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Learn Reproduction in Organism with Class 12 Biology Chapter 1 Notes: Download PDF Now


Class 12 Biology Chapter 1 Notes PDF Download




Biology is the study of life and its processes. It is a fascinating subject that covers a wide range of topics, from the molecular level to the ecosystem level. One of the most important topics in biology is reproduction, which is the process by which living organisms produce new individuals of their own kind. In this article, we will provide you with the notes for Class 12 Biology Chapter 1, which deals with reproduction in organisms. You can download the PDF of these notes for free and use them for your exam preparation.


Introduction




Reproduction is a vital phenomenon for all living organisms, as it ensures the continuity of their species from generation to generation. It also leads to the creation of genetic variation, which is essential for adaptation and evolution. Reproduction can be classified into two types: asexual and sexual. Asexual reproduction involves only one parent and produces offspring that are genetically identical to the parent. Sexual reproduction involves two parents of opposite sex and produces offspring that are genetically different from both the parents.




class 12 biology chapter 1 notes pdf download



What is reproduction?




Reproduction is defined as the biological process by which an organism gives rise to another organism similar to itself. It involves the transfer of genetic material from one or more parents to the offspring. Reproduction can be either natural or artificial. Natural reproduction occurs without any human intervention, while artificial reproduction involves human manipulation of the reproductive process, such as cloning, in vitro fertilization, etc.


Types of reproduction




There are two main types of reproduction: asexual and sexual. Let us look at each type in detail.


Asexual reproduction




Asexual reproduction is a type of reproduction in which only one parent is involved and no gametes (sex cells) are formed. The offspring produced by asexual reproduction are called clones, as they are genetically identical to the parent. Asexual reproduction is common in simple organisms, such as bacteria, algae, fungi, protozoa, etc. It is also seen in some plants and animals with relatively simple organization.


Sexual reproduction




Sexual reproduction is a type of reproduction in which two parents of opposite sex participate and gametes (sex cells) are formed. The male gamete (sperm) fuses with the female gamete (egg) to form a zygote, which develops into an offspring. The offspring produced by sexual reproduction are genetically different from both the parents, as they inherit traits from both of them. Sexual reproduction is seen in most plants and animals with complex organization.


Reproduction in Organisms




In this section, we will discuss how different organisms reproduce by asexual or sexual methods. We will also look at some examples of each type of reproduction.


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Asexual Reproduction in Animals




The most commonly seen modes of asexual reproduction in animals are as follows:


Fission




Fission is a mode of asexual reproduction in which an organism splits into two or more independent organisms after attaining a certain size or age. Fission can be binary or multiple. Binary fission occurs when an organism divides into two equal halves, each forming a new individual. For example, amoeba, parame cium, etc. Multiple fission occurs when an organism divides into many small individuals at once. For example, plasmodium, sporozoans, etc.


Budding




Budding is a mode of asexual reproduction in which an outgrowth or bud develops on the body of the parent organism and detaches to form a new individual. The bud may remain attached to the parent for some time before separating. Budding is seen in organisms with high regenerative capacity, such as hydra, yeast, sponges, etc.


Regeneration




Regeneration is a mode of asexual reproduction in which an organism can regrow a lost or damaged part of its body and form a new individual. Regeneration is also a means of repairing injuries and maintaining homeostasis. Regeneration is seen in organisms with simple body organization and high cellular differentiation, such as planaria, starfish, earthworms, etc.


Parthenogenesis




Parthenogenesis is a mode of asexual reproduction in which an unfertilized egg develops into a new individual without the involvement of a male gamete. Parthenogenesis can be natural or induced. Natural parthenogenesis occurs in some animals that can switch between sexual and asexual modes of reproduction, such as honeybees, aphids, rotifers, etc. Induced parthenogenesis occurs when an egg is artificially stimulated to develop without fertilization, such as by chemical or physical means.


Asexual Reproduction in Plants




The most commonly seen modes of asexual reproduction in plants are as follows:


Vegetative propagation




Vegetative propagation is a mode of asexual reproduction in which a vegetative part of a plant, such as root, stem, leaf, or bud, gives rise to a new plant. Vegetative propagation can be natural or artificial. Natural vegetative propagation occurs when plants produce specialized structures that can grow into new plants, such as runners, rhizomes, tubers, bulbs, corms, etc. Artificial vegetative propagation occurs when humans manipulate the vegetative parts of plants to produce new plants, such as by cutting, grafting, layering, tissue culture, etc.


Spore formation




Spore formation is a mode of asexual reproduction in which plants produce spores that can germinate and grow into new plants. Spores are microscopic structures that are produced by the sporophyte generation of plants. Spore formation is seen in lower plants, such as algae, fungi, bryophytes, pteridophytes, etc.


Fragmentation




Fragmentation is a mode of asexual reproduction in which a plant breaks into fragments that can develop into new plants. Fragmentation is seen in plants with simple body organization and high regenerative capacity, such as algae, mosses, liverworts, etc.


Sexual Reproduction in Animals




The main steps involved in sexual reproduction in animals are as follows:


Gametogenesis




Gametogenesis is the process by which gametes (sex cells) are produced from germ cells (precursor cells) by meiosis (a type of cell division that reduces the chromosome number by half). Gametogenesis occurs in the gonads (reproductive organs) of animals. In males, gametogenesis is called spermatogenesis and produces sperms. In females, gametogenesis is called oogenesis and produces eggs.


Fertilization




Fertilization is the proces


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