STRAND 1: Molecules and Cells Biology Standard 2

STRAND 1: Molecules and Cells Biology Standard 2

Students shall demonstrate an understanding of the structure and function of cellsSTRAND 1: Molecules and CellsBiology Standard 2The GoalsMC.2.B.1Construct hierarchy of life from cells to ecosystemsMC.2.B.2Compare and contrast prokaryotes and eukaryotesMC.2.B.3Describe the role of subcellular structures (organelles, ribosomes, cytoskeleton) in the life of the cell.MC.2.B.4Relate the structure of the cell membrane to its functionMC.2.B.5C/C the structures of an animal cell with a plant cellMC.2.B.6C/C the functions of autotrophs with heterotrophs

The Goals continuedMC.2.B.7C/C active and passive transport mechanisms (diffusion, osmosis, exocytosis, endocytosis, phagocytosis, pinocytosis)MC.2.B.8Describe the main events of the cell cycle, including differences in plant and animals (interphase, mitosis, cytokinesis)MC.2.B.9List in order and describe the stages of mitosis (prophase, metaphase, anaphase, telophase)MC.2.B.10Analyze the meiotic maintenance of constant chromosome number from one generation to the next.MC.2.B.11Discuss homeostasis using thermoregulation as an example

Getting to Where We Are NowMicroscopes began being used to study small things in the 1600s. 1665 Englishman Robert Hooke observes the bark of the cork oak and notices small open spaces that he calls cells.After that Holland man Anton von Leeuwenhoek finds first living cells in pond water and in samples from human mouths.Von Leeuwenhoeks drawing

Developing Cell Theory1805 Lorenz Oken suggests that cells may be coming from other cells.1838 Matthias Schleiden concludes that all plants are made of cells.1839 Theodor Schwann concludes that all animals are made of cells.1855 Rudolf Virchow verifies Okens hypothesis that all cells come from pre-existing cells.

Current Cell TheoryAll living things are composed of cells.

Cells are the basic units of structure and function within an organism.

Cells come from pre-existing cells.Microscope FunctionAll microscopes work by focusing either light or electron beams to produce an image.Light microscopes can magnify an object up to 1000x.Since individual cells are mostly clear they are stained in order to better observe certain parts of the cell.

Electron MicroscopesCan view objects up to 1m or 1 millionth of meter.

1m is called 1 micrometer or 1 micron.Electron MicroscopesOffer much better resolution.Sample must be placed within a vacuum to keep electrons from scattering in all directions.Samples must be non-living due to:Placement in vacuum to be hit with electron beam.Removal of all water from specimen prior to placement in vacuum.Coating/preserving of specimen to be viewed with SEM.Sample must be ultra thin for TEM.Types of Electron MicroscopesSEM SCANNING electron microscope: shows a 3-D view of outer surface of specimen. Electron beam is bounced off or scanned across a coated surface.TEM TRANSMISSION electron microscope: shows internal parts of specimen. Electron beam passes through or transmits through the specimen.MC.2.B.1Construct a hierarchy of life from cells to ecosystems amoCTOOOPCEMC.2.B.2C/C prokaryotes and eukaryotes

MC.2.B.3Describe the role of sub-cellular structures in the life of a cellOrganellesRibosomesCytoskeleton

NUCLEUSControls most functions of the cellFilled with liquidy nucleoplasmHouses/protects genetic info/DNASurrounded by a double membrane nuclear envelopeCovered in protein lined holes called poresRNA and others enter and leave hereNucleolus is where DNA is concentrated and rRNA is made.

Vacuoles Many cells contain large, saclike, membrane-enclosed structures calledvacuoles that store materials such as water, salts, proteins, andcarbohydrates.

Lesson OverviewCell StructureCENTRAL VACUOLELarge reservoir in plants that stores water, enzymes, waste, and other materialForms as smaller vacuoles fuse togetherMakes up to 90% of plant cells volumePushes organelles into a thin layer against plasma membranePressure helps give plant cells their rigidity to support

OTHER VACUOLESSome store toxic materialsVacuoles in acacia trees store poisons for defense

How do these defend the tree?

