Content Benchmark L.8.B.4

Students know cells combine to form tissues that combine to form organs and organ systems that are specialized to perform life functions. E/S

The smallest unit of life is a single cell. A single-celled organism must perform all of the functions of life independently of other cells. In contrast, multicellular organisms have differentiated cells that perform specific tasks that collectively perform all of the functions of life.

Levels of Organization

Multicellular organisms exhibit many levels of organization starting with cells. Cells are differentiated, meaning that not all cells are identical within an organism. Each cell has the same genetic code (DNA) but not all genes are active within a cell. For example, a skin cell has a different structure and function than a liver cell. Therefore, these cells look different and perform a different task.

One type of cells working together to perform a specific function is called a tissue. Examples of tissue are muscle (Figure 3), nerve (Figure 4), epithelial (Figure 5), and connective tissues. These tissues are made of many cells performing a function together. Muscle tissues have the ability to contract and relax performing movement, nerve tissue responds to stimuli and conducts impulses, epithelial cells provide a continuous protective barrier between the body and the environment, and connective tissue supports and binds other tissues.

The heart is an example of an organ. It is made up of several types of tissues like muscle, nerve, and connective tissues working together to move blood around the body.

The next level of hierarchy is the organ system. An organ system is composed of several organs working together to perform a specific function. The heart is part of the circulatory system which heart works together with the veins, arteries, blood, and capillaries to transport oxygen and nutrients to all of the cells in an organism and carry away metabolic wastes.

Finally, several organ systems working collectively comprise the whole organism. Each system depends on the others to complete the activities of life. For example, the circulatory system is responsible for delivery of materials, including oxygen, around the body. Therefore, the circulatory system is linked with the respiratory system which absorbs oxygen from the air and transfers it to the bloodstream.

To review, multicellular organisms have multiple levels of organization. An organism is made up of several organ systems. Each organ system is made up of several organs that work together. Each organ is made up of several tissues working together. Finally, each tissue is made up of similar cells working together. Figure 9 illustrates this hierarchy within a frog starting with a muscle cell. This muscle cell works with other muscle cells to form smooth muscle tissue. The muscle tissue works with other tissues to form a heart which combines with other organs to form the circulatory system. Finally, the respiratory system works with other organ systems to form the frog.


Human Organ Systems

There are several organ systems that comprise the human body. Each organ system performs a function necessary for survival. However, organ systems do not work in isolation. The organ systems must interact with each other to complete whole organism activities necessary to remain alive. For example, the circulatory system functions to transports materials to body cells and remove metabolic wastes. These transported materials may have origins in the respiratory system (oxygen, carbon dioxide), endocrine system (hormones), digestive system (nutrients), immune system (white blood cells), and the excretory system (metabolic wastes).

The following table summaries the structure and function of the major organ systems of the human body.

Table 1. Summary of the Major Organ Systems of the Human Body

Organ system / Organs / Function
Circulatory / Heart, arteries, veins, blood / Transports oxygen, hormones, and nutrients to cells and removes metabolic wastes
Digestive / Mouth, esophagus, stomach, intestines, liver, pancreas / Breaks down food and absorbs nutrients
Endocrine / Pituitary, adrenal, thyroid, hypothalamus, and others / Coordinates the activities of the body including growth and metabolism
Immune / Lymph, lymph nodes and vessels, white blood cells / Removes foreign bodies from the bloodstream
Integumentary / Skin hair, nails, sweat glands / Provides barrier between body and outside environment
Muscular / Skeletal muscle, cardiac muscle, smooth muscle / Produces body movement
Nervous / Nerves, sense organs, brain, spinal cord / Relay electrical signals throughout the body, directs behavior and movement
Reproductive / Testes, ovaries, associated reproductive structures / Carries out reproduction
Respiratory / Lungs, nose, trachea / Captures oxygen and exchanges gasses
Skeletal / Bones, cartilage, ligaments / Provides protection and provides support for movement
Urinary / Kidneys, bladder, urethra / Removes metabolic wastes from the bloodstream and excrete from the body

For further detail on organ systems visit TIPS Benchmark L.12.B.2
Content Benchmark L.8.B.4

