Theory & Procedure, Asexual Reproduction in Amoeba and Yeast Class 10 Notes | EduRev

Science Class 10

Class 10 : Theory & Procedure, Asexual Reproduction in Amoeba and Yeast Class 10 Notes | EduRev

The document Theory & Procedure, Asexual Reproduction in Amoeba and Yeast Class 10 Notes | EduRev is a part of the Class 10 Course Science Class 10.
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Objective

Our objective is to study using the prepared slides;

  1. Binary fission in Amoeba.
  2. Budding in Yeast.

The Theory

Reproduction

All living things produce their own kind through the process called reproduction. Reproduction takes place sexually and asexually.

Sexual reproduction

Sexual reproduction is the primary method of reproduction for the vast majority of macroscopic organisms, including almost all animals and plants. Here are two main processes during sexual reproduction in eukaryotes: meiosis, involving the halving of the number of chromosomes; and fertilisation, involving the fusion of two gametes and the restoration of the original number of chromosomes. During meiosis, the chromosomes of each pair usually cross over to achieve homologous recombination that helps produce genetic diversity when cells divide in meiosis.

Asexual reproduction

Asexual reproduction is the primary form of reproduction for single-celled organisms such as the archaea, bacteria, and protists. Many plants and fungi reproduce asexually as well. Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only. The offspring will be the exact genetic copies of the parent.

New organisms are produced in rapid multiplication by the process of amitotic or mitotic divisions. Amitosis is the process by which a cell directly separates, as the nucleus and cytoplasm are directly cut in two. Mitosis is the process by which a cell, which has previously replicated each of its chromosomes, separates the chromosomes in its cell nucleus into two identical sets of chromosomes, each set will have its own new nucleus. It is a form of nuclear division.

Binary fission and budding are two common method of asexual reproduction. Binary fission is found in unicellular organisms like Amoeba, Paramaecium and Euglena, to name and few. Budding is found in Yeast and Hydra.

Binary fission in Amoeba

Amoeba is a shapeless tiny unicellular organism that has a porous cell membrane which encloses the cell organelles and cytoplasm. Amoeba reproduces by the common asexual reproduction method called binary fission. After replicating its genetic material through mitotic division, the cell divides into two equal sized daughter cells. The genetic material is also equally partitioned; therefore the daughter cells are genetically identical to each other and the parent cell. In this process, the nucleus of the Amoeba first divides to form two daughter nuclei by the process of Karyokinesis. After the nucleus has divided into two, the process of Cytokinesis takes place in which the cytoplasm in the mother cell divides into two daughter cells. This leads to the formation of the two daughter Amoebae cell having a nucleus and its own cell organelles.

Karyokinesis is the process of the division of the nucleus. It corresponds to the separation of the daughter chromosomes into two daughter nuclei. Karyokinesis is usually followed by Cytokinesis.

Cytokinesis is the process of the division of the cytoplasm. It corresponds to the separation of the daughter nuclei into two daughter cells. Cytokinesis occurs immediately after mitosis.

Theory & Procedure, Asexual Reproduction in Amoeba and Yeast Class 10 Notes | EduRev

Budding in Yeast

Yeast are unicellular (some are multicellular) eukaryotic micro-organisms belonging to the kingdom fungi. Yeast size can vary greatly depending on the species, typically measuring 3-4 µm in diameter. Most yeasts reproduce asexually by an asymmetric division process called budding. First it produces a small protuberance on the parent cell that grows to a full size and forms a bud. The nucleus of the parent cell splits into a daughter nucleus and migrates into the daughter cell. The bud detaches from the mother’s body by forming a constriction at the base. Budding will repeat to form a chain of bud cells. The daughter cell produced during the budding process is generally smaller than the mother cell.

Theory & Procedure, Asexual Reproduction in Amoeba and Yeast Class 10 Notes | EduRev

Learning Outcomes

  • Students understand the terms budding, binary fission and a few other terms.
  • Students understand the different stages of binary fission in Amoeba.
  • Students understand the different stages of budding in Yeast.
  • Students understand the experiment better through the animated demonstration.

Materials Required

  1. Permanent or prepared slides of;
    • Binary fission in Amoeba
    • Budding in yeast
  2. Compound microscope

Binary fission in Amoeba

Real Lab Procedure

  • Take the prepared slide of binary fission in amoeba and place it on the stage of the compound microscope.
  • Adjust the mirror of the microscope so that maximum light is reflected from the mirror on to the slide.
  • Focus the slide under the microscope’s lens carefully, first under low power and then under high power.
  • Observe the different phases of binary fission in Amoeba through the lens of the compound microscope.

Observations

  • Amoeba cells are irregular in shape.
  • Karyokinesis can be observed in some stages, with the mother cell elongating and its nucleus dividing into two.
  • Cytokinesis can be observed in some stages, with the division in cytoplasm that forms two daughter cells.

Conclusion

This slide shows the nucleus of Amoeba in the process of division. The body of Amoeba is elongated and has a constriction in the middle. Hence the given slide is the one that shows the asexual reproduction process of binary fission in Amoeba.

Budding In Yeast

Real Lab Procedure

  • Take the prepared slide of budding in Yeast and place it on the stage of the compound microscope.
  • Adjust the mirror of the microscope so that maximum light is reflected from the mirror on to the slide.
  • Focus the slide under the microscope’s lens carefully, first under low power and then under high power.
  • Observe the different phases of budding in Yeast through the lens of the compound microscope.

Observations

  • We can observe that the yeast cells are spherical or oval in shape.
  • Outgrowths called buds can be seen on the yeast cells. At times a chain of buds are seen on the parent cells.
  • Buds that have separated from the parent cells can also be seen.

Conclusion

The slide shows some yeast cell protuberance or buds. In a few yeast cells a chain of buds can be observed. Hence the given slide is one that shows the asexual reproduction process of budding in Yeast.

Precautions

  • Before placing the slide on the stage of the microscope, ensure the settings of the microscope mirror and diaphragm are correct.
  • Focus the slide under the microscope’s lens carefully, first under low power and then under high power.
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