The Living Environment

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The Living Environment

• The study of organisms and their interactions
  with the environment.

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Topics

• Unit 1 Ecology
• Unit 2 The Cell
• Unit 3 Genetics
• Unit 4 History of Biological Diversity
• Unit 5 The Human Body

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Unit 2 The Cell

• Chemistry in Biology
• Cellular Structure and Function
• Cellular Energy
• Cellular Reproduction

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The Building Blocks of Life

• All organisms are made up of carbon-based
  molecules. Specifically molecules called
  hydrocarbons. (...they contain C and H)
• Macromolecules are large molecules that are
  formed by joining smaller organic molecules
  together. There are four major categories of
  biological macromolecules
• Carbohydrates store energy and provide
  structural support.
• Lipids store energy and provide barriers
• Proteins transport substances, speed reactions,
  provide structural support, and make hormones
• Nucleic Acids store and communicate genetic
  information

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Carbohydrates

• The diagram to the right is glucose molecule.
• Carbohydrates are compounds composed of carbon,
  hydrogen, and oxygen. CH2O
• Carbohydrates can be simple sugars,
  monosaccharides, or complex sugars,
  polysaccharides.

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Carbohydrates

• Glucose is a simple sugar or monosaccharide.
  Glucose plays a central role as an energy source
  for organisms.
• Sucrose, such as table sugar and lactose, is a
  disaccharide. They also serve as an energy
  source for organisms.
• Glycogen is a polysaccharide found as long chains
  of glucose molecules in the liver and skeletal
  muscle to be used as stored energy.
• Cellulose is also a polysaccharide which is used
  to give structural support in the cell walls of
  plant cells.
• Chitin is another polysaccharide and is the main
  component in the hard outer shell of shrimp,
  lobster, and many insects.

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Carbohydrates
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Lipids

• The diagram to the right is a phospholipid.
• Lipids are composed of fatty acids, glycerol, and
  other components.
• Phospholipids act as barriers because of their
  hydrophilic, water-loving heads and their
  hydrophobic, water-fearing tails.

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Proteins

• Proteins are made of small carbon compounds
  called amino acids. There are 20 different amino
  acids.
• There are four conformations of proteins.
• Cells contain about 10,000 different proteins
  that transport substances within the cell and
  between cells, speed up reactions, communicate
  signals, and control cell growth.

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Proteins as Enzymes

• Catalysts are substances which increase the speed
  of a chemical reaction.
• Enzymes are biological catalysts, composed of
  amino acids, that will speed up the rate of
  reactions such as photosynthesis and digestion.
• Reactants of a chemical reaction are called
  substrates.

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Proteins as Enzymes

• When a substrate binds to the active site of an
  enzymatic protein a reaction occurs forming the
  products.
• Specific enzymes are designed to function only
  with specific substrates for specific reactions.
  The two fit like a lock and key.
• If a drug is introduced that chemically fits
  into the active site of an enzyme, the enzymatic
  reaction can be blocked.

How Enzymes Work
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Proteins as Enzymes

• The effectiveness of an enzyme on the rate of the
  reaction can be affected by factors such as pH
  and temperature.
• Enzymes are typically named after the molecule
  with which they will interact but end in ase or
  in. For example, amylase, lipase, pepsin, and
  trypsin are all enzymes.

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Nucleic Acids

• Nucleic acids are made up of smaller repeating
  subunits called nucleotides.
• There are six major nucleotides all of which
  contain a phosphate, nitrogenous base, and a
  ribose sugar.
• The main function of nucleic acids is to store
  and transmit genetic information such as DNA and
  RNA.

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Nucleic Acids

• Adenosine triphosphate or ATP is a storehouse of
  chemical energy used by cells.

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Summary of Macromolecules
Carbohydrates Lipids Proteins Nucleic Acids
Sugars/starches Fats/oils/ steroids Amino acids Nucleotides
Short term energy storage Provides structural support Long term energy storage Provides a barrier Transports substances Enzymes Structural support Make hormones Communication Store and communicate genetic info Storehouse of chemical energy
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Describe what you see in the following slide.
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Describe what you see in the following slide.
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The Cell

• First discovered in 1665 by Robert Hooke who
  built one of the first light microscopes and
  viewed dead cork cells. He is credited for
  calling them cellulae which eventually became the
  word cell.
• Not long after Hooke, Anton van Leeuwenhoek
  designed a microscope and viewed living organisms
  in pond water, milk, and other substances.

