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Chapter 3 Cellular Hierarchy ASA Chapter 3 Cellular Hierarchy ALABAMA 7TH GRADE SCIENCE STANDARDS COVERED IN THIS CHAPTER INCLUDE: 3 Relate major tissues and organs of the skeletal, circulatory, reproductive, muscular, respiratory, nervous and digestive systems to their functions. CELLULAR HIERARCHY In Chapter 2, you learned about the structure ofplant and animal cells. How does this relate to actual plants and animals? As you may have already guessed, the microscopic differences between plant and animal cells translate into macroscopic (larger) differences in organisms. This fact is explained by the cellular hierarchy. As we will discover during this chapter, differences in cells mean differences in larger structures like tissues or organs. You can think of it like the foundational difference between two different types of houses in a neighborhood — build a different foundation, get a different house. The cellular hierarchy starts with one cell and works its way to more complex Co In structures that eventually form the most complex ofliving things: an organism. Take Co CO . Co a look at the cellular hierarchy flow diagram in Figure 3 1 You should recognize 0? most of the words; they relate to systems within the human body. ui 0 1 D I- z0 0 Cellular Hierarchy 0.CO E Cells — Tissues —> Organs —> Organ systems —> Organism 00 .0 0 C CO 0 E © Figure 3.1 Cellular Flow Diagram 00 33 Cellular Hierarchy CELLS Recall, multicellular organisms are composed of many cells that work together to carry out life processes. In multicellular organisms, cells group together and divide the labor. Cells in a multicellular organism are specialized to perform specific figure 3.2 functions. These specializations usually cause the Figure 3.3 Red Blood Cells cells in a multicellular organism to take on special Nerve Cell shapes. Examine Figures 3.2 and 3.3. These images show the differences in external structures of two different types of cells. Figure 3.2 shows the round disk shape of red blood cells. This shape maximizes surface area, allowing lots of oxygen and carbon dioxide to move into and out ofthe red blood cells. Essentially, their disk shape allows red blood cells to transport gases efficiently. Figure 3.3 shows a nerve cell; you can see it has many long finger-like extensions. This shape helps transmit information over long distances, throughout the entire human body. There are thousands of examples of cellular specialization in plants and animals. Some more examples of cells are skin cells, liver cells, leaf cells and root cells. TISSUES Cells group together to perform the same function and are called tissues. The human body is made up of four basic types of tissue: epithelial, connective, muscle and nervous. Epithelial tissue usually surrounds and protects the things beneath it. Epithelial cells can also filter, secrete and absorb substances. Some examples include skin, ducts, glands and the outer layer of your eye called the sciera (the white part). Connective tissue connects and supports body parts. Cartilage and blood are two examples ofconnective tissue. Muscle tissue helps move the body. Muscle tissue moves (0 (0 bones, digestive Co organs and the heart. Nervous tissue carries messages from the body C? and environment to the brain and back. LU C) -J ORGANS I- Several types of tissues group together and form an organ. The brain, z0 0 heart, stomach and lungs are some examples of organs. Organs usually 0 perform a complex task. Figure 3.4 shows a four chambered human CC E heart. This organ is made of specialized tissues that act as 0 a pump to .C) 0 move blood (and other fluids) through the body. Cardiac muscle tissue 0 C contracts and causes the heart to beat. Nervous tissue in the heart CC Figure 3.4 Heart C.) C) receives signals from the brain to make the heart beat at the correct rate. E Epithelial tissue (called the pericardium) forms a protective sac around the heart. © Connective tissues form the valves ofthe heart, preventing the backflow ofblood in the .C 0. heart’s chambers. Not to mention blood itself is a type of connective tissue mentioned 0 C) earlier in this text. 34 ____________ _______ Chapter 3 ORGAN SYSTEM An organ system is a group of organs working together for a particular function. Examples of organ systems are the digestive system, circulatory system and nervous system. The organ systems ofmulticellular organisms work together to carry out the life processes of the organism, with each system performing a specific function. All the organ systems combine to make up the organism. 11;21111111j111111 . —.- Blood vessel finiismi11iith.sttne M . -- tissue • . Conecve -:s ::: ( clix CC)m13111C 4 to make tissues Tissues combine organs combine Organ systems to make small to make digestive combine to make intestine organ organ system an organism Figure 3.5 Cellular Hierarchy As living things become more complex, their cells become more specialized, forming specific types oftissues and organs. c c : :z : ._ z..........z..zzzz :c:zzz.zzz z.==:===:: z:zz...z Activity Fill in the blanks in the table below. Cell Tissue Organ Organ System Lymphocyte Lymph fluid Spleen Co In Tendon Muscular system In C4 CO cell Bone marrow Co Red blood Liver* Digestive system LU 0 . Egg Ovarian follicle -J I- z0 BONUS: Complete the last row all on your own. 0 0 *Hjnt. The liver is the largest gland in the human body and secretes many substances used in digestion. CO E 00 Activity 0 0 Use a sheet of paper to draw your own cellular hiearchy image similar to Figure 3.5. — CO :IBe sure to show each level of organization from cell tissue —> organ —> organ 0 E system —> organism. ©. 0. 00 35 ________ Cellular Hierarchy CHAPTER 3 REVIEW 1. A(n) is a group of different tissues that work together to perform a certain function. A organ system B organ C cell organelle B 2. Your heart functions because of tissues like cardiac muscle, blood and : connective tissues. At which level of organization is your heart? A an organ system C a cell B an organ B an organelle 3. The central nervous system (CNS) consists of the brain and spinal cord. What is the CNS an example of? A organ system C cell B organ B organelle 4. Which of the following is listed from least to most complex? A organ, organism, cells B cells, tissues, organism, organ system C cells, organ, organism D tissues, organism, organ 0 5. Which of the following is an example of a tissue? A chloroplast B stomach C human D bicep E 36.
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