All Free Biology MCQs with Answers

1181. Body is globular in_________?

• A. Cake urchin
• B. Sea Urchin
• C. Sea cucumber
• D. Brittle star

Explanation: A sea urchin has a compact, rounded or globular body enclosed by a rigid test and movable spines. Cake urchins are flattened, sea cucumbers are elongated, and brittle stars have a distinct central disc with slender arms. The likely mistake is choosing a because both are echinoderms, despite their different body shapes.

1182. Body is eel like in___________?

• A. Cyclostomata
• B. Chondrichthyes
• C. Osteichthyes
• D. None of these

Explanation: Cyclostomes, such as lampreys and hagfishes, have long, eel-like bodies and lack paired fins. Chondrichthyes and Osteichthyes include many body forms, but their typical textbook distinction is cartilaginous and bony fishes, not an eel-like body. Students may choose c because it includes some elongated bony fishes, but the group characteristic points to Cyclostomata.

1183. Notochord is present throughout life in___________?

• A. Urochordates
• B. Cephalochordates
• C. Chordates
• D. Vertebrates

Explanation: In cephalochordates, such as Amphioxus, the notochord extends from the head region to the tail and remains present throughout life. In urochordates it is mainly a larval feature, and in vertebrates it is largely replaced by the vertebral column. Students may choose c because all listed groups are chordates, but not every chordate retains the notochord for life.

1184. Which of the following fishes contained lungs?

• A. Lamprey
• B. Perch
• C. Plaice
• D. Dipnoi

Explanation: Dipnoi are lungfishes, named for their functional lungs that allow them to breathe atmospheric air, especially when water oxygen is low. Lampreys, perch, and plaice primarily use gills and are not lungfishes. The likely trap is a because lampreys are unusual jawless fishes, but they do not possess lungs.

1185. Which of the following are motile zooids in cnidarians?

• A. Polyps
• B. Medusae
• C. Both of these
• D. None of these

Explanation: Medusae are the free-swimming, motile zooid form of cnidarians, whereas polyps are generally attached and cylindrical. Students may choose c because many cnidarians show alternation between polyp and medusa forms, but only the medusa is the motile form in this comparison.

1186. In sponges fertilization takes place in____________?

• A. Ectoderm
• B. Mesenchyme
• C. Endoderm
• D. Uterus

Explanation: In sponges, sperm released into the water are captured and carried into the mesenchyme or mesohyl, where fertilization occurs. This internal gelatinous region contains the reproductive cells and amoeboid transport cells. Students may choose c by assuming fertilization occurs in the digestive lining, but sponge fertilization takes place in the mesenchyme.

1187. 80% of the food of sponges consists of__________?

• A. Detrital organic particles
• B. Zooplankton and small animals
• C. Phytoplanktons
• D. all of these

Explanation: Sponges obtain most of their food by filtering fine detrital organic particles from the water, which are taken up by collar cells and other feeding cells. Zooplankton and phytoplankton can also be consumed, but they are not the category identified here as making up about 80 percent. Students may choose d because all listed materials can occur in the diet, confusing possible food items with the major proportion.

1188. The single main opening of the sponge cavity is____________?

• A. Osculum
• B. Ostia
• C. Spongocoel
• D. None of these

Explanation: The osculum is the single main outlet through which water leaves a sponge after passing through its canals and spongocoel. Ostia are numerous small incoming pores, while the spongocoel is the internal cavity rather than an opening. Students commonly choose b because ostia are also openings, but they are many small inlets, not the main outlet.

1189. Sperms released in water are carried to the mesenchyme in sponges by__________?

• A. Amoeboid cell
• B. Stipules
• C. Spicules
• D. Spines

Explanation: Amoeboid cells in the sponge mesohyl capture sperm from the water and transport them to the region containing eggs. Spicules form part of the skeleton, while stipules and spines are not the sperm-transport cells. Students may choose c because spicules are prominent sponge structures, but they provide support rather than transport.

1190. The skeleton of sponges is made up of___________?

• A. Calcium
• B. Silica
• C. Both of these
• D. None of these

Explanation: Sponge skeletons may contain calcium carbonate spicules or silica spicules, depending on the group, and some also contain spongin fibres. Since both calcium and silica occur as skeletal materials, option c is correct. Students may choose a or b by remembering only one major sponge type instead of the diversity among sponge classes.