An illustration showing Levels of organization in a multicellular organism.

FIGURE 7–24 Levels of Organization From least complex to most complex, the levels of organization in a multicellular organism include cells, tissues, organs, and organ systems.

d

Levels of Organization The specialized cells of multicellular organisms are organized into tissues, then into organs, and finally into organ systems, as shown in Figure 7–24. A tissue is a group of similar cells that performs a particular function. Many tasks in the body are too complicated to be carried out by just one type of tissue. In these cases, many groups of tissues work together as an organ. For example, each muscle in your body is an individual organ. Within a muscle, however, there is much more than muscle tissue. There are nervous tissues and connective tissues too. Each type of tissue performs an essential task to help the organ function. In most cases, an organ completes a series of specialized tasks. A group of organs that work together to perform a specific function is called an organ system. For example, the stomach, pancreas, and intestines work together as the digestive system.

Analyzing Data

Mitochondria Distribution in the Mouse

Scientists studied the composition of several organs in the mouse. They found that some organs and tissues contain more mitochondria than others. They described the amount of mitochondria present as a percentage of total cell volume. The higher the percentage volume made up of mitochondria, the more mitochondria present in the cells of the organ. The data are shown in the graph.

Bar graph titled 'Mitochondria Distribution'.d

  1. Interpret Graphs What approximate percentage of cell volume in the mouse liver is composed of mitochondria?

  2. Calculate Approximately how much more cellular volume is composed of mitochondria in the left ventricle than in the pituitary gland?

  3. Infer There are four chambers in the mouse heart, the right and left ventricles, and the right and left atria. Based on the data given, which chamber, the left ventricle or left atrium, do you think pumps blood from the heart to the rest of the body? Explain your answer.

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Table of Contents

Miller & Levine Biology
About the Authors
Changing the World of Biology Education
Contents
Diversity of Life: A Visual Guide DOL•1–DOL•64
Labs and Activities
Features
UNIT 1 The Nature of Life
1 The Science of Biology
2 The Chemistry of Life
Unit Project
UNIT 2 Ecology
3 The Biosphere
4 Ecosystems and Communities
5 Populations
6 Humans in the Biosphere
Unit Project
UNIT 3 Cells
7 Cell Structure and Function
8 Photosynthesis
9 Cellular Respiration and Fermentation
10 Cell Growth and Division
Unit Project
UNIT 4 Genetics
11 Introduction to Genetics
12 DNA
13 RNA and Protein Synthesis
14 Human Heredity
15 Genetic Engineering
Unit Project
UNIT 5 Evolution
16 Darwin's Theory of Evolution
17 Evolution of Populations
18 Classification
19 History of Life
Unit Project
UNIT 6 From Microorganisms to Plants
20 Viruses and Prokaryotes
21 Protists and Fungi
22 Introduction to Plants
23 Plant Structure and Function
24 Plant Reproduction and Response
Unit Project
UNIT 7 Animals
25 Introduction to Animals
26 Animal Evolution and Diversity
27 Animal Systems I
28 Animal Systems II
29 Animal Behavior
Unit Project
UNIT 8 The Human Body
30 Digestive and Excretory Systems
31 Nervous System
32 Skeletal, Muscular, and Integumentary Systems
33 Circulatory and Respiratory Systems
34 Endocrine and Reproductive Systems
35 Immune System and Disease
Unit Project
A Visual Guide to The Diversity of Life
HOW TO USE THIS GUIDE
THE TREE OF LIFE
Bacteria
Protists
Fungi
Plants
Animals
Appendices
Appendix A Science Skills
Appendix B Lab Skills
Appendix C Technology & Design
Appendix D Math Skills
Appendix E Periodic Table
Glossary
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q, R
S
T
U
V
W
X, Y, Z
Index
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
Credits
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