-The nucleus is the cell organelle whose function resembles the function of the brain in higher animals.
-The Nucleus is the largest organelle in a cell. It contains a dense structure called the Nucleolus and is surrounded by the Nuclear Envelope.
-It stores the cell's hereditary material, or DNA, and coordinates the cell's activities, which include growth, intermediary metabolism, protein synthesis, and reproduction, just like the brain which controls or the activities of a higher organism.
Fish are a class of aquatic vertebrates. The combination of gills, fins and the fact that they live only in the water make fish different from all other animals.
Chloroplasts are found in plant cells only because chloroplasts contain chlorophyll which is essential for photosynthesis. Chlorophyll traps sunlight and uses it to prepare food for plants by the process of photosynthesis.