All Free Biology MCQs with Answers

1341. Who discovered the peptic ulcer causing bacteria H.PYLORI?

• A. Robert Hook
• B. James parkinson
• C. Dr Barry Marshall and dr Robin Warren
• D. None of these

Explanation: Barry Marshall and Robin Warren discovered the association between Helicobacter pylori and peptic ulcer disease, showing that many ulcers are caused by bacterial infection rather than only stress or excess acid. Their work changed the treatment of ulcers toward antibiotic therapy. Students may choose Robert Hooke because he is famous in biology, but Hooke studied cells and had no role in discovering H. pylori.

1342. Chemical substances used on living tissues that inhibit the growth of micro organism are called___________?

• A. Antiseptics
• B. Disinfectants
• C. Antibiotics
• D. Vaccines

Explanation: Antiseptics are chemicals applied to living tissues, such as skin, to inhibit or kill microorganisms. Disinfectants are used on non-living surfaces, so choosing them confuses the treatment of tissues with the sterilization of objects.

1343. Who developed the vaccine against anthrax?

• A. Louis Pasteur
• B. Edward Jennar
• C. Leuvenhoek
• D. Alexander Fleming

Explanation: Louis Pasteur developed an attenuated vaccine against anthrax and demonstrated its protective effect in livestock. Edward Jenner is the likely alternative because he developed the smallpox vaccine, not the anthrax vaccine.

1344. Germ theory of disease has________________postulates?

• A. 3
• B. 5
• C. 4
• D. 6Standardized & Admissions Tests

Explanation: Koch's germ theory is expressed through four postulates linking a specific microorganism with a specific disease: presence in diseased hosts, isolation in pure culture, reproduction of disease, and re-isolation. Students may choose three by omitting the final re-isolation step, but the classical formulation contains four.

1345. Which of the following statement is incorrect regarding germ theory of diseases postulated by Robert Koch_____________?

• A. A specific organism can always be found in association with a given disease
• B. The organism can be isolated and grown in pure culture in the laboratories
• C. The pure culture cannot produce the disease when inoculated into susceptible animal however the causative organism isolated from pure culture can do so.
• D. It is possible to recover the organism in pure culture from the experimentally infected animals

Explanation: Koch's third postulate requires that the isolated organism, when introduced into a healthy susceptible host, reproduce the same disease. A pure culture contains only that isolated organism, so saying it cannot cause disease makes option c incorrect. Students may choose b by confusing isolation of an organism with proving that it causes disease.

1346. Who coined the term Animalcules for microorganisms like Bacteria and protozoa______________?

• A. Robert Koch
• B. Louis Pasteur
• C. Alexander Fleming
• D. Leeuwenhoek

Explanation: Antonie van Leeuwenhoek first observed microorganisms with his improved microscopes and called them animalcules, meaning tiny animals. Students may select Robert Koch because he is strongly associated with bacteria and disease, but Koch worked much later and did not coin this term. The submitted key matches.

1347. The word Archaeobacteria (a division of bacteria) derived from Greek means___________?

• A. True bacteria
• B. False bacteria
• C. Recent bacteria
• D. Ancient bacteria

Explanation: The prefix archae- comes from the Greek word meaning ancient or primitive, so Archaebacteria means ancient bacteria. Students may choose true bacteria because bacteria are commonly described as prokaryotes, but true bacteria are eubacteria, not archaebacteria. The submitted key matches.

1348. In which of the following pigments major energy reserves and cell wall are like plants?

• A. Rhodophyta
• B. Chlorophyta
• C. Phaeophyta
• D. Chrysophyta

Explanation: Chlorophyta, or green algae, contain chlorophyll a and b, store food mainly as starch, and commonly have cellulose-rich cell walls, features resembling green plants. Students may choose Phaeophyta because brown algae are also large and plant-like, but their stored food and pigments differ from those of green plants. The intended answer is b.

1349. Which of the following statement is incorrect about algae______________?

• A. Their zygote unlike plants is protected by parental tissue
• B. Their classification is based on pigment composition
• C. Most of them have different morphological forms in-different stages of their life cycle
• D. Almost all of them are aquatic

Explanation: Algal zygotes generally develop outside the parental body and are not protected by parental tissues as plant embryos are, making statement a incorrect. Students may choose c because algal life cycles can show striking changes in form, but this is a genuine characteristic of many algae. The submitted key matches.

1350. Most of the photosynthesis on earth is carried by__________?

• A. Kelps
• B. Gymnosperms
• C. Angiosperms
• D. Algae

Explanation: Algae, especially marine and freshwater phytoplankton, carry out a very large share of Earth's photosynthesis because they are abundant and spread throughout aquatic environments. Students may choose angiosperms because they dominate visible land vegetation, but terrestrial plant abundance does not mean they perform most global aquatic photosynthesis. The submitted key matches.