BIOLOGY TUTORIALS

CELL DIVISION  CELL CYCLE- When cell divides.It synthesise its components including genetic material in duplicate. After division This passes to DAUGHTER CELLS. Sequence of events by which cell duplicate its contents & divides into two called CELL CYCLE. IMPORTANCE IN EUKARYOTES- From single cell trillions of cells develop.Rate & no. officer division vary.In adult tissues like bone marrow division is continuous.In fully formed organism less division occurs. CELL CYCLE  It Has two periods: 1- INTERPHASE : - Period of rest or RESTING STAGE .Preparatory phase for cell division. 2- MITOSIS : -  Three processes occurs during this phase: REPLICATION OF DNA & SYNTHESIS OF PROTEINS AS HISTONES. IN ANIMALS-DUPLICATION OF CENTRIOLE -Two daughter centrioles formed at right angle to each other. SYNTHESIS OF ENERGY RICH COMPOUNDS -Provides energy for mitosis & synthesis of proteins MITOSIS  ITS DIFFERENT PHASES & SIGNIFICA

 NUCLEIC ACIDS  [DNA &RNA] There are chromosomes in the nucleus of cell,which are thread like.They are visible only during cell division.Chromosomes are uncoiled in loose network called chromatin contains DNA,RNA,& PROTEINS.                                  DNA means DEOXYRIBONUCLEIC ACID  RNA means RIBONUCLEIC ACID. DNA & RNA both are information storage devices of cell.These are two kinds of nucleic acids. DNA: It has special coded genetic programme with detailed & specific instructions for each organism heredity.[one gene one character passed to offspring]. Its model was proposed by WATSON & CRICK In 1953. It consists of linear polymers of repeating monomer subunits called nucleotides. Each nucleotide contains A PENTOSE SUGAR,A PHOSPHATE GROUP,NITROGENOUS BASE[PURINE or PYRIMIDINE] A ,G ,C,T SUGAR RIBOSE in RNA DEOXYRIBOSE In DNA[One oxygen lacking] DNA is double helicle, two polynucleotide chains he

It develops from ovule inside ovary [female reproductive part of flower]after fertilisation with pollen. SEED has four parts  1 OUTER SEED COAT 2 COTYLEDONS 3 PLUMULE 4 RADICLE                                            DICOT  Means if two cotyledons are present.Two chambers which stores food .They have seed coat Ex PEA ,GRAM.[ALL PULSES]  Embryo is embedded inside endosperm has two thin cotyledons joined to an axis called  TIGELLUM  It shows  RADICLE & PLUMULE  hidden between cotyledons.Ex GRAM PEA. HILUM  Point of attachment of seed with stalk.    MONOCOT  Means if one cotyledon stores food as in RICE, WHEAT ,MAIZE. Monocot have no seed coat. Single cotyledon,endospermic, NO SEED COAT .Outer covering is membranous fused with fruit wall. ENDOSPERM  is separated from embryo by  ALEURONE LAYER .Embryo is small in a groove at one end.It consists of one cotyledon called  SCUTELLUM ,a short axis with plumule & radicle

     Matured Ovary is FRUIT .As ovary ripens its outer wall becomes outer fruit wall or PERICARP . TRUE FRUIT : It is product of ovary after fertilisation & encloses seeds in it.ex. TOMATO , ORANGE . FALSE FRUIT : It is formation of fruit from PARIANTH or THALAMUS not true ovary also called  PSEUDOCARP means false.ex APPLE . PARTHENOCARPIC FRUIT Ovary ripens into fruit without fertilisation & seedless in BANANA . TRUE FRUITS are of three types : 1 SIMPLE FRUIT 2 AGGREGATE FRUIT 3 MULTIPLE FRUIT SIMPLE FRUIT  It develops from single ovary( MONOCARPELLARY ) EX DRY FRUIT one seeded or many seeded like cashew nut walnut coconut etc.                                                                        AGGREGATE FRUIT  It develops from two or more carpels of single flower [ BI OR POLYCARPELLARY ] Apocarpous pistil [ FREE OVARIES ] ex. ROSE , STRAWBERRY ETC.                                            

                                      FLOWER Flower is the most beautiful & essential part of plant. It is a modified shoot & sexual reproductive organ lead to the formation of FRUIT& SEED.Seed give rise to new plant.                                 PARTS OF FLOWER Flower born in the axil of leaf called BRACT .Long stalk is called PEDICEL .If no pedicel then flower is SESSILE .Pedicel ends in upper swollen structure called THALAMUS . MAIN FOUR PARTS OF A FLOWER 1 SEPALS or CALYX 2. PETALS or COROLLA 3. ANDROECIUM or MALE REPRODUCTIVE PART 4. GYNOECIUM or FEMALE REPRODUCTIVE PART SEPAL First & outermost whorl ,green,free from one another or fused. FUNCTION : To protect the inner parts of flower in bud condition.       PETAL Forms the second whorl. colourful,may be free or united. FUNCTION : To attract INSECTS.2 It protects the inner reproductive organs. ANDROECIUM   Also calle