All Free Biology MCQs with Answers

• A. unipotent
• B. multipotent
• C. totipotent
• D. pluripotent

Explanation: Totipotent is an immature cell that is capable of giving rise to any cell type or even a complete embryo.

• A. ectoderm
• B. mesoderm
• C. endoderm
• D. all of the above

Explanation: Muscles develop from the mesoderm, which is one of the three primary germ layers in the early embryo.

• A. Ectodermal
• B. Endodermal
• C. Mesodermal
• D. Preformed

Explanation: The correct answer is Endodermal. The endoderm, one of the three primary germ layers formed during embryonic development, is responsible…

• A. 2nd week
• B. 3rd week
• C. 7th week
• D. 5th week

Explanation: Implantation is the process of the blastocyst embedding into the endometrial lining of the uterus, which typically occurs in Week 2 of…

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

Explanation: The embryonic mass is the mass of cells inside the embryo that will eventually give rise to the definitive structures of the fetus.

• A. X selection
• B. D selection
• C. L selection
• D. C selection

Explanation: Trophoblast cells begin to display adhesion molecules on their surface soon after the blastocyst hatching.

• A. First trimester
• B. Second trimester
• C. Third trimester
• D. Both A and B

Explanation: During pregnancy, the fetal sex becomes apparent during the second trimester, which is around the 13th to 16th week of pregnancy.

• A. A
• B. B
• C. C
• D. D

Explanation: The primitive streak is a key structure that forms during early embryonic development and marks the beginning of gastrulation.

• A. Brain
• B. Muscles
• C. Skeleton
• D. Bones

Explanation: The brain is formed from ectodermal tissue. During embryonic development, the ectoderm is one of the primary germ layers that gives rise…

• A. Multicellular fertilised egg
• B. Single fertilised egg
• C. Hollow blastula
• D. Gastrula

Explanation: All animals, from simple sponges to complex humans, begin their lives as a single fertilized egg cell, also known as a zygote.

• A. Urea
• B. Uric acid
• C. Creatinine
• D. Ammonia

Explanation: Urea is the major and immediate nitrogenous waste product of protein metabolism in humans and most mammals.

• A. Kidney
• B. Liver
• C. Spleen
• D. Lungs

Explanation: b) Liver:This option states that urea formation occurs in the liver. This statement is correct.

• A. urine
• B. ammonia
• C. uric acid
• D. urea

Explanation: Malphigian tubules are specialized excretory organs found in insects like cockroaches.

• A. Spleen
• B. Kidneys
• C. Liver
• D. Pancreas

Explanation: The liver is the primary organ where surplus amino acids are broken down.

• A. Anaemia
• B. Diabetes
• C. Rickets
• D. Jaundice

Explanation: The correct answer is Jaundice. Jaundice is characterized by a yellowing of the skin, eyes, and mucous membranes due to elevated levels of…

• A. Ammonia
• B. Urea
• C. Uric acid
• D. Acetic acid

Explanation: Birds excrete nitrogenous waste primarily in the form of uric acid. This adaptation is crucial for conserving water, as uric acid requires…

• A. Coxal glands
• B. Flame cells
• C. Malpighian tubules
• D. Nephridia

Explanation: Crustaceans are members of the subphylum Crustacea (phylum Arthropoda), a group of invertebrate animals consisting of some 45,000 species…

• A. Thyroid gland
• B. Pituitary gland
• C. Adrenal gland
• D. Rectal gland

Explanation: The correct answer is the rectal gland, which is a specialized salt-secreting organ found in cartilaginous fishes like sharks.

• A. Onion
• B. Potatoes
• C. Guava
• D. Tomatoes

Explanation: Ovalates are abundantly present in tomatoes. They are a type of organic acid found in various fruits and vegetables, including tomatoes.

• A. Specific Temperature
• B. Specific pH
• C. Specific Co-enzyme
• D. All the above

Explanation: The correct answer is 'All the above' because enzymes require specific conditions to function at their best.