Predict • Are the following statements true or false? • ___ Unicellular organisms can reproduce by cell division. • ___The only function of cell division is reproduction. • ___ In multicellular organisms, cell division can help repair injured areas. • ___ Cell division produces two cells that are different from each other. True False True False
Infer • A giant redwood tree weighs tons and has billions of cells. These trees start out as tiny seeds. • Predict how these trees get so large.
Why do Cells Divide? • Cell division happens in all organisms for different reasons. • For example, unicellular organisms only reproduce through cell division. • In multicellular organisms, cell division is used to grow, develop, repair, AND reproduction.
Reproduction • Cell division is important in asexual reproduction, which only involves one parent. • In unicellular organisms, the parent cell divides into two identical offspring (called daughter cells). • In unicellular organisms and some multicellular organisms, a parent organism can “bud”, resulting in offspring.
Took a Look! View this Brain Pop video about Asexual Reproduction.
Growth & Repair • Remember, one characteristic of ALL living things is that they grow. • Multicellular organisms are able to grow because more cells are produced in that organism. • This is how the redwood tree is able to become so large. • Cell division also produces new cells that are used to repair injured areas of an organism. The damaged cells are replaced by the new cells made during cell division.
Key Terms • DNA – The genetic material found in eukaryotic cells and contains the blueprint for that organism. • Chromosomes – Structures in the nucleus that are made of DNA and proteins. • Cell Cycle – The life cycle of a cell cycle. • Interphase – The stage of the cell cycle in which the cell grows and prepares for mitosis. • Mitosis – The stage of the cell cycle in which the nucleus is duplicated. • Cytokinesis – The stage of the cell cycle in which the cytoplasm is divided.
The Cell Cycle • The 3 stages of the cell cycle are: Interphase, Mitosis, and Cytokinesis • Which part of the cell cycle takes the longest?
Interphase • Interphase is the part of the cell cycle during which the cell is not dividing and engages in normal life activities. • During this stage, the cell grows to be twice as large as it was when it was first produced. • At the end of the interphase, the cell duplicates its DNA, so it can be ready for mitosis.
Mitosis • Mitosis is the part of the cell cycle by which the nucleus divides. • What types of cell go through mitosis? • Mitosis produces two identical nuclei. • At the end of mitosis, the cell will have TWO identical sets of chromosomes.