CHAPTER ONE
GENERAL INTRODUCTION
Biology developed from two Latin words BIOS meaning life and LAGOS meaning study or discourse. Biology therefore is a branch of natural science that deals with the study of life and living organism including their structure, function, growth, evaluating distribution and taxonomy
ORGANISM AND VARIETY OF LIFE
It is estimated that there are about 10million kinds of living organisms on earth and many more are still to be discovered for man to study properly and to appreciate these diversities these organisms must be grouped of classified
PRINCIPLES OF CLASSIFICATION
The principles of classification deals with the description, identification of organisms as well as their classification into different groups according to their similarity and difference that is their common characteristic
Classification refers to the grouping of organisms together on the basis of the features they have in common for better understanding
Classification is important because it helps us to study organisms in an orderly way so as to avoid confusion
The study of biological classifications known as TAXONOMY. Taxonomy therefore deals with the study of the principles of classification
TAXONOMY
The science of taxonomy has two branches
- The placing of organisms into groups or systematic
- The naming of organisms or Nomenclature
1. SYSTEMATICS:
Systematics deals with the classification of organisms into groups and it is done with regards to their descent from a common ancestor. Systematic is an important aspect of taxonomy because it indicates the genetic of organisms in a group.
Systematic involves
- PHENETIC CLASSIFICATION: which uses up observable characteristics to place organisms into groups
- PHYLOGENY: which is the grouping of organisms according to how recently they are believed to have diverted from common ancestor
There are two types of systematics namely the NATURAL and ARTIFICIAL systems of classification
1.1. The artificial system of classification
These systems is based on external observable features such as colors, size, habit, function of part etc. it is designed for practical purpose for convenience and simplicity.
The characteristic may carry out the same function in the adult organism but of different origins.
They may change with time and may vary from one environment to another since the evolution trend is not followed for this reason the artificial system of classification is based on analogous characteristics. These characteristics which have different origins but carry out the same function in the adult e.g. the wings of a bird and of an insect have different origin but are used for the same purpose which is flight.
1.2. THE NATURAL SYSTEM OF CLASSIFICATION.
These system groups organisms on the bases of the evolutionary relationship irrespective of size color, function of part, locomotion etc.(phylogeny).
The natural system of classification is said to be based on HOMOLOGOUS CHARACTERISTICS (these are characteristics that have the same origin regardless of their functions in the adult). They may perform the same or different functions e.g. the forelimbs of a vertebrate have the same origin and structure but adapted for different functions as the human and dogs forelimbs.
The natural system uses natural relationship between organisms including internal and external features. It employs embryology, morphology, anatomy physiology, biochemistry, cell structure and behavior.
2. NOMENCLATURE
It is the branch of taxonomy which involves the naming of organisms.
a. Vernacular naming:
This are names given in the natural language (diet or mother tongue) and are also known only by particular localities or tribes. If an attempt is made to use this naming widely, it will bring a lot of confusion.
b. Common names:
These are names given to organisms in ENGLISH, GERMAN, FRENCH, SPANISH etc. or any conventional language. Common names are widely known by those who speak the language but can be confusing since they vary from one country to another. A single organism may have several common names in different localities and sometimes the same common names is given to completely different organism TIGER or CYBERIAN CAT.
C. SCIENTIFIC NAME (BINOMIAL SYSTEM OF NOMENCLETURE)
SCIENTIFIC NAMES are given to organisms by scientists according to the international agreed system of nomenclature. It is called binomial system of nomenclature and it was introduced in 1758 by a SWEEDISH BOTANIST called CAROLUS LINAEUS. In this system each organism has two names the genus name or generis name and the specie name or specific name. the name is always in Latin or Greek and it is written in two parts.
- The first name which is the generic name is always written with an initial capital letter.
- The second name is the specie name which is always written with an initial small letter.
The two names are called a scientific name. in text books or when typed it is in italics. when handwritten, the names are underlined separately example.
MAN: Homo Sapiens.
2.3. UNITS OF CLASSIFICATION OR TAXONOMY NHIERACHY
Once organisms have been named they are placed into a group or texa(taxon in singular) on the basis of observed features. The groups are arranged in a hierarchy. The largest group which is the kingdom is placed at the top. The groups in descending order are as follows
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
A specie: is a group of organisms capable of interbreeding to produce fertile offspring.
A genus: is a group of similar and closely related species.
A family: is a group of apparently related general(genus)
An order: is a group of apparently related families.
A class: is a group of apparently related phylum.
A phylum: is a group of organisms resulting from group of classes.
A kingdom: is the largest and the most inclusive grouping resulting from a number of phyla. Examples of kingdom are.
- ANIMALIA
- PLANTAE
- PROTOCTISTA
- FUNGI
- MONERA
2.4. REASONS FOR CLASSIFYING ORGANISMS
- To create order out of disorder
- To ease the identification of organisms
- To facilitate the study of organisms by studying only representative types
- To trace the evolutional relationship between organisms
- To ensure that newly observed species can be fitted easily into the classification scheme
- To bring morphological and anatomical relationship between organisms
- To ensure communication between researchers all over the world
