Population is the number of individuals of a particular species in an area. Animal and plant populations depend on many things for survival. Limiting factors like the availability of food, water and shelter can impact an organism's population.
In nature, populations of animals and plants are linked together like a puzzle. So form the population dynamics. The pieces of the plant and animal puzzle depend on each other to form a complete picture. If something is wrong with any of the pieces, it affects the whole puzzle.