Biodiversity or Diversity in Living Organisms
= different types of living organisms having variations among each other which make them unique from others.
Living organisms are diverse among each other based on different criteria such as cell type, cell orientation, feeding habits, living habits, biological metabolic pathways, biological transport mechanisms, phylogenetic relationships, etc.
- In spite of having variations some have similar criteria. For this reason, living organisms are classified based on different criteria.
Fig.1. (a) Living organisms having diversity (b) Living organisms in classification
Classification and Evolution
History of living organisms started long ago when only one type of live form was present on Earth which we call the early ancestor.
- Due to different changes in the environment such as increase of oxygen molecules in air, decrease of carbon dioxide molecule in air, decrease in environmental temperature etc., living cells started to form. As the changes remain to accumulate, the single living organism got separated from each other by location.
- The different groups of living organisms tried adapting to their current environmental condition and tried hard to survive in that condition. Trying to adapt, the living organisms made changes within them by changing their feeding habit and lifestyle.
- The changes accumulated in their life span got transferred to their offspring through reproduction. After many years of adaptation, the living organism has totally evolved to survive in that environmental condition which made them totally different from their original form.
- So, evolution is the process which takes many years to occur and totally changes a living organism from its original form to a different form to help it survive in their current environmental condition.
Fig.2. Process of evolution of a living organism from its original form
- Evolution forms new organisms.
- Due to evolution, the original form of living organisms on getting separated become completely different of each other.
- A relationship can be drawn between Classification and Evolution.
There are many organisms whose basic body structure have similarities with their original form and can have similarities with the other group of living organisms who got separated from them and had evolved in course of time. Based on these similarities, living organisms can be classified based on their evolution.
Hierarchy of Classification – Groups
Ernst Haeckel (1894) and Carl Woese (1977) helped in classifying the different living organisms. American taxonomist, Robert H. Whittaker (1969) classified living organisms into five kingdoms. Carl Woese (1977) sub-divided Kingdom Monera into Archaebacteria and Eubacteria.
- Kingdom consists of living organisms having similar phyla.
Kingdoms can be sub-divided into the following in descending order :
- Phylum consists of living organisms having similar class.
- Class consists of living organisms having related order.
- Order consists of living organisms having related family.
- Family consists of living organisms having related genera.
- Genus consists of living organisms having related species.
- Species consists of living organisms who are closely related and can reproduce freely to produce healthy offsprings.
Five kingdoms are Monera, Protista, Plantae, Fungi and Animalia based on the following criteria :
i. Cell types – Prokaryotic cells (cells lacking membrane-bound nucleus and other organelles) and Eukaryotic cells (cells having nucleus and organelles enclosed within plasma membranes)
ii. Cell orientation – Unicellular (Single cell) organism and Multicellular (More than one cell) organism
iii. Cell wall and Nucleus orientation
iv. Feeding habit – Autotrophs (can prepare their own food) and Heterotrophs (dependent on others for food)
v. Mode of Reproduction – Asexual Reproduction (only one parent involved) and Sexual Reproduction (two parents involved and fusion of sex cells called gametes)
vi. Ecological life style – Producers, Consumers and Decomposers
|Fig.3. Hierarchy of Classification of Living Organisms|
Structure of fungi which range from unicellular forms to thread-like structure.
Mycelium = thread-like structure of fungi
Hypae = interconnected filaments of mycelia
Fungal hyphae can be
- Aseptate – the cytoplasm is continuous throughout the hyphae
- Septate – the hyphae have cross walls
- Cotyledons = area in the seed where food is stored to provide nutrition to the baby plant
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