(a) Reproduction at its most basic level involves making copies of the blueprints of body design. The DNA in the cell nucleus is the information source for making proteins. If the information is changed, different proteins will be made. Different proteins will eventually lead to altered body designs.
(b) The male gamete must be transferred to the female gamete for fertilization in flowering plants. The process of transfer of male gamete is pollination. Hence, if pollination does not take place, fertilization will not occur.
(c) Complex multicellular organisms cannot give rise to new organism because the tissue and specialized cell make up the organs in the body. Due to this high degree of specialization, multicellular organisms cannot reproduce by regeneration of a part of some tissue.
(d) Vegetative propagation is practised for growing only some types of plants because of the following reasons:
1. Plants that have lost their capability to produce seeds can be propagated by this method.
2. It helps to grow plants bearing superior traits, as they are genetically identical to the parent plant.
3. It is used for growing plants which require a longer time to grow and become mature.
However, there are certain disadvantages such as:
1. No genetic variations, so less adaptability to the environment.
2. The disease of plants gets transferred to the offsprings.
(e) Gametes of sexually-reproducing animals have half the number of chromosomes as that of the parents. Thus, during fertilisation, when two gametes i.e., male and female gametes, fuse the offspring produced will have the same amount of DNA of the same number of chromosomes as that of the parent. Thus, the parents and off-springs of organisms reproducing sexually have the same number of chromosomes.