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Content Benchmark L.8.B.1
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Life Science
Heredity
Structure of Life
  L.8.B.1
  L.8.B.2
  L.8.B.3
  L.8.B.4
  L.8.B.5
Organisms and Their Environment
Diversity of Life
Content Areas
Nature of Science (NOS)
Life Science
Earth Science
Physical Science

Students know all organisms are composed of cells, which are the fundamental units of life. E/S

The cell is the fundamental unit of life. All organisms are composed of one or more cells. Scientists have been studying cells through microscopes for about 350 years, exploring the structure of organisms, making observations, and drawing conclusion based upon these observations.  The discoveries of these early scientific pioneers led to what is known as the cell theory.

The components of the cell theory are:

  1. All living things are composed of at least one cell.
  2. Cells are the most basic unit of structure and function.
  3. All cells come from preexisting cells.


A Brief History of the Cell Theory


Robert Hooke (1635 – 1703)
Robert Hooke is famous for his microscopic description of cork (observation XVII of the Micrographia) that he viewed through a compound light microscope.  He described the box-like structures he observed as “cells.” In fact, Hooke was observing what is now known as the cell wall of the cork tissue. He called the structure a cell because it reminded him of the cells of a monastery.  Robert Hooke is given credit for discovering the plant cell and coining the term cell
 

Figure 1. Hooke devised the compound microscope and illumination system shown above, one of the best such microscopes of his time.
(From http://www.ucmp.berkeley.edu/history/hooke.html)

 

Figure 2. Robert Hooke's 1664 Micrographia showing a drawing of the cell like structure of cork, from which the name cell originated.
(From http://www.ucmp.berkeley.edu/history/hooke.html)

Anton Van Leeuwenhoek (1632 – 1723)
Anton Van Leeuwenhoek was a Dutch tradesman that had a knack for grinding optical lenses and is credited with creating over 400 microscopes.  He was the first to record microscopic observation of muscle fibers, bacteria, and blood flow through capillaries.  Furthermore, he described many specific forms of microorganisms (which he called “animalcules” or animal molecules), including protozoa and other single-celled organism.


 Figure 3. Anton Van Leeuwenhoek along side one of his 400 microscopes.
(From http://ez002.k12.sd.us/Chapter%20One%20Science.htm)

 

Matthias Schleiden (1804 – 1881) & Theodor Schwann (1810 – 1882)
Matthias Schleiden was a German Botanist that viewed plant structures under a microscope. In 1838, he concluded that all plants are composed of cells. The following year, a similar conclusion was made for animals. A German zoologist, Theodor Schwann, extended Schleiden’s theory by stating that all living things were composed of cells. Schleiden and Schwann are credited with the initial formulation of the cell theory.

  1. All living things are composed of at least one cell.
  2. Cells are the most basic unit of structure and function.

Figure 4. Plant cells magnified 100x.
(From http://www.moe.gov.sg/edumall/tl/digital_resources/biology26.htm)

 

Figure 5. Human Liver Cells Magnification 200x.
(From http://www.histol.chuvashia.com/atlas-en/cytol-en.htm)

 

Rudolf Virchow (1821 -1902)
Rudolf Virchow was a German physician who extensively studied pathology (the study of diseases) and in 1858 published his theory “Omnis cellula e cellula” which translates to “every cell comes from another existing cell.” Virchow’s conclusion was based on the observation of cell formation by mitosis and cytokinesis. Virchow’s theory contributed the third part of the cell theory:

3. All cells arise from pre-existing cells.


Figure 6. Brief diagram of the cell cycle emphasizing mitosis.
(From http://www.biology.iupui.edu/biocourses/
N100/images/8mitosiscropped.jpg
)

For detailed information on cell division, see MS TIPS Benchmark L.8.B.2

 

Cell Types: Prokaryotic and Eukaryotic
Prokaryotic cells (from the Greek meaning “before nucleus”) are the simplest cellular organisms.  They have DNA, a cell (plasma) membrane, cytoplasm, and ribosomes but lack a nucleus and membrane-bound organelles. Examples of prokaryotic cells are bacteria and archaebacteria.

