Tag: introduction to reproduction

Earthworms are hermaphrodites; that is, they have both male and female sexual organs.  The two or four pairs of seminal vesicles produce, store and release the sperm via the male pores. Ovaries and oviducts are in segment 13 release eggs. Ovarian funnels are present beneath the ovaries which continue into the oviduct, join together.

The spermathacae are also called as receptaculum seminis. species of earthworms have four pairs of spermathecae one pair each in the 6th, 7th, 8th, and 9th segments. The spermathecae receive and store the spermatozoa of another earthworm during copulation. They are lined with epithelium and are variable in shape: some are thin, heavily coiled tubes.

Two pairs of accessory glands are present in 17th and 19th segments. Four pairs of spermathecae are located in 6th-9th segments. They receive and store spermatozoa during copulation. One pair of ovaries is attached at the inter-segmental septum of the 12th and 13th segments.

Tapeworm and fluke worms belong to class Platyhelminthes. They both are having well developed reproductive systems.

The menstrual cycle refers to the series of events that periodically modifies the female reproductive tract of humans and advanced primates. In other mammals, a cycle of receptivity to sexual activity occurs that is probably less complex than the menstrual cycle and is known as the estrous cycle.

Those structures which are directly concerned with reproduction are considered primary sex characteristics. Secondary sexual characters can be used to differentiate between males and females and usually serve the purpose of attracting potential mates. Testosterone is responsible for male secondary sex characteristics such as a deep voice and facial hair. In the female, the hormones that most nearly parallel testosterone in their actions are the estrogens. Estrogens contribute to the development of the female secondary sex characteristics and stimulate the development of the mammary glands (breast in this question), the onset of menstruation, and the development and functioning of the reproductive organs. The other hormone produced by the female sex glands, called progesterone, assists in the normal development of pregnancy.

The process of formation of mature female gametes is called oogenesis. The reproductive cycle of female primates is called menstrual cycle. Menstrual cycle starts only after attaining sexual maturation (puberty). During ovulation only one ovum is released per menstrual cycle. The cyclical changes in the ovary and the uterus during menstrual cycle are induced by changes in the levels of pituitary and ovarian hormones.

Blastogenesis is the process of formation of offsprings asexually from reproductive bodies and does not include meiosis and fertilization. 

The recurring physiological changes induced and regulated by reproductive hormones in non-primates constitute oestrous cycle. It consists of short period of heat generation which is then followed by anoestrous phase. Oestrous cycle is initiated as a result of no fertilization and is characterized by sloughing off of uterine endometrium, which was proliferated for implantation of fertilized egg, and its reabsorption. Since, non primate females become receptive to male during oestrous phase, it is indicator of breeding period. Estrogens are secreted by developing follicles in ovary during follicular phase coincide with first oestrous (low estrogens) and then proliferative phase (high level of estrogens by developing follicles) in uterus.This makes option B incorrect since, estrogens level is low during oestrous cycle.