1. Levels of Organization
How do unicellular and multicellular organisms differ?
How does cell differentiation lead to the organization within a multicellular organism?
Lesson 2 Reading Guide

2. Unicellular Organisms
Unicellular organisms carry out all characteristics of life within one cell.
A unicellular organism made of one prokaryotic cell is called a prokaryote.
A unicellular organism made of one eukaryotic cell is called a eukaryote.
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3. Unicellular Organisms- Review
A cell without a membrane-bound nucleus is a prokaryotic cell.
A eukaryotic cell has a membrane-bound nucleus and many other specialized organelles.
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4. Multicellular Organisms
Multicellular organisms are made of many types of eukaryotic cells working together, each with a specialized function.
How do unicellular and multicellular organisms differ?
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5. Multicellular Organisms (cont.)
All cells in a multicellular organism come from preexisting cells
Mitosis
Meiosis
Cell differentiation- the process by which cells become different types of cells
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6. Multicellular Organisms (cont.)
Stem cells are unspecialized animal cells that are able to develop into many different cell types.
Ex:
Muscle cells
Blood cells
Nerve cells
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7. Multicellular Organisms (cont.)
Plants have unspecialized cells similar to animal stem cells.
These cells are grouped in areas of a plant called meristems.
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8. Multicellular Organisms (cont.)
Tissues- groups of similar types of cells in multicellular organisms that work together to carry out specific tasks.
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9. Multicellular Organisms (cont.)
Humans, like most other animals, have four main types of tissue: muscle, connective, nervous, and epithelial.
The three main types of plant tissue are dermal, vascular, and ground tissue.
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10. Multicellular Organisms (cont.)
Organs- groups of different tissues working together to perform a particular job.
Organ systems- groups of different organs that work together to complete a series of tasks.
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12. Multicellular Organisms (cont.)
Multicellular organisms usually have many organ systems that work together to carry out all the jobs needed for the survival of the organism.
How does cell differentiation lead to the organization within a multicellular organism?
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13. Lesson 2

14. Levels of Organization
Atoms
Molecules
Cells
Tissue
Organs
Organ Systems
Organisms

15. Bones of the Human Arm Upper arm Lower arm Between shoulder and elbow
One long bone Humerus
Lower arm
Elbow to wrist
Radius and Ulna
Ulna in fixed position, radius can rotate over the ulna
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16. Muscles and tendons Skeletal muscles- responsible for movement
Tendons connect bones and muscles
Muscles work in pairs
Example: Bicep and tricep
Bicep contracts (gets shorter), tricep extends (stretches)
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17. Chicken wing bones Upper wing Lower wing
Humerus
Lower wing
Ulna and radius
These bones connect at the elbow joint
Bicep contracts (gets shorter), tricep extends (stretches)
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19. Joints and ligaments Bones come together at a joint
Ligaments connect bones to other bones at a joint
Cartilage is found BETWEEN bones
Helps bones move without grinding against one another
Bicep contracts (gets shorter), tricep extends (stretches)
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20. What you should look for…
Bones
Skin
Fat- yellowish tissue clumped together
Muscle- bundles of pale pink tissue
Tendons- shiny white tissue at the end of muscles that connect to bones
Ligaments- shiny white covering of the joint surfaces
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21. Integumentary System: Allows body to sweat to help cool down and maintain core body temperature.
Muscular System:
Muscles begin to rapidly contract and relax involuntarily when you are cold. Friction from this rapid movement generates heat and helps your body maintain its core temperature.
Digestive System: Large intestine absorbs excess liquids to help maintain the proper amount of water in the body.
Nervous System:
Allows all parts of your body to communicate with each other; controls all functions of the body to allow organ systems to carry out processes in order to maintain homeostasis.
Lymphatic System:
Returns extra cellular fluids to your bloodstream to be removed by the excretory system. This prevents you from swelling up like a balloon!
HOMEOSTASIS
From the Greek words homoios which means “same” and stasis which means “stationary, stay still”.
Endocrine System:
Produces hormones that allow your body to function normally. EX – When you are scared, your endocrine system produces adrenaline so you can react quickly (“Fight or Flight” Response)
Respiratory System:
Exchanges carbon dioxide in your lungs with oxygen. Keeps them in the correct amounts so that you don’t have too much or not enough of both.
Excretory System:
Removes wastes and toxins from your body so you can remain in a healthy, normal state.