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Cellular Reproduction: Cells from Cells
CH. 8
Ms. Haut
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Onion Root Tip Lab ActivityOnion Root Tip Lab Activity
http://www.biology.arizona.edu/cell_bio/http://www.biology.arizona.edu/cell_bio/activities/cell_cycle/Cell_cycle.htmlactivities/cell_cycle/Cell_cycle.html
Connections between Cell Division and Reproduction
Asexual reproductionindividual parent divides into two genetically
identical daughter cells
Sexual reproductiontwo parents contribute genetic material to the
offspring which is genetically unique
1. Replacement of lost or damaged cells
2. Growth—multicellular organisms grow and develop from single cell (fertilize egg)
3. Cell Reproduction
Roles of Cell DivsionRoles of Cell Divsion
Cell replacement (seen here in skin)
Deadcells
Figure 8.11B
Dividingcells
Epidermis, the outer layer of the skin
Dermis
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
ProkaryotesProkaryotes
Genes usually carried on a single circular DNA molecule
DNA has a few proteins and is attached to the plasma membrane at one point
DNA not bounded by membrane (nucleoid region)
Cells divide by binary fission
http://www.karlloren.com/biopsy/images/TEM-Fission_rod.jpg
Binary Fission Before dividing, an exact copy of
the chromosome is made The attachment point divides so the
2 new chromosomes are attached at separate parts of the membrane
The cell elongates and a new plasma membrane is added and the attachment points move apart
The plasma membrane and new cell wall pinch through the cell, separating the 2 chromosomes into two new, identical cells
Copyright © 2001 Pearson Education, Inc. publishing Benjamin Cummings
Eukaryotic Cell Cycle and Mitosis
Genome—a cell’s total hereditary endowment of DNAGenome is specific to species
• Human DNA extends about 3 meters, so how is it possible to copy all of it and ensure cells get even distrubution?
-DNA molecules are packaged into linear chromosomes which are more manageable
Eukaryotic ChromosomesEukaryotic Chromosomes
Are made of chromatin, a combination of DNA and protein molecules.
Are not visible in a cell until cell division occurs. The DNA in a cell is
packed into an elaborate, multilevel system of coiling and folding.
Figure 8.5
Eukaryotic ChromosomesEukaryotic Chromosomes
Before a cell starts dividing, the chromosomes are duplicated
This process produces sister chromatids
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Centromere
Sister chromatids
Figure 8.4B
Eukaryotic ChromosomesEukaryotic Chromosomes
When the cell divides, the sister chromatids separate Two daughter cells are
produced Each has a complete and
identical set of chromosomes
Copyright © 2003 Pearson Education, Inc. publishing Benjamin CummingsFigure 8.6
Chromosome NumberChromosome Number
Human somatic cells contain 46 chromosomes (23 pairs)
Human reproductive cells, gametes—sperm and egg cells—have 23 chromosomes Normal karyotype
http://members.aol.com/chrominfo/images/bigktype.gif
Mitotic Cell Cycle
In a dividing cell, the mitotic phase (M) phase alternates with interphase, a growth period. Mitotic phase—usually
the shortest part of cell cycle
Interphase—accounts for –90% of the cycle
Figure 8.7
Interphase Subphases
G1 phase (first gap)—cell grows by producing proteins and cytoplasmic organelles
S phase (synthesis of DNA)—cell continues to grow as in G1 phase, while duplicating chromosomes
G2 phase (second gap)—grows more as it completes preparations for cell division
Mitosis
ProphaseMetaphaseAnaphaseTelophase
G2 of Interphase
Nucleus well-defined and bounded by nuclear envelope
Contains one or more nucleoli. 2 centrosomes (with centriole
pairs) visible Chromosomes duplicated
Still seen as chromatin (DNA + protein)
No individual chromosomes seen
Figure 8.8.1
Prophase
Chromatin fibers become more tightly coiled, condensing into discrete chromosomes
Nucleoli disappear Chromosomes appear as 2
identical sister chromatids joined together by centromere
Mitotic spindle begins to form (made of microtubules), radiating from centrosomes
Centrosomes move to opposite poles
Figure 8.8.2
Prophase
Nuclear envelope fragments-disintegrates
Microtubules of spindle extend from poles and invade nucleus and interact with chromosomes
Kinetochore forms on chromatids
Some spindle fibers connect with kinetochores; some attach to opposite pole Figure 8.8.2
Metaphase
Centrosomes at opposite poles of cell
Chromosomes convene on the metaphase plate
Centromeres of all chromosomes are aligned with one another, and sister chromatids straddle metaphase plate
Mitotic spindle completely
formed
Figure 8.8.2
Anaphase
Paired centromeres of each chromosome separate
Each chromatid is now considered a full-fledged chromosome and move to opposite poles as kinetochore microtubules shorten
Figure 8.8.3
Chromosome MovementChromosome Movement
Chromosomes move Chromosomes move to the poles in to the poles in anaphase as anaphase as chromosomal spindle chromosomal spindle microtubules shorten microtubules shorten by dissociation of by dissociation of tubulin dimers at the tubulin dimers at the kinetochore. kinetochore.
