Скачать или смотреть || Part-03-Reproduction in organisms ncert class 12 chapter 1 ||

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● In this video you will learn about sexual reproduction of reproduction in organisms chapter 1 class 12 biology Part-03

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Key topics covered include:

This video, "Part-03-Reproduction in organisms ncert class 12 chapter 1," focuses on sexual reproduction in organisms (0:19). The speaker explains that sexual reproduction primarily involves the fusion of male and female gametes (0:46-0:54), which can come from either the same individual or different individuals of opposite sexes (1:54-2:09). This fusion results in the formation of a zygote, which then develops into a new organism (2:12-2:20).

Key characteristics and phases of sexual reproduction discussed include:
Complexity and Pace: Sexual reproduction is described as a more elaborate, complex, and slower process compared to asexual reproduction (2:21-2:32).
Offspring Diversity: Due to the fusion of two different gametes, the offspring produced through sexual reproduction are not identical to their parents or to each other (2:33-2:50).
Common Patterns: Despite diverse external morphology, internal structure, and physiology across different organisms (plants, animals, fungi), they share a similar pattern in sexual reproduction (2:51-3:05). This pattern involves a sequence of events: pre-fertilization, fertilization, and post-fertilization (3:30-3:39, 19:36-19:39).
Life Phases: Organisms must reach a certain stage of growth and maturity before sexual reproduction (3:50-4:04). This period of growth is called the juvenile phase (in animals) or vegetative phase (in plants) (4:15-4:25). The end of this phase marks the beginning of the reproductive phase (4:42-4:54). The final phase discussed is the senescent phase or old age, which ultimately leads to death (7:06-7:10, 15:24-16:27).
Hormonal Regulation: Hormones are responsible for the transition between these three life phases in both plants and animals, and their interaction with environmental factors regulates reproductive processes (16:41-17:29).
Examples of Unique Flowering: The video highlights unusual flowering phenomena in some plants, such as bamboo species that flower only once in their lifetime (after 50-100 years) and Strobilanthes kunthiana (Neelakurinji) which flowers once every 12 years (8:21-9:51).
Reproductive Cycles in Animals: In placental mammals, females exhibit cyclical changes in their ovaries, accessory ducts, and hormones during the reproductive phase (13:00-13:04). These are categorized into the estrous cycle for non-primates (e.g., cow, sheep, rat) and the menstrual cycle for primates (e.g., monkey, ape, human) (13:12-13:41).
Seasonal vs. Continuous Breeders: Some mammals are seasonal breeders, exhibiting reproductive cycles only during favorable seasons (14:07-14:27), while others are continuous breeders, remaining reproductively active throughout the year (14:29-14:53).

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