2 Asexual vs. Sexual Reproduction Part 1:Asexual vs. Sexual Reproduction
3 I. Asexual Reproduction Form of reproduction where only one parent is involved.Also reproduction without the fusion of gametes (sperm and egg)Primary form of reproduction for single-celled organisms such the bacteria, and protists. Many plants, fungi, and even some animals reproduce asexually as well.
4 II. Types of Asexual Reproduction: Binary Fission: used by bacteriaFragmentation/Regeneration: used by organisms such as Fungi, Moss, Sea Stars, PlanariaBudding: used by organisms such as yeast and hydra
5 Binary Fission Asexual Cell splits and replicated DNA goes with each partProkaryotes, Bacteria+ Fast and easy- Everybody has the same DNA
6 Fragmentation/ regeneration AsexualBody of parent breaks and produces offspringFungi, moss, sea stars, planarian+ Easy- Parent broken, same DNAFragmentation or Clonal Fragmentation is a form of asexual reproduction or cloning where an organism is split into fragments. The splitting may or may not be intentional. Each of these fragments develop into mature, fully grown individuals that are a clone of the original organism. If the organism is split any further the process is repeated.Fragmentation is seen in many organisms such as molds, some annelid worms, and starfish. Binary fission of single-celled organisms such bacteria, protozoa and many algae is a type of fragmentation.Molds, yeast, and mushrooms, all of which are part of the Fungi kingdom, produce tiny filaments called hyphae. These hyphae obtain food and nutrients from the body of other organisms to grow and fertilize. Then a piece of hyphae breaks off and grows into a new individual and the cycle continues.Fragmentation is observed in nonvascular plants as well, liverworts and mosses.
7 Fragmentation/ regeneration Fragmentation or Clonal Fragmentation is a form of asexual reproduction or cloning where an organism is split into fragments. The splitting may or may not be intentional. Each of these fragments develop into mature, fully grown individuals that are a clone of the original organism. If the organism is split any further the process is repeated.Fragmentation is seen in many organisms such as molds, some annelid worms, and starfish. Binary fission of single-celled organisms such bacteria, protozoa and many algae is a type of fragmentation.Molds, yeast, and mushrooms, all of which are part of the Fungi kingdom, produce tiny filaments called hyphae. These hyphae obtain food and nutrients from the body of other organisms to grow and fertilize. Then a piece of hyphae breaks off and grows into a new individual and the cycle continues.Fragmentation is observed in nonvascular plants as well, liverworts and mosses.Moss
8 Budding Asexual Offspring grows out of parent Yeast, hydras + Fast, somewhat easy- Same DNA
10 III. Asexual Advantages Need one individual to reproduce; can conserve energyNo genetic change “good” if environment is stableAll individuals are producing offspringMore efficient passing genes, “faster”
11 IV. Asexual Disadvantages No recombination of genes An asexual population tends to be genetically staticMutant allelesBeneficial alleles
12 V. Sexual Reproduction: Processes that pass a combination of genetic material to offspring, resulting in diversity.The main two processes are:meiosis (involving the halving of the number of chromosomes)fertilization (involving the fusion of two gametes and the restoration of the original number of chromosomes.
13 VI. Advantages of Sexual Reproduction Offspring are genetically unique from:A. Crossing overB. Independent assortment C. Random fusion of gametesFavorable when the environment is not stableSlower rate of reproduction but faster adaptation/evolutionLower extinction ratesFast removal of bad mutations or can put two beneficial mutations togetherBetter adaptation to host-parasite arms race.Offspring are dispersed widely to endup in different places from their parents
14 VII. Disadvantages of Sexual Reproduction 1. Need two parents “must expend energy” to find, identify (court), and copulate with mate2. Genetic recombination is counter productive if conditions are stable
17 Why Cell Division? Necessary for the growth of organisms. Necessary for every cell in organism to have the genetic instructions to survive.Genetic instructions passed through DNA in chromosomes.
18 The Cell Cycle: Cell division occurs during the cell cycle It is the repeating set of events that make up the life cycle of a cell.Divided into two phases:Interphase: time between cell divisionsCell Division: consists of two stagesMitosis: division of nucleus.Cytokinesis: division of cytoplasm of the cell.
21 Stages of Interphase: 1. G1 Phase: cell growth. 2. S Phase: DNA replication.G2 Phase: growth and prep***G0 Phase: used by some cells to exit cell cycle
22 Stages of Cell Division in Eukaryotes: ProphaseMetaphaseAnaphaseTelophase
23 Events of Prophase: DNA coils into chromosomes. Nucleolus disappears; nuclear membrane disappear.Centrioles appear and migrate to opposite sides of cell.Spindle fibers form
24 Events of Metaphase:Chromosomes migrate to the center of the dividing cell. Held in place by the spindle fibers.
25 Events of Anaphase: Sister Chromatids pulled apart by fibers. Chromatids pulled toward centrioles.Now have individual chromosomes at opposite ends of cell.
26 Events of Telophase and Cytokinesis: Spindle fibers disassemble.Nuclear membranes form around chromosomes at each end.Chromosomes uncoil.Nucleolus forms in each new nucleus.CYTOKINESIS occurs.Cell membrane pinches inward (forms cleavage furrow) until two cells form.
27 Stages of Cell Division in Prokaryotes: Process called Binary Fission.Chromosome makes copy of itself.2. Cell grows until it is twice its normal size.Cell wall forms between two chromosomes, and splits into two new cells.
28 Multicellular Organization: Levels of Organization:Tissue: groups of CELLS carrying out specific function (EX. epithelial).Organ: groups of TISSUES performing specific function (EX. stomach).Organ system: group of ORGANS performing specific function (EX. digestive system).*** SEE FIGURE 4-18 (p. 88)
30 I. Meiosis:A. Meiosis is a reduction division, which means dividing cells begin as diploid (2n) and divide by mitosis into four haploid (1n) cells.B. Meiosis involves two mitosis divisions.The first cell division is called Meiosis I and the second cell division is called Meiosis II.Cells preparing for meiosis first undergo G1, S, and G2 phases of Interphase.
31 II. Steps of Meiosis I:Prophase I: Same as prophase in mitosis, but Synapsis (the pairing of tetrads- does not occur in mitosis) and CROSSING-OVER occurs (does not occur in mitosis).Metaphase I: Tetrads line up randomly along the equator of the cell.Anaphase I: Each homologous chromosome moves to opposite pole of cell (called Independent Assortment).Telophase I: Chromosomes reach opposite sides of cell, cytokinesis begin. Result is two new cells that contain a haploid number of chromosomes.
32 III. Steps of Meiosis II: Prophase II: Spindle fibers form in each cell from Meiosis I.Metaphase II: Chromosomes move to the equator of the daughter cells.Anaphase II: Chromatids separate and move towards the poles of the cell.Telophase II: Nuclear membrane and nucleolus reappears in each of four new cells; each cell contains half of the original cell’s number of chromosomes.