http://www.dentistry.leeds.ac.uk/biochem/MBWeb/mb2/part1/images/anaphase.gif
Chromosomemovement
Microtubule Motorprotein
Chromosome
Kinetochore
Tubulinsubunits
Telophase and Cytokinesis
Nonkinetochore microtubules elongate the cell
Daughter nuclei form at two poles of cell
Nuclear envelopes arise from fragments of parent cell’s nuclear envelope and other portions of endomembrane system
Chromatin fibers become less tightly coiled
Cytokinesis—division of cytoplasm Formation of cleavage furrow, which
pinches cell in twoFigure 8.8.3
CytokinesisCytokinesis
Typically occurs during telophase.Is the division of the cytoplasm.Is different in plant and animal cells.
CytokinesisCytokinesis
Figure 8.9bFigure 8.9a
Cytokinesis in Plants
No cleavage furrowDuring Telophase, vesicles derived from Golgi
apparatus move along microtubules to middle of cell producing cell plate
Cell plate enlarges until its surrounding membrane fuses with the plasma membrane
The Cell CycleThe Cell Cycle
Review & PracticeReview & Practice
InterphaseInterphase
ProphaseProphase
MetaphaseMetaphase
AnaphaseAnaphase
TelophaseTelophase
MetaphaseMetaphase
InterphaseInterphase
ProphaseProphase
MetaphaseMetaphase
AnaphaseAnaphase
AnaphaseAnaphase
TelophaseTelophase
InterphaseInterphase
TelophaseTelophase
ProphaseProphase
AnaphaseInterphase
Metaphase
Interphase
Anaphase
Anaphase
Telophase
Most animal cells divide only when stimulated, and others not at all
In laboratory cultures, most normal cells divide only when Attached to a surface—anchorage dependentHave enough space Have enough growth factor
Factors that affect cell division
Cell Cycle Control SystemCell Cycle Control SystemG1 checkpoint
G1
S
M
M checkpointG2 checkpoint
G2
Controlsystem
Cells continue dividing until they touch one another (density-dependent inhibition)
Cells anchor to dish surface and divide.
Figure 8.8A
When cells have formed a complete single layer, they stop dividing (density-dependent inhibition).
If some cells are scraped away, the remaining cells divide to fill the dish with a single layer and then stop (density-dependent inhibition).
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Cells are Density DependentCells are Density Dependent
Growth factors are proteins secreted by cells that stimulate other cells to divide
After forming a single layer, cells have stopped dividing.
Figure 8.8B
Providing an additional supply of growth factors stimulates further cell division.
