In the alveoli, where there is high pO2, low pCO2, lesser H+ concentration and lower temperature, the factors are all favourable for the formation of oxyhaemoglobin, whereas in the tissues, where low pO2, high pCO2, high H+ concentration and higher temperature exist, the conditions are favourable for dissociation of oxygen from the oxyhaemoglobin. Answer : (a)

The correct sequence for transport of sperm cells in male reproductive system is: Seminiferous tubules → Rete testis → Vasa efferentia → Epididymis → Vas deferens → Ejaculatory duct → Urethra → Urethral meatus. Answer : (b)

Oral administration of small doses of either progestogens or progestogen–estrogen combinations is another contraceptive method used by the females. They are used in the form of tablets and hence are popularly called the pills. They inhibit ovulation and implantation as well as alter the quality of cervical mucus to prevent/retard entry of sperms. Saheli–the new oral contraceptive for the females contains a non-steroidal preparation. Answer : (c)

Infections or diseases which are transmitted through sexual intercourse are collectively called sexually transmitted infections (STI) or venereal diseases (VD) or reproductive tract infections (RTI). Gonorrhoea, syphilis, genital herpes, chlamydiasis, genital warts, trichomoniasis, hepatitis-B and AIDS are some of the common STIs. Answer : (c)

Fertilization induces the completion of the meiotic division of the secondary oocyte. The second meiotic division is also unequal and results in the formation of a second polar body and a haploid ovum (ootid). The process of fusion of a sperm with an ovum is called fertilisation. Answer : (b)

Placenta also acts as an endocrine tissue and produces several hormones like human chorionic gonadotropin (hCG), human placental lactogen (hPL), estrogens, progestogens, etc. Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules in the testicle. They produce testosterone (androgens) in the presence of luteinizing hormone (LH). The zona pellucida is the extracellular coat of the mammalian oocyte. It acts as a selective filter before fertilization that can only be penetrated by sperm that have completed the acrosome reaction. The secretions of bulbourethral glands also helps in the lubrication of the penis. Answer : (b)

The secretion of gonadotropins (LH and FSH) increases gradually during the follicular phase, and stimulates follicular development as well as secretion of estrogens by the growing follicles. Both LH and FSH attain a peak level in the middle of cycle (about 14th day). Rapid secretion of LH leading to its maximum level during the mid-cycle called LH surge induces rupture of Graafian follicle and thereby the release of ovum (ovulation). Answer : (c)

Dermis of skin, connective tissue, muscles, skeleton, blood, heart,notochord, blood vessel, adrenal cortex, urino – genitals system except part of urinary bladder, lining of coelom, spleen and eyes are produced by mesoderm. Answer : (a)

Characteristics of placenta : (i) Acts Nutritive organs – Food materials from the mother’s blood into the foetal blood through the placenta (ii) Acts as Digestive organ – Trophoblast of placenta digests proteins before passing them into the foetal blood. (iii) Acts as Respiratory organ – Oxygen diffuses from the maternal blood into the foetal blood through the placenta. Carbon dioxide diffuses from the foetal blood into the maternal blood also through the placenta for elimination by the mother’ lungs. Foetal haemoglobin has a greater affinity for oxygen than adult haemoglobin (iv) Acts as Excretory organ – Nitrogenous waste such as urea, pass form the foetal blood into the maternal blood via placenta for elimination by mother’s kidney (v) Acts as Endocrine organ – Placenta secretes some hormone such as estrogens, progesterone, human chorionic gonadotropin ( hCG), human placental lactogen ( hPL) chorionic thyrotropin, chorionic corticotrophin and relaxin. The hCG stimulates and maintains the corpus luteum to secrete progesterone until the end of pregnancy. The hPL stimulates the growth of the mammary glands during pregnancy. Relaxin facilitates parturition by softening the connective tissue of pubic symphysis (vi) Acts as Storage organ – The placenta stores glycogen for the foetus before liver is formed Answer : (d)

Tunic albuginea, is the actual covering of the testes. The covering is made up of dense bluish with fibrous or collangenous connective tissue Answer : (d)

Basis for comparison	Human sperm	Human ovum
Size	Very small	Large in size
Mitochondria	In the middle piece, mitochondria form a spiral and are compactly arranged.	Mitochondria are scattered in the cytoplasm.
Cytoplasm	Present in the small amount	Present in large amount.
Nucleus	It is condensed with no nucleoplasm. The nucleus contains X or Y chromosome.	Ovum contains nucleoplasm, called as the germinal vesicle. The nucleus contains only X chromosome
Centrioles	Present.	Absent.
Produced in	Sperms are produced in the testes.	Ovum is produced in ovaries
Number of sperms formed	Four sperms are formed from one spermatogonium.	Only one ovum is formed from one oogonium
Differentiated into	Sperms are separated into head, neck, middle piece and tail.	Ovum is not externally separated into regions.
Movement	Can move.	Not able to move.
Surrounded by	Surrounded by plasma membrane only.	Ovum is surrounded by the egg envelopes.or Accessory membranes

Answer : (b)

The amnion is a tough, thin membrane that surrounds a developing fetus in mammals, reptiles, and birds. amnion to expand and become the amniotic sac which serves to provide a protective environment for the developing embryo or fetus. Answer : (a)

