Cooksonia pertoni with sporangia Shrewsbury England Upper Silurian

Cooksonia pertoni with sporangia Shrewsbury, England Upper Silurian Size of the plant 2. 5 cm Cooksonia pertoni South Wales

Homework!!!! Your Plant Evolution Lab is due tomorrow! Do Not Waste your time!!!

Do IT NOW!!!! 1. When two gametes unite, they form a ______. 2. After meiosis, a diploid cell produces _____ cells. 3. If haploid cells undergo mitosis, what type of cells are formed? 4. What does a gametophyte produce? 5. What does a sporophyte produce?

Charophyta – green algae Green algae in the group Charophyta are commonly known as charophytes. They include many freshwater and terrestrial green algae. Chara and other stoneworts are among the largest and most structurally complex of the charophytes. Their main branches have whorls of short lateral branchlets at intervals. They usually grow submerged in mainly still, fresh or slightly brackish waters.

Chlorphyta and charophyta

Chlamydomonas will “mate” When gametes of opposite mating types are mixed, their flagella immediately agglutinate. This initial recognition event (Stage 1 in the diagram below), which is both gamete and mating type specific, is followed by one or more signals. These signal(s) trigger a series of events (Stage 2): (a) the cells release autolysin, an enzyme which digests the cell walls, (b) the flagella, which initially show a loose interaction along their entire length, now demonstrate tipping, a tighter interaction that occurs only at the flagellar tips, and (c) the mating structures, located on the cell (plasma) membrane, in close proximity to the flagellar origin, become "activated". Activation of cells of mating type + (mt+) results in production of a long, membrane-enclosed mating tubule (the activated mating structure) covered with a glycoprotein "fringe", and containing polymerized actin filaments. This activated mating structure is analogous to the acrosome found on sperm (the first sperm component to react with the egg). The mt- cells respond by moving membrane proteins (particles) to the center of the mating structure, a region of the plasma membrane that had been cleared of particles during gametogenesis, and producing a short-lived tubule with no microfilaments. When the two activated mating structures come into contact, they appear to be held together by an adhesive interaction (Stage 3), finally leading to fusion between opposite mating type cells (Stage 4) Stages in the mating reaction Mating-Defective Mutants A sex-limited mutant is expressed in only one mating type. Cells of the other mating type may carry the gene but do not express it, presumably because the gene is for a function specific to only one mating type. See the description of the fusion-defective mutants on the next page, or click the phase contrast image of the mutants below. Phase contrast image of adhering mutants These mutants are adhering by their mating structures