Tag: reproduction in organisms

Parthenogenesis (virgin development) is a form of asexual reproduction in which an unfertilized egg develops into an adult animal. The adult is typically haploid. Parthenogenesis is common among insects (especially honeybees and wasps, aphids etc.) and crustaceans; it also occurs among some other invertebrate and vertebrate groups, including some species of nematodes, gastropods, fishes, amphibians, and reptiles. Although a few species appear to reproduce solely by parthenogenesis, in most species episodes of parthenogenesis alternate with periods of sexual reproduction. Parthenogenesis may occur for several generations, followed at some point by sexual reproduction in which males develop, produce sperm and mate with the females to fertilize their eggs. In some species, parthenogenesis is a means of rapidly producing individuals when conditions are favorable.

Parthenogenesis refers to the development of an individual from unfertilized eggs. In honey bees, parthenogenesis is common and here, drones develop as a result of parthenogenesis only. The mode of parthenogenesis is arrhenotoky in which only females are produced. Frog and sea urchin reproduces by artificial parthenogenesis.

Monocarpic plants are those that flowers once during their Iife time, set seeds and then die, e.g.,bamboos.

Oestrous cycle occur in non-primates such as cows, dogs, etc. Menstrual cycle occurs in primates only. Menstrual cycle shows monthly recurrence but oestrous cycle does not.

The reproductive cycle of the non-primate females is called oestrous cycle. For example, in rats, horse etc. It can be divided into four phases proestrus, estrus, metestrus and diestrus. The word estrus means heat. It is a sign of sexual receptivity and fertility.

On the basis number of estrous cycle (breeding cycle), females of some species can be monoestrous and diestrous. Monoestrous animals are those in which only one estrous cycle can be seen in a year. For example, dogs, fox etc. Whereas, diestrous animals are those in which two estrous cycles are seen in a year. For example, horse, goats etc. So, the correct option is A.

The reproductive cycle of the non primate females is called estrous cycle. For example, in rats, horse etc. It can be divided into four phases proestrus, estrus, metestrus and diestrus. Proestrus stage is the building up phase. The ovarian follicle becomes large and secretes estrogen which is necessary for the preparation of estrus and pregnancy. Estrus is the phase when ovulation takes place. It is also known as the period of heat and female is sexually receptive. Metestrus is the phase where corpus luteum forms under the influence of decreased estrogen and increased progesterone level. Diestrus is the phase where corpus luteum becomes functional and the progesterone level increases. So, the correct option is C.

The reproductive cycle of the non-primate females is called oestrous cycle. For example, in rats, horse etc. It can be divided into four phases proestrus, estrus, metestrus and diestrus.