Reproduction

Reproduction

How organisms produce offspring

There are two kinds of Reproduction

1. Asexual reproduction2. Sexual reproduction

Asexual reproduction

• The organism makes two or more offspring which are exact genetic copies of itself.

• There are several methods of asexual reproduction:

http://www.brainpop.com/science/cellularlifeandgenetics/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 mustenlarge and divide into twonew cells.

This results in growth ofThe organism or replacementOf new tissue. MITOSIS

Cell Division!

How do organisms grow bigger?

This regular sequence of growth and cell division 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 DNA replication. Each daughter cell must have a complete 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 the DNA is distributed into each of the two

daughter cells.

There are 4 phases in mitosis

Prophase

•Mitosis begins

•Centrioles (or poles) appear and begin to move to opposite ends of the cell

•Spindle fibers form between the poles

•The nuclear membrane breaks down

Metaphase

•The chromosomes line up across the center of the cell (meet in the middle)

• the chromatids (or pairs of chromosomes) attach to the spindle fibers at the centromeres

Anaphase

• Chromatids separate and begin to move 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 two daughter cells –each with its own nucleus with identical chromosomes.

Remember this for mitosis:

Make your own “Mnemonic”I

PMAT C

Animal Cells –

•During cytokinesis, the cell membrane squeezes together around the middle of the cell.

•The cytoplasm pinches into two cells.

•Each get about half of the organelles.

Plant Cells –

•The rigid cell wall cannot squeeze together.

•Instead, a cell plate forms across the middle of the cell and then a new cell wall forms

Mitosis Review

Biology is the only science in which multiplication means the

samething as division

- Unknown

To Review

http://www.nclark.net/MitosisRap.mp3

http://www.nclark.net/itsmitosistime.ppt

Meiosis is the type of cell division by which gametes (eggs and sperm) are produced.

Makes gametes used in sexual reproduction.

•Meiosis involves a reduction in the amount of genetic material.

•The final cells have half the number of chromosomes.

•When sperm and egg combine during fertilization all required genetic information is in the fertilized egg.

•Interphase Before meiosis begins, genetic material is duplicated.

•First division of meiosis •Prophase 1: Duplicated chromatin condenses. Each chromosome consists of two, closely associated sister chromatids.

•Metaphase 1: Chromosomes align at the equatorial plate. “meet in the middle”

•Anaphase 1: Pairs separate with sister chromatids remaining together.

•Telophase 1: Two daughter cells are formed with each daughter containing only one chromosome of the pair.

•Second division of meiosis: Gamete formation

•Prophase 2: DNA does not replicate.

•Metaphase 2: Chromosomes align at the equatorial plate.

•Anaphase 2: Centromeres divide and sister chromatids migrate separately to each pole.

•Telophase 2: Cell division is complete. Four haploid daughter cells are obtained

Haploid means that each cell has half the number of chromosomes.

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)

When sperm and egg combine during fertilization all required genetic information is in the fertilized egg. 2N

http://www.brainpop.com/science/cellularlifeandgenetics/genetics/

Comparing Mitosis and Meiosis

http://www.pbs.org/wgbh/nova/baby/divide.html#

Comparison Mitosis(somatic/body)

Meiosis(gamete/sex cell)

Number of cell divisions One Two

Exchange of genetic material between

chromosomes

No Yes

Number functioning cells produced from original

Two Four sperm (male)One Egg (female)

Genetic makeup of functioning cells produced

Same as original Variable-gametes produced from two

parents

Functioning of cells produced in multicellular

organisms

Growth or replacement of

body cells

Combine to form the zygote for

reproduction

Asexual Reproduction Review

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

http://www.brainpop.com/science/cellularlifeandgenetics/cloning/

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