Common features of prokaryotic and eukaryotic <a href=cells">
Figure 7. Comparative diagram of the similarities between
prokaryotic and eukaryotic cells.
(From http://www.schenectady.k12.ny.us/putman/
biology/data/images/cells/allcell.jpg
)

Eukaryotic cells (from the Greek meaning “truly nuclear”) are complex cells that contain a nucleus and membrane bound organelles, such as, an endoplasmic reticulum (smooth and rough), Golgi apparatus (body), mitochondria, and chloroplasts.  Each organelle performs a specific function in order for the cell to maintain homeostasis.  Examples of organisms that contain eukaryotic cells are animals, plants, fungus, and protists.

Cellular Organelles

Cell Membrane
The cell membrane is a complex structure consisting of a lipid-bilayer embedded with proteins and carbohydrates. The scientific model used to describe the cell membrane is the Fluid Mosaic Model (Figure 8). The cell membrane has several functions including: separating the inside of the cell from the outside environment, regulating what enters and exits the cell, and it is responsible communication among cells.


Figure 8. Diagram of the Fluid Mosaic Model.
(From http://sun.menloschool.org/~cweaver/cells/c/cell_membrane/)

The cell membrane is semi-permeable, meaning it allows some materials to move through while preventing other materials from entering or exiting the cell. Movement into or out of a cell along a concentration gradient is passive transport.  Passive transport does not require energy. An example of passive transport is osmosis (diffusion of water). Active transport requires energy and occurs when transport is occurring against a concentration gradient, or when the material is too large to fit through the membrane. Proteins play an integral role in transport through the cell membrane. The proteins that are embedded and extend through in the cell membrane are also used for communication.  These proteins allow the cell to respond to environmental conditions as well as communication with other cells

A resource that provides explanations and analogies for the cell membrane and its functions is available at http://www.beyondbooks.com/lif71/4b.asp.

For a detailed explanation of cellular transport, see MS TIPS Benchmark L.8.B.2

Cell Wall
The cell wall is found in plant, fungus and bacteria cells.  The cell wall provides structural support and helps to protect the cell. The cell wall is located outside the cell membrane and is primarily composed of cellulose.

 


Figure 9. Anatomy of a typical plant cell that shows the cell wall in
relation to the cell (plasma) membrane.
(From http://micro.magnet.fsu.edu/cells/plantcell.html)

Nucleus
The nucleus contains and protects the DNA.  The DNA within the nucleus controls the cell’s activity by regulating what proteins are made. The nucleus has two major parts, the nuclear membrane (nuclear envelope), and the nucleolus.  The nuclear membrane regulates what enters and leaves the nucleus.  The nucleolus makes ribosomes which are the site of protein synthesis.



Figure 10. The Structure of the Nucleus.
(From http://www.cartage.org.lb/en/themes/Sciences/Zoology/
AnimalPhysiology/Anatomy/AnimalCellStructure/Nucleus/Nucleus.htm
)

Endoplasmic Reticulum
The endoplasmic reticulum helps to make, refine, and transport chemicals used inside and outside the cell. There are two types of endoplasmic reticulum; the smooth and the rough.  The smooth ER is involved in making fats, breaking down carbohydrates, and removing toxins and poisons. The rough ER has ribosomes attached to it.  Proteins are made at the ribosomes and transported by the rough ER. Ribosomes can also be free floating in the cytoplasm.


Figure 11. Rough and Smooth Endoplasmic Reticulum.
(From http://student.nu.ac.th/u46410288/endoplasmic.htm)

Golgi Apparatus (Body)
The Golgi apparatus takes the products made in the endoplasmic reticulum, like proteins and fats, modifies them and prepares them for export outside the cell. Students typically are not required to know the function of the golgi apparatus until high school.


Figure 12.
Diagram shows the relationship between the
endoplasmic reticulum and the Golgi apparatus.
(From http://employees.csbsju.edu/hjakubowski/
classes/ch331/cho/glycoproteinshtm.htm
)

Vacuole
Vacuoles are found in both plant and animal cells.  There are several types of vacuoles with different functions such as storage, digestion, and elimination of waste. The vacuoles in plant cells are much larger than in animal cells.  In plant cells, the vacuole plays a very important role in helping to maintain the shape and the structure of the plant.  When a plant has not been watered it wilts or sags.  This is due to empty vacuoles. The function of vacuoles in animals may include storage of food and waste.


Figure 13. Comparing plant and animal cells
Notice the difference in the size of the vacuole.
(From http://evolution.berkeley.edu/evosite/lines/IIDmolecular.shtml)

 

Chloroplast and Mitochondria
Chloroplasts are found exclusively in plant cells and are the site of photosynthesis.  Photosynthesis is the process of converting radiant energy into chemical energy in the form of a simple sugar, glucose. Mitochondria are found in both plant and animal cells and are the site of cellular respiration.  Cellular respiration is the process of breaking down glucose into energy usable at the cellular level. No matter how much “food” a cell has, without the mitochondria to make the energy stored in the food usable, the cell will die.