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The Cell Theory

• Developed in the mid 1800s by German and
  Prussian scientists it states
• 1. All living organisms are composed of one or
  more cells.
• 2. Cells are the basic unit of structure and
  organization of all living things. basic unit of
  life cells perform life functions.
• 3. Cells arise only from previously existing
  cells, with cells passing copies of their genetic
  material on to their daughter cells.

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The CellPlant cell using light microscope
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The CellPlant cell using electron microscope
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Describe what you see in the following slides.
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Types of CellsProkaryote Eukaryote
Visualizing Cells
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The Plasma Membrane

• The main function of the plasma membrane is to
  maintain the cells homeostasis.
• A cells homeostasis is controlled by the plasma
  membrane due to its selective permeability.

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The Plasma Membrane

• The Fluid Mosaic Model

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The Plasma Membrane

• Composed of a phospholipid bilayer, the plasma
  membrane can maintain its structure due to the
  polar heads and non-polar tails of the lipids.
• Cholesterol molecules between the lipids keep
  them from sticking together and help the membrane
  maintain its fluidity.
• Carbohydrate chains identify the cell and help
  the cell identify incoming chemical signals.

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The Phospholipid Bilayer
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The Plasma Membrane

• Transport Proteins move needed substances or
  waste materials through the plasma membrane.
• Receptor Proteins transmit signals to the
  inside of the cell.
• Support Proteins anchor the plasma membrane to
  the cytoskeleton and give the cell its shape.

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The Plasma MembraneThe Fluid Mosaic Model

• The phospholipids can move sideways within the
  membrane as well as the proteins. This constant
  motion of molecules sliding past one another
  creates a fluidity of the membrane.
• Because there are different substances in the
  membrane, a pattern, or mosaic, is created on its
  surface.

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The Cytoplasm

• Cytoplasm is the semi-fluid substance that fills
  the inside of all cells.
• It is composed mostly of water.
• In prokaryotes, chemical processes occur directly
  in the cytoplasm. In eukaryotes these processes
  occur in organelles.

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The Cytoskeleton

• The cytoskeleton is a supporting network of long,
  thin protein fibers that form a framework for the
  cell.
• It is composed of microtubules and microfilaments
  that support the cell and allow movement of
  substances within the cell.

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Cell Structures
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Cell Structures
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The Nucleus

• The nucleus is the cells control center.
• It contains most of the cells DNA which is used
  to make proteins for cell growth, function, and
  reproduction.
• The nucleus is surrounded by a double membrane
  called the nuclear envelope. It has pores to
  allow substances to move in and out of the
  nucleus.

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The Nucleus continued

• Within the nucleus is the site of ribosome
  production called the nucleolus.
• As ribosomes are produced they move out of the
  nucleus and either attach to endoplasmic
  reticulum or are free floating in the cytoplasm.

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The Ribosome
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Ribosomes

• Ribosomes are composed of RNA and protein, and
  are NOT membrane bound organelles.
• The function of ribosomes is to synthesize
• PROTEINS!

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Endoplasmic Reticulum

• ER is composed of folded membrane and sacs and is
  a site for protein and lipid synthesis.
• Rough ER is covered by ribosomes that produce
  proteins.
• Smooth ER lacks ribosomes and is a site for
  polysaccharide and phospholipid synthesis.

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Golgi Apparatus

• Golgi Apparatus, or Golgi Body, is a flattened
  stack of folded membranes.
• Its function is to modify, sort, and package
  proteins into sacs called vesicles.
• These vesicles can then be shipped outside of the
  cell.
• Sometimes referred to as the cells post office.

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Vacuoles

• A membrane bound sac used to temporarily store
  food, water, enzymes, and sometimes waste.
• Plant cells require very large central vacuoles
  for storing water.

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Mitochondria

• Mitochondria have an outer membrane and a folded
  inner membrane that forms many cristae.
• Cristae provide a large surface area for breaking
  down sugar molecules.
• Mitochondria are known as the powerhouse of the
  cell.

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Mitochondria

• Mitochondria are found in all eukaryotes and are
  responsible for cellular respiration.
• Mitochondria release the energy from nutrients
  obtained by the cell.
• They have their own DNA called mDNA. Because of
  this fact, they are believed to have once been
  single celled organisms themselves.

