All Free Biology MCQs with Answers

• A. Human chorionic gonadotropin
• B. Prolactin
• C. Estrogen
• D. Progesterone

Explanation: Prolactin is not primarily produced by the placenta. Prolactin is mainly produced by the anterior pituitary gland in the brain and plays a…

• A. Organizer phenomena
• B. Axis formation
• C. Anamorphosis
• D. Pattern formation

Explanation: The term "organizer phenomena" refers to specific signaling centers within developing embryos that play a critical role in the…

• A. Size of embryo increases
• B. Size of cells decreases
• C. Size of cells increases
• D. Size of embryo decreases

Explanation: During cleavage, the zygote undergoes rapid cell divisions without a significant increase in overall size.

• A. Mesolecithal
• B. Aalecithal
• C. Microlecithal
• D. Macrolecithal

Explanation: In human beings, the eggs (oocytes) are alecithal, which means they have a relatively small amount of yolk (or cytoplasmic nutrient…

• A. The amount and distribution of yolk
• B. The number of egg membranes
• C. The shape and size of the sperm
• D. The size and location of the nucleus

Explanation: The amount of yolk and how it is distributed determines the type of cleavage.

• A. It starts while the egg is in the fallopian tube
• B. It starts when the egg reaches the uterus
• C. It is meroblastic
• D. It is identical to the normal mitosis

Explanation: Cleavage is a series of rapid mitotic divisions of the zygote which convert the single-celled zygote into a multicellular structure called…

• A. Trophoblast
• B. Inner cell mass
• C. Formative cells
• D. Follicle cell

Explanation: The trophoblast is the outer layer of cells that forms after the blastocyst stage during embryonic development.

• A. Obliteration of blastocoel
• B. Obliteration of archenteron
• C. Closure of blastopore
• D. Closure of neural tube

Explanation: During gastrulation, the blastula undergoes significant changes to form the three germ layers: ectoderm, mesoderm, and endoderm.

• A. All over the egg
• B. On one side
• C. Both the sides
• D. Centre

Explanation: In telolecithal eggs, the yolk is found predominantly on one side of the egg, forming a distinct yolk mass.

• A. Horizontal
• B. Partial/parietal
• C. Total
• D. Spiral

Explanation: Meroblastic cleavage is partial or parietal cleavage. In eggs with a large amount of yolk, like those of birds and reptiles, only a…

• A. Ectoderm
• B. Mesoderm
• C. Endoderm
• D. Ectoderm and Mesoderm

Explanation: The eye lens is primarily formed from the ectoderm. During early embryonic development, a portion of the ectoderm on the surface of the…

• A. Nucleocytoplasmic ratio remains unchanged
• B. Size does not increase
• C. There is less consumption of oxygen
• D. None of these

Explanation: Let's evaluate each statement about cells during cleavage to determine what is false: a.

• A. Alecithal
• B. Microlecithal
• C. Mesolecithal
• D. Macrolecithal

Explanation: a. Alecithal: Alecithal eggs have a very small amount of yolk, and most of the cytoplasm is evenly distributed throughout the egg.

• A. Secondary oocyte stage
• B. Primary oocyte stage
• C. Oogonial stage
• D. All of these

Explanation: The correct answer is: a. Secondary oocyte stage Now, let's explain all the options along with the reasons: a.

• A. Condoms
• B. IUDs
• C. Lippes loop
• D. Tubectomy

Explanation: a. Condoms: Condoms are a popular method of contraception. They are physical barriers made of latex, polyurethane, or other materials.

• A. Embryo only, upto 8 cell stage
• B. Either zygote or early embryo upto 8 cell stage
• C. Embryo of 32 cell stage
• D. Zygote only

Explanation: In in vitro fertilization, the fertilized eggs are grown for about 2 days usually upto 2 to 8 cell stage.

• A. dN/dt = rN
• B. dt/dN = rN
• C. dN/rN = d
• D. rN/dN = d

Explanation: Nearly all populations will tend to grow exponentially as long as there are resources available.

• A. Biotic potential
• B. Fertility rate
• C. Carrying capacity
• D. Birth rate

Explanation: The biotic potential is defined as the physiological capacity of organisms to produce their offspring under natural conditions.

• A. Four viable sperms
• B. Two viable sperms
• C. One viable sperm
• D. Three viable sperms

Explanation: Spermatogonia differentiates into primary spermatophytes which undergo meiotic division to form 2 secondary spermatocytes which gives 4…

• A. Oogonia
• B. Primary oocytes
• C. Secondary oocytes
• D. Ova

Explanation: Germ cells in the ovary produce many oogonia which divide mitotically to form primary oocytes.