Cells must have Growth FactorsCells must have Growth Factors
Proteins within the cell control the cell cycleSignals affecting critical checkpoints determine
whether the cell will go through a complete cycle and divide
Growth factors signal the cell cycle control system
G1 checkpoint
M checkpoint G2 checkpoint
Controlsystem
Figure 8.9ACopyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
For many cells, the G1 checkpoint is the “restriction point” A go-ahead signal indicates that the cell
will complete the cycle and divideIn the absence of a go-ahead signal, the
cell may exit the cell cycle and remain in the non-dividing state called G0 phase
Many human cells are in the G0 phase until they die—muscle and nerve cells
G1 Checkpoint:The binding of growth factors to specific
receptors on the plasma membrane is usually necessary for cell division
Growth factor
Figure 8.8B
Cell cyclecontrolsystem
Plasma membrane
Receptorprotein
Signal transduction pathway
G1 checkpointRelayproteins
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
G2 Checkpoint:Repair enzymes make sure DNA has been copied correctlyThere are plenty of proteins (growth factors) and organelles present
G2 checkpoint
Controlsystem
Figure 8.9A
M Checkpoint:Anaphase does not begin until all chromosomes are attached to spindle at metaphase plate
Metaphase Anaphase
Cancer cells have abnormal cell cyclesThey divide excessively and can form abnormal masses
called tumors
Cancer cells do not respond normally to the body’s control mechanisms and divide excessively1. Density-independent—make their own growth factors and
continue to divide uncontrolled (“immortal”)
2. Anchorage-independent
Radiation and chemotherapy are effective as cancer treatments because they interfere with cell division
Cancer cells: Growing out of Control
Abnormal cells that escape cell-cycle control are products of mutated or transformed normal cells
1. May proliferate to form a tumor—an unregulated growing mass of cells within normal tissue Benign tumor—if cells remain at the original site Malignant tumor—if mass impairs normal
function of one or more organs of the body Excessive proliferation Cells with unusual number of chromosomes Aberrant metabolism Detaches and migrates through body
(metastasis)
Malignant tumors can invade other tissues Malignant tumors can invade other tissues and may kill the organismand may kill the organism
Tumor
Figure 8.10
Glandulartissue
1 2 3
A tumor grows from a single cancer cell.
Cancer cells invade neighboring tissue.
Lymphvessels
Cancer cells spread through lymph and blood vessels to other parts of the body.
Metastasis
Acknowledgements Essential Biology with Physiology 2nd Edition, by Campbell, Reece,
and Simon, ©2007. These images have been produced from the originals by permission of the publisher. These illustrations may not be reproduced in any format for any purpose without express written permission from the publisher.
BIOLOGY: CONCEPTS AND CONNECTIONS 4th Edition, by Campbell, Reece, Mitchell, and Taylor, ©2003. These images have been produced from the originals by permission of the publisher. These illustrations may not be reproduced in any format for any purpose without express written permission from the publisher.
BIOLOGY: CONCEPTS AND CONNECTIONS 4th Edition, by Campbell, Reece, Mitchell, and Taylor, ©2001. These images have been produced from the originals by permission of the publisher. These illustrations may not be reproduced in any format for any purpose without express written permission from the publisher.
MeiosisMeiosis
Introduction to HeredityIntroduction to Heredity
Offspring acquire Offspring acquire genes from parents by genes from parents by inheriting inheriting chromosomeschromosomes
Inheritance is possible Inheritance is possible because:because:
– Sperm and ova Sperm and ova carrying each parent’s carrying each parent’s genes are combined in genes are combined in the nucleus of the the nucleus of the fertilized eggfertilized egg
http://www.fertility-treatment.org/images/egg_and_sperm.jpg
•Chromosome-organizational unit of hereditary material in the nucleus of eukaryotic organisms
•Contain hundreds of thousands of genes, each of which is a specific region of the DNA molecule, or locus
Human Life CycleHuman Life Cycle
Each Each somatic cellsomatic cell (body cell) has 46 (body cell) has 46 chromosomes or 23 matching pairs chromosomes or 23 matching pairs ((diploiddiploid))
Karyotype: male
Autosomes: non-sex chromosomes