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Chloroplasts

• Chloroplasts are found only in photosynthetic
  cells such as plant cells.
• They have an outer and inner lipid membrane and
  contain stacks of thylakoids.
• In many ways they are similar to mitochondria but
  DO NOT perform the same function.

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Chloroplasts

• Chloroplasts are responsible for using sunlight
  to produce chemical energy through a process
  called photosynthesis.
• Chloroplasts contain a green pigment that traps
  sunlight called chlorophyll.
• They also have their own DNA and are believed to
  have once been a single celled organism known as
  cyanobacteria, possibly the first life forms on
  Earth.

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Lysosomes

• Lysosomes are membrane bound vesicles that digest
  excess or worn out organelles and food particles.
• They will also digest bacteria and viruses that
  have entered the cell.
• Lysosomes function to keep the inside of the cell
  clean.

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Centrioles

• Centrioles are groups of microtubules that
  function during cell division.
• They produce the spindle fibers that separate
  chromosomes during mitosis and meiosis.
• Usually found in pairs called centrosome.

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Cell Wall

• The cell wall is a thick, rigid, mesh composed of
  cellulose and structural proteins.
• It surrounds the cell membrane of plant cells and
  provides protection and structural support for
  the cell.

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Cilia and Flagella

• Cilia and flagella are both composed of
  microtubules.
• They are used for locomotion and/or feeding in
  different types of cells.
• Cilia are usually very numerous although there
  are typically only one or two flagella if they
  are present.
• Not all cells have cilia or flagella.

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Cellular Transport

• Cellular Transport moves substances within the
  cell and moves substances into and out of the
  cell.
• Cellular Transport is primarily carried out by
  the plasma membrane and the cytoskeleton,
  specifically the cells microtubules.

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Passive Transport Diffusion

• Diffusion is the net movement of particles down
  the concentration gradient.
• Particles always move from an area of high
  concentration to an area of low concentration
  until an equilibrium has been reached.

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Diffusion...continued

• Once the concentrations are equal, particles will
  continue to move randomly but will maintain a
  dynamic equilibrium.
• Factors affecting the rate of diffusion are
  concentration, temperature, and pressure.

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Diffusion across the plasma membrane

• Facilitated diffusion uses transport proteins to
  move ions and small molecules across the plasma
  membrane.
• Figure (a) is a channel protein and figure (b) is
  a carrier protein.

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Osmosis...

• ...the diffusion of water across a selectively
  permeable membrane.
• Regulating the movement of water across the
  plasma membrane is an important factor in
  maintaining homeostasis within the cell.

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Cells in solution...

• When a cell is in an isotonic solution, the
  concentration of water and solutes outside the
  cell is equal to the concentration inside the
  cell...effectively creating a dynamic
  equilibrium.
• When a cell is in a hypotonic solution, the
  concentration of water is greater outside the
  cell than inside...causing water to rush into the
  cell and causing it to swell and possibly burst.
  (cellular lysing)
• When a cell is in a hypertonic solution, the
  concentration of water is greater inside the cell
  than outside...causing water to rush out of the
  cell, resulting in the cell shriveling.

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Cells in solution...

• Osmosis in Various Solutions

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Passive Transport vs. Active Transport

• Passive transport, such as diffusion and osmosis,
  does not require the use of any energy to move
  the substance because substances naturally flow
  with the concentration gradient.
• Active transport is necessary when substances
  must move against the concentration gradient,
  that is, from areas of low concentration to areas
  of higher concentration.
• Therefore, active transport typically requires
  the use of an energy source, usually ATP.

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Passive Transport vs. Active Transport

• Figure (a) is a channel protein used for passive
  transport because it does not require the use of
  energy to change its conformation.
• Figure (b) is a carrier protein used for active
  transport which does require the use of energy
  because the protein must change its conformation.

Passive Transport
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Active Transport

• In order to maintain homeostasis, cells often
  need to remove substances or absorb substances
  against their concentration gradients.
• Moving substances from lower concentrations to
  higher concentrations across the plasma membrane
  requires energy.
• Active transport occurs with the aid of carrier
  proteins, sometimes called pumps.

Active Transport
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Sodium/Potassium ATPase Pump

• The pump uses energy in the form of ATP to
  transport sodium out of the cell, while moving
  potassium into the cell.
• This pump moves ions against their concentration
  gradient and is therefore an example of active
  transport.

