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Chapter 9 Flowers and Reproduction, Cross-Link Description: Cross…

- - - - producing offspring that have
        
        identical copies of
        
        parental genes
      - generating new individuals that
        
        are genetically different
        
        from the parents
  - - - survive better
        
        than genetically homogenous species
    - - opposite is true
  - - - it is selectively advantegous
        
        for organism to reproduce asexually
        
        by budding or
        
        sending out runners
        
        thus producing new
        
        similarly adapted individuals
    - - offspring may find themselves
        
        in conditions
        
        for which they
        
        are poorly adapted
        
        if all are identical
        
        all may die
      - instable environment
        
        can result from
        
        many factors
        
        landslides
        
        avalanches
        
        road buildings
  - - - disrupt plant communities
        
        if species genetically same
        
        all may die
        
        if genetically different
        
        some individuals may survive
        
        may be sufficient enough
        
        to repopulate species
  - - - progeny are never
        
        more fit than parent
    - - sex cells of one plant
        
        with those of one or
        
        several others
        
        resulting in many
        
        new gene combinations
        
        small cells so
        
        many can be produced
        
        by single plant
        
        so many new combinations
        
        of genes can be "tested"
        
        1 more item...
      - can have negative effects
        
        two individuals are required
        
        potential sex partners
        
        may be widespread
        
        sex cells must move
        
        from one plant to another
        
        move by wind
        
        insects or birds
        
        results in loss
        
        1 more item...
    - - both sexual and sexual
        
        example
        
        strawberries
        
        have flowers and
        
        sexual reproduction
        
        involving genetically diverse
        
        1 more item...
        
        have runners
        
        for asexual reproduction
    - - produced by sexual reproduction
      - often means of
        
        long-distance dispersal
        
        can be have consequences
        
        seeds may be widespread
        
        germinate in numerous sites
        
        each site differing
        
        3 more items...
        
        if produced in large numbers
        
        some will land
        
        in suitable habitat
- - - - grows to several
        
        meters in length
      - individual plants
        
        become self sufficient
        
        by establishing adventitious roots
    - - branches are poorly attached
        
        breaks off easily
        
        parts then form roots
        
        and become independent
  - - - flowers would be expected
        
        look like small bulbs
        
        called bulbils
  - - - form on roots
        
        then grow into plants
      - may grow even when
        
        parent plant still alive
- - - - sporophytes always diploid
        
        have organs with cells
        
        capable of undergoing meiosis
        
        results in haploid spores
        
        cannot undergo syngamy
        
        each undergoes mitosis and
        
        1 more item...
      - two types of gametes
        
        microgametophytes are "male"
        
        produce sperm
        
        grow from microspore
        
        megagametophytes are "female"
        
        produce eggs
        
        grow from megaspore
        
        produced by
        
        one kind of sporophyte
  - - - basically a stem
        
        with leaf-like structures
      - stalk is pedicel
      - receptacle
        
        at very end of axis
        
        where other flower parts
        
        are attached
      - four types of floral appendages
        
        sepals
        
        petals
        
        stamens
        
        carpels
      - complete flowers
        
        have all four
        
        types of appendages
      - incomplete flowers
        
        lack one or two
        
        types of appendages
    - - lower and outermost
        
        of four floral appendages
      - modified leaves that
        
        surround and enclose
        
        other flower parts
        
        as they mature
      - typically are the
        
        thickest, toughest, and waxiest
        
        of the flower parts
      - protect flower bud as
        
        it develops
        
        keeping bacterial and
        
        fungal spores away
        
        maintaining a high humidity
        
        inside the bud
        
        1 more item...
      - all sepals together
        
        called calyx
      - may be colorful (pelatoid)
        
        to help attract pollinators
    - - together make up
        
        a corolla
      - located above sepals
        
        on the receptacle
      - sepals + petals
        
        constitute flower's perianth
      - "leaf-like"
        
        being broad and
        
        flat and thin
        
        differ from leaves in that
        
        they contain pigments
        
        other than chlorophyll
        
        have fewer or
        
        no fibers
        
        tend to be thinner
        
        and more delicately constructed
      - important in that they
        
        attract the CORRECT pollinators
      - many have pigments
        
        that absorb ultraviolet light
        
        attracting insects
      - Do not develop if
        
        pollen is carried by
        
        wind or water
    - - located above petals
      - known collectively as androecium
      - frequently referred to as
        
        "male" part of flower
        
        because they
        
        produce pollen
        
        technically not
        
        because they are
        
        part of sporophyte
      - have two parts
        
        filament
        
        its stalk
        
        anther
        
        where pollen is produced
        
        composed of diploid cells
        
        in each anther
        
        four long columns of
        
        tissue become distinct
        
        as some cells enlarge and
        
        1 more item...
        
