Title Chapter - 3 How_Do_Organisms_Reproduce.pdf ✅

ChemContent How Do Organisms Reproduce? Reproduction Reproduction is the ability of living organisms to produce living beings similar to themselves. The two modes of reproduction, i.e. asexual reproduction and sexual reproduction can be seen in animals. Importance of Variation • Sexual reproduction provides great scope for variation. • Variation is important for the survival of a species. • Variation helps a species to adapt to different environmental changes. Reproduction and its Kinds Sexual Reproduction Asexual Reproduction • It involves the formation ofspecial reproductive cells called gametes. • It does not involve the formation of gametes. • Male and female gametes fuse to form the zygote which develops into a new individual. • New organisms are formed either by the division of the parent body or by the differentiation of the parent body. Modes of Asexual Reproduction Plants and animals from lower classes reproduce by asexual methods. Method Description Example Binary Fission • Most common method in unicellular organisms. • It is division of the parent cell into two identical daughter organisms. Amoeba, Paramecium, bacterium Multiple Fission • Parent cell divides to produce many identical new individuals. Plasmodium vivax, Leishmania


ChemContent Stalk/Pedicel •Point of attachment. Thalamus •It is an enlarged, flattened tip of the stalk. •Petals and other parts arise from the thalamus. Calyx •Outermost whorl of the flower consisting of sepals. • The calyx protects the inner parts of the flower in their bud stage. Corolla •Second whorl of the flower which is made up of petals. •Helps flowers in attracting insects to carry out pollination. Androcium •Third whorl and the male organ of the flower. •Consists of stamens. •Each stamen is made of the filament and anther. •Anthers store pollegrains. Gynoecium •Innermost whorl and the female reproductive organ. •Consists of pistils or carpels. •Carpel is made of stigma, style and ovary. also ensures the survival of the species as this process generates more variations due to the genetic recombination. • The process of combining DNA of two different individuals during sexual reproduction will lead to an offspring with twice the amount of DNA than their previous generation. • The solution to this lies in the fact that there are certain specialised cells in such organisms called germ cells or gametes. These have half the number of chromosomes and, therefore half the amount of DNA in comparison to the other non-reproductive cells. The combination of these germ cells from two different individuals during the process of sexual reproduction restores the original number of chromosomes and DNA content in the new offspring. • The germ cells may be similar and not much different from each other in simple organisms. With the complexity of the organisms the germ cell also becomes specialised. One of the germ cells becomes large and stores food. This is known as the female gamete. The other germ cell which is small and motile is called the male gamete. These gametes lead to the differences in the bodies and reproductive systems of males and females. Sexual Reproduction in Flowering Plants A flower is the reproductive organ in angiosperms.