# The living world is full of amazing diversity of living organisms.
# The diversity of habitats of organisms is also very vast and amazing.
# This diversity makes us deeply reflect on "What indeed is life" ? This question actually asks to solve two problems
problems.
(a) First is a technical `->` What living is as opposed to the non living means Living v/s Non-living
(b) Second is a philosophical one `->` what the purpose of life is ?
As scientists we will try to solve the first question, because the second question is more related to philosophy
rather science.

# Reproduction is of two types :
(A) Asexual Reproduction :- Reproduction in which gametic fusion or fertilisation and meiosis are not
involved is Asexual Reproduction. Many methods of asexual reproduction are there.
(a) By Asexual spores :- In algae and fungi
(b) By Budding :- In Yeast and hydra
(c) By Fragmentation :- In Filamentous algae, fungi and the protonema of moss plants
(d) True Regeneration (Morphallaxis type) : Fragmented organisms regenerate the lost part of
its body and become a new organism. eg- Planaria
Note : Regeneration (Epimorphosis type) is a process in which only the lost part of the body is
repaired or regained e.g., Star fish, lizards.
(B) Sexual Reproduction :- Reproduction in which gametes are formed by meiosis and fertilisation also
takes place to form progeny is called as sexual reproduction.

# The sum total of all the chemical reactions occuring in our body is metabolism.
# All living organisms. both unicellular and multicellular exhibit metabolism.
# No non-living object shows metabolism.
# In this way metabolism is a defining character of living organisms because it has no exceptions.
# Now we have known most of the chemical or metabolic reactions occuring in our body so we can demonstrate many of them in a cell free medium or in a test tube in lab.
# The isolated metabolic reaction outside the body of an organism, performed in a test tube (in-vitro) is neither living nor nonliving.
# These isolated reactions can not be regarded as living things, but they are definitely living reactions because they are similar to the reactions performing in our body.
# Here we should not forget the fact that metabolism is the total sum of all the chemical reactions performing in our body, it is not the sum of few or more living reactions.
# All organisms are made of small or big chemicals. These chemicals perform thousands of reactions and form some other chemicals also in the bodies of living organisms.
# All plants, animals, fungi and microbes exhibit metabolism.

# Cell is the basic unit of life .
# AlI living organisms are composed of cells. Some are composed of a single cell and are called as Unicellular Organisms while other like us composed of many cells, are called multicellular organisms.
# Unicellular organisms are capable of independent existence and performing essential function of life.
# Anything less than a complete structure of a cell, does not ensure independent living. Hence cell is the fundamental structural and functional unit of all living organisms.
# In this way the cellular organisation is proved to be defining property of all living organisms.

# Ability to sense the surrounding environments and respond to these environmental stimuli is called as
consciousness.
# Consciousness is the most obvious and technically complicated feature of all living organisms.
# We sense these physical, chemical or biological stimuli through our sense organs.
# Plants also sense and respond to external factors like light, water, temperature, other organisms. pollutants etc.
# All organisms from the prokaryotes to complex eukaryotes show consciousness to environmental cues.
# Some common examples of consciousness can be seen in organisms. like - Plants performs flowering in a particular season (photoperiodism), Some animals perform breeding in a particular season only (seasonal breeders) and all organisms handle the chemicals entering their bodies etc.
# When human is concerned a very high level of consciousness is found in us because of our very well developed nervous system and supreme level of skill of communication which is called as self-consciousness.
# Human is very fast to respond towards the external stimuli and even it can think or predict about possible changes of surroundings also so it can prepare itself according to the surrounding situations. Further human can even change its surrounding situations upto a limit so this topmost or climax level of consciousness is regarded as self-consciousness, which can not be seen elsewhere.
# Self-consciousness is thought to be present only in human.
# The brain dead coma patient who is supported by machines which replace heart and lungs also has consciousness so it is living but it does not has self consciousness because it has lost the co-ordination of organs of different body parts.
# Means all the living phenomena are due to underlying interactions between different components of an individual or organ or tissue or cell.
# Living organisms are self replicating, evolving, and self regulating interactive system capable of responding to external stimuli. Adaptations and homeostasis are also very important characters of living.