Biology 2014 JAMB Past Questions - Question 15: A circulatory system is very essential in mammals but not in smaller organisms like Amoeba because

Correct Answer

B

Explanation

In smaller organisms such as protozoans of Amoeba , -Paramecium etc., the surface area represented by plasma or cell membrane is large while the volume as represented by the size of the organism or number of cells that make up the organism is small. Therefore, diffusion as one of the processes of distributing materials between an organism and its surrounding environment or medium is enough to allow adequate oxygen to get into the organism. The oxygen is used to breakdown or oxidize food to release energy and eliminate carbon IV oxide as metabolic waste by the same diffusion However, multicellular organisms such as mammals have specialised systems such as circulatory system for distributing materials