FINALS

• • Deposition of yolk
  • most obvious feature of egg maturation
  • The accumulation of yolk reserves allows the egg to grow in size to support future growth
• • Egg cytoplasm 
  • contains vast amounts of messenger RNA, ribosomes, transfer RNA and other substances that will be required for protein synthesis.
• • Nucleus 
  • also grows rapidly in size during egg maturation, becoming bloated with nuclear sap.
• • As the egg becomes larger, the available surface per unit of cytoplasmic volume becomes smaller. 
  • Thus, the metabolic rate of the egg gradually diminishes until, when mature, the ovum is in suspended animation awaiting fertilization. 
  • In this condition, the egg is supported by different membranes to maintain a good condition.
• 1. Egg shell. 
  2. outermost membrane layer of the egg.
  3. composed mainly of calcium carbonate (CaCO3).
• 1. Egg yolk. 
  2. composed of high-energy nutrients such as 
  3. glycoproteins, 
  4. carbohydrates and 
  5. lipids. 
  6. These are broken down during embryogenesis into small molecules which are used by embryonic cells to synthesize new molecules.
  7. Deutoplasm. 
  8. Blastodisc. 
• 1. Deutoplasm. 
  2. yolk mass.
• 1. Blastodisc. 
  2. appears as a circular whitish area lying atop the yolk. 
  3. Generally it floats around to the most dorsal position.
• 1. Egg white. 
  2. second innermost membrane layer of the egg. 
  3. consist of 85% water and a mixture of albumin and other proteins.
• 1. Chalaza. 
  2. the inner heavier layer of albumin around the yolk. 
  3. appears twisted into rope-liked strands on either side of the spherical yolk mass.
• 1. Vitelline membrane. 
  2. the noncellular innermost membrane that encloses the egg cell. 
  3. this membrane develops in the ovary between the oocyte and the follicle cells.
• 1. Shell membranes. 
  2. located right after the egg white. 
  3. made of keratin fibers matted together. 
  4. their connection covers all areas except at the blunt part where they are separated.
  5. Inner shell membrane. 
  6. Outer shell membrane. 
• 1. Inner shell membrane. 
  2. adheres to the egg white.
• 1. Outer shell membrane. 
  2. adheres to the egg shell leaving a space in between air spaces.
• 1. Airspace. 
  2. at the broad end of the hard boiled egg. 
  3. vertically positioned at the marked area of the blastodisc, exposing the neck of the latebra.
• 1. Latebra. 
  2. flask-shaped area where the principal accumulation of white yolk lies
• 1. Nucleus of pander. 
  2. part of the latebra that extends toward the blastoderm, the aggregation of cells in the fertilized eggs from which the embryo and all its membranes are derived.
• 1. Concentric rings. 
  2. formed at the area that separates the yellow and white yolk.
• • Yolk 
  • serves as the nourishing part of the egg, furnishing essential nutrients for embryo development. 
• • Albumin
  • also known as egg white, 
  • comprises water and proteins, offering a protective layer against microbes and providing moisture. 
• • Shell 
  • composed of calcium carbonate (CaCO3)
  • acts as a semi-permeable barrier, safeguarding the egg from harm and microbial intrusion while facilitating the exchange of air and moisture.
• • Embryonic respiration
  • This process relies on passive diffusion for gas exchange. Oxygen (O₂) enters the egg through the porous shell and the surrounding albumin (egg white), while simultaneously, carbon dioxide (CO₂) diffuses out. 
  • The chorioallantoic membrane (CAM), which is analogous to a placenta, lines the inner surface of the shell. 
• • Mating or copulation 
  • sexual union to facilitate fertilization which is the process by which the male and female gametes fuse. 
• • Mating or copulation accomplishes two things 
  • provides the recombination of paternal and maternal genes to restore the original diploid number of the chromosomes of the species
  • Activates the egg to begin development
• • different modes of sexual reproduction. 
  • External fertilization
  • Internal fertilization 
• • External fertilization
  • organisms of which fertilization is completed in the environment 
  • Examples
  • some fishes and amphibians 
• • Internal fertilization 
  • fertilization happens entirely inside the body 
  • Example
  • mammals.
• Both male and female mice should be about 6 weeks of age (this is the time that they reach sexual maturity, thus, have functional gametes).
• 1. Female mice have an estrus cycle, characterized by:
  2. the swollen vaginal lips; 
  3. the vaginal mucosa are dry and lusterless which last for 4-5 days.
• 1.  Mating behavior of the mice can be observed in terms of:
  2. Sound produced.
  3. Body movements.
  4. Duration of copulation. 
  5. Type of fertilization. 
• 1. Sound produced.
  2. Any sound produced by male or female animals before, during or right after mating.
• 1. Body movements.
  2. Any peculiar movement manifested by either male or female animals as a gesture of courtship/mating.
• 1. Duration of copulation. 
  2. Length of time of mating.
• 1. Type of fertilization. 
  2. Either internal or external.
• 1. Copulation and fertilization of Mice
  2. Mature male mice are capable of copulation at any time
  3. female mating function is restricted to a time during the periodic cycle, the estrous cycle.
• 1. The female receives the male only during a relatively brief period known as estrus. The males, on the other hand, recognize the females estrus period.
• 1. Female mice are polyestrous, that is, they have a recurrence of estrus during the breeding season.
• 1. The reproductive pattern in mice is that of the viviparous placental mammals.
• 1. During mating, the male takes the copulatory position over the female. The male reproductive organ enters the female reproductive organ to release its sperm. This is fast accomplished through coordinated body movements of the animals.
• 1. Mature egg is released from the ovary and ready for union with the sperm, thus, fertilization occurs. This provides the fusion of pronuclei of the egg and the sperm. With this fusion, the zygote nucleus is formed. Mice have a gestation period of 21 days with several youngs produced.