Sodium Potassium Pump
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Transport of Large Particles

• Exocytosis is the secretion of materials at the
  plasma membrane.
• Cells use exocytosis to expel waste and secrete
  substances with the use of vesicles produced by
  the Golgi apparatus.

• Endocytosis is the process by which a cell
  surrounds a substance in the outside environment,
  enclosing the substance in a portion of the
  plasma membrane.
• The membrane then pinches off, creating a vacuole
  containing the substance within the cell.

Endocytosis and Exocytosis
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Cellular Energy

• All of the chemical reactions that take place
  within a cell are referred to as the cells
  metabolism.
• A common example of metabolism that takes place
  within your body is the bodys ability to
  breakdown food into nutrients and utilize the
  carbohydrates and fats as a source of energy.

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Cellular Energy

• Photosynthesis and Cellular Respiration are
  examples of metabolic pathways, whereby chemical
  reactions take place that result in energy
  transfer.
• Photosynthesis occurring in autotrophs and
  Cellular Respiration occurring in heterotrophs,
  results in a natural cycle known as the
  Carbon-dioxide/Oxygen cycle.

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ATP The Unit of Cellular Energy

• Adenosine Tri-Phosphate is a biological molecule
  that provides chemical energy.
• ATP is composed of an adenine base, ribose sugar,
  and three phosphate groups.
• ATP releases energy when the bond between the
  second and third phosphate groups is broken
  producing ADP Energy

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PHOTOSYNTHESIS

• Photosynthesis occurs in all autotrophic
  organisms including plants, algae, and some
  bacteria.
• Photosynthesis is the chemical process of using
  carbon-dioxide and water, in the presence of
  sunlight, to produce glucose and oxygen.

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PHOTOSYNTHESIS

• Photosynthesis occurs inside organelles called
  chloroplasts, which contain a green pigment
  called chlorophyll.
• Other photosynthetic pigments, such as
  ß-carotene, result in other colors such as the
  orange-yellow color of carrots and sweet potatoes.

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PHOTOSYNTHESIS

• Photosynthesis typically occurs in two phases
• Phase I Light Reactions light is captured and
  the energy is temporarily stored as NADPH and
  ATP.
• Phase II The Calvin Cycle NADPH and ATP
  produced from the light reactions are converted
  to and stored as glucose.

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PHOTOSYNTHESIS Reaction

• 6CO2 6H2O sunlight C6H12O6 6O2
• Carbon-dioxide Water sunlight Glucose Oxygen

Photosynthesis
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Cellular Respiration

• Cellular respiration occurs in both autotrophs
  and heterotrophs.
• Cellular respiration is the chemical process of
  releasing energy from glucose and using that
  energy to make ATP.

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Cellular Respiration

• Cellular respiration occurs within organelles
  called mitochondria, found in all Eukaryotes.
• Similar to photosynthesis, cellular respiration
  occurs in two stages.

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Cellular Respiration

• The first stage of cellular respiration is called
  glycolysis which is an anaerobic process, and
  therefore does not require oxygen.
• The second stage of cellular respiration is an
  aerobic process and includes the Krebs cycle.
  This stage does require the use of oxygen.

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Cellular Respiration Reaction

• C6H12O6 6O2 6CO2 6H2O ATP
• Glucose Oxygen Carbon-dioxide
  Water ENERGY

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Photosynthesis Cellular RespirationReactions
Compared

• Photosynthesis Reaction
• 6CO2 6H2O sunlight C6H12O6 6O2
• Cellular Respiration Reaction
• C6H12O6 6O2 6CO2 6H2O ATP

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The Cell Cycle / Cellular Reproduction

• The Cell Cycle is essentially the life cycle of a
  cell.
• The Cell Cycle includes three phases Interphase,
  Mitosis, and Cytokinesis.
• Interphase is divided into 3 subphases G1, S,
  and G2.

The Cell Cycle
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The Cell Cycle

• Interphase is the first and longest phase of the
  cell cycle.
• During G1 (Gap1), the cell grows and performs
  normal functions.
• During S (synthesis), DNA in the nucleus is
  replicated.
• During G2 (Gap2), the cell prepares for Mitosis.

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During Interphase S...

