SBI3U The Principles of Cell Division PDF

SBI3U THE PRINCIPLES OF CELL DIVISION Genetic Processes Section 4.1a Learning Goals 1. Students will be able to understand the reasons that cells divide 2. Students will be able to identify the three distinct parts of a cell cycle. 3. Students will be able to differentiate betw...

SBI3U THE PRINCIPLES OF CELL DIVISION Genetic Processes Section 4.1a Learning Goals 1. Students will be able to understand the reasons that cells divide 2. Students will be able to identify the three distinct parts of a cell cycle. 3. Students will be able to differentiate between sexual and asexual reproduction 4. Students will Understand the difference between haploid and diploid cells Cells Divide… In unicellular organisms, for ► reproduction of the species, ► e.g. binary fission in bacteria In multicellular organisms, for ► regeneration ► e.g. starfish, worms ► to replace damaged and dead cells ► e.g. scar tissue formation ► for growth ► e.g. one cell at conception to trillions at birth Why do they have to divide for an organism to grow? → Surface Area to Volume Ratio ►Cells can only grow to a certain size then they must divide or die ►As the cell size increases, the amount of cytoplasm and organelles increase BUT the cell membrane surface area does not increase at the same rate SO… ►Cell division maintains surface area to volume ratio, allowing a constant amount of materials to diffuse through the cell membrane Notice what happens when the dimensions of the box change! If you only increase the size of the box, the volume increases faster than the surface area does… BUT if you increase the number of boxes of the original size you can get a structure of the same size with the same surface area!  Adipose tissue containing adipocytes Human cheek tissue containing epidermal cells Human blood containing red blood cells Onion skin tissue containing epidermal cells How Do Cells Divide? ► Mitosis ► the duplication of the nucleus ► Cytokinesis ► the division of the cytoplasm and all its organelle contents ► Cell Division ► http://www.youtube.com/watch?v=rgLJrvoX_qo The Cell Cycle (2 stages) ► Interphase (in between) ► Growth ► Synthesis of DNA ► Mitosis (1) ► Prophase ► Metaphase ► Anaphase ► Telophase ► Cytokinesis (2)  Types of Reproduction: 1. Asexual Reproduction: ► offspring is genetically identical to the parent ► new cells are produced by mitosis ► parent and daughter cells have the same number of chromosomes ► only one parent is required ► ensures genetic continuity Types of Reproduction: 2. Sexual Reproduction: ► two parents are required ► gametes (male sperm and female egg) come together in fertilization to form a zygote ► each gamete has half the number of chromosomes ► ensures genetic variation For example: ► Humans have 46 chromosomes in their somatic cells → diploid (2n) number ► Human gametes have 23 chromosomes → haploid (n) number ► Chromosomes HOMEWORK Read Chapter 4.1 p.160-161 Do p.164 #1, 2, 5 p.168 #1-3