Figure14. Left – Mitochondria, Right – Chloroplast
Diagram depicting the relationship between the
mitochondria (site of cellular respiration)
and chloroplast (site of photosynthesis).
(From http://ebiomedia.com/prod/LC/LCcellunit.html)

Table 1: Types of Eukaryotic Cells: Plants and Animals
The following table compares the cellular structures of a typical animal and plant cell.

Cellular Structures

Plant

Animal

Cell Membrane

Yes

Yes

Cell Wall

Yes

No

Nucleus

Yes

Yes

Endoplasmic Reticulum

Yes

Yes

Golgi Apparatus

Yes

Yes

Chloroplast

Yes

No

Mitochondria

Yes

Yes

Ribosome

Yes

Yes

Vacuole

Yes

Yes

 

Single-celled (Unicellular) Organisms
(Uni = one; Unicellular = one celled organisms)
A cell is the basic structural and functional unit of all organisms. Cells may exist as independent units of life, single-celled (unicellular) organism, or may form colonies or tissues as in higher plants and animals (multicellular).  Organisms that are made up of only one cell are unicellular.  Uni- means one, like a unicycle has only one wheel. The smallest living organisms are unicellular. The four main groups of unicellular organisms are bacteria, protozoa, unicellular algae, and unicellular fungi.


Figure 15. The 3 bacteria shown above are unicellular organisms.
(From www.sustainablesoilcip.org.uk/obj1.htm)

 
Figure 16. The paramecium is a single-celled organism.
  This organism has only one cell.
(From http://www.ndpteachers.org/perit/biology_image_gallery1.htm)


  Figure 17. Phytoplankton is unicellular algae.
Each organism above consists of only one cell.
(From www.waterencyclopedia.com/Oc-Po/Plankton)

courtesy of universe-review.ca/
Figure 18. Yeast is a type of unicellular fungus.
(From http://lpec.virtualschools.net/folders/learning_
zone/ks3_and_ks4/bread_and_yeast/
)

Multicellular Organisms
(Multi = many; Multicellular = composed of many cells)
Multicellular organisms are composed of more than one cell, and have differentiated cells that are responsible for specific functions.  The levels of organization are cellstissues → organ → organ system → organism. The main groups of multicellular organisms include: plants, animals and fungus. Several types of multicellular organisms are illustrated below.

rainforest
Figure 19. Variety of plants in Costa Rica’s rainforest.
(From http://www.casarioblanco.com/rainforest.html)

 


Figure 20. Variety of animals both living and extinct.
(From http://www.ucmp.berkeley.edu/phyla/phyla.html)


Clockwise from top left: Amanita muscaria, a basidiomycete; Sarcoscypha coccinea, an ascomycete; black bread mold, a zygomycete; a chytrid; a Penicillium conidiophore.
Figure 21. Variety of Fungi.
(From http://www.nationmaster.com/encyclopedia/Fungus)

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Content Benchmark L.8.B.1

Students know all organisms are composed of cells, which are the fundamental units of life. E/S

Common misconceptions associated with this benchmark

1. Many students incorrectly believe that simple organisms came from non-living objects through spontaneous generation.

In 1668, Francesco Redi, an Italian physician and poet, was the first person to address the notion of spontaneous generation. At that time, it was believed that maggots arose spontaneously in rotting meat. Redi believed that maggots developed from eggs laid by flies. To test his hypothesis, he set out meat in a variety of flasks, some open to the air, some sealed completely, and others covered with gauze. As he had expected, maggots appeared only in the open flasks in which the flies could reach the meat and lay their eggs.

In 1860, Louis Pasteur, a French chemist and microbiologist, was one of the first to disprove spontaneous generation. He concluded through his experiment with swan-neck flasks and sterile fermentable juice that microorganisms are carried on dust particles and that air alone could not trigger the growth of microorganisms.
Read about Redi’s experiment and address some of the questions at the following website, http://www.kent.k12.wa.us/staff/TimLynch/sci_class/chap01/redi.html


2. Many students incorrectly believe that photosynthesis is a plant process and respiration is a process carried out exclusively by animals.