Tobacco plants store the toxin nicotine in a vacuoleRoses are colorful due to pigments found in vacuoles of the petalLYSOSOMESIs a digestive vesicleCome from GolgiBreaks down proteins, NA, carbs, phospholipidsIn liver they break down glycogen to realease glucose into bloodWhite BC use them to break down bacteriaDigest worn out organelles in process called autophagyBreak down cells when cell is dying in process called autolysisThey play large role in organisms overall healthhow?

PeroxisomeVesicleNot produced by GolgiHigh in liver and kidney cellsNeutralize free-radicals which are oxygen ions that do lots of damageDetox alcohol and drugsNamed after hydrogen peroxide which is what they release when breaking down alcohol and killing bacteriaBreaks down FA which mitochondria can use for energyOTHER VESICLESGLYOXYSOMESFound in plant seedsBreak down stored fats to nourish developing plant embryoENDOSOMESMaterial engulfed by cell and surrounded w/ a membrane pocketWill fuse with lysosome to be digestedFOOD VACUOLESStore nutrients for a cellCONTRACTILE VACUOLESContract to dispose of excess water in cell

CYTOSKELETONThin tubes and filaments that crisscross the cytosolGive shape and support to cellActs as internal tracks that allow things to move around on3 main typesMicrotubulesMicrofilamentsIntermediate filamentsMICROTUBULESHollow protein tubes made of tubulinRadiate out away from the nucleus at a point called centrosomeHold organelles in placeMaintain cell shapeGuide organelles and molecules around cellArranged in a pattern called 9+2MICROFILAMENTSLong threadlike w/ beadlike proteins called actinAllow cell movementCrawling of white BC and contraction of muscleINTERMEDIATE FILAMENTSRods that anchor nucleus and other MBOs in place in cellMaintain shape of nucleusMake up the shaft of hair/hair follicles

CENTRIOLESTwo short cylinders of microtubules perpindicular to each otherFound in animal cells

RIBOSOMESPartly sphericalResponsible for building proteinsNo membraneMade of protein and RNAMade partly in nucleus and completed in cytoplasm

ENDOPLASMIC RETICULUMCalled ERSystem of membranous tubes and sacs called cisternaeActs as an intracellular highwayMoves molecules from one area to anotherAmount of ER depends on how active the cell isTwo types: Smooth and Rough

ROUGH ERSystem of connected flattened sacs covered w/ ribosomesProduces proteins and phospholipidsProteins made here are incorporated into the cells membranesMakes digestive enzymes that are stored in the rough ER until needed to be used/releasedMost abundant in digestive glands and antibody-producing cells

SMOOTH ERLacks ribosomesMost cells have little SERBuilds lipids like cholesterolProduces steroid hormones in ovaries and testesReleases Ca in skeletal and heart muscles which causes contractionsLots in the liver and kidneys where it helps detox drugs/posionsAlcohol/drug abuse causes increase of SER which leads to drug/alcohol tolerance

GOLGI BODYSystem of flattened membrane sacsSacs closest to nucleus receive vesicles from ERTravel from one part of GB to next transporting substances as they goSacs modify contents as it movesProteins get address labels that direct them to their destination in cell

CELL MEMBRANEComposed of phospholipid bilayerActs more like a fluid than a solidHas proteins embedded within itMarker proteins extend only from one sideReceptor and transport proteins go all the way throughProteins going all the way through can detect changes in envi and then adaptMarker proteins help similar cells ID and linkAlso allows viruses to ID and enter cellFLUID MOSAIC MODELCurrent idea of cell membrane is that it allows proteins in the PLBL to move around like boats on the water, so the picture (mosaic) of the cell membrane is constantly changing

