Chapter 3: Cell Division3.1 Cell division occurs in all organisms3.2 Cell division is part of the cell cycle

3.3 Both sexual and asexual reproduction involve cell division

3.3 Both sexual and asexual reproduction involve cell division

Multicellular organisms: cell division functions in growth, repair and development

Unicellular organisms: each cell is itself and organismCell division is to reproduce:

asexual reproductionOne organisms produces one or

more new organisms that are identical to itself

Paramecium(binary fission)

Asexual reproduction involved one parent

Cells divide to produce two daughter cells

When the cell is a whole organism, cell division = reproductionAn offspring is produced – can live independently

Identical to parent: parent’s genes = offspring’s genes

“asexual reproduction”

Cell Division in Unicellular Organisms

BuddingBoth unicellular and multicellualr

organisms can reproduce using this methodThe organism develops tiny buds on its

body – same genetic material as parent

Most often, reaches a certain size and breaks away (can sometimes remain attached to parent)

Some unicellular and some multicellular organisms reproduce by budding: In some multicellular: buds form from any

cell of the body In other multicellular organisms, on

specialized cells may bud

How different in unicellular and multicellular organisms? In unicellular organisms, the bud is a

single cell. In multicellular organisms, the bud grows by cell division, becoming multicellular

RegenerationThe process in which missing

body parts are replaced by the growth of new tissue

Specialized cells at the site of a wound or lost limb are able to become different types of tissuesTypically for regrowth of

damaged or missing body partsSometimes for asexual

reproductionNew organism is genetically

identical to the original organism

Asexual Reproduction and Health

How can you get so sick so fast?

Bacteria are unicellular prokaryotes, reproduce by binary fission (can occur very fast!)

Bacterial reproduce asexually through binary fission: 2 become 4 become 8…

Generation time of bacteria is often very short: <30 minutes!

After 24 generations…millions of bacteria!

Some bacteria are good for your health

Sexual reproduction involves two parent organisms

Cell division produces cells identical to the parent cell

One organism can produce offspring through asexual reproduction Parent genetically identical to offspring

Many multicelluar organisms reproduce by sexual reproduction Genes of two parents are combined to produce offspring

Offspring are not exactly the same as either parent

Diversity of life possible because of the combining of genetic materials from two parents in sexual reproduction

Genes from the parents have to be combined in a way that gives the offspring the right number and types of genes to become the same type of organism

1. Cancer is a disease characterized by rapid, uncontrolled cell division. Explain why you think colchicine is sometimes used in cancer chemotherapy.

2. How would a colchicine-treated cell differ from a nontreated cell?

1.Colchicine can stop cancer cells from dividing.2.The colchicine-treated cell would have twice as many chromosomes as a nontreated cell.

1. Suggest a reason why bacteria do not undergo mitosis.

2. Why are employees in the food service industry required to wash their hands frequently?

3. Why do you think it is important to defrost foods in the refrigerator instead of at room temperature?

Answers 1. Suggest a reason why bacteria do not undergo mitosis.

2. Why are employees in the food service industry required to wash their hands frequently?

3. Why do you think it is important to defrost foods in the refrigerator instead of at room temperature?

1. Bacteria have no nuclei or chromosomes, so they do not undergo mitosis when they divide.

2. To prevent the spread of bacteria

3. Refrigeration greatly slows the growth of bacteria.