Meiosis

stages of meiosis

1. TOPIC : MEIOSIS

2. MEIOSIS Meiosis is the mode of cell division in which gametes are formed. Meiosis occurs in the germinal cells of the reproductive organs. Human beings have 46 chromosomes. Germinal cells with 46 chromosomes divide continuously two times. These divisions in meiosis are known as Meiosis 1 and Meiosis 2 .

3. MEIOSIS 1 and 2 Two daughter cells with half the number of chromosomes (23 chromosomes) are formed in meiosis 1. Each daughter cell again divides in meiosis 2. There is no change in the chromosome number n this division. Meiosis 2 is similar to mitosis. As a result of meiosis, four daughter cells, each with 23 chromosomes, are formed from a germinal cell.

4. STAGES OF GAMETOGENESIS

5. POLAR BODY When meiosis occurs in the female germinal cell, a large ovum and three small cells are formed. The smaller cells are the polar bodies. These sterile cells get destroyed.

6. DIFFERENCE BETWEEN MITOSIS AND MEIOSIS MITOSIS MEIOSIS In which kind of cell does it takes place? Body cells Stoma tic cells The change in the number of chromosome. Same as that of the parent nucleus Half of the parent nucleus Number of daughter cells Two Four

7. STAGES OF GROWTH OF HUMAN BEING INFANCY CHILD HOOD ADOLESCENCE OLDAGE

8. PHYSICAL PECULARITIES OF OLDAGE Rate of cell division decreases. Availability of oxygen to the cells decreases. Deterioration of cells increase. Muscles shrink. Production of energy decreases. Efficiency of sense organs decreases.

9. QUESTIONS What is meiosis? What is the number of chromosomes in germinal cells? What is the number of chromosomes in the daughter cells formed after meiosis 1 ? What is the peculiarity of meiosis 2 ? What is polar bodies?

10. HOME WORK Write the differences between mitosis and meiosis? Draw the stages of gametogenesis in your science diary?