Cilia/FlagellaHairlike extending from surface of cellAssisst in movementCillia is in inner ear and vibrate due to soundCilia on protists row to move them

MITOCHONDRIATransfer energy from organic molecules to ATP.Muscle cells have highest concentration of mitochondriaInactive cells (fat) have fewHas an inner and outer phospholipid membraneOuter separates it from the cytosolInner has many folds called cristae.Cristae contains proteins that gather energy from the reactions that produce energyMITOCHONDRIAHas its own DNA that is different from the DNA of the organismCan reproduce only by division of other mitochondriaMay have originated as a prokaryotic invader that developed a symbiotic relationship with a eukaryotic cell.Your mitochondria are inherited via the ovum, so they inherited through your mother.

PlastidsChloroplastsChromoplastsContain colorful pigments that may or may not be used during photosynthesisCarrots are orange due to CAROTENECause the reds,purples, yellows, of flowersCHLOROPLASTUse light energy to make carbs from CO2 and waterContains a system of flattened, membrane sacs called thylakoidsThylakoids contain chlrophyllFound in plants and algaeHas a double membraneHas its own DNACHLOROPLASTSThey are produced only by other chloroplastsAlso thought to be a prokaryotic invader that developed a symbiotic relationship with eukaryotic cell.

CELL WALLRigid layer outside plant cells cell membraneMade of carb cellulose, directly on plasma membrane PG.88Contains pores that allow things to go in and outSome plants have secondary cell walls between the primary cell wall and plasma membrane

MC.2.B.4Relate the function of the plasma (cell) membrane to its structureCELL MEMBRANEComposed of phospholipid bilayerActs more like a fluid than a solidHas proteins embedded within itMarker proteins extend only from one sideReceptor and transport proteins go all the way throughProteins going all the way through can detect changes in envi and then adaptMarker proteins help similar cells ID and linkAlso allows viruses to ID and enter cellFLUID MOSAIC MODELCurrent idea of cell membrane is that it allows proteins in the PLBL to move around like boats on the water, so the picture (mosaic) of the cell membrane is constantly changing

MC.2.B.5C/C the structures of an animal cell to a plant cellANIMALS ONLYPLANTS ONLYBOTHMC.2.B.6C/C the functions of autotrophs and heterotrophs_________TROPHTroph = to nourishAutotroph = self nourishingHeterotroph = non self nourishing, obtains energy from outside sources

Lets look at this on a cellular levelAutotrophUses specialized organelles within the cell to capture light energy and use it to convert carbon dioxide and water into glucose and some energy and oxygen gas

What organisms do this?What organelle is doing this?HeterotrophHas to eat or consume other organismsThose organic molecules that are obtained from the consumed food are broken down within the cell by organelles (lysosomes, mitochondria) in order to provide energy to the cell to functionSIMILARITIESDIFFERENCESMC.2.B.7C/C active transport and passive transport mechanismsDiffusionOsmosisEndocytosisExocytosisPhagocytosisPinocytosis Passive TransportThe ability for molecules to be moved around a cell without the cell using energy to move them.Molecules move due to their own kinetic energyMoves from high to low concentrationDIFFUSIONSimplest type of PTMovement of molecules from an area of HIGH to LOW concentration.The range in high to low is CONCENTRATION GRADIENT.Driven by the molecules kinetic energy, matter is always in motion.Continues until equilibrium is reached.Diffusion Suppose a substance is present in unequal concentrations on either side of a cell membrane.

Lesson OverviewCell Structure

Diffusion If the substance can cross the cell membrane, its particles will tend to move toward the area where it is less concentrated until it is evenly distributed. Lesson OverviewCell Structure

Diffusion At that point, the concentration of the substance on both sides of the cell membrane is the same, and equilibrium is reached.

Even when equilibrium is reached, particles of a solution will continue to move across the membrane in both directions. Because almost equal numbers of particles move in each direction, there is no net change in the concentration on either side.