Students know cells combine to form tissues that combine to form organs and organ systems that are specialized to perform life functions. E/S

Common misconceptions associated with this benchmark

1.  Students incorrectly believe that digestion is the process that releases usable energy from food.

Students confuse digestion with cellular respiration. It is difficult for students to understand that digestion is only the breakdown of food, both mechanically and chemically, into absorbable substances necessary for growth and maintenance. Digestion begins in the mouth with chewing and the enzyme activity of saliva. Acid and different enzymes in the stomach continue the breakdown of macromolecules. The majority of digestion and absorption actually takes place in the small intestine. Nutrients pass through the wall of the small intestine and enter the blood stream. The large intestine absorbs water and stores feces for elimination from the body. Carbohydrates in the bloodstream are broken down into glucose and delivered to every cell in the body. Energy is derived from the glucose at the cellular level through the process of respiration.

For more information on digestion visit http://digestive.niddk.nih.gov/ddiseases/pubs/yrdd/

For more information on cellular respiration visit http://www.phschool.com/science/biology_place/biocoach/cellresp/intro.html

2.  Students incorrectly believe that respiration is synonymous with breathing.

Breathing refers to the process that brings about an exchange of gases between the organism and its environment. Respiratory tissue absorbs oxygen and expels carbon dioxide. On the other hand, respiration refers to the process that releases energy from food substances in living cells. At the primary level, students do not make the distinction between breathing as a physical process and respiration as a chemical process.

For further explanation of this misconception visit http://www.ied.edu.hk/apfslt/v8_issue1/boohk/boohk3.htm

For more information on cellular respiration visit http://www.biology.iupui.edu/biocourses/N100/2k4ch7respirationnotes.html

For more information on the process of breathing visit http://yucky.discovery.com/flash/body/pg000138.html

3.  Students incorrectly believe that organ systems work independently of each other.

Students usually learn the body systems in isolation and memorize the parts and function of each organ, but lack understanding of how the systems work together. For example, the circulatory system functions to transports materials to body cells and remove metabolic wastes. These transported materials may have origins in the respiratory system (oxygen, carbon dioxide), endocrine system (hormones), digestive system (nutrients), immune system (white blood cells), and the excretory system (metabolic wastes).

For information on how the body systems interact with the nervous system visit http://faculty.washington.edu/chudler/organ.html

An article on how organ systems communicate can be found at http://www.merck.com/mmhe/sec01/ch001/ch001d.html

4.  Students incorrectly think muscles are only used for voluntary physical actions like walking, running, or throwing.

“Skeletal muscles are probably most familiar to middle school students even though other types of muscles, cardiac and smooth, are essential for life functions. The heart muscle is composed of a different type of muscle cell (cardiac muscle cells) and beats to move blood throughout the body. Smooth muscle cells line blood vessels and the intestinal tract to help move blood or food through those passages. The tongue is made up of muscle cells that enable us to speak and is also an important part of the digestive system.”

An article on misconceptions associated with the muscular system can be found at

http://science.education.nih.gov/supplements/nih6/Bone/guide/info_musculo_skin-a.htm

5.  Students incorrectly think that muscles turn to fat if you quit exercising.

Students believe that if they stop exercising their muscles will turn into fat. Students must understand that muscle cells cannot change into adipose (fat) cells and understand the definition of a tissue. Cells are differentiated. This means that cells may differ from one another in structure and function but they retain that same function through out the life of the cell. Muscles cells and fat cells may increase or decrease in volume or quantity due to changes in nutrition and activity, but the cells do not convert from one form to another.

The following link provides and explanation of different types of human body cells http://www.cancerhelp.org.uk/help/default.asp?page=98

6.  Students do not relate the concept of tissues, organs, and organ systems to plants.

Students can easily identify roots, stems, and leaves in a plant but do not understand that plants are also made of cells organized into tissues, organs, and organ systems. For example, vascular plants have a circulatory system composed of xylem (transports water from the roots to the leaves) and phloem (transports sugars from the leaves to the rest of the plant) tissues that work together to circulate materials around a plant. Xylem is made up of two main types of cells: tracheids and vessel elements. Xylem also contains other kinds of cells, such as parenchyma, that function in structure and storage. Phloem is made up of sieve tube cells and companion cells, as well as parenchyma cells. Therefore, together xylem and phloem comprise the circulatory system of a vascular plant.

