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Plant Evolution (Exam 3) - Coggle Diagram

- - - - gametophyte is the leafy structure that is visible and dominant in this life cycle
      - sporophyte is a temporary diploid structure that grows from the gametophyte
        
        completely dependent on the gametophyte for survival
    - - zygote formation
        
        life cycle begins with the zygote
        
        diploid cell formed after fertilization
      - sporophyte development
        
        zygote undergoes mitosis to develop into a multicellular sporophyte
        
        it is parasitic on the gametophyte
      - meiosis and spores
        
        inside the sporophyte, meiosis occurs to produce haploid spores
        
        spores are then dispersed into the environment
    - - archegoniophore
        
        holds the sporophyte above the gametophyte
        
        aiding in spore disperal
      - capsule and sporangium
        
        sporophyte contains a capsule where sporangia are located
        
        meiosis occurs within the sporangia to produce spores
  - - - haplontic cycle
        
        ancestor of land plants is believed to have a haplontic life cycle
        
        zygote (diploid) undergoes meiosis to form haploid cells
        
        then undergoes mitosis to create a multicellular haploid individual that produces gametes
        
        fusion of gametes forms a new zygote, restarting the cycle
      - haplo-diplontic cycle
        
        sporophyte
        
        multiceullular diploid stage that undergoes meiosis to produce haploid spores
        
        gametophyte
        
        multicellular haploid stage that develops from spores and produces gametes
        
        land plants exhibit a haplodiplontic life cycle
    - - heteromorphic
      - short-lived
      - simple
    - - thought to have evolved from the haplontic life cycle of green algae
      - evolution involved the zygote not undergoing immediate meiosis but instead replication through mitosis
        
        leads to a multicellular diploid stage
      - antithetic theory
        
        suggests that the sporophyte was inserted into the haplontic cycle
        
        results in a new multicellular diploid stage that wasn't present in the original cycle
  - - - pine life cycle
        
        zygote formation
        
        zygote undergoes mitosis to form an embryo
        
        part of the seed that will germinate into a large sporphyte
        
        microsporangia
        
        located in male cones
        
        undergoes meiosis to form microspores
        
        develops into pollen grains
        
        fetilization
        
        pollen grains can travel through the air to fertilize the egg in female cones
        
        eliminates the need for water
      - reduced gametophyte stage
        
        significantly smaller and dependent on the sporophyte for nutrition
      - dominant sporophyte stage
        
        sporophyte is the main plant structure
        
        diploid and produces spores through meiosis
    - - female cones
        
        larger
        
        megasporangia
        
        produces megaspores
        
        only one megaspore survives after meiosis
      - male cones
        
        smaller
        
        microsporangia
        
        where microspores develop
    - - aka embryo sac
      - contains 8 nucleu
        
        including egg and synegrids
    - - diversity of sporopyhtes
        
        angiosperms exhibit a lot of diversity
      - carpals and stamens
        
        carpal (female structure) contains the ovule
        
        male structure (stamen) contins microsporangia
    - - pollen grain structure
        
        mature pollen grains are multi-nucleated and adapted for air travel
      - germination
        
        upon landing on a female cone, the pollen grain germinates and grows a pollen tube to reach the egg
  - - - sporophyte
        
        diploid
        
        larger
        
        more complex
        
        often the dominant stage
        
        produces spores through meiosis
      - gametophyte
        
        halploid
        
        produces gametes through mitsos
        
        gametes- sperm and eggs
    - - heterosporous
        
        produces 2 types of spores
        
        megaspores
        
        female gametophytes
        
        microspores
        
        male gametophytes
        
        spores are within sporangia
        
        microsporangia
        
        contains male spores
        
        megasporangia
        
        contains female spores
      - flagellated sperm
        
        sperm swim to the egg
        
        require water for fertilization
- - - - crucial for sexual reproduction
      - develops from microspores
      - responsible for producing male cells
    - - greatly reduced structure
      - initially contains antheridia that produce sperm
        
        these structures became less prominent
        
        led to a focus on sperm production only
    - - early land plants had flagellated sperm
        
        it required water for movement to the egg
      - plants developed adaptations to reduce dependence on water
      - evolved to the formation of pollen grains that can be dispersed without water
    - - pollen grains have a protective covering called the exine
        
        prevents desiccation
      - dome grains develop air bladders to help with wind dispersal
    - - the pollen grain germinates and grows a pollen tube when it lands on a female structure (cone)
        