Lesson OverviewCell Structure

EQUILIBRIUMA steady state within a solution.Molecules have been evenly distributedMolecules move into an area at the same rate that other molecules of the same type move out of that area.Motion DOES NOT STOP in equilibriumSIMPLE DIFFUSIONThis is diffusion across a cell membrane.Only allows specific molecules to pass through.Non polar molecules can pass directly through the lipid bilayer (CO2 and O2)Polar molecules must pass through the protein channels (pores) within the membrane.

FACILITATED DIFFUSIONStill passive transportFor insoluble molecules and large molecules.These molecules are moved by carrier proteinsTransport molecules from high to low.This is how glucose (too large) is transported in/out of cells

BIG IDEAFacilitated Diffusion can move molecules around depending on internal/external environment conditions.

Carrier proteins are specific for particular molecules.CP that move glucose and other simple sugars DO NOT move amino acids.

A SPECIFIC FACILITATED DIFFUSION: OSMOSISDiffusion of water molecules across the cell membrane.Occurs through protein channels called aquaporins.Moves from high to low concentration.

How Osmosis Works In the experimental setup below, the barrier is permeable to water but not to sugar. This means that water molecules can pass through the barrier, but the solute, sugar, cannot.

Lesson OverviewCell StructureDIRECTION of OSMOSISHYPOtonic solution below strength - water will flow into the cellHYPERtonic solution above strength - water will flow out of the cellISOtonic solution same strength - water flows in and out at the same rate

Water moves from hypo to hyper

Osmotic Pressure Some cells, such as the eggs laid by fish and frogs, must come into contact with fresh water. These types of cells tend to lack water channels.

As a result, water moves into them so slowly that osmotic pressure does not become a problem. Lesson OverviewCell StructureDEALING w/ OSMOSISMost organisms live in an isotonic environment. Sono big deal

Some live in a hypotonic environment. What is happening to these cells?D w/ OSome paramecia have a contractile vacuole which will contract and cause water to be pumped out.

Is this still passive transport? Explain.

D w/ OSome cells will remove solutes out of the cell to bring the internal environment close to the external environment.Plant roots are in a hypotonic environment so water is always being pulled into the plant. So the cell membrane is pushed against the cell wall.The cell wall is strong enough to resist this force called turgor pressure.

D w/ OIn a hypertonic environment, water will leave the cell causing the membrane to pull loose from the cell wall.This results in a loss of turgor pressure.This condition is called plasmolysis.This is why plants wilt when left unwatered.

D w/ OSome cells cannot change to match their environment.This is true for red blood cells.They lack organelles to remove the water and have no cell wall to contain the pressure.When in a non-isotonic environment these cells will change shape.In hypertonic environment water leaves.In hypotonic water enters and if it gets large enoughcell explodes in process of cytolysisION CHANNEL DIFFUSIONIon channels are membrane proteins.Moves ions from high to low.Moves ions like, Na+, K+, CA2+, Cl-They are _____________ so they cannot cross the lipid bilayer.These ions must pass through ion channels to get into or out of the cell.Ion channels are specific for the ion they transport.ION CHANNELSSome are always openOthers are gatedCell membrane stretches and gate opensElectrical signals cause channel to openCytosol/external environment chemicals open the gates

These stimuli control whether or not certain ions are moved

ACTIVE TRANSPORTMoves molecules UP the concentration gradient.Molecules move from low to high.Requires energy form the cell to do this.The energy needed to do this comes from ATP.CELL MEMBRANE PUMPSIon channels and cellular membrane proteins also assist with active transport.They are often called pumps because they move molecules against the concentration gradient.This is similar to water naturally flowing down hill but needing a pump to go uphill.SODIUM-POTASSIUM PUMPOccurs in animal cells.Transports Na+ and K+ up their concentration gradient.For normal function, some animals need to have higher Na+ outside the cell and higher K+ inside the cell.The sodium-potassium pump maintains these differences.

