The carrying capacity depicts the largest population of an organism which can be easily sustained and supported by an ecosystem. If the population increases beyond carrying capacity, the ecosystem destabilizes as it do not have sufficient resources to feed/nourish such large population.
Population density is the number of individual living in an ecosystem in a given unit area. Thus, it is nothing but the population living in a confined boundary. Thus, the maximum population density or the maximum number of organism in a given unit area of an ecosystem that can be easily supported by the ecosystem is called the carrying capacity of the ecosystem.
Most autotrophs use a process called photosynthesis to make their food. In photosynthesis, autotrophs use energy from the sun to convert water from the soil and carbon dioxide from the air into a nutrient called glucose. Glucose is a type of sugar. The glucose gives plants energy