What Characteristics Make a Living Thing an Animal?

Movement

• One of the most obvious differences between animals and other forms of living things, but especially plants, is the ability to move, often long distances and with little relative effort expended in the process. Plants, because they extract nutrients from the ground, are tethered to a single spot and cannot move to a different spot if it suits them. Some plants, like the Touch-Me-Not plant, can rapidly move its leaves in response to environmental queues, but cannot move its location.

Cell Walls

• One of the reasons that animals find it so easy to move is that they lack the rigid cell walls typically found in plants. Animals usually rely on a skeleton, exoskeleton or a similarly rigid body structure to give their body shape, but plants rely on their rigid cell walls for this. This is one of the most fundamental physical differences between animals and many other living things.

Sustenance

• Another essential difference between animals and other forms of living things are animal's reliance on the tissue of other living things for sustenance. Plants, for example, rely on minerals extracted from the ground and photosynthesis from the sun to provide what they need to survive. Many animals, in turn, rely on plants to provide what they need to survive, or on other animals to provide what they need to survive. Some animals, like humans, can survive on other animals, on plants, or a mixture of both.

Multi-Cellular

• One of the characteristics that separates animals from other, smaller things which are not plants, like bacteria, for example, is that they are multi-cellular. The primary difference between single celled organisms and multi-celled organisms is complexity. Single-celled organisms must contain everything needed to survive within that one cell, whereas multi-celled organisms can have specialized cells that are created for a specific purpose, which allows for larger and more complex organisms.