The nucleus is an organelle found in eukaryotic cells. Inside its fully enclosed nuclear membrane, it contains the majority of the cell's genetic material. This material is organized as DNA molecules, along with a variety of proteins, to form chromosomes.
 
        
             
        
        
        
Answer:
The evolution of the heart is based on the separation of oxygenated blood from deoxygenated blood for efficient oxygen transport. pisces have a dual chambered heartwhile reptiles and amphibians are having a three chambered finally aves and mammals have four chambered hearts. 
Explanation:
please mark as brilliant answer 
 
        
             
        
        
        
Answer:d
Explanation:nematodes are round worms.they live in sea ,land or freshwater habitat.they have an hydrostatic skeleton for movement. They possess a flexible and non-cellular cuticle.They are known for shedding their cuticle. This process is necessary for their growth.an example of nematode is the hookworm.
Arthropods are the most diverse phylum in the animal kingdom.they have jointed appendages and an exoskeleton containing chitin.they may be segmented into head and truck, head, thorax and abdomen or cephalothorax and abdomen.they tend to shed of their exodkeleton during the process of metamorphosis . examples of arthropods include ticks, cockroaches