Class 11th Biology - BACKLOG MARATHON 4 Chapter in One Shot Prarambh 2.0 Next Toppers Science

Biology: Living Organisms, Cell Structure, and Life Processes

Biology is the scientific study of life. It encompasses the structure, function, growth, evolution, and distribution of living organisms — from bacteria to blue whales. This chapter covers fundamental biology concepts for CBSE examinations.

The cell is the basic unit of life. Cell theory: all organisms are composed of cells; the cell is the basic unit of structure and function; all cells arise from pre-existing cells. Prokaryotes (bacteria, archaea) lack a true nucleus and membrane-bound organelles. Eukaryotes (plants, animals, fungi, protists) have a true nucleus and membrane-bound organelles (mitochondria, ER, Golgi, lysosomes, and in plants, chloroplasts and large central vacuole). The plasma membrane is a selectively permeable phospholipid bilayer. Transport: passive (diffusion, osmosis) and active (requiring ATP).

The five-kingdom system (Whittaker): Monera (prokaryotes), Protista (unicellular eukaryotes), Fungi (heterotrophic, chitin cell walls), Plantae (autotrophic, cellulose cell walls), Animalia (heterotrophic, no cell walls). Plant kingdom: algae, bryophytes (mosses), pteridophytes (ferns), gymnosperms (conifers), angiosperms (flowering plants — dicots and monocots). Animal kingdom: Porifera (sponges), Cnidaria, Platyhelminthes, Annelida, Arthropoda, Mollusca, Echinodermata, Chordata (including vertebrates).

Life processes: nutrition (autotrophic — photosynthesis 6CO2+6H2O -> C6H12O6+6O2; heterotrophic), respiration (aerobic 36ATP/glucose; anaerobic 2ATP, ethanol or lactic acid), transport (circulatory system — heart, blood, vessels; xylem and phloem in plants), excretion (kidneys filter blood via nephrons), control/coordination (nervous and endocrine systems), and reproduction (asexual — fission, budding; sexual — gametes, fertilisation). Genetics: DNA -> RNA -> Protein (central dogma); Mendelian inheritance (dominant/recessive, segregation, independent assortment).

• Cell theory: all organisms made of cells; cells from pre-existing cells. Prokaryotes (no nucleus, no organelles) vs eukaryotes (nucleus, organelles).
• Five kingdoms: Monera, Protista, Fungi, Plantae, Animalia. Plants: algae -> bryophytes -> pteridophytes -> gymnosperms -> angiosperms.
• Animal phyla: Porifera (filter feeders) to Chordata (notochord, dorsal nerve cord). Vertebrates: fish, amphibians, reptiles, birds, mammals.
• Photosynthesis: 6CO2+6H2O -> C6H12O6+6O2. Aerobic respiration: 36 ATP. Anaerobic: 2 ATP (fermentation in yeast, lactic acid in muscle).
• Central dogma: DNA -> RNA -> Protein. Mendelian inheritance: law of segregation, law of independent assortment, dominant/recessive.