CONCEPT OF SPECIES It is already been stated that individual organisms which have many features in common and able to interbreed in natural conditions are encompassed by the term species. Species is the smallest basic unit of classification. Its proper characterization is, therefore, of vital importance for a 'Natural' scheme of classification. Identifying species on the basis of reproduction, John Ray (1693) considered all individuals produced by parents of the same types as members of the same species. Linnaeus and Some others distinguished species merely on the basis of structure. Morphological Concept of Species This is the most practical and widely used species concept to describe species since people began to classify organisms. Taxonomists use this concept mostly by default because they know most of the species on Earth only from their morphology. New species are usually named on the basis of morphological species concept; morphological descriptions are all that we need
The process involved in the basic necessary activities and function for the survival or maintenance of a living body are called life processes or maintenance processes. A living body needs continuous repair and maintenance whether we are active, sitting or sleeping. It means that the maintenance processes should occur continuously to repair the damage or worn out cells or tissues. Hence, these processes are termed as life processes as they work in coordination to support the body to be in a living state. Let's understand some important life processes.
1- Nutrition:
All the maintenance processes need a regular supply of energy to occur. The living organism derive this energy from the food they eat. So the process of taking in food and obtaining energy from it for growth, repair and metabolism is called nutrition. The nutrients obtained through food are essential for an organism to grow and develop. As life on earth depends mainly on Carbon-based molecules such as fats and proteins, most of the food sources are also carbon-based. Based on the complexity of carbon sources available as food, different organisms use different nutritional processes to obtain energy. For example, plants make their food using the process of photosynthesis, animals obtain food from outside and break it down into simpler substances.
2- Respiration:
The food consumed by living organism cannot be directly observed by their body. It needs to be broken down so that it can be transformed into a source of energy that can be used for Molecular movements involved in the growth and maintenance processes. For this, various chemical reactions occur in the body. To carry out these chemical reactions, most of the living organisms take oxygen from the outside. This process of using oxygen from outside to breakdown food to obtain energy for cellular needs is term as respiration.
3- Transportation:
In unicellular organisms, the entire surface of the cell remains in contact with the outside environment. So, no specific organs for taking in food, exchange of gases or removal of wastes are required. Simple diffusion is sufficient for these organisms for the life processes like nutrition and respiration. In multicellular organisms, all the cells may not be in direct contact with the environment. Due to this, simple diffusion cannot fulfill the requirements of cells for food, oxygen or removing metabolic waste products. Food and oxygen obtained by these organisms need to be supplied to the entire body. This is done by the process of transportation.
4- Excretion:
The nutrition and respiration processes create by products which need to be removed as they are useless and toxic for the body. The removal of waste products from the body is called excretion. Multicellular organisms have special excretory organs for the removal of waste products. The excretory system is the system in an organism's body that performs the function of discharging wastes from the body.
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