Living things are made up of cells, maintain homeostasis, move, feed, grow, reproduce, respire, respond to environmental stimuli and excrete waste, while nonliving things do not have all of these characteristics. Biologists define life using a body of traits that living organisms share.
Multicellular living organisms are composed of building blocks called cells. Cells form tissues, which form organs. Organs form organ systems that work to form an entire organism.
Nonliving things do not undergo homeostasis as living things do. Homeostasis is the process of maintaining the internal environment within an organism despite changes in the external environment. All living things move in some way. Plants shift their positions to keep up with the sunlight in surrounding areas. Living organisms require nutrition to survive.
Nutrients give them the energy they need to develop. Using that energy, they grow and change. For example, a seedling sprouts into a plant, and a frog morphs into a tadpole. Eating also gives organisms energy to undergo respiration. The remains of food are expelled as waste from the living organism's body. Living things also pass on their genetic information by reproducing.
Living things die and, without reproduction, disappear. Reproduction takes place either sexually or asexually, the former by the combination of genes from two different parents and the latter by an organism splitting into two or more different organisms. The resulting organisms are more closely identical to the parent in asexual reproduction than in the case of sexually reproducing organisms. Many organisms also grow through an accumulation of new cells that they produce, a process that does not occur in nonliving entities.
Another key difference between living and nonliving things is that living things respond to their environment. Animals become startled by loud noises and cry out if injured. However, nonliving things, such as rocks, make no response to their surroundings regardless of what occurs around them.