Biology 1442 Week 3 of notes for exam 2
Biology 1442 Week 3 of notes for exam 2 BIOL 1442
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This 3 page Class Notes was uploaded by Kristin O'Flaherty on Wednesday March 9, 2016. The Class Notes belongs to BIOL 1442 at University of Texas at Arlington taught by Dr. Roelke in Winter 2016. Since its upload, it has received 66 views. For similar materials see Evolution and Ecology in Biology at University of Texas at Arlington.
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Date Created: 03/09/16
3/7 Angiosperms are seed plants with reproductive structures called flowers and fruits They are the most widespread and diverse of all plants Sister to the gymnosperms In a single phyla Anthophyta Flower is an angiosperm structure specialized for sexual reproduction Pollinated by insects or animals or wind Specialized shoots o sepals, enclose the flower o petals, attract the pollinators o stamens, produce pollen o carpels, produce ovules Complete flowers have all four organs Those lacking one or more organs are incomplete flowers Radial symmetry multiple lines of symmetry Bilateral symmetry only one line of symmetry Most species have flowers with both functional stamens and carpels, but in some species they occur on separate flowers Flowers with stamens may be on the same plant as those with carpels, or they may occur on different plants Fruits protect seeds Tomatoes and grapefruits are considered fleshy fruits Various fruit adaptations help disperse seeds Seeds can be carried by wind, water, or animals to new locations Flower of the sporophyte is composed of both male and female structures Male gametophytes are contained within pollen grains produced by the microsporangia of anthers The female gametophyte, or embryo sac, develops within an ovule contained within an ovary at the base of a stigma Most flowers have mechanisms to ensure crosspollination between flowers from different plants of the same species A pollen grain that has landed on a stigma germinates and the pollen tube of the male gametophyte grows down to the ovary The ovule is entered by a pore called the micropyle Double fertilization occurs when the pollen tube discharges two sperm into the female gametophyte within the ovule One sperm fertilizes, and the other starts the food storage (endosperm) Triploid endosperm nourishes the developing embryo Within a seed, the embryo consists of a root and two seed leaves called cotyledons Darwin called the origin of angiosperms an “abominable mystery” Originated 140 million years ago Chinese fossils of 125 million years ago share some traits with living angiosperms Archaefructus sinensis has anthers and seeds but lacks petals and sepals Ancestors of angiosperms and gymnosperms diverged about 305 million years ago Angiosperms closely related to Bennettitales, extinct seed plants with flowerlike structures Likely small flowered shrubs Animals influenced the evolution of plants, vice versa Bilateral symmetry affects animals Two main groups: o Monocots o Dicots o Eudicots (true dicots) Basal angiosperms include the flowering plants Magnoliids evolved later Monocots are more than ¼ of the angiosperm species are monocots The largest groups are the orchids, grasses, and palms Eudicots are more than ⅔ of the angiosperm species Including legume fam and the economically important rose fam Human welfare depends on seed plants (key sources of food, fuel, wood products, and medicine 80% of all the calories on earth come from 6 species Destruction of habitat is causing extinction of many plant species 55,000 km of tropical forests are cleared each year The remaining tropical forests will be eliminated in 200 years Loss of forests reduces the absorption of atmospheric CO2 that occurs during photosynthesis 3/9 Loss of plant habitat is often accompanied by loss of the animal species that plants support At the current rate of habitat loss, 50% of Earth’s species will become extinct within the next 100200 years The tropical rain forests may contain undiscovered medicinal compounds CH 31: FUNGI Fungi are diverse and widespread They are essential for the wellbeing of most terrestrial ecosystems because they break down organic material and recycle vital nutrients About 100,000 species of fungi have been described It is estimated there are actually 1.5 million species of fungi Fungi are heterotrophs that feed by absorption Fungi exhibit diverse lifestyles o Decomposers o Parasites o Mutualists Most common body structures are multicellular filaments and single cells (yeasts) Some species grow as either filaments or yeasts; others grow as both Morphology of multicellular fungi enhances their ability to absorb nutrients Fungi consist of mycelia, networks of branched hyphae adapted for absorption A mycelium’s structure maximizes its surfacetovolume ratio Fungal cell walls contain chitin Most fungi have hyphae divided into cells by septa Coenocytic fungi lack septa Some fungi have specialized hyphae called haustoria that allow them to penetrate the tissues of their host Mycorrhizae are mutually beneficial relationships between fungi and plant roots Ectomycorrhizal fungi for sheaths of hyphae over a root Arbuscular mycorrhizal fungi extend hyphae through the cell walls of root cells and into tubes formed by invagination of the root cell membrane Fungi can produce spores from different types of life cycles Fungi propagate themselves by producing vast numbers of spores, either sexually or asexually Fungi use sexual signaling molecules called pheromones to communicate their mating type Plasmogamy is the union of cytoplasm from two parent mycelia In most fungi, the haploid nuclei from each parent do not fuse right away; they coexist in the mycelium called a heterokaryon In some fungi, the haploid nuclei pair off two to a cell; such a mycelium is said to be dikaryotic Hours days or even centuries may pass before the occurrence of karyogamy, nuclear fusion Become diploid Produce haploid cells Produces genetic variation Molds produce haploid spores by mitosis and form visible mycelia Yeasts can reproduce asexually Yeasts reproduce asexually by simple cell division and the pinching of “bud cells” from a parent cell Some fungi can grow yeasts and as filamentous mycelia Deuteromycetes are fungi that don't have a sexual stage Fungi are most closely related to unicellular nucleariids Animals are most closely related to unicellular choanoflagellates This suggests that multicellularity arose separately in animals and fungi The oldest undisputed fossils of fungi are only about 460 million years old (animals are about 700 million years old) Chytrids are responsible for amphibian deaths worldwide Fungi were among the earliest colonizers of land Fossil evidence indicates fungi form mutualistic relationships with early land plants Genomic analysis indicates genes involved in mycorrhizal formation, sym genes, were likely present in the common ancestor to land plants