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					                                                                                    Seth Claycomb
                                       Chapter 12 Biology
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                                      Key Terms for Section 1
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Radiometric dating: The estimation of the age of an object by measuring its content of certain
radioactive isotopes.
Radioisotope: Also known as Radioactive isotopes, are unstable isotopes that break down and
give off energy in the form of charged particles (radiation).
Half-life: The time it takes for one-half of a given amount of radioisotope to decay is called the
radioisotope’s half-life.
Microsphere: In water, short chains of amino acids can gather into tiny droplets called

                                        Section 1 Review
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       1) Scientists measure the radioisotopes in the rock and compare it to a chart of common
          amounts and their concurrent ages.
       2) A) The redundant molecules used in Miller’s experiment to prove the Primordial
          Soup model could not have existed in abundance on the early Earth. Four billion
          years ago, Earth did not have a protective layer of ozone gas. Without ozone, UV
          radiation would have destroyed any ammonia and methane present in the atmosphere.
          B) In the laboratory scientists have not been able to make either proteins or DNA
          form spontaneously in water.
       3) The first step is believed to have come from the joining of micro molecules that
          became dependent on one another to support their individual needs.
       4) Through the warm pond method.
       5) D. Ozone
                                   Key Terms for Section 2
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Fossil: The preserved or mineralized remains or imprint of an organism that lived long ago.
Cyanobacteria: Photosynthetic prokaryotes that released oxygen into the Earth’s oceans. After
hundreds of millions of years, the oxygen they released began to escape into the air.
Eubacteria: Prokaryotes that contain a chemical called peptidoglycan in their cell walls.
Eubacteria include many bacteria that cause disease and decay.
Archaebacteria: Prokaryotes that lack peptidoglycan in their cell walls and have unique lipids
in their cell membranes.
Endosymbiosis: Theory that proposes that mitochondria are the descendants of symbiotic,
aerobic (oxygen-requiring) eubacteria and chloroplasts are the descendants of symbiotic,
photosynthetic eubacteria.
Protists: A large, varied group that includes multicellular and unicellular organisms.
Extinction: The death of all members of a species.
Mass Extinction: An episode in which large numbers of species become extinct.
                                    Section 2 Review
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1) Eubacteria are prokaryotes that contain a chemical called peptidoglycan in their cell
   walls. Eubacteria include many bacteria that cause disease and decay. Archaebacteria are
   prokaryotes that lack peptidoglycan in their cell walls and have unique lipids in their cell
2) The endosymbiosis theory attempts to explain how chloroplasts and mitochondria came
   to be. In a nut shell, a larger organism engulfed a smaller prokaryotic organism, but
   offered protection instead of digesting it. In turn the smaller organism offered a benefit--
   increased ATP, photosynthesis, ect. Over a long enough time period the two became one.
   Strengths: Mitochondria and chloroplasts both divide by binary fission, like prokaryotes.
   They consist of 1 single circular chromosome. Each have an electron transport chain,
   regular eukaryotic cells do not. They are the same size as a prokaryote. They have their
   own set of ribosomes, used to synthesize their own proteins.
   Weaknesses: The theory doesn't explain other organelles such as the endoplasmic
   reticulum or the golgi apparatus. This theory has not been strongly observed.
3) Bacteria reproduce by a cell division process called binary fission, which involves one
   single parental chromosome, (bacteria have circular DNA, not double strand), and there
   is no mitotic spindle.
   Eukaryotes general sexually reproduce by meiosis, a two stage type of cell division in
   organisms that result in cells with half the chromosome number of the original cell.
4) The first were likely sponges. It allowed them to use specialized cells to move water to
   bring potential nutrients to other cells specialized in consuming them. It allowed other
   cells to create an external structure that enabled the first multicellular organism to form.
   By creating this group of different cells that worked together, it made it much more
   difficult for the prey to evade them. It allowed the formation of much more complex
   organisms. The ability to force water through a sort of filter may seem primitive
   compared to later adaptations but this was a weapon of mass destruction in its day.
5) The mass extinction produced changes in the world that produced today’s organisms.
6) B. Protists
                                 Key Terms for Section 3
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Mycorrhizae: Symbiotic associations between fungi and roots of plants. The fungus
provides minerals to the plant, and the plant provides nutrients to the fungus.
Mutualism: The type of relationship in which both species benefit if called mutualism.
Arthropod: A type of animal with a hard outer skeleton, a segmented body, and paired,
jointed limbs. Examples of arthropods include lobsters, crabs, insects, and spiders.
Biologists think a type of scorpion was the first arthropod to live on land.
Vertebrate: An animal with a backbone, vertebrates are the animals most familiar to us.
Humans are vertebrates, and almost all other land animals bigger than our first are
vertebrates as well.
Continental drift: The movement of Earth’s land masses over Earth’s surface through
geological time. Continental drift resulted in the present-day position of the continents.
                                  Section 3 Review
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1) The ozone layer protects the planet from harmful UV rays from the sun. This allows
   organisms to thrive without getting hit by deadly UV rays. The ozone layer acts
   somewhat like primitive sunscreen for the Earth.
     2) Standards Assessment
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dually replaced by bone as minerals are deposited.
4. Immovable joints, cranial joints. S0lightly movable joints, spine vertebrae. Freely
   movable joints, saddle joint.
5. Their bones are weaker in the first place, and not as big. And after menopause certain
   hormones production rates drop.
6. Easier to make their way out of the birth canal. Also, they aren’t as heavy.
                                    Key Terms for Section 3
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Tendon: Muscles can move body parts because muscles are attached to the bones of the
skeleton. Most skeletal muscles are attached to bones by strips of dense connective tissue called
tendons. One attachment of the muscle, the origin, is a bone that remains stationary during a
muscle contraction. The muscle pulls against the origin. The other attachment, the insertion, is
the bone that moves when the muscle contracts. Movement occurs when a muscle contraction
pulls the muscle’s insertion toward its origin.
Flexor: A flexor muscle causes a joint to bend.
Extensor: An extensor muscle causes a joint to straighten.
Actin and Myosin (not always grouped): Protein filaments that enable muscles to contract.
Actin and Myosin are usually found in the cytoskeleton of eukaryotic cells, but they are far more
abundant in muscle cells. The thin filaments are actin, and the thick filaments are myosin.
Myofibril: Skeleton muscle tissue consists of many parallel elongated cells called muscle fibers.
Each muscle fiber contains small cylindrical structures called myofibrils. Myofibrils have
alternating light and dark bands that produce a characteristic striated, or striped, appearance
when viewed under a microscope. In the center of each light band is a structure called a Z line,
which anchors actin filaments.
Sarcomere: The area between two Z lines. This, a myofibril is a grouping of sarcomeres linked
end to end. Each sarcomere contains overlapping thin and thick protein filaments that move and
interact with each other. The dark bands that occur in the middle of the sarcomere are regions
where the thick filaments and the thin filaments overlap.

                                       Section 3 Review
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   1. There is usually a flexor and an extensor to straighten and bend a joint.
   2. Standards Assessment
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1. B
2. C
3. C
4. A
5. A

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