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Learning Objective

Identify the characteristics of living matter.

All living things, animals, and plants are organisms that undergo chemical processes by which they sustain life and regenerate cells. The difference between animals and plants is that animals have sensations, the power of voluntary movement, and they require oxygen and organic food. Plants require only carbon dioxide and inorganic matter for food and have neither voluntary movement nor special sensory organs.

In man, some of the characteristic functions necessary for survival include digestion, metabolism, and homeostasis. Digestion involves the physical and chemical breakdown of food into its simplest forms. Metabolism is the process of absorption, storage, and use of these foods for body growth, maintenance, and repair. Homeostasis is the body's self-regulated control of its internal environment. It allows the organism to maintain a state of constancy or equilibrium, in spite of vast changes in the external environment.

The human body is broken down into various levels of organization, the chemical, organelle, cellular, tissue, organ, organ system, and the organism levels.

Chemical level: The chemical level is the beginning level of the organization of the body. There are more than a hundred different chemical building blocks of nature called atoms (tiny spheres of matter so small they are invisible). Every living thing in the universe, including the human body, is composed of atoms.

 Organelle level: Organelles consist of chemical structures organized within larger units (cells) to perform a specific function. It is within a cell and allows the cell to live; without it the cell is unable to live.

Cellular level: Cells consist of the smallest and most numerous structural unit that possess and exhibits the basic characteristics of living matter. Although all cells have certain features in common, they specialize to perform unique functions.

Tissue level: Tissues are a group of many similar cells that all develop together from the same part of an embryo and all perform a certain function. Tissues are the “fabric” of the body. Epithelial and muscular tissues are examples.

Organ level: Organs are more complex than tissue. An organ is defined as a structure made up of several different kinds of tissues arranged so that, together, they can perform a special function. Each organ is unique in shape, size, appearance and placement in the body. The heart, lungs, spleen, and liver are examples of some of the organs found in the human body.

System level: Systems are the most complex of the organizational units of the body. The system level of organization involves varying numbers of kinds of organs arranged so that, together, they can perform complex functions for the body. There are 11 major systems that make up the human body: integumentary, skeletal, muscular, nervous, endocrine, circulatory, lymphatic, respiratory, digestive, urinary, and reproductive.

Organism level: Organisms, such as the human body, are a collection of interactive parts that are capable of surviving in hostile environments, with the ability to reproduce and repair damaged parts.

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David L. Heiserman, Editor

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Revised: June 06, 2015