Explanation

Main Parts of a Cell:

Last verified on 09-05-2026

Explanation

• Syncytial theory explains the origin of multicellular animals (metazoa).
• It suggests that metazoans evolved from a multinucleated single cell (syncytium).
• Cell membranes later formed around nuclei to create separate cells.
• It explains early evolution of multicellular organisms.

Last verified on 04-06-2026

Explanation

• In dragonfly, the circulatory system does not transport gases.
• Gas exchange occurs through a tracheal system.
• Air directly reaches tissues through spiracles and tracheae.
• Blood is not involved in oxygen transport.

Last verified on 04-06-2026

Explanation

• Bronchioles are the narrowest and most numerous air passages in lungs.
• They branch from bronchi and lead to alveoli.
• They help in controlling airflow in the lungs.
• They are an important part of the respiratory system.

Last verified on 04-06-2026

Explanation

• Zymogen cells are found in the stomach lining.
• They secrete inactive enzyme precursors called zymogens.
• These are activated into digestive enzymes in the stomach.
• They help in protein digestion.

Last verified on 04-06-2026