Cell Growth / Division / Reproduction (Ch 10.1)

Cell Size Cells will grow and divide because of the following: the larger the cell, the more demands the cell places on the DNA DNA contains all the information in a cell to build molecules for cell growth Just because the cell increases, it does not mean the DNA increases in the cell Library → If there is an increase in people and not books, there will not be enough books to lend out the larger a cell, the less efficient in moving nutrients and waste across the cell membrane Everything enters and leaves the cell through the membrane surface area: the exchange of nutrients and waste depends on surface area volume: the rate at which oxygen and food are used and waste is produced depends on volume We need to look at the cell surface area to volume ratio to understand

Surface Area to Volume Ratio By using a cube as a reference, we can see what happens to the surface area to volume ratio as it grows in size Surface Area: length x width x number of sides Volume: length x width x height Results:

Cell Division Cell division: the process of the cell dividing into two daughter cells The DNA is copied before cell division so each daughter cell can each get the genetic code Surface area to volume ratio increases making it efficient for the nutrients and waste materials to enter and leave the cell Two Types: Mitosis: making identical cells Meiosis: dividing the chromosomes and creating genetic variation

Cell Reproduction Two Types: Asexual Reproduction Sexual Reproduction the production of genetically identical offspring from a single parent used in single-celled organisms (bacteria) simple, efficient, effective, and quick Can be used in multicellular organisms (Ex: hydra) Sexual Reproduction offspring inherits some of their genetic information from each parent fusion of two parents’ genetic information combined in the offspring Mostly in plants and animals (multicellular), but can occur in single- celled organisms

Cell Reproduction Asexual Reproduction Advantages conditions are right → fast reproduction Survival of the fittest → the most fit for the environment survive Disadvantage When conditions change, lack of genetic diversity will hinder survival Sexual Reproduction Disadvantage requires more time → finding a mate / growth and development of offspring Advantage genetic diversity more time to get optimal conditions for reproduction