CLASSIFICATION OF LIVING THINGS

CLASSIFICATION OF LIVING THINGS

Classification is a grouping of organisms based on their similarities and differences organisms that are similar are placed in one group. These similarities could be in terms of ancestry structure or the way they carry out life processes such as feeding and reproduction. 

Classification is a branch of biology that deals with the grouping of living organisms according to their structure, way of life and origin.

TAXONOMY

It is a branch of biology that deals with classifying organisms.

TAXONOMIST

A person (biologist) who studies about classification.

TAXON

Is any named established group in the ranks of classification.

IMPORTANCE OF CLASSIFYING LIVINGTHINGS

1. There are millions of livings things in the world, grouping them make it easy to study and identify them.
2. Scientific names enable scientist to identify organisms easily, no matter which part of the world they are in.
3. It easier to study organisms in a group, because the members of a group have many things in common.
4. Classification enables scientists to make predictions.
5. It provides an organized system in which newly identified similar organism can be fitted in future
6. It helps man arrange the information about living organisms in an orderly manner to avoid confusion.

CLASSIFICATION SYSTEM

There are two main types of biological classification namely: -

1. Artificial classification
2. Natural classification

ARTIFICIAL CLASSIFICATION

Artificial classification system is grouping of organism according to observable features. For example presence of legs or wings based on bees, birds and bats would be grouped together because they have wings. Snakes, earth worm and snails would also be grouped together because they do not have legs.

Artificial classification also involves classifying organisms according to their size how they move, where they live or what they eat.

Advantage of artificial classification

• It straight forward and easy to use
• It can be done very fast
• Artificial classification is less costly than natural.

Disadvantage of artificial classification

-Some organisms that are dissimilar in their internal make up are grouped together because of the resemblance of their external features.

-Some similar organisms are put in different groups because they do not have a lot of physical remembrance.

-It is less accurate because it uses only few observable characteristics.

-Artificial classification depends a lot on what the scientist is interested in therefore it varies from person to person.

NATURAL CLASSIFICATION

              In this system classification is based on evolutionary relationship and presence of large number of common and similar characteristics feature that show homology and analogy structure.

     Homologous structures: Are the structure having the same origin but perform different function. Eg, Forelimbs of whale and forelimbs of man .
    Analogous structure; Are structure having different origin but perform the same function. Eg, Wings of birds and wings of insect

Advantage of natural classification

1. It gives a lot of information of living things
2. It is most accurate
3. It is universal
4. It avoids confusion

Disadvantage of natural classification

1. It requires a lot of time
2. It needs high skills
3. It is difficult to classify
4. It is expensive
5. It is not stable.

Difference between artificial and natural classification

1. Artificial is not accurate and natural is most accurate
2. Artificial is cheap while natural is expensive
3. Artificial classify living organism according to the external features while natural classification classify living organism according to the internal features.

      4. Artificial does not require scientific skills while natural classification requires scientific skills and knowledge.

MAJOR GROUP OF LIVING ORGANISM

There are five major groups of living organism

1. Kingdom animalia eg. Cow, cockroach
2. Kingdom plantae eg. Maize tree, peas
3. Kingdom monera eg. Bacteria
4. Kingdom protoctista eg. Amoeba
5. Kingdom Fungi eg. yeast

RANKS OF CLASSIFICATION

1. Kingdom
2. Phylum or Division
3. Class
4. Order
5. Family
6. Genus 

-Kingdom has a greatest variety of organism

-At kingdom level, organism shows  few features in common as you move down the rank each unit has lesser and lesser organisms and the members of each unit have more and more features in common.

At the species level organisms are least varied but share more features. Members of the same species can interbreed and produce viable off spring that can turn reproduce. But organisms from different species do not usually interbreed different species. Do not interbreed because of differences in genetic makeup, physical features, size and geographical location. However these are few exceptions to this rule.  Dogs and Wolves can interbreed to produce viable offspring.

In table below some few common organisms have been classified from kingdom to species level. This should guide you in classifying other organisms.

CLASSIFICATION OF SOME COMMON ORGANISM

                      

TAXONOMY UNIT	HUMAN BEING	DOG	MAIZE PLANT	EUCALYPTUS TREE
Kingdom	Animalia	Animalia	Plantae	Plantae
Phylum or division	Chordata	Chordata	Spermatophyta	Magnoliophyta
Class	Mammalia	Mammalia	Argiospermae	Magnoliopsida
Order	Enirate	Carnivore	Graminales	Myrtalesa
Family	Hominidae	Canidae	Graminales	Myrtaceae
Genus	Homo	Canis	Zea	Eucalyptus
Species	Sapiens	Familiars	Mays	Regnans
Scientific name	Homo sapiens	Canis familiaris	Zeamays	Eurcalyptus regnans

KINGDOM

For example human being and donkey

Kingdom Animalia is subdivided into phyla or phylum in singular

Kingdom plantae subdivided into division, The phyla or division are further subdivided into class, each classes is subdivided into orders every order is subdivided into families and families are subdivided into genera (genus in singular)

A genus is subdivided into species. Kingdom, phylum, divisions, classes, orders, families, genera and species are ranks of classification and are called units or taxa.

The following flow chart shows how kingdom plantae and kingdom Animalia are subdivided   

                                                                                               

BINOMIAL NOMENCLATURE

Nomenclature is a system of naming organism where by every name is made up of two Latin words.

This system was divided into two parts

The first part of the name represents the genus it is also called the genetic name.

The second part of the name represents the species it is also called the specific names

For example: The specific name of human being is Homo sapiens. Homo is generic name and sapiens is the specific name. The following rules are observed when writing scientific names.

1. The generic name is written before the specific name 
2. The generic name must start with capital letter.
3. The specific name is written in small letter
4. In publisher document such as books scientific name is written in italics eg, Zea mays and Homo sapiens when hand written or typed the names should be underlined.

                                            SCIENTIFIC NAMES OF SOME COMMON ORGANISMS

COMMON NAME	SCIENTIFIC NAME
Coconut plant	Cocos nucifera
Mango tree	Mangifera Indica
Garlic plant	Allium sativum
Pea plant	Pisum sativum
Domestic cat	Felis catus
Housefly	Musca domestica
Lion	Panthera leo
Donkey	Equus asinus

 

VIRUSES

A virus is an extremely small micro organism.

It is smaller than a living cell. A virus is not a cell

The study of viruses is called virology

Different types of viruses:

STRUCTURE OF VIRUSES

A virus has a very simple structure consisting of genetic material with a protein shell. The protein shell is called a capsid. Viruses do not have a nucleus or complex membrane cell organelles. Some viruses have viral envelopes.

There are membranes enclosing the host cell.

Viruses cannot reproduce its own. It must attack a host cell and uses the material in that cell to reproduce.

This is called oblige parasitism.

                  

  CHARACTERISTICS OF VIRUSES
 

• Viruses do not grow, feed, excrete or respire. Viruses exist in a dormant state when outside a host cell.

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