Hermaphroditism can only occur as a result of having both female and male reproductive organs. Reproduction can happen through self-fertilization where diploid offspring can be created. This process can be commonly observed in organisms such as snails and earthworms. On the other hand, pathogenesis refers to reproduction that happens in an unfertilized ovum. Haploid offspring are produced and this process is usually observed among lower plants and insects. Internal fertilization requires gametes to be fertilized within the female organism during sexual reproduction. It is characterized by fewer gamete production, and higher survival rates of the embryos, and is common among mammals, reptiles, certain fish, and birds. External fertilization requires gametes to fuse outside the female organism during sexual reproduction and therefore happens in an external environment. It produces a large number of gametes, and greater genetic diversity and is often observed in algae, frogs, fish, mollusks, and crustaceans.
Pheromones have a number of roles throughout the reproductive cycle. They can influence the presence of estrus in female organisms and can affect the behaviors of individuals of the opposite sex. Even throughout the pregnancy, pheromones can contribute to the successful development of a fetus. The menstrual cycle can only occur in primates and involves bleeding due to the broken down endometrium in the blood flow. Copulation can occur at any time during the cycle among female primates. On the other hand, the estrous is prevalent in other mammalian species and does not involve bleeding as the broken down endometrium is absorbed. Female individuals only permit copulation when in the estrous cycle. Andrea suspects that her body produced multiple ovulations due to the fact that she had just stopped taking birth control pills, which can be a common side effect in the first month of not taking pills (Powell & Tillman, 2011). As such, she became pregnant from the two or more ovulations she experienced, with sperm from different fathers and two different times of conception.
Reference
Powell, J., & Tillman, E. (2011). Case study: An unusual case of animal reproduction. National Center for Case Study Teaching in Science.