HOW IT WORKSTHREE Na+ binds to the carrier protein on cytosol side.Which side is this?At the same time the carrier protein strips a phosphate from ATP.The phosphate group binds to the carrier protein.The carrier protein can then change shape to shield the sodium from the hydrophobic tails of the ________________ molecules.Where does the carrier protein get the energy to change shape?NEXTWith the new shape, the carrier proteins force the three Na+ ions outside the cell where their concentration must remain high.

AND THENThis new shape is the shape required by cells to bind to TWO K+ ions that are outside the cell.When the K+ bind, the phosphate group is released and the carrier protein can resume its original shape while releasing the two K+ into the inside of the cell.Nowit can do this all over again.At top speed, the sodium-potassium pump can move 450 Na+ and 300 K+ per second.Na-K Pump Videohttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html EFFECTS OF Na-K PumpThe exchange of 3 Na+ and 2 K+ creates an electrical gradient across the cell membrane.Outside gets positive and inside gets negative.This causes the membrane to have a positive and negative end much like a battery.This is essential for nerve impulses.WHY????VESICULAR MOVEMENTReserved for macromolecules and nutrients that are too large to get through by previous means.This is where endo/exo cytosis are used.Also used to transport large quantities of small molecules out of the cell.They both require cell to use energy.ENDOCYTOSISProcess that cells use to ingest external fluids, macromolecules, large particles, and other cells.These external portions get enclosed by a layer of the cells membrane.The membrane folds in and pinches off on itself to form a pouch.This forms a membrane bound organelle called a vesicle.These can then fuse with other MBOs.

ENDOCYTOSIS TYPESPINOcytosisTransport of solutes or fluidsPHAGOcytosisTransport of large molecules or entire cells

PHAGOCYTOSISMany unicellular organisms feed this way.Certain cells in animals (phagocytes)use this method to ingest certain bacterial and viral cells that get into the body.Phagocytes allow lysosomes to fuse with them.What will the lysosome do to the materials within the vesicle?

EXOCYTOSISProcess that releases substances from the cell.Vesicles are transported to cell membrane.They then fuse w/ membrane and release their packages to outside of cell.Cells release contents to the external environment.What is the external environment of a cell?

What is the purpose of this?

What microscope made these images?

Maintaining HomeostasisCells must be able to keep their internal conditions at a steady state.What happens if they cannot do this?Cells often become like a baseball team, where each cell in a system or cells of different systems do a specific task in order to achieve the overall success of the organism.Multicellular SpecializationIn multicellular organisms (like us), it is essential that different parts of the body are bale to communicate with one another and perform certain tasks.This causes some cells to have the ability to move around, react with their environment, or to produce specific necessary substances.Each specific role of a cell contributes to the overall homeostasis of the organism.Specialized Animal Cells Particles of dust, smoke, and bacteria are part of even the cleanest air.

Specialized animal cells act like street sweepers to keep the particles out of the lungs.

These cells are full of mitochondria, which provide a steady supply of the ATP that powers the cilia on their upper surfaces.

Lesson OverviewCell StructureSpecialized Plant Cells Pollen grains are highly specialized cells that are tiny and light, with thick cell walls to protect the cells contents.

Pine pollen grains have two tiny wings that enable the slightest breeze to carry them great distances. Lesson OverviewCell StructureCellular Communication Cells in a large organism communicate by means of chemical signals that are passed from one cell to another.

These cellular signals can speed up or slow down the activities of the cells that receive them, and can cause a cell to change what it is doing.

Some cells form connections, or cellular junctions, to neighboring cells.

Some junctions hold cells firmly together.

Lesson OverviewCell StructureCellular Communication Other junctions allow small molecules carrying chemical messages to pass directly from one cell to the next.

To respond to one of these chemical signals, a cell must have a receptor to which the signaling molecule can bind. Sometimes these receptors are on the cell membrane, although the receptors for certain types of signals are inside the cytoplasm.

