Biology

• Sexual reproduction requires Meiosis and fertilization, a union of two cells from two individual organisms
• Diploid cells


  Cells that carry chromosomes from two parents
• Sexual reproduction


  • Genetic contribution of two cells
  • Meiosis occurs during gamete formation, producing cells with half the normal number of chromosomes
• Meiosis


  Division process: from a diploid one cell with two sets of chromosomes (2n) to haploid cells with a single set of chromosomes
• Phases of meiosis


  1. Meiosis I: Homologous pairs separate

  2. Meiosis II: Sister chromatids separate
• Meiosis I

  • Homologous pairs align at the equator of the cell
  • Homologous pairs are pulled apart, one duplicated homologous goes to one pole, the other to the other pole
  • Sister chromatids do not separate
• Meiosis II


  • Sister chromatids are pulled apart
• • After meiosis I, the cell has n=23 chromosomes
  • After meiosis II, the cell has 23 chromosomes (Haploid)
• During meiosis, a process known as crossing over occurs


  Segments of DNA are exchanged between homologous chromosomes
• Student: 'What is mean in reproduction? Think about the traits you share with your parents, like eye color or height. Why do you think you share these traits? How does reproduction play a role in passing on characteristics from one generation to the next? What makes you similar to, yet different from, your parents?'
• Meiosis


  • Two nuclear divisions with no DNA replication between them
  • Produces four daughter cells, each with half the original number of chromosomes
  • Crossing over occurs in prophase I
• Mitosis


  • A single nuclear division after DNA replication
  • Produces two daughter cells, each containing the original number of chromosomes
• Meiosis II


  1. Prophase II

  2. Metaphase II

  3. Anaphase II

  4. Telophase II
• Prophase II


  A new spindle apparatus forms in each cell, and the nuclear envelope breaks down
• Metaphase II


  Chromosomes consisting of sister chromatids joined at the centromere align along the metaphase plate in each cell. Kinetochore microtubules from opposite poles attach to kinetochores of sister chromatids, as in mitosis
• Anaphase II


  When microtubules shorten in anaphase II, sister chromatids are pulled to opposite poles of the cells, as in mitosis
• Telophase II


  The nuclear membranes reform around four different clusters of chromosomes. After cytokinesis, four haploid cells result. No two cells are alike due to the random alignment of homologous pairs at metaphase I and crossing over during prophase I
• Meiosis II is like a mitotic division without DNA replication. The interphase between meiosis I and meiosis II is brief and does not include an S phase
• Meiosis II resembles a normal mitotic division. Prophase II, metaphase II, anaphase II, and telophase II
• During meiosis, a process known as crossing over occurs
• Statements about crossing over


  • Segments of DNA are traded between unrelated chromosomes
  • Crossing over occurs more often in male gametes than female gametes
  • A chiasma indicates that a crossover has occurred
  • Most homologous pairs do not have any crossover events
• Meiosis produces four haploid cells, while mitosis produces two diploid cells
• Crossing over during meiosis I creates genetic diversity in the resulting gametes
• The class activity aims to engage students in understanding the step-by-step process of meiosis and the creation of genetic diversity
• The reflection journal prompts students to write about the challenges and exciting moments the cell faces during meiosis, and how the meiosis vs. mitosis diagram helps them understand the differences between the two processes
• ឈាម


  Connective tissue: several types of cells with fluid, a tissue with a fluid matrix that can move
• Functions of blood cells

  • Delivers oxygen and removes waste products from the body's cells
  • Delivers nutrients, hormones, enzymes, and many other critical substances to points throughout the body
  • Helps stabilize the body's acid-base balance; it also helps regulate body temperature
  • Plays multiple roles in protecting the body against infection
• សមាសធាតុរបស់ឈាម


  • Plasma: Clear, extracellular matrix of this liquid connective tissue
  • Cells and cell fragments
• Plasma is 55% of blood, cells and cell fragments are 45% of blood
• Components of blood


  • Plasma
  • Erythrocytes (red blood cells, or RBCs)
  • Leukocytes (white blood cells, or WBCs)
  • Platelets

  
• Main component of plasma


  Water, also proteins (the main one being albumin), nutrients, electrolytes, hormones, and gases
• Role of plasma


  • Blood clotting, the immune system, and the regulation of fluid volume
• Blood cell formation


  1. The body works continually to replace blood cells that are old or damaged or that have been used up in body processes

  2. The production of blood is called hematopoiesis; tissues that produce blood cells are called hemopoietic tissues

  
• Hemopoietic tissues


  • Red bone marrow: found in the ends of long bones and in flat irregular bones, produces all types of blood cells
  • Lymphatic tissue: found in the spleen, lymph nodes, and thymus gland, supplements blood cell production by producing lymphocytes, a specific type of WBC

  
• The body has two types of hemopoietic tissue: red bone marrow and lymphatic tissue

  
• Red bone marrow produces all types of blood cells
• Lymphatic tissue supplements blood cell production by producing lymphocytes, a specific type of WBC

  
• ជាលិកាផ្លិតគ្រាប់ឈាមមាន ២ គ្បតេទ


  • ខ្ួរឆ្អឹង
  • ជាលិកាាំាំ្វាទិ
• ការផ្លិតគ្រាប់ឈាម


  1. ខ្ួរឆ្អឹង

  2. ជាលិកាាំាំ្វាទិ
• ខ្ួរឆ្អឹង


  • រានត ាេុងននឆ្អឹងតវង ត ើយឆ្អឹងសាំសប /ឆ្អឹងរ៉ូប ាងមិនតទៀង ដ៉ូេជា ឆ្អឹងសនទោះគ្ទ៉ូង ឆ្អឹងលលាដ៏កាល ឆ្អឹងខ្នង ត ើយឆ្អឹងគ្ រាក
  • សគ្រាប់សលិ កាសិកាឈាមគ្រប់គ្បតេទ