Sex chromosomes:determine gender (XX; XY)
Human Life CycleHuman Life CycleGametesGametes (sex cells) have a single set (sex cells) have a single set
of 22 autosomes and a single sex of 22 autosomes and a single sex chromosome, either X or Ychromosome, either X or Y
With 23 chromosomes, they are With 23 chromosomes, they are haploidhaploid
haploid number: n = 23
diploid number: 2n = 46
Haploid sperm + haploid ova zygote (2n)fertilization
2nn n
2n = 26n = ? 13
2n = 44n = ? 22
http://www.davieblint.com/images/http://grove.cs.jmu.edu/parih/images/
2n = 8n = ? 4
http://www.geneticarchaeology.com/Images/Drosophila_With_Extra_Set_Of_Eyes.jpg/
2n = 24n = ? 12
http://mips.gsf.de/projects/plants/images/tomato.jpg
MeiosisReduces chromosome number
(diploid →haploid) Increases genetic variation among
offspringSingle replication of DNA followed by 2
consecutive cell divisions Meiosis IMeiosis II
Produces 4 genetically different haploid daughter cells
In the first division, meiosis I, homologous In the first division, meiosis I, homologous chromosomes are pairedchromosomes are pairedWhile they are paired, they cross over and While they are paired, they cross over and
exchange genetic informationexchange genetic informationThe homologous pairs are then separated, and The homologous pairs are then separated, and
two daughter cells are producedtwo daughter cells are produced
Interphase IInterphase I
Chromosomes replicate (still as chromatin)
Duplicated chromosomes consist of 2 identical sister chromatids attached by centromere
Centriole pairs replicate
Prophase IProphase I
Chromatin condensesChromatin condenses SynapsisSynapsis occurs occurs
(homologues pair)(homologues pair) Chromosomes seen as Chromosomes seen as
distinct structures; distinct structures; each chromosome has each chromosome has 2 chromatids, so each 2 chromatids, so each synapsis forms a synapsis forms a tetradtetrad
Prophase IProphase I
Sister chromatids Sister chromatids held together by held together by centromeres; non-centromeres; non-sister chromatids sister chromatids held together by held together by chiasmata where chiasmata where crossing-overcrossing-over occurs (exchange of occurs (exchange of DNA)DNA)
Late Prophase ILate Prophase I
Centriole pairs move Centriole pairs move apart and spindle fibers apart and spindle fibers formformNuclear envelope Nuclear envelope disappears and nucleoli disappears and nucleoli dispersedisperse
Prophase I
Metaphase IMetaphase I
Homologous Homologous chromosome pairs line chromosome pairs line up along metaphase up along metaphase plateplate
Metaphase Iwww.library.wisc.edu/.../Metaphase_I.html
Anaphase IAnaphase I
Homologous Homologous chromosomes chromosomes separate, separate, independently from independently from othersothers
Anaphase Iin a lily
www.sinauer.com/cooper/4e/micrographs1603.html
Telophase I and CytokinesisTelophase I and Cytokinesis
Each pole now has a Each pole now has a haploid set of haploid set of chromosomes (each with chromosomes (each with 2 sister chromatids)2 sister chromatids)
Usually, cytokinesis Usually, cytokinesis occurs simultaneously occurs simultaneously with telophase I, forming with telophase I, forming 2 haploid daughter cells 2 haploid daughter cells (cleavage furrow forms in (cleavage furrow forms in animals; cell plate forms animals; cell plate forms in plants)in plants)
Telophase I
Stop
Meiosis II is essentially the same as mitosisMeiosis II is essentially the same as mitosisThe sister chromatids of each chromosome The sister chromatids of each chromosome
separateseparateThe result is four haploid daughter cellsThe result is four haploid daughter cells
Prophase IIProphase II
Spindle apparatus Spindle apparatus forms and forms and chromosomes move chromosomes move toward metaphase II toward metaphase II plateplate
Prophase II
Metaphase IIMetaphase II
Chromosomes align Chromosomes align singly on the singly on the metaphase platemetaphase plate
Metaphase II
Anaphase IIAnaphase II
Sister chromatids of Sister chromatids of each pair (now individual each pair (now individual chromosomes) separate chromosomes) separate and move toward and move toward opposite poles of the cellopposite poles of the cell
Anaphase II
Telophase II and CytokinesisTelophase II and Cytokinesis
Nuclei form at Nuclei form at opposite poles of the opposite poles of the cellcell
Cytokinesis occurs Cytokinesis occurs producing 4 haploid producing 4 haploid daughter cells (each daughter cells (each genetically different)genetically different)
