Concept of Living and Need for Classification MCQ - Practice Questions with Answers

What is living
 
The beings or objects showing growth, development, responsiveness, adaptation, and reproduction are called living beings.
 
Important characteristics of living beings
 
Cellular structure
 

• All living beings are made up of a number of cells. These cells contain protoplasm or living matter. 
• The cellular structure is the defining property of living beings as all the processes are related to the structure of cells. 
• Protoplasm and cellular structure are absent in viruses.  

Metabolism  
 

• It refers to all the chemical reactions, occurring within the body of living organisms.  These reactions can be grouped into two types i.e. anabolism and catabolism.
• Anabolism: Processes or reactions including the formation of complex substances from simpler ones. E.g. photosynthesis
• Catabolism: Processes or reactions including the breakdown of complex substances into simpler ones. E.g. respiration

Growth 

• It refers to an irreversible increase in the mass of an individual.
• In plants, growth continues throughout life due to the presence of meristematic tissue. In animals, growth is definite.
• Growth in unicellular organisms is through cell division.

Reproduction

Organisms can produce new individuals that are similar to them through a process called reproduction. It is required for the perpetuation of living organisms. 

Consciousness/ Response to stimuli

• It refers to the awareness of surroundings by showing a response to an external stimulus. All organisms can sense and respond to the environment. 
• The ability of organisms to react to an external stimulus is called irritability.  
• Higher animals possess sense organs for sensing the stimuli. Plants do not have sense organs but they respond to stimuli by showing some movement. 

Movement

• All organisms show some kind of movement. 
• Animals show locomotion.
• Plants, though do not show locomotion, but exhibit movements. 

Homeostasis

• It refers to maintaining a favorable internal environment despite fluctuations in the external environment. 
• Livings beings have a self-regulated system to adjust and maintain the internal environment. 

Adaptations 

Adaptations refer to changes acquired by an organism over a period of time in order to survive in a particular environment. 

Death 

• It refers to the stoppage of all vital activities due to ageing, disease, accident, etc. Complete death is absent in unicellular organisms. 
• They multiply by fission and the parent cell continues living as a daughter cell however, it loses its own identity. 
• Unicellular organisms are thus immortal.
   

• There is a wide variety of living organisms differing in their size, colour, behaviour, habits etc. This diversity is referred to as biodiversity. 
• The term biodiversity was coined by Edward Wilson. 
• Currently, there are some 1.7-1.8 million species known to mankind. 
• It is believed that this is 2 % of all the species occurring on earth. 

Need for classification 

• Due to such a large diversity of life forms, a proper system of classification is required because it is not possible to study every organism. 
• We can study, some members of a group to ultimately know about the whole group. 
• Without any classification system, organisms cannot be identified.
• classification also helps in knowing the relationships amongst different groups of organisms.