Plants have chloroplasts which are the organelles where photosynthesis takes place.  The process of photosynthesis takes the carbon from carbon dioxide and the hydrogen from water to convert radiant energy into chemical energy in the form of carbohydrates.  Cellular respiration, or the process of breaking carbohydrates down into usable energy for the cell, takes place in the mitochondria.  Both plants and animals have mitochondria, both plants and animals must respire in order to breakdown sugar into ATP.  Animal cells do not contain chloroplast and therefore, do not have the ability to photosynthesize. 

To access a lab on plant respiration, go to http://www.teachervision.fen.com/tv/printables/SRPA03201_3.pdf

The following website is a resource provided by the Missouri Department of Elementary and Secondary Education that informs teachers of common misconceptions students have about specific science concepts. Page 5 of the document highlights misconceptions related to this benchmark. http://www.dese.mo.gov/divimprove/
curriculum/science/SciMisconc11.05.pdf


3. Many students have difficulty with the concept that living things contain cells (rather than they are made up or composed of cells).

Cells are considered the smallest structure that is alive.  Cells are often too small to be seen without a microscope. After 150 years of research, scientists concluded that organisms are composed or made up of cells.  The smallest organisms are composed of a single cell, while larger organisms are composed of multiple cells that have specialized functions. In order to understand this concept, use the analogy of a brick wall.  It does not contain bricks, it is made of bricks.

The following website is a resource provided by the Missouri Department of Elementary and Secondary Education that informs teachers of common misconceptions students have about specific science concepts. Page 6 of the document highlights this misconception.  

http://www.dese.mo.gov/divimprove/
curriculum/science/SciMisconc11.05.pdf

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Content Benchmark L.8.B.1

Students know some characteristics of an organism are composed of cells, which are the fundamental unit of life. E/S

Sample Test Questions

1st Item Specification: Know organisms are unicellular or multicellular.

Depth of Knowledge Level 1

  1. Which of the following is NOT a part of the Cell Theory?
    1. Cells are the basic unit of life.
    2. All living things are composed of cells.
    3. Cells come from the process of spontaneous generation.
    4. All cells are produced by pre-existing cells.
  1. The Cell Theory does NOT apply to
    1. bacteria.
    2. plants and animals.
    3. multicellular organisms.
    4. viruses.
  1. The cells of multicellular organisms are
    1. smaller than those of unicellular organisms.
    2. simpler than those of unicellular organisms.
    3. specialized to perform different tasks.
    4. not dependent on one another.
  1. The smallest living organism
    1. is made up of only one cell.
    2. has specialized functions among cell types.
    3. can only be seen with an electron microscope.
    4. is composed of multiple cells.

Depth of Knowledge Level 2

  1. A group of scientists were asked to observe an organism using an electron microscope.  Below is one of the tables used to record their observations. X indicates that the cell contains the organelle while the 0 indicates no organelle present.

 

Nucleus

Mitochondria

Ribosomes

Muscle Cell

X

X

X

Skin Cell

X

X

X

Blood Cell

0

0

0

Nerve Cell

X

X

X

What conclusion can be draw about the organism represented in the table? The organism is

    1. prokaryotic and multicellular.
    2. eukaryotic and multicellular.
    3. prokaryotic and unicellular.
    4. eukaryotic and unicellular.
  1. Below is a diagram of a euglena. 

http://www.biologycorner.com/resources/euglena.jpg

Euglena contain chloroplast and can make their own food through the process of photosynthesis. Which of the following statements about the euglena are true? Euglena are

  1. prokaryotic multicellular organisms.
  2. eukaryotic multicellular organisms.
  3. prokaryotic unicellular organisms.
  4. eukaryotic unicellular organisms.

2nd Item Specification: Recognize that cells are made of many specialized parts (i.e., nucleus, cell membrane, cell wall, chromosomes, chloroplast, vacuole, mitochondria)

Depth of Knowledge Level 1

  1. Which cellular organelle contains DNA and controls the function of the cell?
    1. Ribosome
    2. Endoplasmic Reticulum
    3. Golgi Body
    4. Nucleus
  1. Which cellular organelle breaks simple sugar (food) down into usable energy for the cell?
    1. Mitochondria
    2. Ribosome
    3. Nucleus
    4. Endoplasmic reticulum

Depth of Knowledge Level 2

  1. Which cell structures are most directly involved in the production and transport of proteins out of the cell?
    1. Mitochondria and rough endoplasmic reticulum
    2. Ribosomes and the rough endoplasmic reticulum
    3. Nucleus and cytoplasm
    4. Vacuole and mitochondria
  1. What would be the result if a plant cell had chloroplast but lacked mitochondria? The cell would be
    1. able to make food but unable to convert the food into usable energy.
    2. unable to make food but could obtain usable energy from the environment.
    3. able to make food and it would have the usable energy to survive.
    4. unable to make food and without food for energy it would die.