• DNA in the nucleus replicates itself forming
  sister chromatids.
• Pairs of identical sister chromatids are
  connected at the center with a centromere forming
  an X shaped chromosome during prophase of mitosis.

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Mitosis

• Mitosis is the stage of the cell cycle during
  which the cells nucleus and nuclear material
  divide.
• Mitosis occurs in four substages Prophase,
  Metaphase, Anaphase, and Telophase.

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Prophase
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During Prophase...

• Nuclear envelope disintegrates.
• Nucleolus disappears.
• Chromatin (DNA strand) condenses forming X-shaped
  chromosomes of identical pairs of sister
  chromatids.
• Centrioles move toward opposite sides of the cell
  and produce the mitotic spindle fibers.

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Metaphase
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During Metaphase...

• Chromosomes align along the cells equator
  forming the metaphase plate.
• Spindle fibers attach to each chromosome at the
  centromere.

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Anaphase
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During Anaphase...

• Sister chromatids are pulled apart at the
  centromeres as the spindle fibers contract.
• Chromosomes move toward opposite poles of the
  cell.

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Telophase
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During Telophase...

• Chromosomes reach opposite poles of the cell.
• Mitotic spindle fibers disappear.
• Nuclear envelope reforms.
• Nucleolus reappears.
• Chromosomes decondense back into Chromatin (DNA
  strand).

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Cytokinesis

• In animal cells microfilaments pinch inward at
  the cells equator until the cell divides in two.
• In plant cells a cell plate forms where the
  metaphase plate had formed earlier and then a new
  cell wall forms on either side, dividing the cell
  in two.

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Mitosis
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Mitosis continued...
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Various Stages of Mitosis Occurring in an Onion
Root Tip
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Results of Mitosis

• Essentially, Mitosis is a form of asexual cell
  reproduction.
• A single parent cell makes a copy of its genetic
  information, then splits into two new cells
  called daughter cells.
• Daughter cells formed as a result of mitosis are
  identical to each other and to the parent cell.

The Cell Cycle Mitosis
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What are the roles of Mitosis?

• Growth and Development
• Replacement of damaged/dead cells

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Abnormal Cell Cycle Cancer

• Cancer is the uncontrolled growth and division of
  cells.
• Cancer is typically the result of a change in the
  DNA that controls the production of proteins that
  regulate the cell cycle.
• Substances known to cause cancer are called
  carcinogens.

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Apoptosis Programmed Cell Death

• Apoptosis occurs to normal cells when they
  receive the signal, usually in the form of
  genetic code, to commit suicide.
• The cell will shrink, the nucleus will collapse,
  and the cell and all organelles will lyse.
• Apoptosis typically occurs in developing fetuses
  as well as in cells with damaged DNA.

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Stem cells

• Stem cells are unspecialized cells that can
  develop into specialized cells under the right
  conditions.
• Stem cells have the potential to replace any
  damaged cell(s) anywhere in the body.

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Meiosis

• Meiosis is a specialized type of cell division
  that results in the production of gametes, or sex
  cells.
• Meiosis only occurs within the reproductive
  organs of organisms that reproduce sexually.
• Because the cells produced by meiosis are only
  used for reproduction, they contain ½ the number
  of chromosomes as the original cell.

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Meiosis

• In order to maintain the same number of
  chromosomes from parent to offspring, sex cells
  can only have ½ the number of chromosomes as
  typical body cells.
• For example Human body cells (somatic cells)
  each contain 46 chromosomes, but human gametes
  (sex cells) only contain 23 chromosomes in each
  cell.

How Meiosis Works
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Meiosis

• Meiosis involves two consecutive cell divisions
  called meiosis I and meiosis II.
• By the end of meiosis I, two new cells are
  produced each containing the same number of
  chromosomes as the parent cell, but with genetic
  variation.
• By the end of meiosis II, four cells have been
  produced, each containing ½ the number of
  chromosomes as the original cell, each with
  genetic variation.

Stages of Meiosis
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Meiosis

• During prophase of meiosis I, homologous
  chromosomes pair together forming a tetrad.
• Once paired, crossing over occurs, resulting in
  recombinant chromosomes that allows genetic
  variation among offspring of the same parents.
• In males, each of the four daughter cells will
  become a sperm cell. In females, only one
  daughter cell will survive to become an egg cell.

Unique Features of Meiosis
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Comparison of Meiosis and Mitosis