Cell Growth and Reproduction Biology Agriculture

Cell Growth and Cell Growth and ReproductionReproductionBiology AgricultureBiology Agriculture

Cell GrowthCell Growth

All cells come in different sizes and All cells come in different sizes and shapes.shapes.

Diffusion in fast and effective over short Diffusion in fast and effective over short distances. distances. It become slow and inefficient over long It become slow and inefficient over long

distances. distances. If a cell and a mitochondria 20cm in diameter – If a cell and a mitochondria 20cm in diameter –

it would take months before it would receive it would take months before it would receive molecules that entered the cell membrane.molecules that entered the cell membrane.


Surface area-to-volume ratioSurface area-to-volume ratio AreaArea: the surface included in a set of lines.: the surface included in a set of lines. VolumeVolume: space occupied as measured in : space occupied as measured in

cubic inches.cubic inches. RatioRatio: the relationship in quantity, amount, or : the relationship in quantity, amount, or

size between two or more things.size between two or more things.


Due to the surface area-to-volume ratio Due to the surface area-to-volume ratio cells divide before they become to large.cells divide before they become to large.

DNA is what directs the cell when it is DNA is what directs the cell when it is becoming to large.becoming to large.

Cell ReproductionCell Reproduction

Cell division in necessary to form Cell division in necessary to form multi-cellular organisms.multi-cellular organisms.

Asexual Reproduction:Asexual Reproduction: Production of offspring from one parent cell.Production of offspring from one parent cell.

Sexual Reproduction:Sexual Reproduction: Formation of offspring from the union of two Formation of offspring from the union of two

gamete cells . gamete cells .

Asexual ReproductionAsexual Reproduction

Steps:Steps: Chromosomes duplicate (called Chromosomes duplicate (called

replication)replication) Both attach to a site located in the cellBoth attach to a site located in the cell They are forced apart.They are forced apart.

Cell membrane constricts them till they Cell membrane constricts them till they separate.separate.

Asexual ReproductionAsexual Reproduction

Some examples include:Some examples include: Strawberry RunnersStrawberry Runners PotatoesPotatoes Star FishStar Fish

Sexual ReproductionSexual Reproduction

Results from the joining of two highly Results from the joining of two highly specialized cells.specialized cells. Sperm CellsSperm Cells Ovum Cells or Egg CellOvum Cells or Egg Cell

Fertilization:Fertilization: Sperm cell and ovum combine to form a Sperm cell and ovum combine to form a

Zygote.Zygote.

ChromosomesChromosomes

Chromatids: Chromatids: Long strands of DNA.Long strands of DNA.

Chromosomes:Chromosomes: Made of two sister chromatids.Made of two sister chromatids.

Held together by a centromereHeld together by a centromere

Diploid (2n) CellsDiploid (2n) Cells

A cell with two of each kind of A cell with two of each kind of chromosomes are called chromosomes are called Diploid CellsDiploid Cells..

Haploid (n) CellsHaploid (n) Cells

A cell with one kind of each chromosome A cell with one kind of each chromosome is called a is called a HaploidHaploid cell. cell.

MitosisMitosis

Cells undergo mitosis as they reach their Cells undergo mitosis as they reach their maximum cell size. maximum cell size.

There are four steps in mitosis:There are four steps in mitosis: ProphaseProphase MetaphaseMetaphase AnaphaseAnaphase TelophaseTelophase

Mitosis:Mitosis:

Stage 1 – Prophase.Stage 1 – Prophase. Chromatids coil up into visible

chromosomes. Nucleus Disappears Centrioles migrate to the polar ends of

the cell Spindle Fibers begin to form.

Mitosis:Mitosis:

Stage 2 – MetaphaseStage 2 – Metaphase Chromosomes become attached to the

spindle fibers by their centromeres. They are lined up across the center of

the cell.

Mitosis:Mitosis:

Stage 3 – AnaphaseStage 3 – Anaphase Sister chromatids begin to separate Chromatids are pulled apart, and

separate from each other.

Mitosis:Mitosis:

Stage 4 – TelophaseStage 4 – Telophase New cells prepare for their new

existence. Chromosomes uncoil and direct

metabolic activity Spindle Fibers break down Nucleolus reappears Double membrane forms between them

MitosisMitosis

CytokinesisCytokinesis AnimalsAnimals – Plasma Membrane pinches – Plasma Membrane pinches

in along the equator of the cell.in along the equator of the cell.

MitosisMitosis

CytokinesisCytokinesis Plants Plants - Cell Plate is laid across the - Cell Plate is laid across the

equator.equator. Cell walls form around the plateCell walls form around the plate

Results of MitosisResults of Mitosis

As a result, As a result, Each daughter cell receives and exact Each daughter cell receives and exact

copy of the chromosomes present in the copy of the chromosomes present in the parent cell. parent cell.

They copy their chromosomes during They copy their chromosomes during Interphase.Interphase.

They become a diploid cell 2nThey become a diploid cell 2n The process can then start over.The process can then start over.


Process that guarantees that genetic Process that guarantees that genetic continuity.continuity.

The two new cells formed will carry out The two new cells formed will carry out the same functions of the parent cell. the same functions of the parent cell.

They will grow and divide just like the They will grow and divide just like the parent cells.parent cells.


