introduction we know that the branch of science which deals with the study of living organisms is called biology or the study of life yes the word biology has been taken from greek words bios is equal to life plus logos is equal to study things which depict growth reproduction ability to sense environment and mount a suitable response are called living things objectives at the end of this lesson you'll be able to define life and living organisms find out various characteristics of living organisms understand cellular structure of living organisms find out organization of living organisms study process of metabolism in living organisms study how do living organisms grow identify what is consciousness find out movements in living organisms study reproduction in various living organisms and understand diversity in the living world what is living life is a characteristic that distinguishes objects that have self-sustaining biological processes from those that do not either because such functions have ceased or else because they lack such functions and are classified as inanimate life is unique complex cellular organization of molecules expressing it through chemical reactions which lead to growth development responsiveness adaptation and reproduction plants and animals both are living therefore biology deals with the study of both plants botany and animals zoology virus is intermittent link between living and non-living viruses consist of only a protein code and an inner core of nucleic acid viruses can reproduce only inside living cells viruses can be crystallized and kept in a bottle for years and still infect their host cells characters of living organisms an organism is any living system example animal plant fungus or microorganism all the living things are called organisms all living organisms share following basic characteristics cellular structure organization energy homeostatis metabolism growth consciousness movements variations adaptations reproduction irritability evolution interactions emergent properties lifespan and life cycle and death characters of living organisms cellular structure each living being has a distinct individuality it can be broken into two or more independent parts the body of a living being is made of one or more cells cells are considered to be structural and functional unit of life the cells are made of protoplasm or living matter all the body functions and properties of life are due to protoplasm characters of living organisms organization living beings have an internal hierarchy of parts where smaller parts cooperate to form larger one the larger ones are still larger part while all the still larger parts are organized to form the individual because of this organization living beings are also called organisms characters of living organisms energy living being constantly requires energy not only to perform various activities of the body but also to overcome entropy or tendency of randomness the source of energy is food it is required by every cell of the body characters of living organisms homeostatis homeostatis is the property of a system either open or closed that regulates its internal environment and tends to maintain a stable constant condition or we can say that as external environment do not have much impact on the internal environment as the living beings have a self-regulated system to adjust and maintain the internal environment the phenomenon is called homeostatis characters of living organisms metabolism a large number of chemical reactions are going on in the body of a living being the sum of all the chemical reactions occurring in an organism is called metabolism metabolism has two main types catabolism and anabolism catabolism involves breakdown of complex organic materials into simpler ones anabolism involves building up of complex organic substances from simpler ones the differences between catabolism and anabolism are characters of living organisms growth growth is a vital characteristic of living organisms growth occurs when anabolism is higher than catabolism all organisms grow develop and reproduce growth results in an increase in size weight and synthesis of new protoplasm characters of living organisms consciousness consciousness is awareness of the surroundings and responding to external stimuli the ability of an organism or organ to respond to external stimuli is called sensitivity characters of living organisms movements movement is of two types movement of parts and movement of whole body or locomotion animals perform both types of movements while plants show only movement of parts some movements occur due to purely internal forces they are autonomic or spontaneous movements while some movements occur in response to an external stimulus they are known as panatonic or induced movements characters of living organisms variation genetic material undergoes mutations and reshuffling of genes this causes variations variations are so abundant that no two individuals of the same race are exactly same characters of living organisms adaptation there are variations which help organisms to modify themselves according to changes in environment and specific requirement of their surroundings example snow leopards have stocky bodies thick fur and small and round ears which help to minimize the heat loss while leaves of cactus are reduced to thorns so that surface area of transpiration is reduced night blooming flowers are adapted as they are whitish in color and scented to attract moths and other insects pollinators birds have wings for flight both shaped body beak pneumatic bones and feathers mimicry's close resemblance with surroundings or other organisms example flowers of office mucifera show mimicry characters of living organisms reproduction young ones grow and become mature they develop the faculty to produce young ones of their own time life comes from pre-existing life characters of living organisms coordination different parts of the body of a living being cooperate with one another for the functioning of the whole example heart pumps blood to all parts of the body lungs provide oxygen digestive system nutrients nerves and hormones information muscles movements bones support etc characters of living organisms irritability irritability is the faculty of responding to a stimulus it is the property of protoplasm and is shown by all organisms both plants and animals animals show quick response to a stimulus because they possess nervous system plants show slow response example bending of shoot towards light characters of living organisms evolution evolution is formation of new species from the pre-existing ones evolution occurs due to accumulation of variations characters of living organisms interaction interactions occur among the levels of organization within organisms and between organisms and their external environments the levels of interaction between organisms and their environment are those of populations communities ecosystems and the biosphere characters of living organisms emergent properties the appearance of new characteristics at a given level of organization is called emergence characters of living organisms life cycle each individual passes through a definite life cycle of birth growth maturation reproduction aging and death this is completed in a definite lifespan ranging from one day to several years characters of living organisms death after a period of time each living being dies death occurs naturally due to wear and tear diversity in the living world the biodiversity is the number and types of organisms present on the earth every organism whether plant or animal is unique in itself there is a wide diversity in the flora plants and fauna animals in the world the diversity we see today is the result of 3.5 billion years of organic evolution during the course of this evolution several species vanished from the surface of the earth and become extinct with such a vast number of organisms both living and extinct it becomes impossible to study every one of them at individual level did you know huxley in 1868 said protoplasm is the physical basis of life lamarck in 1809 said nobody can have life if its constituent parts are not cellular tremly was first to study regeneration in hydra summary let us summarize what we have learned in the world there are two types of structures living and non-living living world has vast range of variety living organisms and many non-living things share three properties complexity movement and response to stimulation the virus is a lifeless particle by itself but it becomes active and multiplies rapidly inside a living cell smallest unit of life is cell while the highest level of biological organization is biosphere living beings are complex entities all living organisms share some basic characteristics cellular structure organization energy homo status metabolism growth consciousness variations adaptations reproduction irritability evolution interactions emergent properties lifespan and life cycle and depth homostatis is maintenance of favorable internal environment of living beings changes in structure and function of every living beings with age are called development growth development and functioning of living body is due to metabolism a living organism can be differentiated from a non-living thing on the basis of its ability for reproduction night blooming flowers are adapted as they are whitish in color and scented to attract moths and other insects pollinators birds have wings for flight boat shaped body big pneumatic bones and feathers mimicry's close resemblance with surroundings and other organisms example flowers of office mucifera show mimicry living organisms interact and function with each other at many different levels these different levels are cellular organizational and population levels [Music]