Answer:
planetesimal is (astronomy) any of many small, solid astronomical objects, that orbit a star and form protoplanets through mutual gravitational attraction while planet is (astronomy) a body which orbits the sun directly and is massive enough to be in hydrostatic equilibrium (effectively meaning a spheroid) 
 
        
             
        
        
        
Comparison of meiosis and mitotic cell division. As in the previous figure, only one pair of homologous chromosomes is shown. In meiosis, after DNA replication, two nuclear (and cell) divisions are required to produce the haploid gametes.
        
             
        
        
        
It will cause the cell to shrivel up. Hypotonic is when there is higher concentration of water inside the cell while hypertonic is less concentration of water inside the cell
        
             
        
        
        
<span>The head of the sperm contains the necessary enzymes to help it penetrate the oocyte. The sperm cell is anatomically structured to have four parts which are the head, neck, midpiece, and a tail. Inside the head of the sperm are densely coiled chromatin fibers that contain the nucleus for helping the sperm penetrate the female fertilized egg necessary for reproduction.</span>