Transcript Lecture 3
Biology 103 - Main points/Questions 1. Remember how plants and animals reproduce? 2. What else makes plants special 3. What is different about the fungi? 4. Are growth and development the same thing? Remember Animal life cycles: • Meiosis produces • Gametes fertilize to make a • This produce a undergoes to . • Few animals have asexual reproduction exclusively Remember Animal life cycles: • Meiosis produces gametes (haploid) • Gametes fertilize to make a diploid zygote • Zygote undergoes mitosis to produce a multicellular diploid organism. • Few animals have asexual reproduction exclusively Fig. 10.3.b Remember plant life cycles: • Meiosis produces • Haploid divide (mitosis) to make haploid a(n) _____ plant • This produces – specialized haploid sex cells (like animals) • These make a fuse (called ) to (grows into an embryo) Remember plant life cycles: • Meiosis produces spores • Haploid spores divide (mitosis) to make haploid a “gametophyte” plant • Gametophytes produce gametes – specialized haploid sex cells (like animals) • These gametes fuse (fertilization) to make a zygote (grows into an embryo) What is a Plant? Some characteristics: (1) Plants are multicellular eukaryotes. (2) Plants are autotrophic (3) Plants alternate multicellular haploid and multicellular diploid generations • What does that mean? Plants: 1. Alternate haploid and diploid stages 2. Each is multicellular 3. Different groups have different stages that are most common. More Plant characteristics (4) Plants have embryos that are dependent on a mature plant for nutrition (5) Plant cells have cellulose cell walls that provide structural support. More Plant characteristics (6) Special adaptations for life on land • • • Most have special transport tissues/structures (roots, vascular tissue…) Can team up with fungi to absorb nutrients (mycorrhizae) Waxy cuticle (slows water loss) & Stomata (allows gas exchange) Fig. 22.2.b More Plant characteristics Subcategories of Plants: • The plant kingdom has many subdivisions we will talk mostly about four: – Mosses – some of the most primitive land plants, lack vascular tissue, dominant gametophyte – Ferns – seedless vascular plants • More subcategories – Conifers/gymnosperms – plants with seeds but without flowers and fruit – Flowering plants (angiosperms) – plants with flowers and fruit for reproduction Last Kingdom to focus on is Fungus • Lots of different types we will focus on one – the group that includes the gilled mushrooms you are most familiar with • Like other groups most fungi use sexual reproduction at least some of the time. What is an Fungus? Four criteria describe the Fungi. (1) Fungal cells have a cell wall of chitin (of course still have membrane!) (2) Fungi are heterotrophic eukaryotes – Fungi secrete exo-enzymes that digest macromolecules outside their bodies. They then absorb the smaller subunits - causing them to be called absorptive heterotrophs. (3) Fungal cells are usually form long threadlike filaments called hyphae – The body of a majority of fungi is a complex mat of these hyphae called a mycellium – Mushrooms are only a small part of the body of a fungus • Mass of hyphae – called a mycelium – the mycelium is the main “body” of the organism – the mycelium usually contains several meters of hyphae • Individual hypha – each hypha is basically a long string of cells – Mitosis generates new cells • cells communicate through gaps in wall called septa (singular, septum) cell wall cytoplasm pore septum two haploid nuclei – cytoplasm can flow freely among the cells of the hypha – 2 haploid nuclei often in a single cell (= dikaryotic) Septum and pore between cells (4) Fungal life cycles are dominated by a haploid phase that grows from a haploid spore by mitosis. – Most fungi reproduce both sexually and asexually – Fungal life cycles are distinctly different from plants an animals Fungal Life Cycle Terminology: • Haploid v. Diploid • Dikaryotic • Spore • Mating type Sexual reproduction in Fungi Haploid Spore Mitosis Meiosis Cells Fuse Mitosis Dikaryotic Cell Fungal life cycles main ideas: • Meiosis produces spores • Haploid spores divide (mitosis) to make haploid mycelium • Any cell can fuse with a cell of another mating type (no specialized gametes!) • Cytoplasm joins but not nucleus at first (dikaryotic cell!) Fig. 21.8.a Some fungi have very long-lived dikaryotic mycelia • These are reproductive structures of mycelium that may be huge • Some spread over 3.4 square miles and may be 2500 years old. Fig. 21.12 • Fairy Rings – A ring of mushrooms may appear overnight. – These are the reproductive structures of an underground mycelium (grown from a spore) – As the mycelium grows out, it decomposes the organic matter in the soil and mushrooms form just behind this advancing edge. Growth vs. Development • These fairy rings help illustrate the difference between growth and development • What do you think is the difference? • The mycellium is growing through the soil but it is only when conditions are right that the fungus triggers the development of mushrooms. Growth vs. Development • Growth occurs as – Cells divide – Cells increase in size • Development occurs as cells alter gene expression (cell differentiation) • Plants and Animals use different strategies Plant and Animal development patterns Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Plant Growth & Development • In flowering plants we still see haploid (gametophyte) and diploid (sporophyte) stages. • Main plant is sporophyte – Gametophyte is retained by sporophyte • Looking at the development of embryo – First look at flowers Fig. 22.17.a Fig. 22.17.a Stamen is both filament sepal petal stigma anthers style Plant Growth & Development • In flowers the sporophyte generation gives rise to the gametophyte in two different places • Male gametophyte produced in Anthers • Female gametophyte is produced in Ovule • Lets see how… • Male gametophytes are produced in the anther… • Meiosis occurs and produces microspores • These undergo mitosis to produce pollen (the male gametophyte) • Female gametophytes are produced in the ovule (inside an ovary)… • Meiosis occurs and produces a megaspore • The megaspore undergoes meiosis to produce an embryo sac (the female gametophyte) mature pollen sperm cells (n) tube cell nucleus stigma sperm style tube cell nucleus ovary integuments egg (n) polar nuclei within central cell Development into an embryo What about animal embryos – do we all have shelled eggs? • Reproduction & Development • In most, a small flagellated sperm fertilizes a larger, nonmotile egg to make a zygote • The zygote undergoes cleavage (mitosis), forming a hollow ball of cells called the blastula. • Some cells of the blastula then “crawl” inside (gastrulation) • This forms a gastrula with 2 tissue layers and an opening (the blastopore!) • Gastrulation produces three tissue layers • Occurs after implantation in humans (and other placental mammals) • The placenta provides continuous nutrition during development instead of stored yolk • Three tissues are: – Ectoderm (outside) – Mesoderm (middle) – Endoderm (inside) • Tissues specialize to become... • Three tissues are: – Ectoderm (outside) – Mesoderm (middle) – Endoderm (inside) • Tissues specialize to become... Protostomes and Deuterostomes • there are two major kinds of animals representing two distinct evolutionary lines – protostomes • the mouth develops from or near the blastopore – deuterostomes • the anus forms from or near the blastopore; the mouth forms on another part of the blastula Figure 25.34 Embryonic development in protostomes and deuterostomes. Protostomes and Deuterostomes • deuterostomes also differ from protostomes in three other fundamental ways – the pattern of cleavage • protostomes have spiral cleavage while deuterostomes have radial cleavage – fating of cells • it occurs later in deuterostome cleavage than in protostome cleavage – origin of the coelom Biology 103 - Main points/Questions 1. Remember how humans reproduce? 2. What makes an organism an animal & how do we subdivide the animal kingdom? 3. What are some other animal reproductive strategies? 4. What is different about the fungi?