Reproduction
How organisms produce offspring
There are two kinds ofReproduction
1.Asexual reproduction
2.Sexual reproduction
Asexual reproduction
•The organism makes two or more offspring whichare exact genetic copies of itself.
•There are several methods of asexualreproduction:
1.Budding
2. Cuttings
3. Runners
Strawberries
4. Cell Division
Bacteria
All living things come from other cells.
To form a new cell, one cell must
enlarge and divide into two
new cells.
This results in growth of
The organism or replacement
Of new tissue. MITOSIS
This regular sequence of growth and celldivision is called the Cell Cycle.
The 3 stages of the cell cycle are:
1.Interphase
2.Mitosis
3.Cytokinesis
Interphase
1.Chromosomes are copied. This is called DNAreplication. Each daughter cell must have acomplete set of DNA to survive.
2. Chromosomes appear as threadlike coils (chromatin)
at the start,but each chromosome and its copy
(sister chromosome) change to sister chromatids
Mitosis
During mitosis, one complete copy of theDNA is distributed into each of the twodaughter cells.
There are 4 phases in mitosis
Prophase
•Mitosis begins
•Centrioles (or poles) appearand begin to move to oppositeends of the cell
•Spindle fibers form betweenthe poles
•The nuclear membrane breaksdown
Metaphase
•The chromosomes line up across thecenter of the cell (meet in the middle)
• the chromatids (or pairs ofchromosomes) attach to the spindle fibersat the centromeres
Anaphase
• Chromatids separate and begin tomove to opposite ends of the cell
•The cell stretches out
•Look for the “A”
Telophase
•Two new nuclei form
•Chromosomes appear as chromatin(threads rather than rods)
•Mitosis ends
Cytokinesis
•Cell membrane moves inward to create twodaughter cells –each with its own nucleuswith identical chromosomes.
Remember this for mitosis:
Individuals(interphase)
Please
(prophase)
Make
(metaphase)
All
(anaphase)
The
(telophase)
Cells
(cytokinesis)
Make your own “Mnemonic”
I
P
M
A
T
C
Animal Cells –
•During cytokinesis, the cell membranesqueezes together around the middle ofthe cell.
•The cytoplasm pinches into two cells.
•Each get about half of the organelles.
Plant Cells –
•The rigid cell wall cannotsqueeze together.
•Instead, a cell plate formsacross the middle of thecell and then a new cellwall forms
Used in all forms ofasexual reproduction
One division of a cell-two identical diploidcell (2N)
The number and typesof chromosomes arethe same in daughterand parent cell
Large organisms usemitosis for growth andhealing.
Simple organisms useit to reproduce
Mitosis Review
Biology is the only science inwhich multiplication means thesamething as division- Unknown
Meiosis is the type of celldivision by which gametes(eggs and sperm) areproduced.
Makes gametes used in
sexual reproduction.
•Meiosis involves a reduction in theamount of genetic material.
•The final cells have half the number ofchromosomes.
•When sperm and egg combine during
fertilization all required geneticinformation is in the fertilized egg.
•InterphaseBeforemeiosisbegins,geneticmaterial isduplicated.
•First division of meiosis
•Prophase 1: Duplicated chromatin condenses. Eachchromosome consists of two, closely associated sisterchromatids.
•Metaphase 1: Chromosomes align at the equatorialplate. “meet in the middle”
•Anaphase 1: Pairs separatewith sister chromatidsremaining together.
•Telophase 1: Two daughtercells are formed with eachdaughter containing only onechromosome of the pair.
•Second division of meiosis: Gameteformation
•Prophase 2: DNA does not replicate.
•Metaphase 2: Chromosomes align at theequatorial plate.
•Anaphase 2:Centromeres divide andsister chromatidsmigrate separately toeach pole.
•Telophase 2: Celldivision is complete.Four haploid daughtercells are obtained
Haploid meansthat each cellhas half thenumber ofchromosomes.
Meiosis I ---
Meiosis II ---
Meiotic Cell Division Reviewed
-makes gametes used in sexual
reproduction.
1. gametes (sperm and egg cells) formed
during meiotic cell division have only ½ of
the organism’s genetic information
(23 chromosomes each)
Whensperm andeggcombineduringfertilization
allrequiredgeneticinformationis in thefertilized
egg. 2N
Comparing Mitosis and Meiosis
Comparison
Mitosis
(somatic/body)
Meiosis
(gamete/sex cell)
Number of cell divisions
One
Two
Exchange of geneticmaterial betweenchromosomes
No
Yes
Number functioning cellsproduced from original
Two
Four sperm (male)
One Egg (female)
Genetic makeup offunctioning cells produced
Same as original
Variable-gametesproduced from twoparents
Functioning of cellsproduced in multicellularorganisms
Growth orreplacement ofbody cells
Combine to form thezygote forreproduction
Asexual ReproductionReview
Cloning:
a.The same result as ASEXUAL
reproduction.
b. Cut a piece of stem from a plant
and it grows roots and develops a
new plant.
**this could be a clone of the plant
Plant cloning
http://www.brainpop.com/science/diversityoflife/dollythesheep/
c. Recently cloning animals that
normally reproduce sexually
has been done. “Dolly The Sheep”.
What is it?
A human ear!!
The mouse lacks an immune system so the ear grows!
Regeneration: asexual reproduction
Sexual Reproduction Review:
•Used to form sperm or an egg (gametes)
•Will result in genetically different
offspring.
•From two parent cells.
Compare Mitosis and Meiosis
