CBSE Class 12 Biology Revision Notes CHAPTER-01 REPRODUCTION IN ORGANISMS Reproduction is a biological process of formation of new offsprings from the pre-existing organism.Reproduction becomes a vital process without which species cannot survive for long It ensures continuity of species generation after generations as older individuals undergo senescence and ultimately they die. Life span  - • The period from birth to the natural death of an organism represents its  life span . Life span of organisms varies from few days (Butterfly-1to 2 weeks) to thousands of years (Banyan tree). Types of Reproduction : Based on whether there is one or two organisms taking part in the process of reproduction ASEXUAL REPRODUCTON SEXUAL REPRODUCTION When the offspring is produced by single parents with or without the involvement of gamete formation, the reproduction is called  asexual reproduction . When two parents (opposite sex) participates in reproduction process and also involves the fusion of m

  CBSE Class 12 Biology Ch 01 – Reproduction in Organisms 1. Why is reproduction essential for organisms? Ans.  Reproduction is a fundamental feature of all living organisms. It is a biological process through which living organisms produce offspring’s similar to them. Reproduction ensures the continuance of various species on the Earth. In the absence of reproduction, the species will not be able to exist for a long time and may soon get extinct. 2. Which is a better mode of reproduction sexual or asexual? Why? Ans.  Sexual reproduction is a better mode of reproduction. It allows the formation of new variants by the combination of the DNA from two different individuals, typically one of each sex. It involves the fusion of the male and the female gamete to produce variants, which are not identical to their parents and to themselves. This variation allows the individual to adapt to constantly changing and challenging environments. Also, it leads to the evolution of better suited organis

  CBSE Test Paper 01 Ch-1 Reproduction in Organisms Which of the following is not correct about artificial means of vegetative propagation Quick production of new plants Economical Genetic variation Combining good qualities of two different varieties Which of the following organism produce gemmules as asexual reproductive structure? Hydra Sponges Pe nicillium Chlamydomonas Senescence in most of the animals is not caused by Loss  of metabolism Wear and tear Genetic damage Lack of Nutrition Flagellated, motile asexual reproductive structure are called Megaspores Aplanospores Zoospores Microspores The internal buds produced by Spongila is known as Spores Blasts Planula Gemmules Explain why meiosis and gametogenesis are always interlinked? Why is the offspring formed by asexual reproduction referred to as clone? Define Parthenogenesis. Given two examples. Why is a whiptail lizard referred to as parthenogenetic. In yeast and Amoeba the parent cell divides to give rise to two new individual

  CBSE Class 12 Biology Revision Notes CHAPTER-02 SEXUAL REPRODUCTION IN FLOWERING PLANTS Reproduction ensures continuity of species generation after generations as the older individuals undergo senescence and die. Flowering plants shows sexual mode of reproduction and bears complex reproductive units as male and female reproductive units along with accessary structures. Flower is a modified stem which functions as a reproductive organ and produces ova and/or pollen. A typical angiospermic flower consists of four whorls of floral appendages attached on the receptacle:  calyx, corolla, androecium  (male reproductive organ consisting of stamens) and  gynoecium  (composed of ovary, style and stigma) . Pre-fertilisation: Structures and Events • Several structural and hormonal changes lead to formation and development of the floral primordium. Inflorescence is formed that bears floral buds and then flower. • In flowers, male (androecium) and female (gynoecium) differentiate and develops in