How can we tell whether a thing is living or non-living?
We can understand whether an entity is living or non-living by looking at its characteristics. If an entity displays all the common features of living things at once, that entity is living.
Common Characteristics of Living Things
Common features of living things are growth, nutrition, movement, reproduction, respiration, sensitivity, excretion, and death.
Growth means the development of living things. Some organisms stop growing when they reach a certain size. Others continue to grow throughout their lives. Under favorable conditions, plants continue to grow throughout their lives. In humans and animals, growth stops after a certain period of time.
Living things need nutrition to survive and thrive. They get their energy from food.
Animals perform movements such as moving, running, walking, leaping, crawling, swimming, and flying. The snake moves by crawling, the birds flying, the fish swimming, the cat walking. Plants cannot move. Plants turn their leaves and flowers towards the light. It directs its roots to places where there is water in the soil. Sunflowers turn their leaves and flowers towards the Sun.
Living things reproduce in order for their own species to continue. Plants usually reproduce by seeds, some animals by giving birth, some by eggs.
Living things produce energy from food. They need oxygen for this. They breathe to provide oxygen. Humans and some animals breathe with their lungs. Plants breathe through their leaves. The respiratory organ of fish is the gills.
All living things are sensitive, that is, they react to their environment. All plants are sensitive to light and water. The sunflower responds by turning its direction towards the Sun. The dandelion flower responds by closing its leaves when touched. Animals recognize their environment through the senses of sight, hearing, touch, taste, and smell and respond to stimuli in the environment.
Living things excrete to remove unnecessary substances from their bodies. Plants excrete by sweating and shedding their leaves. Animals excrete through urine, feces, and perspiration.
Living things live for a certain period of time from the moment they are born, and then they die. Elephant, cat, plane tree, violet, and human have a certain life span.