The chemical signals sent by various types of cells can cause important changes in cellular activity. For example, such junctions enable the cells of the heart muscle to contract in a coordinated fashion.

Lesson OverviewCell StructureMC.2.B.8Describe the main events of the cell cycle, including differences in plant and animal cell division.InterphaseMitosisCytokinesis MC.2.B.9List in order and describe the stages of mitosis:ProphaseMetaphaseAnaphaseTelophaseCHROMOSOMESMade of DNAContains our genesHelps make RNA and proteins

CHROMOSOMESThe proteins that help DNA coil up are called HISTONES.A chromosome consists of two identical halves called CHROMATIDS.The sister chromatids attach together at the CENTROMERE.When the DNA uncoils it is called CHROMATIN.

CHROMOSOME TYPESSEX CHROMOSOMESDetermine the sex of the organismThey are X or YMales are _________ & Females are ________AUTOSOMESThese are the remaining non-sex chromosomesCome in pairsHOMOLOGOUS CHROMOSOMESThese are the pairs of autosomesCalled HOMOLOGUESSame size and shape and carry the same genes

KARYOTYPESPicture of an organisms chromosomes matched up with their homologues

DIPLOD & HAPLOIDCells with two sets of chromosomes are DIPLOID. Two autosomes for each homologous pair.Two sex chromosomes per cellAbbreviated as 2nFor humans, 2n = 46Cells with one set of chromosomes are HAPLOID.Half the number of chromosomesOne autosome of each homologous pair.Abbreviated as 1nFor humans, 1n = 23

IF the sex cells were diplod, the offspring would have too many chromosomes and would not be functional

CELL DIVISION2 trillion cells per day25 million cells per secondPROKARYOTIC DIVISIONBinary FissionThe offspring cell will be identical to the parent cell.The bacteria will replicate its DNA (single, circular chromosome) while the cell itself doubles in sizeThe cell wall/membrane will begin pinching inward in two form two new cells identical to the original in size and genetics(except for any genetic mutations that may have occurred)

Eukaryotic DivisionMITOSIS occurs in organisms going through growth, development, repair, or asexual reproduction (production of offspring from only ONE parent).

MEIOSIS occurs during gamete (sex cell) formation.These are haploid cells so they contain ___________ the number of chromosomes that a normal body cell contains.

CELL CYCLEThe life cycle of a cell.A series of repeating events in a cells life.Time between divisions is called INTERPHASE.Interphase is divided into three phases (G1, S, G2) while cell division has two phases (Mitosis and cytokinesis).During cell division chromosomes and cytoplasm are equally divided between the two offspring (daughter) cells.INTERPHASECells spend most of their time in interphase.After cell division, new cells are normal size.1st phase is G1: (gap after cell division, before DNA replication) phase, cell grows to mature size.2nd phase is S: (synthesis of DNA) DNA in new cell is copied3rd phase is G2: cell prepares for cell division.Cells can exit the cell cycle usually after G1 to enter G0, these cells will not copy their DNA or divide again.Many cells are in G0, such as fully developed central nervous system cells will stop dividing at maturity and never divide again.

MITOSISHas FOUR stagesCalled PMATPROPHASEMETAPHASEANAPHASETELOPHASEPROPHASEDNA condenses into chromosomes.The nucleus and nuclear membrane break down and disappear.2 pairs of dark spots called centrosomes appear next to the disappearing nucleus.In animals, each centrosome contains a pair of centrioles.Centrosomes move to opposite ends (poles) of the cell.As centrosomes separate, spindle fibers come out of centrosome in preparation of metaphase. These will help separate the chromosomes.There are 2 types of mitotic spindle fibers: kinetochore and polar fibers.Kinetochore fibers will separate the chromosomes, polar fibers go across the cell but do not touch the chromosomes.

