Tiêu đề 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 Different methods used to develop plants which can bears fruits and flowers by vegetative propagation are as follows: • Stem cutting: This involves cutting a part of the stem and planting it in the soil to allow the growth of roots and buds into shoots. Examples: sugarcane, pear, china rose • Grafting: In grafting, the stem or bud of two best quality plants is combined to form a new plant. Examples: guava, apple, mango • Layering: In this, the lower branch of a plant is bent and covered with soil. Once new roots start developing on the branch, it is cut from the parent plant and allowed to grow as an individual plant. Examples: rose, jasmine Tissue Culture • Cells from the growing tip of a plant are separated and are grown on a nutrient medium containing all nutrients and hormones necessary for plant growth. • These cells form a mass called callus. • The callus develops plantlets. • These plantlets are transferred to the soil and grow as new individuals. Advantages of Vegetative Reproduction Disadvantages of Vegetative Reproduction Sexual Reproduction • The sexual mode of reproduction involves two organisms, a male and a female to create a new organism or offspring. • The sexual reproduction allows greater variations in a species as the two individuals involved in producing the offspring would have different patterns of variations. This process includes the combination of DNA of two different individuals and the resultant combination and variation would be unique. • Hence this ensures a mixing of the gene pool of the species within a population and it