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Levels of Organization

All living things are organized into several basic levels. The most basic level of organization for all living things is the cell. In unicellular (single-celled) organisms, a single cell performs all life functions. Multicellular (many-celled) organisms have various levels of organization. Individual cells may perform specific functions as well as work together with other cells for the good of the entire organism. These cells become dependent on one another.
Within an organism, groups of cells with similar functions combine to make up tissues. A tissue is a group of cells which work together to perform a specific activity.
Groups of tissues with similar functions combine to make up organs.
Groups of organs working together combine to make up organ systems.

The Human body has 11 organ systems - circulatory, digestive, endocrine (glands), excretory (urinary), immune (lymphatic), integumentary (skin), muscular, nervous, reproductive, respiratory, and skeletal.

Several organ systems working together combine to make up an organism. An organism is an entire living thing that can carry out all basic life processes. This means the organism can take in materials, release energy from food, release wastes, grow, respond to the environment, and reproduce.

Examples of organisms include: bacteria, amoeba, mushroom, sunflower, human (while an organism may be unicellular, most organisms are made up of more than a single cell)

1. Using the following terms, show the correct sequence from simplest to most complex.

Brain – Nerve cell – Nerve tissue – Human – Nervous system

Highlight the box below to check your answer.
Nerve cell-Nerve tissue-Brain-Nervous System-Human

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Updated October 24, 2008 by: Glen Westbroek

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