All Free Biology MCQs with Answers

• A. Adventitive embryony
• B. Polyembryony
• C. Parthenocarpy
• D. Parthenogenesis

Explanation: Development of an organism from female gamete/egg without involving fertilization is parthenogenesis and when a fruit is developed by this…

• A. Hofmeister
• B. Nawaschin and Guignard
• C. Leeuwenhoek
• D. Strasburger

Explanation: Double fertilization is the characteristic feature of angiosperms. This phenomenon first observed by Nawaschin, 1898 in Lilium and…

• A. 100
• B. 75
• C. 125
• D. 50

Explanation: For formation of 100 zygotes, 100 male gametes and 100 female gametes (eggs) are required.

• A. Four celled pollen grain
• B. Three celled pollen grain
• C. Microspore mother cell
• D. Anther

Explanation: The male gametophyte or microspore is shed at 3rd ­nucleate stage. The microspore undergoes only two mitotic divisions.

• A. Development of embryo with fertilization
• B. Development of fruit without fertilization
• C. Development of fruit without hormones
• D. Development of embryo from egg without fertilization

Explanation: Development of an organism from female gamete/egg without involving fertilisation is parthenogenesis and when a fruit is developed by this…

• A. Apospory
• B. Apogamy
• C. Parthenogenesis
• D. Amphimixis

Explanation: Formation of gametophyte directly from sporophyte without meiosis and spore formation is apospory.

• A. Progesterone only
• B. Progesterone and inhibin
• C. Estrogen and progesterone
• D. Estrogen and inhibin

Explanation: GnRH is secreted by the hypothalamus which stimulates the anterior lobe of pituitary gland to secrete luteinising hormone (LH) and FSH.

• A. LH and FSH decrease gradually during the follicular phase
• B. LH triggers secretion of androgens from the Leydig cells
• C. FSH stimulates the sertoli cells which help in spermiogenesis
• D. LH triggers ovulation in ovary

Explanation: During follicular phase FSH secretion increases. Follicular phase (proliferative phase) usually includes cycle days 6­13 or 14 in a 28…

• A. Uterine implantation
• B. Birth
• C. Puberty
• D. Fertilization

Explanation: In human beings, ovum is released from the ovary in the secondary oocyte stage.

• A. B­-Corpus luteum - Secretes progesterone
• B. A­-Tertiary follicle ­- Forms Graafian follicle
• C. B­-Corpus luteum - Secretes estrogen
• D. A­-Primary oocyte ­- It is in the prophase I of the meiotic division

Explanation: The zona granulosa and theca cells of Graafian follicle remaining in the ovary after ovulation and some surrounding capillaries and…

• A. Oxytocin from foetal pituitary
• B. Human chorionic gonadotropin (hCG) from placenta
• C. Human placental lactogen (hPL) from placenta
• D. Oxytocin from maternal pituitary

Explanation: Parturition is induced by a complex neuroendocrine mechanism. The signals for parturition originate from the fully developed foetus and…

• A. Testes to epididymis
• B. Epididymis to vas deferens
• C. Ovary to uterus
• D. Vagina to uterus

Explanation: The male sex accessory ducts include rete testis, vasa efferentia, epididymis and vas deferens.

• A. Maintaining the scrotal temperature lower than the internal body temperature
• B. Escaping any possible compression by the visceral organs
• C. Providing more space for the growth of epididymis
• D. Providing a secondary sexual feature for exhibiting the male sex

Explanation: The testes are situated outside the abdominal cavity within a pouch called scrotum.

• A. Secretions of acrosome helps one sperm enter cytoplasm of ovum through zona pellucida
• B. All sperms except the one nearest to the ovum lose their tails
• C. Cells of corona radiata trap all the sperms except one
• D. Only two sperms nearest the ovum penetrate zona pellucida

Explanation: Secretions of acrosome help one sperm enter the cytoplasm of the ovum through the zona pellucida.

• A. Shortly after ovulation, the ovum makes entry into the fallopian tube
• B. Until after the ovum has been penetrated by a sperm
• C. Until the nucleus of the sperm has fused with that of the ovum
• D. In the Graafian follicle following the first maturation division

Explanation: The correct option is: b) Until after the ovum has been penetrated by a sperm.

• A. Forms placenta even before implantation
• B. Gets implanted into uterus 3 days after ovulation
• C. Gets nutrition from uterine endometrial secretion only after implantation
• D. Gets implanted in endometrium by the trophoblast cells

Explanation: Note: Implantation in endometrial uterine wall takes place at blastocyst stage of embryonic development.

• A. Pattern of cleavage
• B. Number of blastomeres produced
• C. Fertilization
• D. Formation of zygote

Explanation: Note: Cleavage is a series of cell divisions by which a single fertilized egg cell is transformed into a multicellular body, the blastula.

• A. Spermatids
• B. Spermatogonia
• C. Primary spermatocytes
• D. Secondary spermatocytes

Explanation: Note: During embryonic development the primordial germ cells migrate to the testis where they become spermatogonia.

• A. Yolk sac
• B. Amnion
• C. Chorion
• D. Allantosis

Explanation: Note: Amnion is a type of extraembryonic membrane formed by the amniogenic cells inside and splanchnopleuric extraembryonic mesoderm…

• A. At the point of entry of sperm into ovum
• B. Just opposite to the site of entry of sperm into ovum
• C. At the animal pole
• D. At the vegetal pole

Explanation: When the sperm enters the egg during fertilization, it creates a "fertilization cone" or "fertilization cone cap" on the surface of the…