METAPHASEChromosomes are easiest to see in this phase.This is when karyotypes are made.Kinetochore fibers move chromosomes to the middle of the cell.Once in the middle, chromsomes are held here by the kinetochore fibers.

ANAPHASEChromatids separate at the centromere.They move centromere first towards the other.After chromatids separate, they are considered to be individual chromosomes.

TELOPHASEChromosomes reach opposite ends of the cell.Spindle fibers disappear.Chromosomes uncoil.Nuclear envelope forms.Nucleolus forms in nucleus.

CYTOKINESISDivision of cytoplasmIn animal cells, cell begins pinching inwards at a place called the CLEAVAGE FURROW.This happens due to action by the microfilaments.In Plant cells, vesicles from the Golgi body form a CELL PLATE at the center of the cell.Offspring cells are usually the same size.

CONTROLLING CELL DIVISIONA cell spends most of its time in interphase.For it to leave interphase and begin division, eukaryotes have special proteins that act as checkpoints or traffic signals.If all things in the cell are right then the proteins allow the next phase to begin; green light.If things are wrong, then the protein signals to stop; red light.Cell Growth (G1) CHECKPOINTProteins here control whether the cell will divide or not.If the cell is proper size and is healthy proteins will signal DNA replication or S phase.If conditions are not right, then the proteins signal the cell to stop completely or to rest until the conditions are met.This is where the G0 phase is entered also.DNA SYNTHESIS (G2) CHECKPOINTDNA repair enzymes check or proofread the DNA for mistakes (mutations)If everything checks out correctly then proteins signal that the cell can enter into mitosis.MITOSIS CHECKPOINTIf a cell passes this checkpoint then proteins signal the cell to exit mitosis.When it exits mitosis, the cell will enter G1 phase and begin growing. UNCONTROLLED CELLULAR DIVISIONIf a mutation occurs in a gene that codes for cell division, the proteins that those genes are supposed to make will not work correctly.This may interrupt cell growth and/or division.These disruptions can lead to CANCER which is the uncontrolled growth of cells; the cells cant stop dividing.Some types of cancer is from increased cellular division; other types are due to the cell cycle being unable to slow down or stop.http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html MC.2.B.10Analyze the meiotic maintenance of a constant chromosome number from one generation to the next.CHROMOSOMES vs. CHROMATIDSThe two chromosomes of a homologous pair are individual chromosomes that were inherited from different parents.Sister chromatids are single, replicated chromatids attached by a centromere.To count chromosomes, count centromeres.One chromosome has one centromere.Two sister chromatids are joined by one centromere UNTIL anaphase II when chromatids separate.When this happens they are still considered to be chromosomes, so when sister chromatids separate they are then called chromsomes.MEIOSISA process of nuclear division that reduces the number of chromosomes in new cells to half of what the original cell contained.In animals, meiosis produces gametes (sperm and egg)These are haploid, 1n, for humans that is 23.When egg and sperm fuse they produce a zygote with 46 or 2n.Cells that go into meiosis do so after interphase.They will then divide TWICE to produce 4, 1n cells rather than dividing once to produce 2, 2n cells.It is divided into two stages: MEIOSIS I and MEIOSIS IIMEIOSIS MEISOSIS IProphase IMetaphase IAnaphase ITelophase ICytokinesis IMEIOSIS IIProphase IIMetaphase IIAnaphase IITelophase IICytokinesis IIPROPHASE IDNA coils into ________________.Spindle fibers appear.Nucleolus and nucleus disappear.Chromosomes will line up next to their homologue.This pairing only occurs in meiosis, called SYNAPSIS.Each homologue pair is called a TETRAD (Greek word tetras = four)Homologues align so that gene segments are adjacent to one another.During synapsis, homologues will twist around each other and chromosomes may switch gene segments, this is called CROSSING OVER.This process ensures genetic variation which keeps a population from becoming __________________.Crossing over

Prophase i

METAPHASE ITetrads line up randomly along the cellular midline or equator.The orientation of the chromosome pairs is random with respect to poles of the cell.Spindle fibers from opposite poles will attach to homologues.