The acrosome is an organelle that develops over the anterior half of the head in the spermatozoa (sperm cells) of many animals including humans Answer : (d)

Definition of amphimixis is the union or the fusion between the male and the female gametes in sexual reproduction Answer : (b)

Sperm consists of head, neck, a middle piece and a tail.When viewed under electron microscope, cross- section of a midpiece of sperm consists of- (i) core of the flagellum is composed of an axoneme surrounded by 9 dense fibres. (ii) axoneme consists of 2 singlet microtubules surrounded by 9 microtubule doublets. (iii) mitochondria is well placed for providing the ATP required for flagellar movement. Answer : (c)

The amnion is a tough, thin membrane that surrounds a developing fetus in mammals, reptiles, and birds. amnion to expand and become the amniotic sac which serves to provide a protective environment for the developing embryo or fetus. Answer : (c)

A type of tissue called trophoblast develops from the fertilized egg and surrounds it. This trophoblast helps to implant the blastocyst(fertilized egg) once it arrives in the uterus. At this point, pregnancy has officially begun. Answer : (d)

Oxytocin (Oxt) is a peptide hormone and neuropeptide. Oxytocin is released into the bloodstream as a hormone in response to stretching of the cervix and uterus during labor. a = s Prolactin (PRL), also known as lactotropin, is a protein best known for its role in enabling mammals (and birds), usually females, to produce milk. b = r Luteinizing hormone (LH) in synergy with follicle stimulating hormone (FSH) stimulates normal follicular growth and ovulation. c= p Progesterone belongs to a group of steroid hormones called progestogens. It is mainly secreted by the corpus luteum in the ovary during the second half of the menstrual cycle. It plays important roles in the menstrual cycle and in maintaining the early stages of pregnancy. d= q Answer : (a)

Sperm entry can occur anywhere in the animal hemisphere. Answer : (a)

In the process of spermatogenesis single secondary spermatocyte produces two sperms thus 50 secondary spermatocytes will produce 100 sperms. In the process of oogenesis single secondary oocyte produces one ova and one polar body. Thus, 50 will produce 50 ovum. Answer : (a)

An Italian biologist, Spallanzani worked on animal reproduction and in the year 1780, described the first two planes of cleavage in an egg. Answer : (a)

The testes are where sperm are manufactured in the scrotum. The vasa efferentia (efferent ducts) connect the rete testis with the initial section of the epididymis. The epididymis is a tortuously coiled structure topping the testis, and it receives immature sperm from the testis and stores it for several days. When ejaculation occurs, sperm is forcefully expelled from the tail of the epididymis into the deferent duct. Sperm then travels through the deferent duct through up the spermatic cord into the pelvic cavity, over the ureter to the prostate behind the bladder. Here, the vas deferens joins with the seminal vesicle to form the ejaculatory duct, which passes through the prostate and empties into the urethra. When ejaculation occurs, rhythmic muscle movements propel the sperm forward Answer : (a)

LH surge is important because it initiates the beginning of ovulation and fertile period. Answer : (a)

Cleavage	Mitosis
Cleavage occurs in the zygote, parthenogenetic egg	Mitosis occurs in most body cells
Size of blastomeres decreases as their number increases	Size of the daughter cells remain nearly contstar due to growth
The total mass of blastomeres decreases as their number increases	The total mass of daughter cells becomes more than that of parent cell
DNA synthesis occurs much faster to form chromosomes for new blastomeres	DNA synthesis occurs at the normal rate
Nuclear/cytoplasmic ratio increases as cleavage progresses	Nuclear/cytoplasmic ratio does not change

SOLUTION Answer : (d)

SOLUTION Production of sperms from spermatids is spermiogenesis. It is the last stage of spermatogenesis. It occurs in testis and begins at puberty. The spermatids are transformed into sperms by the process of metamorphosis. Sperms are also known as spermatozoa. After spermiogenesis, the sperm heads become embedded in the Sertoli cells, and are finally released from the seminiferous tubules by the process called spermiation. Answer : (a)

SOLUTION Sperm motility is produced through activation of the sperm flagellum, which core structure, the axoneme, resembles motile cilia Answer : (d)

SOLUTION Menopause is the time that marks the end of your menstrual cycles. It's diagnosed after you've gone 12 months without a menstrual period. Menopause can happen at age 40s or 50s Answer : (a)

SOLUTION During ovulation, the mature follicle or Graafian follicle bursts and the ovum is released. After ovulation, the granulosa cells and the interstitial cells form a mass of large and yellowish conical cells. This is named as Corpus luteum which serves as a temporary endocrine gland by releasing progesterone and estrogen. Answer : (d)

Immediately after implantation, the inner cell mass (embryo) differentiates. The human foetus within the uterus into an outer layer called ectoderm and an inner layer called endoderm. A mesoderm soon appears between the ectoderm and the endoderm. Answer : (d)

All female mammals have a menstrual cycle. Humans, primates and some other mammals (bats, African elephant shrews and certain tree shrews) have such a thick endometrial lining that part of it is being shed through the vagina. Answer : (d)