botany intro1

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  • Course: Biology 3000, Botany

  • Instructor: Stacy T. Bennetts

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  • Introduction: Overview of key events and concepts in plant evolution.

  • Key Concepts: Alternation of Generations.

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Geologic Time Scale

  • Paleozoic Era: Encompasses early development of life on land.

  • Mesozoic Era: The age dominated by dinosaurs, significant for flowering plants (angiosperms).

  • Cenozoic Era: Known as the "age of mammals," following the extinction of dinosaurs.

Timeline of Plant Evolution

  • Age of Earth: 4600 million years ago (mya)

  • Origin of Life: 3800 mya

  • First Eukaryotes: 1800 mya

  • First Multicellular Life: 700 mya

  • First Land Plants: 500 mya

  • Angiosperms: 145 mya

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Concepts in Plant Evolution

  • Plant Classification

  • Plant Phylogenetics

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Carl Linnaeus (1707 - 1778)

  • Developed a Binomial System for naming organisms.

  • Example: "Catnip" (5 Latin words to 2): Nepeta cataria (L.) Candolle.

  • Introduced "taxonomy"; categorized organisms into taxa.

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Biological Classification Overview

  • Kingdoms Plantae and Fungi belong to the domain Eukarya.

  • Key Categories:

    • Kingdom: Plantae

      • Organisms primarily terrestrial, containing chlorophylls a and b in chloroplasts.

    • Phylum (Division): Anthophyta

      • Vascular plants with seeds and flowers.

    • Class: Monocotyledones

      • Embryo with one cotyledon, floral parts usually in threes.

    • Order: Commelinales

    • Family: Poaceae

    • Genus: Zea

    • Species: Zea mays (Maize/Corn)

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Standard Rank Ending Example

  • Division (Phylum): -phyta

  • Class: -opsida

  • Order: -ales

  • Family: -aceae

  • Genus: Lilium

  • Species: Lilium superbum L.

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Taxonomic Hierarchy Example

  • Phylum (division)

  • Kingdom: Plantae

  • Phylum: Anthophyta

  • Class: Magnoliopsida

  • Order: Fagales

  • Family: Fagaceae

  • Genus: Quercus

  • Species: Quercus virginiana (Live Oak)

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Phylogenetic Concepts

  • Phylogenetic Trees: Diagrams showing evolutionary relationships.

  • Cladistics: A method of classifying species based on common ancestry.

  • Cladogram: A branching diagram depicting clades.

  • Synapomorphy: A shared derived trait.

  • Monophyletic: A group from a single ancestor.

  • Paraphyletic: A group excluding some descendants.

  • Polyphyletic: A group with multiple ancestors.

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Homology in Plants

  • Similar structures indicating common ancestry:

    • Tendril

    • Spine

    • Leaflet

    • Leaf Petiole

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Not All Traits Indicate Common Descent

  • Homoplasy: Similar traits not due to common descent.

  • Convergent Evolution: Independent evolution of similar traits.

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Selected Characters for Phylogenetic Analysis

  • Parsimony Principle: The simplest explanation with the fewest assumptions is preferred.

  • Character States:

    • Present (+) and absent (-) conditions utilized in classification.

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Plant Evolution Concepts

  • Sexual Reproduction and Life Cycles

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Zygotic Life Cycle

  • Haploid Dominant:

    • Meiosis produces haploid cells; haploid adult develops via mitosis.

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Gametic Meiosis Life Cycle

  • Diploid Dominant:

    • Adult is diploid, producing haploid gametes through meiosis.

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Spores and Sporic Meiosis Life Cycle

  • Higher Plants Dominated by:

    • Alternating between haploid (gametophyte) and diploid (sporophyte) stages, with sporangia present during sporophyte stage.

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Alternation of Generations

  • Key definitions:

    • Gametophyte: Haploid stage.

    • Sporophyte: Diploid stage.

    • Exemplars: Ectocarpus, primitive brown algae, ferns.

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Generational Examples

  • Plants Examples:

    • Moss: Gametophyte dominant.

    • Fern: Both forms present.

    • Gymnosperms: Dominant sporophyte generation.

    • Angiosperms: Flowering plants with evolutionally advanced reproductive forms.