To live in groups is beneficial because :

• feeling of security
• can obtain food easily
• Partner is available for mating
• All the above

Ants give information to their companions :

• by dancing
• by secretion of pheromones
• by making sound
• by defecating

Population density is denoted by the symbol

• N
• D
• M
• D

The number of births during a given period in the
population that are added to the initial density is 

 :

• Natality
• Mortality
• Migration
• Immigration