Sexual reproduction in organisms - class-XII

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. 

Estrous cycle is a reproductive cycle of females of non-primate vertebrates. The gap between two estrus periods is known as estrous cycle. The females are highly receptive during estrus period. It is an indication of breeding period because one or more periods of estrus may occur during the breeding season of a species. Polyoestrus are the animals which ovulates more than once in each breeding season. For example, rabbit. Cats are polyestrous but experience a seasonal anestrus in autumn and late winter. Horses are seasonal polyestrous. Humans have menstrual cycle they lack estrous cycle.

• Conjugation is merely the fusion of two compatible bacterial cells. Bringing two genotypes together and allowing them to conjugate is the equivalent of making a cross in eukaryotes.
• Our discussion of conjugation will center on the gut bacterium Escherichia coli ($E$. coli). Conjugation and gene transfer in $E$. coli are driven by a circular $DNA$ plasmids called the fertility factor or sex factor $(F)$, which is found in some but not all cells. Hence to understand how to make a cross in $E$. coli, we have to understand the properties of $F$.

Organisms produced by sexual reproduction have characters from both the parents and are not exactly identical to the parents.

Conjugation is an exchange of genetic material i.e, mode of sexual reproduction in lower organisms.
Scalariform conjugation: It takes place during the night and between the recently divided cells of the conjugating participating filaments. Opposite cells of two filaments develope a conjugation tube by lying side by side and parallel to each other. The conjugation tube between two filament looks like a ladder, through which gamete from one gametangia passes through to fuse with the passive gamete of another filament.

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. Swelling in vulva and vagina can be noticed which indicates the preparation of sexual receptivity. The glands of uterus show hypertrophy due to the heat. 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 D.

• Hysterical pregnancy is the appearance of signs and symptoms associated with pregnancy when the person is not actually pregnant.
• It is also known as false pregnancy, phantom pregnancy, pseudopregnancy or pseudocyesis, 
• False pregnancy may sometimes be purely psychological.
• So, the correct option is 'All of the above'.

Estrous cycle comprises of the recurring physiologic changes that are induced by reproductive hormones in females of mammals. Monoestrous means having one estrous cycle per year. Diestrous means having two estrous cycles per year. Polyestrous means having many estrous cycles per year. A female dog is an example of diestrous. 

• Anestrus is a state or interval of sexual inactivity between periods of activity in periodically breeding mammals.
• The first phase (proestrus) of the estrous cycle is the building-up phase. During this phase the ovarian follicle (under the influence of FSH and LH) enlarges and begins to secrete estrogens.
• The end of sexual receptivity marks the beginning of metestrus, the post-ovulatory phase dominated by corpus luteum function. 
  
• So, the correct option is 'Anestrus'.

• The first phase (proestrus) of the estrous cycle is the building-up phase. During this phase the ovarian follicle (under the influence of FSH and LH) enlarges and begins to secrete estrogens.
  
• Estrus is the period of sexual receptivity. It is primarily initiated by the elevation in estrogens from mature follicles just prior to ovulation.
  
• The end of sexual receptivity marks the beginning of metestrus, the post-ovulatory phase dominated by corpus luteum function. 
  
• Anestrus is a state or interval of sexual inactivity between periods of activity in periodically breeding mammals.
  
• So, the correct option is 'Anestrus'.

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 ( can receive the male gamete). 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 B.

• The first phase (proestrus) of the estrous cycle is the building-up phase. During this phase the ovarian follicle (under the influence of FSH and LH) enlarges and begins to secrete estrogens.
• The end of sexual receptivity marks the beginning of metestrus, the post-ovulatory phase dominated by corpus luteum function. 
  
• Anestrus is a state or interval of sexual inactivity between periods of activity in periodically breeding mammals.
  
• So, the correct option is 'Anestrus'.

The reproductive cycle of the non primate females is called estrous cycle. The phase when the female is sexually receptive is called as estrus and the phase when the female is not sexually receptive is called as anestrus. When the pineal gland is exposed to light, there is release of the hormone melatonin. The hormone causes stimulation and repression of reproduction in different kind of breeders. This hormone regulated the activity and the release of GnRH (gonadotropin releasing hormone).

Estrous cycle is the reproductive cycle seen in non-primates female. It is the time from one heat period (estrous) to another heat period (estrous). This time period can vary from one species to another species. In goat the estrus frequency is of 21 days. So, the correct option is D.

Estrus cycle is the indication of the breeding period because it is a reproductive cycle of females of non-primate vertebrates and it is the period in which the female is highly receptive. One or more periods of estrus may occur during the breeding season of a species. Some animals like dogs are monoestrous as they have only one oestrous phase in their breeding cycle. Males can recognize a female in heat by the smell of pheromones.

Root tip cells are diploid (2n = 42), which means the haploid number n is 21. Aleurone cells in cereal grains are triploid (3n) endosperm tissue, so their chromosome number is 3 times 21, which equals 63.

•  Animals that have estrus cycles resorb the endometrium if conception does not occur during that cycle. 
• Animals that have menstrual cycles shed the endometrium through menstruation if conception does not take place.
• So, the correct option is 'Menstruation at the end of the estrus cycle'.

Sexual receptivity is the stage when the female accepts the sperms for fertilization during the process of intercourse. The female becomes sexually receptive during the estrus phase of the menstrual cycle. 

• Metestrus phase is characterized by the activity of the corpus luteum, which produces progesterone. 
• The uterine lining begins to appear and hypertrophy of glands is observed due to increased progesterone.
  
• Just like menstrual cycle, absence of fertilisation leads to degeneration of corpus luteum in estrus cycle.
• So, the correct option is 'All of the above'.

• Estrus cycle is the period of sexual activity in female mammals except for higher mammals, during which they are in heat i.e. ready to mate.
• Cows can go into heat several times per year.
  
• Estrus frequency of cow is 21 days i.e. it goes into heat with a duration of 21 days.
• So, the correct option is '21 days'.

The reproductive cycle of the non primate females is called estrous cycle. It can be divided into four phases: proestrus, estrus, metestrus and diestrus. Proestrus stage is the building up phase. There is bleeding found in dogs during the proestrus phase. There is increase in the level of estradiol-17 hormone. This results in the movement or diapedesis of the red blood cells in the blood vessels which causes bleeding. 

• Estrus is the period in the sexual cycle of female mammals, except the higher primates, during which they are in heat—i.e., ready to accept a male and to mate.
• The female cat stays in heat for 14-21 days i.e. it is ready to mate for this duration.
• So, the correct option is '14-21 days'.

Menstrual cycle occurs in primates (monkeys, apes and human beings). This cycle consists of the menstrual phase, the proliferative phase and the secretory phase and the broken endometrium is passed out during menstruation. The oestrous cycle occurs in non-primates such as cows, dogs, etc. It consists of a short period of estrus or heat followed by anoestrus or passive period. The broken endometrium is reabsorbed during the oestrous cycle.

Estrus is the period in the sexual cycle of female mammals, except humans during which they are in heat, i.e ready to mate. Prior to ovulation, the endometrium (uterine lining) thickens, in preparation for holding the fertilized ova. As the proliferation of uterine tissue reaches its peak, receptivity is the highest which is called the oestrous period. The period of sexual receptivity is primarily initiated by the elevation in estrogens from mature follicles just prior to ovulation. The basic pattern of the oestrous cycle is the same in all domestic animals, but some specific differences are found in specific parts of the cycle.