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CHAPTER 4 - PRINCIPLES OF INHERITANCE AND VARIATION

  Principles of Inheritance and Variation Principles of Inheritance and Variation deals with the study of inheritance and variation through genetics. Genetics Genetics is the branch of biology which deals with study of inheritance and variation of characters from parents to offspring. Term 'genetics' was given by W. Bateson (Father of Modern Genetics). Inheritance Inheritance is the process by which characters are passed on from parent to progeny. Variation Variation is the degree of characters by which progeny differ from their parents, siblings. It may be natural and artificial. Mendel’s Laws of Inheritance Gregor Mendel, conducted hybridisation experiments on garden peas for seven years (1856-1863) He proposed the laws of inheritance in living organisms. He conducted cross pollination experiments using several true-breeding pea lines. He selected 14 true-breeding pea plant varieties, as pairs which were similar except for ...
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   Population Interactions For any species, the minimal requirement is one more species on which it can feed. Even a plant species, which makes its own food, cannot survive alone; it needs soil microbes to break down the organic matter in soil and return the inorganic nutrients for absorption. In nature, animals, plants and microbes interact in various ways to form a biological community. Interspecific interactions arise from the interaction of populations of two different species. They could be beneficial, detrimental or neutral (neither harm nor benefit) to one of the species or both. Assigning a ‘+’ sign for beneficial interaction, ‘-’ sign for detrimental and 0 for neutral interaction, look at all the possible outcomes of interspecific interactions. Species A Species B Name of Interaction + + Mutualism - - Competition + - Predation + - Parasitism + 0 Commensalism - 0 Amensalism Both the species benefit in mutualism and both lose in competition in their interactions with ea...
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