The Female Gametes - SS2 Biology Lesson Note

The female gametes, or sex cells, are called eggs or ova. They are the reproductive cells produced by the ovaries in female organisms, including humans. Here are some key features of female gametes:

 

1.       Structure: The female gametes are larger and more complex in structure compared to male gametes (sperm). Each egg consists of a haploid nucleus, surrounded by cytoplasm containing various organelles, and is enclosed by a protective outer layer called the zona pellucida.

2.       Production: The production of female gametes, or oogenesis, begins during fetal development. At birth, a female has all the immature eggs she will have in her lifetime. These immature eggs, called primary oocytes, are arrested in the prophase of the first meiotic division until they are activated for maturation during puberty.

3.       Maturation: During each menstrual cycle, one or more primary oocytes are selected for further development. The selected oocyte undergoes meiosis I, resulting in the formation of a secondary oocyte and a polar body. The secondary oocyte then progresses to meiosis II but stops at metaphase II, awaiting fertilization.

4.       Fertilization: If fertilization occurs, the secondary oocyte completes meiosis II, resulting in the formation of a mature ovum (egg) and another polar body. Fertilization typically happens in the fallopian tube when a sperm penetrates the zona pellucida and fuses with the egg, combining their genetic material.

5.       Characteristics: Female gametes contain half the number of chromosomes (n) as compared to other body cells. In humans, the egg contributes 23 chromosomes, including the X sex chromosome, to the zygote upon fertilization. The remaining 23 chromosomes come from the sperm, determining the genetic characteristics of the offspring.

6.       Size and Energy Reserves: Female gametes are relatively large compared to male gametes. They contain abundant cytoplasm, organelles, and nutrients necessary to support the developing embryo during early stages before it establishes its own source of nutrition.

7.       Limited Number: Unlike males, who continuously produce sperm throughout their reproductive life, females have a finite number of eggs. Over time, the supply of eggs in the ovaries decreases due to aging, with menopause marking the end of reproductive capacity.

The female gametes play a vital role in sexual reproduction by providing the genetic material and necessary resources for fertilization and embryonic development. They are central to the continuation of a species and contribute to the diversity and genetic inheritance of future generations.