        this tube penetrates the megametophyte to deliver sperm to the egg
      - process takes over a year
    - - pollen tube growth is directed by the megagametophyte
        
        specifically by 2 cells called synergids that guide the tube to the egg
    - - the pollen tube can develop haustoria
        
        absorbs nutrients from surrounding tissues to support the growing microgametophyte until fertilization occurs
    - - the generative cell undergoes mitosis to produce 2 sperm nuclei while the tube nucleus helps control the growth of the pollen tube
  - - - key features
        
        naked seeds
        
        seeds are exposed on the surface of sporophylls
        
        ovule structure
        
        ovule consists of integuments, a spore wall, and the nucellus
        
        megagametophyte develops within the ovule
      - example
        
        pine ovule
        
        pine ovule includes
        
        integuments
        
        protective layers surrounding the ovule
        
        megasporangium
        
        contains the megasporocyte
        
        has not yet undergone meiosis
      - definition
        
        group of land plants that produce naked seeds
        
        ovules are not enclosed by an ovary
    - - definition
        
        flowering plants that produce seeds enclosed within a fruit (ovary)
      - key features
        
        double fertilization
        
        one sperm fertilizes the egg, the other fuses with polar nuclei to form endosperm
        
        ovule structure
        
        two integuments surrounding the nucellus and megasporangium
      - example
        
        lily ovule
        
        single megasporocyte
        
        undergoes meiosis to produce 4 megaspores, only one retained to develop into the megagametophyte
  - - - meiosis and megaspore development
        
        megasporocyte undergoes meiosis to produce 4 megaspores
        
        usually only one megaspore survives while the others degenerate
        
        allows for the retention of resources for the developing gametophyte
      - endosporic development of megagametophyte
        
        the retained megaspore undergoes mitosis to form the megagametophyte
        
        develops within the megasporangium
      - formation of megasporangium
        
        megasporangium contains the megasporocyte
        
        enclosed within protective integuments
        
        crucial for the development and protection of megaspores
      - fertilization and embryo formation
        
        fertilization occurs when sperm, produced by microspores, swims to the egg within the megagametophyte
        
        results in the formation of an embryo, which develops within the protective layers of the megasporangium
      - transition from homospory to heterospory
        
        heterospory is the production of two different types of pores
        
        microspores and megaspores
        
        microspores are small and develop into male gametophytes
        
        megaspores are larger and develop into female gametophytes
        
        more efficient reproduction and resource allocation
      - development of seed structures
        
        integuments surrounding the megasporangium evolve into the seed coat
        
        provides extra protection for the embryo
        
        megagametophyte serves as a nutrient source for the developing embryo
    - - megasporangium and integuments
        
        integuments protect the developing seeds
        
        vital in seed plant reproduction
      - endosporic development
        
        allows for the protection and nurishment of the developing gametophyte and embryo
  - - - mature ovules containing an embryo
      - provides protection and nutrition for the plant
      - crucial for survival and propogation
    - - progymnosperms
        
        likely ancestors of modern gymnosperms, also extinct
      - gymnosperms
        
        includes various species that produce seeds without flowers
      - seed ferns
        
        extinct group believed to be the first to develop seeds
      - angiosperms
        
        flowering plants divided into two main groups
        
        monocots
        
        eudicots
    - - integuments
        
        protective layers surrounding the megasporangium (nucellus)
      - micropyle
        
        opening allowing sperm to fertilize the egg
    - - fossils show early ovules with integument fusion
      - dates back to the late Devonian period (~360 mya)
      - gradual evolution of seeds
    - - heterospory
        
        production of different types of spores
      - protection mechanisms
        
        complete enclosure of the megasporangium enhances protection from desiccation and herbivory
        
        crucial for the survival of the developing embryo
  - - - nutrient storage
        
        seeds are packaged with nutrients
        
        allows them to sustain themselves during early growth stages
      - colonization of habitats
        
        seeds enable plants to colonize drier upland habitats
        
        moving away from water sources
      - dormancy
        
        seeds can remain dormant until conditions are favorable for growth
        
        increases the chances of survival for the embryo
    - - seed coat
        
        formed from the integuments
        
        protects the seed
      - endosperm
        
        specialized nutritive tissues formed from the triploid tissue
        
        provides nourishment to the embryo
      - cotyledons
        
        seed leaves that provide initial nutrient to the developing plant
        
        gymnosperms usually have multiple cotyledons
        
        monocots have one and eudicots have two
    - - gymnosperms
        
        seeds are often exposed and can have a fleshy outer layer
      - angiosperms
        
        seeds often undergo a process called double fertilization
        
        unique to flowering plants
    - - pollen grain germination
        
        the pollen grain lands on the stigma, germinates, and grows a pollen tube down the style
      - fertilization process
        