GENETIC VARIATIONDuring metaphase I, the alignment of homologues is random, so the X/Y chromosomes could be on either side of the to be divided midline.The number of possible chromosome combinations in an organism is 2n. 2 = number of homologues in a pair.n = haploid chromosome number.For humans: 2n = 223 = 8,388,608 possible combinations.ANAPHASE IEach homologue (two chromatids and a centromere) move to opposite ends of the cell.This random separation of homologues is called INDEPENDENT ASSORTMENT.This also ensures genetic variation.

TELOPHASE I and CYTOKINESIS IChromosomes reach opposite ends of the cell.Each new cell contains a haploid (1n) number of chromosomes.The new cells contain half the number of chromosomes as the original cell, HOWEVEReach new cell contains two copies (as chromatids) due to DNA copying before meiosis I.

MEIOSIS IIOccurs in each cell formed during meiosis I and is not preceded by the copying of DNAPROPHASE IIMETAPHASE IIANAPHASE IIP II: spindle fibers form and begin moving chromosomes toward center.M II: chromosomes align at center with each chromatid facing an opposite pole of the cell.A II: Chromatids separate and move toward opposite poles of the cell

TELOPHASE IICYTOKINESIS IIT II: nuclear membrane forms around chromosomes in each of the 4 newly forming cells.C II: The cells split which results in 4 new individual cells with half of the original cells number of chromosomes.

GAMETE DEVELOPMENTThe only cells in animals that go through meiosis are those that produce gametes within the reproductive organs.In humans, gamete formation is with the gonadsTestes for malesOvaries for femalesSPERMATOGENESISThe male gametes are called sperm cells or spermatozoa.A diploid reproductive cell divides MEIOTICALLY to form four haploid SPERMATIDS.Each spermatid will develop into a mature sperm cell.The production of sperm cells is called spermatogenesis.

OOGENESISThe production of mature egg cells or OVA.A diploid reproductive cell divides MEIOTICALLY to produce one mature egg or OVUM.During meiotic cytokinesis the cytoplasm of the newly formed cells divides unequally.The newly formed cell that receives the most cytoplasm will become a mature egg.Only one mature egg will form through meiosis, the other three products are called polar bodies and will eventually degenerate.

SEXUAL REPRODUCTIONProduction of offspring through meiosis and the union/fusion of sperm and egg cells.Offspring formed by sexual reproduction will be genetically different from the parents because of new gene combos.Evolution favors sexual reproduction because of the variety of genetic combinations it can create.Greater genetic variety within a species gives it a higher chance to survive and adapt to changing conditions.If disease strikes a population, some members may have a genetic variation that gives it a resistance.Many members may die, but the resistant ones can survive to reproduce and create a new population with their immunity.http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__comparison_of_meiosis_and_mitosis__quiz_1_.html

MC.2.B.11Discuss homeostasis using thermoregulation as an exampleHYPOthermiaWhen the core of the body gets too COLD and systems begin to shut down, will result in death if too severe or if untreated.HYPERthermiaWhen the bodies core gets too HOT. Heat stroke results if action is not taken and death can result in severe casesREGULATIONPositive Feedback MechanismsCause a system to move away from normalNegative Feedback MechanismsCause a system to return to normalRegulationTEMP INCREASESBlood flows to areas near the skin (skin color reddens)Heat in blood can escape when near the skin by transferring out of skin.Sweat will begin to form on skin to cause heat to be pulled from bodyTEMP DECREASESBlood flows deeper into body (skin gets paler)Blood stays closer to core and vital organs.Muscles will begin involuntary contractions (shivering) to activate mitochondria and provide heat energy to warm body.

QUESTIONAre the mechanisms used to regulate our bodys temperature positive or negative feedback mechanisms?