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Reproduction in Animals Class 8 Science (Chapter 9) in One Shot | BYJU'S - Class 8

BYJU'S - Class 6, 7 & 8・2 minutes read

Ankita introduces the topic of reproduction, discussing the importance of reproduction for species continuation, including asexual and sexual reproduction with examples like binary fission and cloning. The text also covers the processes of fertilization, zygote formation, and the role of gametes in genetic inheritance.

Insights

  • Asexual reproduction involves only one parent and creates identical offspring, while sexual reproduction involves two parents, combining genetic material through gametes to create unique offspring.
  • Cloning, exemplified by Dolly the sheep, involves transferring genetic material from one cell to another, resulting in an identical copy of the original organism, showcasing the potential for human intervention in reproduction processes.

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Recent questions

  • What is reproduction?

    Reproduction involves producing offspring similar to the parent organism. It is essential for the continuation of species and has led to the Earth's population reaching 8 billion.

  • How does asexual reproduction occur in amoeba?

    Asexual reproduction in amoeba occurs through binary fission, where the cell splits into two identical daughter cells. This process results in the production of offspring that are genetically identical to the parent organism.

  • What is cloning?

    Cloning is a process that involves creating exact copies of an organism by combining genetic material from different sources. Dolly the sheep was the first cloned sheep, created through a unique process that included taking a cell from one sheep and the nucleus from another sheep's egg.

  • What is the role of gametes in sexual reproduction?

    Gametes are specialized reproductive cells involved in sexual reproduction. In males, sperm is the gamete, while in females, the ovum serves as the gamete. The fusion of these gametes during fertilization results in the formation of a zygote, which is the first cell of a new organism.

  • What is the function of the placenta during pregnancy?

    The placenta is a vital organ that provides nutrition and waste removal between the mother and fetus during pregnancy. It plays a crucial role in supporting the developing baby by facilitating the exchange of nutrients and oxygen between the mother's and baby's bloodstreams.

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Summary

00:00

"Reproduction: Essential for Species Continuation"

  • Ankita welcomes students to the class and introduces the topic of reproduction.
  • The class discusses the importance of reproduction for the continuation of species.
  • Reproduction involves producing offspring similar to the parent organism.
  • The population of Earth has reached 8 billion due to reproduction.
  • Asexual reproduction involves one parent, no gametes, and fission.
  • Sexual reproduction involves two parents, gametes, and fusion.
  • Gametes are germ cells, with sperm in males and ovum in females.
  • Asexual reproduction in amoeba occurs through binary fission, producing identical daughter cells.
  • Budding is another form of asexual reproduction where a bud grows on the parent organism and detaches to become a new individual.
  • Binary fission is the process of splitting a cell into two identical daughter cells.

19:27

"Dolly the Sheep: First Cloned Animal"

  • Dolly the sheep was the first cloned sheep, created through a unique process involving human intervention.
  • The cloning process involved taking a cell from one sheep and the nucleus from another sheep's egg.
  • The nucleus containing genetic material was inserted into the cell, resulting in the creation of Dolly, an identical copy of the sheep providing the nucleus.
  • Dolly had two mothers in this process, one providing the cell and the other providing the nucleus.
  • The cells used in the process were somatic cells from the body, with the nucleus coming from mammary gland cells of the sheep.
  • The fusion of the nucleus and cell, followed by embryo formation and implantation into a foster mother, led to the birth of Dolly.
  • Clones are exact copies formed through this process, where genetic material is combined from different sources.
  • Sexual reproduction involves the fusion of specialized reproductive cells, known as gametes, from male and female individuals.
  • DNA, present in the nucleus, contains genes that determine characteristics like hair color, eye color, and skin color.
  • Chromosomes, formed from coiled DNA during cell division, carry genes that pass on hereditary traits from one generation to the next.

38:18

Female Reproduction: From Ovum to Zygote

  • Female gamete is the ovum, a reproductive cell with a large nucleus produced in the ovary.
  • Females have 23 pairs of chromosomes, with one pair being sex chromosomes (XX for females, XY for males).
  • Female gametes are non-motile, meaning they do not move.
  • Fertilization is the fusion of male and female gametes, resulting in the formation of a zygote.
  • Zygote is a single cell formed after fertilization, with the nuclei of sperm and ovum fusing.
  • The zygote divides rapidly, reaching the blastula stage before attaching to the uterus lining.
  • Placenta is a vital organ providing nutrition and waste removal between mother and fetus during pregnancy.
  • Oviparous animals lay eggs, while viviparous animals give birth to young ones directly.
  • Internal fertilization occurs within the female reproductive system, while external fertilization happens outside the female's body.
  • Metamorphosis is a process involving drastic changes in an animal's body during its life cycle, like the transformation of a larva into an adult butterfly.

57:38

Animal Life Cycle and Reproductive Processes

  • Metamorphosis is a process where animals like butterflies undergo different stages such as larva, cocoon, and finally becoming a butterfly, experiencing drastic changes.
  • Frog eggs lack a hard shell and are protected by a jelly layer to prevent exposure to predators like fishes, leading to the production of numerous eggs for survival.
  • Amniotic fluid surrounds the growing baby in the uterus, providing protection and support during development.
  • The sperm duct, also known as vas deferens, carries sperm from the testes to the urethra for ejaculation.
  • Menstrual cycle occurs when an egg is not fertilized, leading to the shedding of the uterine lining, a process essential for reproductive health in females.
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