Telophase II
Key Differences Between Key Differences Between Mitosis and MeiosisMitosis and Meiosis
Meiosis is a reduction divisionMitotic cells produce clones (same xsome #)Meiosis produces haploid cells
Meiosis creates genetic variationMitosis produces 2 identical daughter cells Meiosis produces 4 genetically different
daughter cells Meiosis is 2 successive nuclear divisions
Mitosis has one division
Copyright © 2001 Pearson Education, Inc. publishing Benjamin Cummings
Spermatogenesis Spermatogenesis
Process of sperm production
Results in 4 viable sperm
Oogenesis Oogenesis
Process of egg (ova) production
Results in 1 viable egg and 3 polar bodies that will not survive
Polar bodies result from an uneven division of cytoplasm
Mechanisms of Genetic Mechanisms of Genetic VariationVariation
Crossing-over—exchange of genetic material between non-sister chromatids Results in genetic recombination
Independent assortment—each pair of homologous chromosomes separate independently Results in gametes with different gene combinations
Random fertilization—random joining of two gametes
Crossing over –exchange of corresponding segments between two homologous chromosomes
Genetic recombination results from crossing over during prophase I of meiosis
Crossing over further Crossing over further increases genetic variabilityincreases genetic variability
TetradChaisma
CentromereFigure 8.18A
How crossing over How crossing over leads to genetic leads to genetic recombinationrecombination
Figure 8.18B
Tetrad(homologous pair ofchromosomes in synapsis)
Breakage of homologous chromatids
Joining of homologous chromatids
Chiasma
Separation of homologouschromosomes at anaphase I
Separation of chromatids atanaphase II and completion of meiosis
Parental type of chromosome
Recombinant chromosome
Recombinant chromosome
Parental type of chromosome
Gametes of four genetic types
1
2
3
4
Coat-colorgenes
Eye-colorgenes
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Figure 8.17A, B
Coat-color genes Eye-color genes
Brown Black
C E
c e
White Pink
C E
c e
C E
c e
Tetrad in parent cell(homologous pair of
duplicated chromosomes)
Chromosomes ofthe four gametes
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Independent AssortmentIndependent Assortment
Figure 8.16
POSSIBILITY 1 POSSIBILITY 2
Two equally probable
arrangements of chromosomes at
metaphase I
Metaphase II
Gametes
Combination 1 Combination 2 Combination 3 Combination 4
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Random FertilizationRandom Fertilization
Random as to which gametes join and Random as to which gametes join and form a zygoteform a zygote
Importance of Genetic VariationImportance of Genetic Variation
Essential to evolution (change over time)Essential to evolution (change over time)Variation can cause changes that leads to Variation can cause changes that leads to
different traitsdifferent traitsSome favorableSome favorableSome unfavorableSome unfavorable
StopStop
Errors and Exceptions in Errors and Exceptions in Chromosomal InheritanceChromosomal Inheritance
Alterations in chromosome number or Alterations in chromosome number or structure causes some genetic structure causes some genetic disordersdisordersPhysical and chemical disturbancesPhysical and chemical disturbancesErrors during meiosisErrors during meiosis
To study human chromosomes To study human chromosomes microscopically, researchers stain and microscopically, researchers stain and display them as a karyotypedisplay them as a karyotypeA karyotype usually shows 22 pairs of A karyotype usually shows 22 pairs of
autosomes and one pair of sex chromosomesautosomes and one pair of sex chromosomes
ALTERATIONS OF CHROMOSOME ALTERATIONS OF CHROMOSOME NUMBER AND STRUCTURENUMBER AND STRUCTURE
Preparation of a karyotypePreparation of a karyotype
Figure 8.19
Blood culture
1
Centrifuge
Packed redAnd white blood cells
Fluid
2
Hypotonic solution
3
Fixative
WhiteBloodcells
Stain
4 5
Centromere
Sisterchromatids
Pair of homologouschromosomes
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Human female bandsHuman female bands
Figure 8.19x1
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Human female karyotypeHuman female karyotype
Figure 8.19x2
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Human male bandsHuman male bands
Figure 8.19x3
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Human male karyotypeHuman male karyotype
Figure 8.19x4
