[Biology Class Notes] on Diversity in Living Organisms Pdf

Biodiversity is used to define the diversity of life forms worldwide. It is a word that is used more often to refer to the classification of living species found in a particular geographic region. The Diversity of living species of a geographic region in an area provides stability in the respective region.

There are numerous living organisms on earth with different sizes, shapes, habitats, nutrition, reproduction, and more.  That depends on their physical features and their habitat. Animals of any kingdom are classified into different orders and classes.

Animals live in different climates like water, land, grasslands, deserts, forests, ice, water, and ice to forests, deserts, and grasslands. All these organisms consist of cells.

Cells are one of the essential characteristics of living organisms.  Cells are structural units of life. It carries out specifically assigned functions in living species.  In this way, a group of cells from tissue in living species.

Diversity in living organisms can be seen everywhere on earth.  The region of the earth is highly diverse and is called the region of mega biodiversity. Twelve countries in the world have more than half of the biodiversity in the world. India is also one of them.

Over millions of years, diversity has been going on in living beings.  Species have evolved from ape-like beings to homo sapiens.  People look for similarities between organisms to classify them, and hence they study them as a whole. Regarding this, fundamental characteristics need to be decided, which would form the foundation for classifying.

Introduction to Diversity in Living Organisms

Life exists in different forms on Earth. When it comes to the question of the number of living organisms found on the earth, the answer is unimaginable. This is so because of the large diversity of organisms continuously evolving into a different variety ever since the origin of life had taken place. Diversity is present at different levels like genetic diversity, species diversity, and ecological diversity. Mango alone has around 10,000 varieties in India. This alone example indicates how large and diverse are the living organisms. Gaining knowledge about this large diversity is impossible without classifying them. Thus classification becomes an important step towards the study of different organisms found on the earth.

Biological Classification

The process of putting all the organisms in certain groups on the basis of certain similarities and differences is known as Classification

Various characteristics are taken into account in order to classify an organism. Some of them are-

• The type of cell present whether the organism is having a eukaryotic cell or a prokaryotic cell. 

• The number of cells whether the organism is unicellular or multicellular.

• Body organization whether the organization is cellular, tissue-level, or organ-level.

•  The nutrition of organisms whether it’s autotrophic or heterotrophic.

• Morphological features of the organisms.

• Anatomical features of the organism etc.

All these features including many others are taken into consideration during the classification

Classification System

Various scientists have proposed their own model of classifying organisms. Some of these are given below.

Two Kingdom Classification

Carolus Linnaeus gave the 2-kingdom system of classification and divided all the organisms into two groups as Plantae and Animalia. This kind of classification brought all the organisms which had a cell wall together within their cell in one group called the Plantae and the rest all were placed in the other group known as Animalia.

Plantae comprises bacteria, fungi with plants. All were very different from each other but still were kept together under two-kingdom classification. There was no distinction between the prokaryotes as well as eukaryotes. Thus this system of classification was not right but surely helped in evolving a better classification system.

Five Kingdom Classification

R.H Whittaker proposed a five-kingdom classification. This classification is accepted and corrected worldwide. A number of criteria were considered for making this model like the cell type, cell number, cell organization, nutrition, etc. 

It consists of 5 groups /kingdoms 

• Monera

• Protista

• Fungi

• Plantae

• Animalia 

Characteristics of Five Kingdom

Kingdom Monera

• This kingdom has organisms that are unicellular and have prokaryotic cell.

• It includes bacteria, cyanobacteria, etc.

• Their cell usually has a cell wall.

• They can be autotrophic or heterotrophic.

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Kingdom Protista

• This kingdom includes organisms that are also unicellular but have a eukaryotic cell.

• They may be photosynthetic or heterotrophic.

• They may possess structures like flagella and cilia.

• Examples are amoeba, euglena, paramecium, etc.

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Kingdom Fungi

• This is the first kingdom with multicellular organisms.

• They exhibit a heterotrophic mode of nutrition more specifically saprotrophic mode of nutrition.

• They have a eukaryotic cell with a cell wall that is made up of chitin.

• < span>Example – yeast, mushroom

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Kingdom Plantae

• All organisms are eukaryotic and multicellular.

• The body can be seen as differentiated into higher groups.

• They are photosynthetic and exhibit an autotrophic mode of nutrition. Some members are partially heterotrophic.

• Their cell has a cell wall made up of cellulose.

• Examples- mango tree, red algae, etc.

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Kingdom Animalia

• All members are eukaryotic and multicellular.

• Their cells lack a cell wall.

• They are heterotrophs.

• Examples- lion, dog, fish, etc.

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Classification Hierarchy

The broadest group Kingdom is further divided into small groups to reach a point of maximum similarity in one group of organisms. Thus a hierarchy of classification is developed when the small groups are arranged from the lowest to the highest order. Each category in the hierarchy is known as Taxon.

Following is the Hierarchy of Classification:

• Kingdom

• Phylum / Division

• Class

• Order

• Family

•  Genus

• Species

Species are the basic unit of classification.

Classification and Evolution

Classification of organisms is related to evolution. Evolution is the change that takes more over the years in the body design of organisms for better survival. Charles Darwin first described the concept of evolution in his book ‘The Origin Of Species’ in 1859.

Lower organisms are the organisms that seem to have not changed over the years.

Higher organisms are relatively recent and have their particular body designs.

Diversity in Living Organisms is a fundamental topic introduced in students in higher and junior classes.  It is a primary and essential topic of Study, for this one can easily follow and know about interesting facts about Diversity.

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