1.3 Specialized Plant and Animal Cells
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Here is a summary of what you will learn in this section:
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Unspecialized cells can become specialized through interactions with their environments.
Specialized cells group together to function as a tissue.
Specialization of cells allows for diversity of function in multicellular organisms.
Current research is on the function and use of unspecialized cells, known as stem cells, in treating disease.
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Key Terms
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regeneration
cell specialization
stem cell
differentiation
meristematic cells
tissues
red blood cells
meristematic tissue
stomate
mesophyll
xylem
phloem
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Regeneration
Regeneration is the ability of a body part to be regrown or replaced. Some organisms are capable of a high degree of regeneration. The salamander is capable of regrowing limbs, tails, eye lenses and parts of the heart. Mitosis plays a vital role in this process. Humans have a more limited ability to regenerate. The liver is best able to repair itself.
Much scientific research is invested to unlock the secrets of regeneration. What would be the possible benefits if the human body had a greater ability to replace or repair tissues or body parts? 4
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The Process of Cell Specialization
Organisms vary greatly in complexity from simple single­celled organisms to huge multi­cellular organisms. Multi­cellular organisms are made up of different types of cells that do specialized jobs. These are called specialized cells that have differentiated from stem cells. Strangely enough, even though the specialized cells of an organism look very different and have different structures that allow them to carry out different functions, they all contain identical DNA.
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Learning Checkpoint
p. 41, # 1­5
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Specialized Cells and Tissues
Tissues are groups of similar cells that are specialized and can do a particular job. In other words, complex, multicellular organisms are made up of many groups of specialized cells(tissues) that perform one or more of the life processes described in section 1.1. Can you think of an example in your life where people work together, completing various tasks, to contribute to the common good?
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Animal Tissues
In animals, cells specialize to form four types of tissues. These four types are epithelial, connective, muscle and nervous tissue.
Epithelial Tissue
This tissue is made up of cells that are tightly packed together to make a protective barrier. Epithelial tissue may be thin (only one cell thick) or consist of several layers of cells. Often serve as membranes separating organs.
Connective Tissue
The main function of this tissue is to join other tissues together, including tendons, ligaments, bones, cartilage and blood. Muscle Tissue
There are three types of muscle tissue; skeletal, smooth and cardiac. Skeletal muscles allow you to move your body in a voluntary way. Smooth muscle occurs in blood vessels, the stomach, and other organs and cannot be controlled, so are involuntary.
Cardiac muscle is only found in the heart and is also involuntary. Nervous Tissue
Your nervous system works by the transmission of electrical impulses, sending messages throughout the body. Their unique structure allow these cells to perform this function. 14
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Why is blood considered to be a connective tissue?
Blood is considered a connective tissue for two basic reasons: (1) embryologically, it has the same origin (mesodermal) as do the other connective tissue types and (2) blood connects the body systems together bringing the needed oxygen, nutrients, hormones and other signaling molecules, and removing the wastes. In circulating blood two different cell types are found: enucleated erythrocytes or red blood cells and nucleated leukocytes or white blood cells. We will study their histology in blood smears. 16
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Plant Tissues
All plants are comprised of different tissues, just as animals are. Describe each of these tissues with examples as we did for animal cells.
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Learning Checkpoint
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p. 45, #1­5
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Practice Quiz
http://www.sciencesource2.ca/resources/hotpotato_quiz_10_01_3.htm
Crossword
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