Hierarchy of organization:- Biological organization is the hierarchy of complex biological structures and systems that define life using a reductionistic approach. Each level in the hierarchy represents an increase in organizational complexity, with each "object" being primarily composed of the previous level's basic unit. For example:- cells, molecules, tissue, organ, organ system, And Organism are different levels of organism. Note:- the systematic presentation of these different level of organization shown in next slides SRV 1

No content

• Living organisms have high degree of complexity and organization • Unicellular (single celled) organisms • Single cell performs all life functions • It functions independently • Bring about the conversion of nutrients into energy, reproduce (cell division) and as the need arises carries out specialized functions Example of these type of organism are :- • Multicellular (many celled) organisms • Have various levels of organization within them • Have the following 5 levels of organization ranging from simplest to most complex • Cells, tissues, organs, organ systems and organisms • Examples - blood cells, nerve cells, bone cells, epithelial cell etc • Example of these type of organisms:- SRV 2

• The differentiation of body of living beings into smaller parts is called organization • The body of living beings is made up of a number of parts as organs, which in turn are made of tissues, tissues from cells and cells from protoplasm, protoplasm in turn contains still smaller structures called organelles • This represents the order of hierarchy from the lowest to the highest levels • Due to the presence of organization, the living beings are named as organisms SRV 3

• Cell • Basic unit or building block of life • Basic unit of structure and function in living things • Structural and morphological unit of living organisms • 2 types :- Prokaryotic and eukaryotic Prokaryotic Cells:- Prokaryotic (Pro:- Before; Karyon :-Nucleus ; Greek) Cells are the cells that lacks membrane Bound Nucleus And there Chromosomal DNA present in the form of circular loop in cytoplasm And they have only few internal Structure. For example:- Bacteria, Paramecium, Amoeba etc.., Eukaryotic cell:- Eukaryotic (Eu:- True; Karyon:- Nucleus;Greek) Cell Are the cell Which have membrane bound Nucleus They Also contain Many Internal Membrane bound organelles e.g. Mitochondria, Golgi Complex, endoplasmic reticulum, lysosomes etc.., SRV 4

• Prokaryotic cells • Smaller and simpler in form • 1-2 μm in diameter • Bound by cell membrane • Lack a nucleus and many of the cell organelles that are found in the eukaryotic ones • Eukaryotic cells • 5-100 μm in diameter • Larger in size (~15 times) than the prokaryotic cells • More specialized in their structure than the prokaryotic cells • Bound by the cell membrane • Has a nucleus which acts as the brain of the cell • Has cytoplasm which surrounds the nucleus and contains the cell organelles like the mitochondria, ribosomes, vacuole, endoplasmic reticulum, chloroplasts and peroxisomes, microtubules SRV 5

• Tissue • Collection of cells that are similar in structure and function and work together to perform a specific function • The cells which form a tissue need not be identical but have the same origin • Forms organs • E.g., in humans, muscle, nervous, connective and epithelial tissues • Connective tissues – fibrous, made up of cells separated by the extracellular matrix • Muscle tissues - active contractile tissues of the body, useful in producing force and motion, e.g., skeletal, cardiac and smooth muscles • Nervous tissues - form organs, like brain, spinal cord, etc. • Epithelial tissues - cover the surface of body organs SRV 6

• Organ • Formed from tissues which serve a common function • Organ performs certain functions with the help of different tissues • Examples, • Animals - skin, lungs, brain, liver, heart, etc. • • Fig :- Lungs Fig :- Liver • Plants - roots, stems and leaves • Classified on the basis of the functions they perform • Animals - tongue, ears, eyes, skin and nose form the sensory organs • Plants - flowers and seeds are the reproductive organs • Two types of tissues that form an organ • Main tissues – they are derived from the primary Growth and termed as primary tissues, e.g., myocardium in heart • Sporadic tissues – they are the tissue which spread all over the body in any interval of space they occur singly or widly apart in loclaty example of these tissues:- blood, nerves and connective tissues for heart SRV 7

• Organ system • Groups of two or more organs work together to perform a specific function for the organism • Complex mechanisms which carry out important functions of the body • E.g., circulatory system in animals and vascular system in plants • Interdependent • Take each other’s help to carry out various functions of the body • E.g., digestive system which carries out the process of digestion is formed of salivary glands, stomach, oesophagus, gallbladder, liver, intestines, pancreas, rectum and anus • Fig:- Digestive System • Fig:- Cirulatory System SRV 8

• Organism • The highest level of organization • Represents an entire living things that can carry out all basic life processes • They can take in materials, release energy from food, release wastes, grow, respond to the environment reproduce and die • E.g., bacteria, amoeba, mushroom, sunflower, mouse, human, etc. Fig:- Mushroom Fig:- Rat Fig:- Amoeba Fig:- Sunflower • Can either be unicellular (single celled) or multicellular (many celled) • Made up of organ systems • May be made up of only one cell such as bacteria or protists species:- The organisms that are closely related are grouped together under a single species SRV 9