        microsporocytes
        
        continue to enlarge
        
        and then undergo meiosis
        
        each producing four microspores
    - - constitute the gynoecium
      - located at highest level
        
        on the receptacle
      - have three main parts
        
        stigma
        
        catches pollen grains
        
        style
        
        elevates the stigma
        
        to a useful position
        
        ovary
        
        where megaspores are produced
        
        inside are placentae
        
        regions of tissue that
        
        bear smalle structures
        
        called ovules
        
        4 more items...
      - usually fused together
        
        called a pistil
  - - - develop from microspores
      - very small
        
        and simple
        
        consisting of three cells
        
        located within the
        
        original pollen cell wall
      - microspore nucleus
        
        migrates to side of
        
        pollen grain
        
        and lies near wall
        
        there it divides mitotically
        
        producing a large vegetative cell
        
        1 more item...
      - consist of vegetative cell
        
        and two sperm cell
        
        the microgametes
    - - develops from megaspore
        
        from within ovule
      - one type of development
        
        nucleus undergoes three
        
        mitotic divisions
        
        producing 2-4-8 haploid cells
        
        all in a
        
        single, undivided cell
        
        form embryo sac
        
        nuclei migrate through cytoplasm
        
        1 more item...
  - - - zygote also begins
        
        to grow
        
        always by both
        
        nuclear and cellular divisions
        
        a co-enocytic stage
        
        never occurs in embryo
        
        into small cluster of cells
        
        part of which later become
        
        the embryo proper
        
        other part becomes
        
        short stalk like structure
        
        called suspensor
        
        3 more items...
  - - - ovary surrounding ovule
      - varies with the nature of
        
        the carpels as
        
        well as nature of
        
        mature fruit
    - - exocarp
        
        the outer layer
        
        the skin or peel
      - mesocarp
        
        the middle layer
        
        or flesh
      - endocarp
        
        innermost layer
        
        may be tough
        
        like pit of cherry
        
        may be thin
      - entire fruit wall
        
        called pericarp
- - - - by pollen from
        
        a different individual
    - - and egg cells
        
        from different plants unite
        
        resulting in
        
        new combinations of genes
        
        at least a few
        
        will be better adapted
        
        1 more item...
  - - - that have both
        
        stamens and carpels
        
        is prevented if
        
        anthers and stigmas mature
        
        at different times
    - - anthers release pollen
        
        while stigma tissue are
        
        immature and unreceptive
        
        the style may not
        
        have elongated yet
        
        and stigmas may be
        
        1 more item...
    - - lives briefly
        
        being susceptible to
        
        desiccation in dry air
        
        and to damage to
        
        its DNA by UV light
    - - become mature
        
        there may be no
        
        living pollen left
        
        in flower
        
        so all pollination
        
        is affected by younger flowers
        
        1 more item...
  - - - self-pollination inhibited
        
        by compatibility barriers
        
        chemical reactions
        
        between pollen and carpels
        
        that prevent pollen growth
    - - as a pollen tube grows
        
        the stigma and style
        
        test proteins
        
        on the tube's surface
        
        if one of the proteins
        
        is produced by a gene
        
        1 more item...
    - - the critical proteins are
        
        deposited on the outer surface
        
        of the developing pollen grain
        
        by the anther's tapetum
        
        any match of proteins
        
        produced by the incompatibility genes
        
        1 more item...
  - - - a pollen grain
        
        reaches a stigma
    - - evolution of flowering plants
    - - increased a plant's distinctiveness
        
        its recogniziability by insect
        
        flower color
        
        size
        
        became selectively advantageous
        
        also rewards such as
        
        sugary nectar or
        
        1 more item...
        
        fragrance
        
        shape
        
        most are radially symmetrical
        
        any longitudinal cut through
        
        the middle produces
        
        1 more item...
        
        Zygomorphic
        
        bilaterally symmetrical
        
        better designed to
        
        1 more item...
- - - - and visited by pollinators
        
        positions of flowers
        
        relative to other flowers
        
        leaves and trunk
        
        height from ground
        
        distance from open
        
        uncluttered flight path
  - - - give a collective
        
        visual signal to pollinators
        
        one small flower may be
        
        overlooked but
        
        not 100 flowers grouped together
    - - of accurately timing
        
        initiation, maturation, and opening
        
        of the flowers
    - - determinate inflorescence
        
        only limited potential for growth
        
        because inflorescence apex
        
        converted to flower
        
        terminal flower opens first
        
        then a bract with axillary flower
        
        then another bract and so on
      - Indeterminate inflorescence
        
        lower or outermost flowers
        
        open first
        
        new flowers still being initiated
        
        at the apex
  - - - can be targeted by
        
        nectar robbers
      - easily seen by herbivores
- - - - fruits containing only
        
        ovarian tissue
    - - fruits with any
        
        nonovarian tissue is present
    - - affects nature of fruits
    - - fruit developed
        
        from single ovary
        
        or fused ovary
        
        of one flower
      - most common kind
    - - if separate carpels
        
        of one gynoecium fuse
        
        during development
      - raspberries is example
    - - examples
        
        figs
        
        pineapples
        
        mulberries
      - during development
        
        all of individual fruits
        
        of an inflorescence fuse
        
        into one fruit
      - largely accessory fruit