For more information on the vascular system of plants visit http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPLANTANAT.html


Content Benchmark L.8.B.4

Students know cells combine to form tissues that combine to form organs and organ systems that are specialized to perform life functions. E/S

Sample Test Questions

  1. Respiration is the process of

a. taking oxygen into our bodies and releasing carbon dioxide.

b. taking carbon dioxide into our bodies and releasing oxygen.

c. converting glucose into energy using oxygen

d. converting glucose into energy using carbon dioxide

  1. Which of the following best explains the interaction between the circulatory system and the respiratory system?

a. The respiratory system adds nutrients to the bloodstream which are delivered to the cells.

b. The respiratory system adds oxygen to the bloodstream which is delivered to the cells.

c. The bloodstream delivers oxygen to the lungs to be exhaled from the body.

d. The bloodstream delivers nutrients to the lungs to be converted to carbon dioxide.

  1. Which organ system is responsible for providing a barrier between the organism and the environment?
  2. Respiratory
  3. Nervous
  4. Digestive
  5. Integumentary
  1. Which human body system controls production of the hormones that regulate body functions?
  2. Digestive
  3. Endocrine
  4. Respiratory
  5. Skeletal

  1. Which organ system in humans performs the same function as shown in the plant in Figure 10?
  2. Circulatory
  3. Respiration
  4. Digestion
  5. Excretory

6.  Which of the following is the correct ranking of organizational hierarchy of organisms from simplest to most complex?

a.  cells, organs, tissues, organ systems, organisms

b.  cells, tissues, organs, organ systems, organisms

c.  tissues, cells, organs, organ systems, organisms

d.  tissues, organs, cells, organ systems, organisms

7.  Which two body systems work together to produce movement?

a.  circulation and skeletal

b.  muscular and excretory

c.  respiration and endocrine

d.  skeletal and muscular


Content Benchmark L.8.B.4

Students know cells combine to form tissues that combine to form organs and organ systems that are specialized to perform life functions. E/S

Answers to Sample Test Questions

1. (c)

2. (b)

3. (d)

4. (b)

5. (a)

6. (b)

7. (d)
Content Benchmark L.8.B.4

Students know cells combine to form tissues that combine to form organs and organ systems that are specialized to perform life functions. E/S

Intervention Strategies and Resources

The following is a list of intervention strategies and resources that will facilitate student understanding of this benchmark.

  1. Online research/writing activity

This lesson asks students to “use the internet and library resources to find out more about the effects of zero gravity and space travel on body systems. Then create a brochure that explains some of the technologies that allow people to live for extended periods of time in space. This is a good chance to have students write. They need to express an understanding of organ systems and explain the effects that space travel would have on those systems. The hook for this activity is students’ natural curiosity of space.

You can access this activity at http://go.hrw.com/resources/go_sc/hst/ia/hstl22.htm

2.  Online organ system game is appropriate for middle school and English Language Learners

“This practice lesson introduces students to several organ systems through an interactive online experience. The objective of the lesson is for students to understand that there are different systems within the body and that they work independently and together to form a functioning human body. Through the use of an online interactive activity, students learn about the concept of separate components working together to build a body system. In addition, this lesson focuses on activities to help students learn that body systems work together to build the functioning human body. This lesson could be used in conjunction with instruction on the human body and/or systems.” http://ohiorc.org/record/3572.aspx

You can access the lesson plan page through the following link

http://www.sciencenetlinks.com/lessons.cfm?BenchmarkID=11&DocID=385

You can directly access the game at

http://www.sciencenetlinks.com/interactives/systems.html

3.  Discover Kids Website “Yucky, Gross, and Cool Body”

Nothing motivates a middle school student more than an explanation of belches, snot, and ear wax. This website lets students “find out all about the human body with Wendell the Worm, Yucky's Ace Reporter.” The website allows students to choose a body function or a body system to investigate. The reading level is appropriate for middle school students and the explanations are grounded in science.

You can access this site at http://yucky.discovery.com/flash/body/index.html

4.  Neuroscience for Kids