        the pollen tube releases 2 sperm nuclei
        
        one fuses with the egg cell to form a diploid zygote
        
        other fuses with 2 polar nuclei to form triploid endosperm
- - - - perfect flowers
        
        both male and female whorls present
      - imperfect flowers
        
        pistillate
        
        only carpals (female)
        
        staminate
        
        only stamens (male)
      - incomplete flowers
        
        missing any whorl (e.g. missing petals)
    - - gynomonoecy
        
        has hermaphroditic and pistillate flowers
      - andromonoecy
        
        has hermaphroditic and staminate flowers
      - dioecious
        
        separate plants for male and female flowers
      - trimonoecious
        
        has hermaphroditic, staminate, and pistillate flowers
      - monoecious
        
        plant has staminate and pistillate flowers
        
        e.g. corn
    - - inferior ovary
        
        located below other floral whorls
        
        e.g. apples (epigynous)
      - perigynous
        
        cup-like structure (hypanthium) partially enclosing the ovary
        
        e.g. cherries
      - superior ovary
        
        located above other floral whorls
        
        e.g. lilies (hypogynous)
    - - clusters of flowers on a common stalk (peduncle)
      - types
        
        umbels
        
        flowers with stems of equal length from a common point
        
        spikes
        
        flowers directly attached to the stem
        
        catkins
        
        astringent flowers, often drooping
        
        heads
        
        dense clusters of flowers
        
        racemes
        
        flowers along a central stem
    - - petals
        
        attracts pollinators
      - stamens
        
        male reproductive part (androecium)
      - sepals
        
        protects the flower bud
      - carpals
        
        female reproductive part (gynoecium)
  - - - calyx (sepals)
        
        outmost whorl
        
        typically green and leaf-like
        
        protects the flower bud as it develops
        
        can be colorful
      - corolla (petals)
        
        whorl of petals
        
        often colorful and attractive to pollinators
        
        helps with reproduction
      - androecium (stamens)
        
        male reproductive part
        
        consists of the filament and anther
        
        anther contains pollen sacs (microsporangia)
        
        where pollen grains develop
        
        produces male gametes (pollen)
      - gynoecium (carpals)
        
        female reproductive part
        
        consists of the stigma, style, and ovary
        
        stigma- catches pollen grains
        
        style- elevates the stigma
        
        ovary- contains ovules, which develop into seeds upon fertilization
    - - petals
        
        leaf-like structures with pigments to attract pollinators
        
        together form the corolla
      - stamens
        
        composed of anther (pollen production) and filament (supports anther)
      - sepals
        
        protect the flower bud, can be modified for color
      - carpals
        
        modified megasporophyll with stigma, style, and ovary
        
        crucial for seed and fruit development
    - - complete
        
        contains all 4 floral organs
        
        sepals, petals, stamens, and carpals
      - incomplete
        
        lacks 1 or more of the organs
    - - megasporophyll
        
        modified structure that produces ovules
      - pollination
        
        the transfer of pollen from anther to stigma
      - microsporangium
        
        site of pollen grain development
  - - - radial symmetry
        
        can be divided symmetrically at any angle
      - multiple whorls of pearls
        
        early flowers likely had many petals and reproductive structures
      - bisexual
        
        contains both female and male organs
    - - fossil evidence
        
        first evidence of flowers in the fossil record comes from Archaefructus sinensis
        
        dates back to around 124.6 mya
        
        believed to be aquatic and herbaceous
      - modern examples
        
        most primitive extant group of angiosperms is Amborella trichopoda
        
        found in New Caledonia
        
        exhibits characteristics of early flowers
        
        like numerous anthers and carpals
    - - patterns of evolution
        
        flowers transitioned from having an indefinite # of parts to a more definite structure
        
        ancient flowers had many petals and reproductive organs
        
        modern flowers tend to have a reduced and specific # of parts
      - arrangement and symmetry
        
        early flowers typically displayed a spiral arrangement of parts
        
        derived flowers often show fused structures and irregular symmetry
    - - androecium
        
        the male structure
        
        consists of anthers
      - gynecium
        
        female structure
        
        consists of carpals, # can vary
      - petals and sepals
        
        perianth consists of petals (corolla) and sepals (calyx)
        
        can be distinct layers in more evolved flowers