Reproduction of Organisms Chapter 10 and 11.4

Reproduction of Organisms Asexual Reproduction—formation of offspring from a single parent

2. Forms of Asexual Reproduction Budding—A form of mitosis used by Hydra, Jellyfish, Sea Anemones, Yeast and some Fungi Spores—haploid reproductive cells produced by plants during meiosis (making sex cells)—grow to haploid organisms (ex: mosses, fungi, ferns) Haploid=a cell that has only one chromosome of each pair—half as many chromosomes as the parent organism (n) Binary Fission—similar to mitosis-cell splits into two new cells of equal size.

Reproduction of Organisms Sexual Reproduction 2 haploid gametes (sex cells) unite to form a zygote (fertilized egg) Animals—almost all multicellular animals exist as Diploid organisms. Diploid= a cell that contains both chromosomes of a pair. (2n) Plants—most plants have a haploid and diploid form during their life cycle.

MITOSIS Mitosis—cell reproduction in which two identical cells are made from one cell All living things start life as a single cell All body growth and repair beyond this first cell happens through a process called mitosis. Chromosomes (contain genes made of DNA) are duplicated for each new cell This process takes from 30 minutes to several hours and occurs continuously in most organisms An exact duplicate of the original cell is made (much like duplicating or photocopying a piece of paper)

4. Steps of Mitosis Interphase Cells not dividing Performs all life functions (respiration and protein synthesis) Late interphase (DNA replicates and the chromosomes double—looks like grainy mass in nucleus)

Steps of Mitosis Prophase Cell gets ready to separate nuclear material Distinct rodlike pairs of chromosomes (chromatids with centromeres) become visible Nucleolus and nucleus breakdown and disappear The centrioles (in animals) move to opposite ends of the cell, making spindle fibers

Steps of Mitosis Metaphase Spindle fibers attached to the chromosomes allow all chromosomes to line up at the center of the cell.

Steps of Mitosis Anaphase The original chromosomes and their copies are guided to the opposite ends of the cells. Division of the cytoplasm begins.

Steps of Mitosis Telophase The cell membrane begins to pinch in the middle as the fibers begin to disappear. The nuclear membrane and nucleolus reappear.

Steps of Mitosis Two new cells have formed. Both cells have the same number of chromosomes as the original.

MEIOSIS Meiosis is cell division in which 4 daughter cells with half the number of chromosomes are formed. Meiosis results in egg and sperm cells (sex cells—gametes) in plants and animals and spores in some plant cells. Meiosis is very much like mitosis except the cell divides twice resulting in haploid daughter cells (they have half as much genetic material as the parent cell)

Mitosis

Cell Cycle