All Free Biology MCQs with Answers

1601. The branch of science dealing with the classification of life forms is called: _____________?

• A. Genetics
• B. Taxonomy
• C. Archeology
• D. Paleontology

Explanation: Taxonomy is the branch of biology concerned with identifying, naming and classifying organisms. Students may choose paleontology because it studies ancient organisms and fossils, but fossil study is not the same as classification of all life forms. The available topic list has no taxonomy slug, so the closest general classification category is used.

1602. In human body 99% of total mass is formed of_____________?

• A. 16 Bio-elements
• B. 12 Bio-elements
• C. 10 Bio-elements
• D. 6 Bio-elements

Explanation: About 99% of the human body's mass is contributed by six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. The other bio-elements are essential but occur in much smaller quantities. Students may choose 12 or 16 bio-elements by confusing the number of biologically important elements with the six that contribute nearly all body mass.

1603. Nutrition in fungi is___________?

• A. Photosynthetic
• B. Chemosynthetic
• C. Completely parasitic
• D. Absorptive heterotrophs

Explanation: Fungi are absorptive heterotrophs: they secrete digestive enzymes onto food outside the body and absorb the soluble products. They cannot normally photosynthesize, and although many fungi are parasitic, not all are, so “completely parasitic” is too narrow. Students may choose that option because disease-causing fungi are familiar, but fungi also include decomposers and mutualistic species.

1604. Pigment present in red algae is_____________?

• A. fucoxanthin
• B. phycocyanin
• C. phycoerythrin
• D. bilirubin

Explanation: Red algae contain the red phycobilin pigment phycoerythrin, which absorbs green and blue light and helps them photosynthesise at greater water depths. A common mistake is phycocyanin, but it is the blue pigment especially associated with cyanobacteria and also occurs in some red algal species in smaller amounts.

1605. Which are the four most abundant elements in living cells ?

• A. carbon, oxygen, nitrogen, sulfur
• B. carbon, oxygen, hydrogen, nitrogen
• C. carbon, oxygen, sulfur, phosphorus
• D. carbon, sulfur, hydrogen, magnesium

Explanation: Carbon, hydrogen, oxygen and nitrogen are the four most abundant elements in living cells because they form carbohydrates, lipids, proteins and nucleic acids. Sulfur and phosphorus are important but occur in smaller overall amounts, so option a is a common distractor because sulfur is present in some proteins.

1606. Which one of them is a micro-molecule?

• A. Polysaccharide
• B. Protein
• C. Hemoglobin
• D. ATP

Explanation: ATP is a relatively small molecule made from adenine, ribose, and three phosphate groups, and it transfers energy directly in cells. Proteins, hemoglobin, and polysaccharides are macromolecules, so choosing protein or hemoglobin confuses a small metabolic molecule with a large biological polymer.

1607. Oxygen accounts for ____ % of totals human body mass?

• A. 65%
• B. 18%
• C. 10%
• D. 3%

Explanation: Oxygen makes up about 65% of human body mass because most body oxygen is present in water, which forms a large fraction of the body, along with oxygen in organic molecules. The 18% figure is close to the approximate contribution of carbon, so it is the likely distractor for students recalling the wrong major element.

1608. Out of 92 naturally occurring chemical elements how many are considered as bio-elements?

• A. 6
• B. 16
• C. 26
• D. 15

Explanation: Although many elements occur naturally, only about 16 are regarded as bio-elements because they are essential components of living matter and support cellular structure or metabolism. Students may choose 6, confusing the major elements with the complete list of essential bio-elements.

1609. On the basis of collected facts and figures, a scientist formulates a factitive statement called:

• A. Observation
• B. Research work
• C. Hypothesis
• D. Inductive Reasoning

Explanation: A hypothesis is a proposed, testable explanation or statement developed from observations and collected facts. Observation is the collection of information, while inductive reasoning is the process used to develop a general idea from specific observations. Students may choose inductive reasoning because it helps form the statement, but the statement itself is the hypothesis.

1610. Which of the following is an example of "molecule"?

• A. Chloroplast
• B. A Nerve Cell
• C. DNA
• D. Hydrogen

Explanation: DNA is a very large molecule made of repeating nucleotide units, and each nucleotide contains a sugar, phosphate group, and nitrogenous base. A chloroplast and nerve cell are cellular structures, while hydrogen is an element rather than a named molecule in this context. Students may choose hydrogen because hydrogen gas exists as H2 molecules, but the option normally refers to the element.