REPRODUCTION 2 Kinds of Reproduction Asexual -- One parent Sexual -- Two parents Specifically-- Sperm and Egg

Chromosomes and Cell Division Chromosomes – Structures in a cell’s nucleus that contain genes. Chromosomes – Structures in a cell’s nucleus that contain genes. Genes – Found on chromosome in cell. Gives living thing a certain trait and tells a cell how to grow/develop.

How do all forms of asexual reproduction end in an organism? Through the process of MITOSIS! (Form of reproduction requiring only one parent.) 1.Grow 2.Repair 3.Replacement Why do organisms go through asexual reproduction??

Cell Division — 6 phases Mitosis — 4 phases 1. Interphase —normal life functions Toward the end—chromosomes duplicate Humans- 46 Once duplicated-92 Sister chromatids held together- centromere 2. Prophase-- Mitosis begins Nuclear membrane breaks down Centrioles begin to move &Spindle forms between 3. Metaphase- Centromeres line up in the MIDDLE 4. Anaphase-- Centromeres split—move to opposite sides

Nuclear membrane appears Cytoplasm divides End result==2 NEW DAUGHTER CELLS Is this a problem?? Why? 5. Telophase-- Mitosis is complete! 6. Cytokinesis-- Exactly like the parent cell!

Cell Division/MITOSIS!! I Painted My Aunt’s Toes Crimson! Interphase Prophase Metaphase Anaphase Telophase Cytokinesis Actual “Mitosis” only happens in phases 2-5!

Sexual Reproduction Process called MEIOSIS Results in the formation of 4 daughter cells called GAMETES (sex cells) Gametes—reproductive cells that have only half the number of chromosomes as the parent cell What is the name of the gametes in humans? SPERM & EGG Production of new organism from 2 parents, a male and a female.

23 46 chromosomes - New person not exactly like each parent. 2 complete cells join, new baby has twice the chromosomes as each parent.

Prophase 1—chromosome number is doubled Metaphase 1--line up in the middle Anaphase 1—sister chromatids begin pulling apart Telophase/Cytokinesis 1-- Two new daughter cells NO PROPHASE!!!! Metaphase 2—Line up in the middle Anaphase 2 & Telophase 2—Pulls apart and separates End Result—4 new cells with half of the number of chromosomes as the parents

Let’s Compare!! Asexual Reproduction Sexual Reproduction Number of parents Type of cell division Number of daughter cells produced Genetic Makeup of offspring 21 Mitosis Meiosis 2 4 (gametes) Identical to the parent Unique; different from parents

Meiosis (Process that produces sex cells with ½ number of chromosomes of parent cell.) 46 chromosomes Sperm or Egg Cell Sperm or Egg Cells

Let’s watch meiosis in action!

Advantages/Disadvantages of Asexual/Sexual Reproduction Asexual Reproduction Advantage Organism does not need a mate to produce offspring. Disadvantage Offspring exactly like parents. Sexual Reproduction Advantage Gives species variation. Disadvantage 2 parents needed for reproduction.

Species (Group of similar organisms that can mate with one another and produce fertile offspring.)

Why mitosis and meiosis?