Biology Chapter 6 Pdf
Magdalena Liendo
NCERT Solutions for Class 12 Biology help students to learn concepts from the CBSE syllabus easily. Furthermore, Biology NCERT Solutions Class 12 is prepared by experienced faculty members and academic professionals. Therefore, students have access to more resources than other similar websites. Moreover, we emphasise understanding the conceptual basis of CBSE Biology subject so that students can comprehend it with ease.
The topics covered in the Class 12 NCERT syllabus carry significant weightage for the competitive exams. Hence, we have compiled these solutions in a manner where students will be able to understand and recall the important topics with ease.
The chapter Reproduction in Organisms explains how various organisms are able to procreate. Reproduction is an important biological process in which an organism gives rise to young ones similar to itself. There are two types of reproduction. When offspring is produced by a single parent with or without the involvement of gamete formation, reproduction is asexual. When two parents (opposite sex) participate in the reproductive process and involve the fusion of male and female gametes, it is called sexual reproduction. These concepts are elaborately explained with relevant diagrams and suitable examples.
Sexual Reproduction in Flowering Plants explains the morphology, structure and processes of sexual reproduction in angiosperms. It also elaborates on subtopics such as pre-fertilisation: Structure and Events, Double fertilisation, Post fertilisation: Structure and Events, Apomixis and Polyembryony.
Reproductive events in humans include the formation of gametes (gametogenesis), i.e., sperms in males and ovum in females. Humans reach sexual maturity after attaining a certain age; this is called puberty. There are remarkable differences between the reproductive events in the male and in the female. In this chapter, students will examine the male and female reproductive systems in humans. The subtopics covered in this chapter are the male reproductive system, the female reproductive system, gametogenesis, the menstrual cycle, fertilisation and implantation, pregnancy and embryonic development, parturition and lactation.
With the ever-increasing population of the world, the enhancement of food production is a major necessity. Biological principles, as applied to animal husbandry and plant breeding, have a major role in our efforts to increase food production. Several new techniques, like embryo transfer technology and tissue culture techniques, are going to play a pivotal role in further enhancing food production. Subtopics that are explained in this chapter are Animal Husbandry, Plant Breeding, Single Cell Proteins and Tissue Culture.
Besides macroscopic plants and animals, microbes are the major components of biological systems on this earth. Students have studied the diversity of living organisms in Class XI. Microbes are diverse-protozoa, bacteria, fungi and microscopic animal and plant viruses, viroids and also prions that are proteinaceous infectious agents. Microbes like bacteria and many fungi can be grown on nutritive media to form colonies that can be seen with the naked eyes. Such cultures are useful in studies on micro-organisms. A few of the subtopics are Microbes in Household Products, Microbes in Industrial Products, Microbes in Sewage Treatment, Microbes in the Production of Biogas, Microbes as Biocontrol Agents and Microbes as Biofertilisers.
Biotechnology, as students would have learnt from the previous chapter, deals with the industrial-scale production of biopharmaceuticals and biologicals using genetically modified microbes, fungi, plants and animals. The applications of biotechnology include therapeutics, diagnostics, genetically modified crops for agriculture, processed food, bioremediation, waste treatment and energy production. The chapter also includes topics such as Biotechnological Applications in Agriculture, Biotechnological Applications in Medicine, Transgenic Animals and Ethical Issues.
Biodiversity and Conservations consist of topics like Genetic diversity, Species diversity, Ecological diversity, Different types of Species, Patterns of Diversity, Loss of Biodiversity, Biodiversity Conservation, etc. Biodiversity conservation may be in situ as well as ex situ. In in situ conservation, the endangered species are protected in their natural habitat so that the entire ecosystem is protected. Ex situ conservation methods include protective maintenance of threatened species in zoological parks and botanical gardens, in vitro fertilisation, tissue culture propagation and cryopreservation of gametes.
The human population size has grown enormously over the last hundred years. This means an increase in demand for food, water, home, electricity, roads, automobiles and numerous other commodities. Pollution is any undesirable change in physical, chemical or biological characteristics of air, land, water or soil. The agents that bring about such an undesirable change are called pollutants. The other subtopics students will study in this chapter are Air Pollution and Its Control, Water Pollution and Its Control, Solid Wastes, Agrochemicals and Their Effects, Radioactive Wastes, Greenhouse Effect and Global Warming, Ozone Depletion in the Stratosphere, Degradation by Improper Resource Utilisation and Maintenance, and Deforestation.