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Alterations of Chromosome Alterations of Chromosome NumbersNumbers
NondisjunctionNondisjunction—pair of homologues do —pair of homologues do not move apart during Meiosis I, or sister not move apart during Meiosis I, or sister chromatids do not separate during Meiosis chromatids do not separate during Meiosis IIIIResults in uneven distribution of Results in uneven distribution of
chromosomes to daughter cellschromosomes to daughter cells
Alterations of Chromosome Alterations of Chromosome NumbersNumbers
AneuploidyAneuploidy: abnormal chromosome : abnormal chromosome numbernumberTrisomy: three copies of chromosomesTrisomy: three copies of chromosomesMonosomy: one copy of a chromosomeMonosomy: one copy of a chromosomeTrisomy and monosomy are usually lethalTrisomy and monosomy are usually lethal
NondisjunctionNondisjunction
Copyright © 2000Pearson Education, Inc. publishing Benjamin Cummings
Fertilization after nondisjunction in the Fertilization after nondisjunction in the mother results in a zygote with an mother results in a zygote with an extra chromosomeextra chromosome
Figure 8.21C
Eggcell
Spermcell
n + 1
n (normal)
Zygote2n + 1
Copyright © 2003Pearson Education, Inc. publishing Benjamin Cummings
Trisomy 21 (Down Syndrome)*Short stature, characteristic facial features, and heart defects (varying severity)*Most common serious birth defect (1 out of 700 births)*Mothers 35+ years of age have higher chance of having a Down baby
The chance of having a Down syndrome The chance of having a Down syndrome child goes up with maternal agechild goes up with maternal age
Figure 8.20C
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Down syndrome karyotypeDown syndrome karyotype
Figure 8.20Ax
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Nondisjunction with Sex Chromosomes
Table 8.22
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Klinefelter SyndromeKlinefelter Syndrome
Figure 8.22Ax
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Male sex organs Male sex organs present, but abnormally present, but abnormally smallsmall
SterileSterile Enlarged breasts and Enlarged breasts and
other feminine contoursother feminine contours Normal intelligenceNormal intelligence The more X-xsomes, the The more X-xsomes, the
more developmental more developmental disabilitiesdisabilities
XYYXYY
Figure 8.22x
Normal malesNormal males Normal testosterone Normal testosterone
levelslevels No increase in No increase in
aggressionaggression
Tend to be taller than Tend to be taller than averageaverage
May have higher risk May have higher risk of learning difficultiesof learning difficulties
Turner SyndromeTurner Syndrome
Lacking a second sex Lacking a second sex chromosomechromosome
Characteristic Characteristic appearanceappearance Short statureShort stature Web of skin b/w neck Web of skin b/w neck
and shoulderand shoulder Sterile—sex organs Sterile—sex organs
do not maturedo not mature Normal intelligenceNormal intelligence
AcknowledgementsAcknowledgements Unless otherwise noted, illustrations are credited to Pearson Unless otherwise noted, illustrations are credited to Pearson
Education which have been borrowed from Education which have been borrowed from BIOLOGY: CONCEPTS BIOLOGY: CONCEPTS AND CONNECTIONSAND CONNECTIONS 4th Edition, by Campbell, Reece, Mitchell, 4th Edition, by Campbell, Reece, Mitchell, and Taylor, ©2003. These images have been produced from the and Taylor, ©2003. These images have been produced from the originals by permission of the publisher. These illustrations may not originals by permission of the publisher. These illustrations may not be reproduced in any format for any purpose without express written be reproduced in any format for any purpose without express written permission from the publisher.permission from the publisher.
BIOLOGY: CONCEPTS AND CONNECTIONSBIOLOGY: CONCEPTS AND CONNECTIONS 4th Edition, by 4th Edition, by Campbell, Reece, Mitchell, and Taylor, ©2001. These images have Campbell, Reece, Mitchell, and Taylor, ©2001. These images have been produced from the originals by permission of the publisher. been produced from the originals by permission of the publisher. These illustrations may not be reproduced in any format for any These illustrations may not be reproduced in any format for any purpose without express written permission from the publisher.purpose without express written permission from the publisher.