As a result of cell division we have As a result of cell division we have groups of cells working together, until groups of cells working together, until they create and organism, i.e.they create and organism, i.e. CellsCells TissuesTissues OrgansOrgans Organs SystemsOrgans Systems OrganismsOrganisms

The Cell CycleThe Cell Cycle

Cell Cycle:Cell Cycle: The sequence of growth and division in The sequence of growth and division in

the cell.the cell.

A cell goes though two periods:A cell goes though two periods: A period of growth A period of growth A period of division A period of division


Mitosis

1 hour

Rapid Growth and Metabolic Activity

9 hours

DNA Synthesis and Replication

10 Hours

INTERPHASE

Prepare for cell division2 hours

InterphaseInterphase

The busiest part of the cell cycleThe busiest part of the cell cycle Part IPart I: Cell grows and protein production : Cell grows and protein production

is high.is high.

Part IIPart II: Cell copies its chromosomes: Cell copies its chromosomes

Part III:Part III: Parts manufactured for cell Parts manufactured for cell division.division.


The cell cycle is controlled by;The cell cycle is controlled by; Proteins Proteins EnzymesEnzymes Area – to – Volume RatioArea – to – Volume Ratio

Occasionally, cells lose control.Occasionally, cells lose control. Cancer, malignant growth resulting from Cancer, malignant growth resulting from

uncontrolled cell division. uncontrolled cell division.

Cancer – A mistake in the Cancer – A mistake in the cell cycle!cell cycle!

TumorsTumors Masses of tissue that deprive normal cells of Masses of tissue that deprive normal cells of

nutrients.nutrients.

Cancer is the second leading cause of Cancer is the second leading cause of death in the United States, exceeded death in the United States, exceeded only by heart disease. only by heart disease.

MeiosisMeiosis

Meiosis forms haploid daughter cells Meiosis forms haploid daughter cells from diploid parent cells. from diploid parent cells.

Meiosis is divided into two parts;Meiosis is divided into two parts; Meiosis IMeiosis I Meiosis IIMeiosis II

Meiosis IMeiosis I

SynapsisSynapsis Homologous Chromosomes line up Homologous Chromosomes line up

next to each other.next to each other.

Forming a structure called a Forming a structure called a tetradtetrad..

Meiosis IMeiosis I

Meiosis I is divided into four stages;Meiosis I is divided into four stages; Prophase IProphase I Metaphase IMetaphase I Anaphase IAnaphase I Telophase ITelophase I

Meiosis IMeiosis I

Prophase IProphase I Homologous Chromosomes are Homologous Chromosomes are

formedformed Spindle fibers formSpindle fibers form Tetrads are visible and have lined up Tetrads are visible and have lined up

along the equator. along the equator.

Meiosis IMeiosis I

Metaphase IMetaphase I Each tetrad becomes attached to the Each tetrad becomes attached to the

spindle fibers spindle fibers

Meiosis IMeiosis I

Anaphase IAnaphase I Homologous chromosomes are pulled Homologous chromosomes are pulled

apart. apart. One pair goes to the on polar end One pair goes to the on polar end

while the other goes to the other end.while the other goes to the other end.

Meiosis IMeiosis I

Telophase ITelophase I Cytokinesis takes place.Cytokinesis takes place. The cell divides. The cell divides.

Meiosis IMeiosis I

At the end of Meiosis I;At the end of Meiosis I; One chromosome from each parent cell is One chromosome from each parent cell is

present in the daughter cell. present in the daughter cell.

Meiosis I is a reductive division;Meiosis I is a reductive division; Reduce the chromosomes from diploid (2n) Reduce the chromosomes from diploid (2n)

to a haploid (n). to a haploid (n).

Meiosis IIMeiosis II

Each daughter cell produced in Each daughter cell produced in Meiosis I undergoes another Meiosis I undergoes another division.division.

Meiosis II is very similar to Mitosis Meiosis II is very similar to Mitosis except, it is not proceeded by a except, it is not proceeded by a replication of the chromosomes. replication of the chromosomes.


There are four stages;There are four stages; Prophase IIProphase II Metaphase IIMetaphase II Anaphase IIAnaphase II Telophase IITelophase II


Resulting in;Resulting in; Four daughter cells Four daughter cells Each daughter cell produced is Each daughter cell produced is

haploid.haploid. Each cell has four chromosomes.Each cell has four chromosomes. One from each of the homologous One from each of the homologous

pairs of parent cells.pairs of parent cells.


Prophase IIProphase II New spindle fibers formNew spindle fibers form around the around the

chromosomes.chromosomes.


Metaphase IIMetaphase II Chromosomes line up along the Chromosomes line up along the

equator.equator. Attach the centromere to the spindle Attach the centromere to the spindle

fibersfibers


Anaphase IIAnaphase II The centromere divides and the The centromere divides and the

chromatids separate.chromatids separate. Each chromatids becomes it on Each chromatids becomes it on

chromosomes with their own chromosomes with their own centromere. centromere.


Telophase IITelophase II The nuclear envelope forms The nuclear envelope forms

around each set of chromosomes. around each set of chromosomes. Cell undergoes Cytokinesis. Cell undergoes Cytokinesis.

Meiosis – Why?Meiosis – Why?

The result; The result; Cells used for reproductionCells used for reproduction

Sperm CellsSperm Cells Ovum CellsOvum Cells

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Cell Growth and Reproduction Biology Agriculture