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# 1.7: Organization of Living Things

Difficulty Level: At Grade Created by: CK-12
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Organization of Living Things. What does this mean?

We know it all starts with the cell. And for some species it ends with the cell. But for others, the cells come together to form tissues, tissues form organs, organs form organ systems, and organ systems combine to form an organism.

### Levels of Organization

The living world can be organized into different levels. For example, many individual organisms can be organized into the following levels:

• Cell : Basic unit of all living things.
• Tissue : Group of cells of the same kind.
• Organ : Structure composed of one or more types of tissues.
• Organ system : Group of organs that work together to do a certain job.
• Organism : Individual living thing that may be made up of one or more organ systems.

Examples of these levels of organization are shown in Figure below .

An individual mouse is made up of several organ systems. The system shown here is the digestive system, which breaks down food into a form that cells can use. One of the organs of the digestive system is the stomach. The stomach, in turn, consists of different types of tissues. Each type of tissue is made up of cells of the same type.

There are also levels of organization above the individual organism. These levels are illustrated in Figure below .

• Organisms of the same species that live in the same area make up a population . For example, all of the goldfish living in the same area make up a goldfish population.
• All of the populations that live in the same area make up a community . The community that includes the goldfish population also includes the populations of other fish, coral, and other organisms.
• An ecosystem consists of all the living things in a given area, together with the nonliving environment. The nonliving environment includes water, sunlight, and other physical factors.
• A group of similar ecosystems with the same general type of physical environment is called a biome .
• The biosphere is the part of Earth where all life exists, including all the land, water, and air where living things can be found. The biosphere consists of many different biomes.

This picture shows the levels of organization in nature, from the individual organism to the biosphere.

#### Diversity of Life

Life on Earth is very diverse. The diversity of living things is called biodiversity . A measure of Earth’s biodiversity is the number of different species of organisms that live on Earth. At least 10 million different species live on Earth today. They are commonly grouped into six different kingdoms. Examples of organisms within each kingdom are shown in Figure below .

Diversity of life from Archaebacteria to Plants and Animals.

### Summary

• Many individual organisms can be organized into the following levels: cells, tissues, organs, and organs systems.
• An ecosystem consists of all the populations in a given area, together with the nonliving environment.
• The biosphere is the part of Earth where all life exists.
• The diversity of living things is called biodiversity.

### Practice

Use this resource to answer the questions that follow.

• http://www.hippocampus.org/Biology $\rightarrow$ Biology for AP* $\rightarrow$ Search: Community Ecology: Overview
1. What is the biological definition of a community?
2. What is species diversity?
3. What type of area may have high species diversity? What type of area may have low species diversity?

### Review

1. Describe the levels of organization of a complex, multicellular organism such as a mouse, starting with the cell.

2. Explain how a population differs from a community.

3. What is biodiversity?

### Vocabulary Language: English Spanish

biodiversity

biodiversity

The variety of life and its processes; including the variety of living organisms, the genetic differences among them, and the communities and ecosystems in which they occur.
biosphere

biosphere

Part of Earth where all life exists, including land, water, and air.
cell

cell

Basic unit of structure and function of living things.
organ

organ

Structure composed of more than one type of tissue that performs a particular function.
organ system

organ system

Group of organs that work together performing a specific function.
organism

organism

An individual living thing.
tissue

tissue

Group of cells of the same kind that perform a particular function in an organism.
population

population

All the organisms of the same species that live in the same area.

Feb 24, 2012

Dec 29, 2014