Constructed Response L.8.B.1

  1. Cells have a variety of organelles, each with a specific function.  The organelles must work together in order for the cell to survive. 
    1. Describe the function of a chloroplast and mitochondria.  Include a basic description of the chemical reaction that takes place in each organelle.
    2. Describe how the chloroplast and mitochondria work together to help a plant cell survive.
    3. Predict what would happen if a plant cell lacked mitochondria. Justify your answer.

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Content Benchmark L.8.B.1

Students know some characteristics of an organism are composed of cells, which are the fundamental unit of life. E/S

Answers to Sample Test Questions

  1. C, DOK level 1
  2. D, DOK level 1
  3. C, DOK level 1
  4. A, DOK level 1
  5. B, DOK level 2
  6. D, DOK level 2
  7. D, DOK level 1
  8. A, DOK level 1
  9. B, DOK level 2
  10. A, DOK level 2

Constructed Response L.8.B.1 Score Rubric:

 

3 points

 

 

Response addresses all parts of the question clearly and correctly.

  1. The chloroplast is the site of photosynthesis where sunlight energy, carbon dioxide and water are converted to simple sugars (food).  The mitochondria is the site of cellular respiration where glucose is broken down into usable cellular energy.
  2. A plant cell contains both chloroplasts and mitochondria.  Food (simple sugars) is made in the chloroplast.  The sugars are stored until the cell needs energy.  The sugars are then transferred to the mitochondria to be broken down into usable energy (ATP?) to carry out cellular activities.
  3. A plant cell that lacked mitochondria would be able to make food but would be unable to convert the food into cellular energy. The cell would die.

 

2 points

 

The response addresses all parts of the question and includes only minor errors.

1 point

 

Response does not address all parts of the question.

0 points

 

Response is totally incorrect or no response provided.

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Content Benchmark L.8.B.1

Students know all organisms are composed of cells, which are the fundamental units of life. 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. Tutor Vista – Cells as a Unit of Life: Why are organisms composed of cells? 

This website gives a brief explanation of the hierarchical organization of cells in multicellular organisms.

To access the website, go to
http://www.tutorvista.com/content/biology/
biology-iii/cell-unit-life/cells-organisms.php



2. Tutor Vista – Cells as a Unit of Life: Cell Theory

The cell theory is the foundation of cell biology.  This website reviews the cell theory and provides statements for the modern cell principle.

To view this information, go to
http://www.tutorvista.com/content/biology/biology-iii
/cell-unit-life/cell-theory-and-principle.php



3. The Cell Theory Rap

This is a fun website that includes the lyrics to a rap song.  The song incorporates the major components of the cell theory into a fun format.

To access the song, go to
http://www.biologycorner.com/worksheets/cellrap.html


4. Cells Alive! Mitosis

This website is an animated tutorial reviewing the phases of mitosis.  This is the process Virchow observed that led to his conclusion that all cell arise from other cells.

To view the animation, go to
http://www.cellsalive.com/mitosis.htm


5. Unlocking the Mystery: Kingdoms

This website provides a general outline review of the following Kingdoms: Monera, Protista, Fungi, Plantae, and Animalia.

For the outline, visit http://www.usoe.k12.ut.us/curr/Science/
sciber00/7th/classify/sciber/5king2.htm



6. Cells Alive!

This website describes the function of cell organelles and provides an interactive cell model for both plant and animal cells. This is a great interactive website for introducing and reviewing cells and cellular structures.

To access the website, go to
http://www.cellsalive.com/cells/cell_model.htm


7. Levels of Organization

Multicellular organisms have levels of organization.  This website provides an outline overview of the levels of organization.

To access the website, go to http://www.usoe.k12.ut.us/curr/Science/
sciber00/7th/cells/sciber/levelorg.htm

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Benchmark
Support Pages

Misconceptions:
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Sample Questions:
Click Here

Intervention Strategies & Resources:
Click Here

Benchmark Related Vocabulary

Cell
Organism
Tissue