How do little elephants grow up to be BIG elephants?

Cell Division Large cells cannot transport nutrients across membrane Cells will divide when they become too large Old cells that become damaged must be replaced Each new cell must be an exact copy of the original

Cells are the basic unit of structure & function of all living things… If all living things are made of cells, what makes each organism different from other organisms? Sea Urchin sperm cells fertilizing egg Human sperm Cell fertilizing egg

DNA (deoxyribonucleic acid) Contains the genetic instructions used in the development and functioning of all known living organisms

Chromosomes Compacted DNA containing cell’s genetic code DNA must compact in order to separate when cells divide Each chromosome has a matching pair (Homologous Pair) One came from your mom & one came from your dad

Three Phases of Cell Division Interphase – cell copies DNA and prepares for division Mitosis – chromosomes line up in middle of cell then separate Cytokinesis – cytoplasm divides

Interphase Cell growth Chromosomes are copied Chromosomes appear as threadlike coils (chromatin)

Mitosis = nuclear division The steps of mitosis ensure that each new cell has the exact same number of chromosomes as the original Mitosis is divided into 4 phases

PMAT Prophase: DNA condenses (coils) into chromosomes Animal Cell Plant Cell Prophase: DNA condenses (coils) into chromosomes - copies of each chromosome stay connected - now called sister chromatids Metaphase: chromosomes move to the center of the cell -spindle fibers help them align Anaphase: sister chromatids separate & move to opposite ends of the cell (spindle fibers pull apart) Telophase: chromosomes begin to uncoil and form two new nuclei

Cytokinesis Cell membrane moves inward to create two new daughter cells each has its own nucleus with identical DNA (chromosomes) The two new cells are genetically identical Animal Cell Plant Cell

Cell Cycle

Bacteria Cell Division (Binary Fission) Bacteria only has one circular chromosome. The chromosome replicates then the cell divides in two. The two daughter cells are identical to each other.

Viruses infectious non-living organism that reproduces within the cells of an infected host. It is composed of DNA inside a protein coat or capsid.