All Free Biology MCQs with Answers

1171. Pseudocoelem develops from____________?

• A. Blastopore
• B. Plastoquinone
• C. Blastocoel
• D. Splitting of mesoderm

Explanation: A pseudocoel is formed when the embryonic blastocoel persists as the body cavity, with mesoderm lining the organs but not completely lining the cavity. Students may choose splitting of mesoderm, which forms a true coelom rather than a pseudocoel.

1172. Excretory system of platyhlminthes consists of___________?

• A. Nephridia
• B. Flame cells
• C. Malpighian tubules
• D. Nephrons

Explanation: Flatworms remove excess water and wastes through protonephridia containing flame cells, whose beating cilia drive fluid through tubules. Students may choose nephridia because annelids use them for excretion, but nephridia are not the excretory structures of platyhelminths.

1173. All of the following coelenterates show alternation of generation except:

• A. Hydra
• B. Obelia
• C. Aurelia
• D. None of these

Explanation: Hydra remains in the polyp form and reproduces asexually by budding, so it does not show alternation between polyp and medusa generations. Students may choose Aurelia because its life cycle is complex, but Aurelia does show alternation of generations, as does Obelia.

1174. Enteron in coelenterates acts as___________?

• A. Digestive cavity
• B. Body cavity
• C. Transporting cavity
• D. all of these

Explanation: The enteron of coelenterates is the gastrovascular cavity, where digestion occurs and through which digested nutrients and materials are distributed because a separate circulatory system is absent. Students may choose only digestive cavity, but it also functions as the body cavity and as a transport space.

1175. Porifera range in size from__________?

• A. Few millimeter wide to more than one meter tall
• B. Few centimeter wide to more than one meter tall
• C. Few decimeter wide to more than one meter tall
• D. One meter wide to more than millimeter tall.

Explanation: Sponges show a wide size range, from only a few millimetres in width to species exceeding one metre in height. The centimetre range in option b is too large for the smallest sponges, while option c and d do not describe the usual range.

1176. Coelom is lined by__________?

• A. Parietal mesoderm
• B. Visceral mesoderm
• C. Mesoderm
• D. Both A & B

Explanation: A coelom is a body cavity completely lined by mesoderm, with parietal mesoderm against the body wall and visceral mesoderm around the organs. Therefore, both layers line it. Students may choose c because mesoderm is the general tissue involved, but it does not identify the two specific linings.

1177. Of the following which one is not the characteristic of Kingdom Animalia.

• A. All animals are ingestive heterotrophs
• B. All animals are eukaryotes
• C. All animals develop from the dissimilar gametes i.e. large sperm and small egg.
• D. It is largest kingdom.

Explanation: Animals develop from dissimilar gametes, but the egg is the large non-motile gamete and the sperm is the small motile gamete, not the reverse stated in option c. Students may choose d if they interpret largest kingdom by total biomass, but Animalia is commonly described as the largest kingdom by number of described species.

1178. _______ are the first group of invertebrates which have developed a closed circulatory system.

• A. Nematods
• B. Annelids
• C. Arthropods
• D. Molluscs

Explanation: Annelids are regarded as the first major invertebrate group with a closed circulatory system, in which blood remains within vessels. Arthropods have an open circulatory system, so students who associate greater structural complexity with closed circulation may choose c.

1179. Main blood vessel of arthropods usually:

• A. Lies on dorsal side
• B. Lies on ventral side
• C. Lies on lateral side
• D. Is not present

Explanation: Arthropods usually have a dorsal tubular heart or main blood vessel that pumps haemolymph forward and backward through the body. Students may choose b because blood vessels in vertebrates are often discussed along the ventral side, but arthropods have an open system with a dorsal vessel.

1180. Second largest phylum of invertebrates is____________?

• A. Porifera
• B. Arthropoda
• C. Mollusca
• D. Chordata

Explanation: Arthropoda is the largest animal phylum, and Mollusca is generally considered the second largest in number of described species. Chordata is much smaller, while Porifera is not the second-largest animal phylum. The likely trap is b, which identifies the largest rather than the second-largest phylum.