organisms.
2) For scientific naming, so as to have universally accepted names.
3) For establishment of relationships between organisms and their ancestry.
4) For easy study of organisms.
5) To facilitate orderly arrangement of biological information to avoid confusion.
AssignmentList down as many living organisms as possible and place them in their respective kingdom
In primary science you placed living things into two groups: plants and animals. Plants make their own food and animals feed on ready made food.
You placed mushrooms in the group of non-green plants since they do not make their own food, but look like plants.
Mushrooms, however, are not plants. Some organisms have been found to possess both plant and animal characteristics. For this reason, taxonomists have now placed organisms into five groups called kingdoms.
NB The kingdoms will be outlined in the course of the lesson.
By the end of the lesson you should be able to;1. Name the five kingdoms, giving an example in each case
2. Name the seven major taxonomic units of a Kingdom
3. Place one plant and animal in the taxonomic units in descending order
Use the drag and drop method to place the taxonomic names listed below into their appropriate taxonomic position.
Animalia, Monocotyledonae, Chordata, spermatophyte, primate, Mammalia, Graminales, Zea, Homo, Hominidae, sapiens, Plantae.
Kingdom Animalia Plantae
Phylum/division Chordata Spermatophyte
Class Mammalia Monocotyledonae
Order Primate Graminae
Genus Homo Zea
Species sapiens mays
Units of Classification
In primary science you placed living things into two groups; plants and animals. Plants make their own food and animals feed on ready made food.
You placed mushrooms in the group of non-green plants since they do not make their own food. Such organisms are not really plants.
Some organisms have been found to possess both plant and animal characteristics. It therefore became necessary for taxonomists to place organisms into five groups called kingdoms.
The kingdoms will be outlined in the course of the lesson.
Currently, the Five-kingdom system of classification is used.
In this classification system, organisms are placed in the following groups:
1. Kingdom Monera- This group consists of bacteria such as Coccus, Bacillus and Vibrio. Examples are shown in the figure.
2. Kingdom Protoctista:- This group contains single celled organisms including; -
Amoeba, Paramecium, Trypanosoma.
See examples (Liver fluke and Trypanosome) in the figure.
3. Kingdom Fungi ;- This kingdom includes Mushroom, Bread mould, Yeast, Rhizopus. The mushroom in the figure are growing on a dead tree trunk.
4. Kingdom Plantae This contains plants such as Maize, Bean and Fern
5. Kingdom Animalia:- Contains animals for example Insect, Fish, Lizard, Bird, Human being.
ANALOGY OF CLASSIFICATION
Planet earth is one huge body which supports life unlike other planets. It can be used as an analogy in classification
This planet is made up of five continents. The continents differ from each other in many ways but have some similarities such as climatic conditions and geographical features.
This can be likened to classification in which organisms are placed into five kingdoms. The organisms in a kingdom have some similarities and a wide range of differences.
Analogy of classification based on the map of Africa
Each continent is made up of regions. The African continent is made up of several regions such as the East African region. This is likened to the classification in which organisms in a kingdom are placed into groups called Phyla/ Divisions. Members of a phylum/division have more in common than members of a kingdom.
Each region is made up of several countries for example Kenya, Uganda, Tanzania. Rwanda and Burundi are countries which make up the East African region.
Similarly, several classes are found in a Phylum/ Division. Members of a class have more in common than members of the same phylum/division.
Provinces Vs Orders
Kenya is divided into provinces just like several orders make up one class. A province has a lot in common just as members of the same order. In Coast Province, for example, the most common group of people are the Mijikenda, who use Kiswahili as their major language.
Members of an order have many similarities.
District Vs Families
A province is further divided into districts, just like Order is made up of several Families.
Members of the same family have more similarities than those of the same order.
Division Vs Genus
A district is further divided into divisions. This is likened to the division of the families into genera. Members of a genus have a lot more in common than members of a family. In a Division the people are closely related, under one ancestry and have one area chief.
They have similar cultural habits.
Location Vs Species
A division is further divided into locations. This is likened to the division of a genus into several species.Members of the same species are so closely related that they can interbreed to give rise to fertile (viable) offspring.
Classification of Bean and Domestic Dog
An individual organism can be placed in different taxonomic units.
2. Domestic Dog
You have already learnt how to classify an organism in various taxonomic units. In this lesson, you will learn how organisms are given scientific names.
This refers to the giving of organisms two names: Genus name and specific name. The first name refers to the genus to which the organism belongs. The first and second names together refer to the species to which the organism belongs.
For example, the scientific name of maize is Zea mays. Zea is the Genus to which maize belongs.is the species.
By the end of this lesson, you should be able to
Use Binomial nomenclature to scientifically name a plant and an animal.
Name the five kingdoms which organisms are classified.
List the taxonomic units in classifying a plant in ascending order.
The scientific name of a housefly is Musa domestica. What does Musa stand for?
(a) Which two of the following organisms are closely related?
(b) Give a reason for your answer in (a) above
(a) Homo sapiens and Homo erectus
(b) They belong to the same genus.
Binomial nomenclature refers to the system of assigning scientific names to organisms. The scientific name is derived from combining the genus name and the specific name.
This system of giving an organism a scientific name was started by Carolus Linnaeus in the 18th century.
The scientific name is given in the Latin language or made to sound Latin. This language which was widely by scientists is accepted as it does not change.
The generic name starts with a capital letter while the specific
name is all written in small letters.
Example 1: The common bean plant belongs to the genus Phaseolus and species vulgaris. The scientific name of the common bean plant is therefore Phaseolus vulgaris. The domestic dog belongs to genus Canis and species familiaris. Its scientific name is thus Canis familiaris.
When hand-written, the two parts of the name are underlined separately as shown:
1. Phaseolus vulgaris
2. Canis familiaris
Example 2: The following is the scientific name of the human being:
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