Several important concepts, such as reproduction, inheritance, evolution, food production, biotechnology, ecosystem, biodiversity, are explained in-depth. The concepts have also been updated as per the latest syllabus prescribed by the CBSE board.
Students will be facing the board exams twice in their lifetime. One is Class 10, and the other one is Class 12. The score obtained in Class 10 helps students to understand the subject in which they are strong, and the marks scored in Class 12 help students plan their future. Keeping this in mind, the CBSE board has equally divided the entire syllabus to help students learn all the concepts easily. Going through the course structure updated by the CBSE board, students will be able to understand the chapters which are of more marks and work on them accordingly.
Biology NCERT Solutions for Class 12 are more effective than any other educational resource. We provide elaborate explanations, detailed solutions, descriptive diagrams and more. Further, we provide accurate and updated answers to all the exercise questions given in NCERT textbooks.
NCERT Textbooks are well known for their simplicity and straightforward description of concepts. These textbooks are ideal for students of CBSE Class 12. It comprises questions that test their conceptual understanding.
Humans are essentially sterile during gestation, but during and after birth, every body surface, including the skin, mouth, and gut, becomes host to an enormous variety of microbes, bacterial, archaeal, fungal, and viral. Under normal circumstances, these microbes help us to digest our food and to maintain our immune systems, but dysfunction of the human microbiota has been linked to conditions ranging from inflammatory bowel disease to antibiotic-resistant infections. Modern high-throughput sequencing and bioinformatic tools provide a powerful means of understanding the contribution of the human microbiome to health and its potential as a target for therapeutic interventions. This chapter will first discuss the historical origins of microbiome studies and methods for determining the ecological diversity of a microbial community. Next, it will introduce shotgun sequencing technologies such as metagenomics and metatranscriptomics, the computational challenges and methods associated with these data, and how they enable microbiome analysis. Finally, it will conclude with examples of the functional genomics of the human microbiome and its influences upon health and disease.
Copyright: 2012 Morgan, Huttenhower. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
The question of what it means to be human is more often encountered in metaphysics than in bioinformatics, but it is surprisingly relevant when studying the human microbiome. We are born consisting only of our own eukaryotic human cells, but over the first several years of life, our skin surface, oral cavity, and gut are colonized by a tremendous diversity of bacteria, archaea, fungi, and viruses. The community formed by this complement of cells is called the human microbiome; it contains almost ten times as many cells as are in the rest of our bodies and accounts for several pounds of body weight and orders of magnitude more genes than are contained in the human genome [1], [2]. Under normal circumstances, these microbes are commensal, helping to digest our food and to maintain our immune systems. Although the human microbiome has long been known to influence human health and disease [1], we have only recently begun to appreciate the breadth of its involvement. This is almost entirely due to the recent ability of high-throughput sequencing to provide an efficient and cost-effective tool for investigating the members of a microbial community and how they change. Thus, dysfunctions of the human microbiota are increasingly being linked to disease ranging from inflammatory bowel disease to diabetes to antibiotic-resistant infection, and the potential of the human microbiome as an early detection biomarker and target for therapeutic intervention is a vibrant area of current research.
Historically, members of a microbial community were identified in situ by stains that targeted their physiological characteristics, such as the Gram stain [3]. These could distinguish many broad clades of bacteria but were non-specific at lower taxonomic levels. Thus, microbiology was almost entirely culture-dependent; it was necessary to grow an organism in the lab in order to study it. Specific microbial species were detected by plating samples on specialized media selective for the growth of that organism, or they were identified by features such as the morphological characteristics of colonies, their growth on different media, and metabolic production or consumption. This approach limited the range of organisms that could be detected to those that would actively grow in laboratory culture, and it led the close study of easily-grown, now-familiar model organisms such as Escherichia coli. However, E. coli as a taxonomic unit accounts for at most 5% of the microbes occupying the typical human gut [2]. The vast majority of microbial species have never been grown in the laboratory, and options for studying and quantifying the uncultured were severely limited until the development of DNA-based culture-independent methods in the 1980s [4].
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