Plants

• Plant evolution occurred in 4 major events

  occurred

  • Vascular Tissue: Lycophytes
  • Megaphylls: Ferns
  • Seeds: Gymnosperms
  • Flowers: Angiosperms
• Alternation of Generation

  • A life cycle in which an organism has both haploid and diploid multicellular stages
  • Each type of plant exists in two forms:
  • Sporophyte(diploid 2n)
  • Produces haploid spores by meiosis
  • Gametophyte(Haploid 1n or n)
  • Produces gametes by mitosis
• The Dominant Generation is the generation that carries out the majority of photosynthesis

  • Non-vascular plants~gametophyte
  • Vascular plants~sporophyte
• Non-vascular plants

  • Dominant gametophyte
  • Lack vascular tissue
  • Ex. Moss and hornworts
  • Receive water and nutrients via diffusion and osmosis
  • Live in moist conditions
  • Lack true roots, stems, and leaves
• Vascular Plants

  • Evolved from non-vascular plants
  • Have vascular system
  • Can live in drier conditions
  • Has a true root, stems and leaves
  • Most of modern plants
• The nonvascular plants collectively are known as the bryophytes
• Gametophyte is the green,"leafy" part
• Adaptations and Uses of Bryophytes

  • The lack of vascular tissue and flagellate sperm accounts for short height
  • Are adapted to varying climates
  • Can colonize various structures
  • They form peat or bog moss
• Seedless vascular plants

  • Club mosses, horsetails, and ferns
  • The dominant sporophyte produces windblown spores
  • The independent gametophyte produces flagellated sperm that require outside moisture to swim to an egg
• A true vascular system

  • Xylem(water conduction)
  • Phloem("food" conduction)
• Lycophytes

  • Were among the first land plants to have vascular tissue
  • Microphylls(small leaves) have a single vein composed of xylem and phloem
  • The sporangia are borne on terminal clusters of leaves called strobila
  • Ex. Clubmosses
• Ferns

  • Have megaphylls(fronds)
  • large leaves with branched veins
  • Sporangia are often located in clusters(sori)
  • Found on underside of the fronds
• Adaptations and Uses of Ferns

  • Sporophyte and gametophyte are separated(physically)
  • Gametophyte is dependent upon water to achieve fertilization
  • Lack of true vascular tissue
  • Some ferns produce rhizomes(horizontal underground plant stems capable of producing the shoot and root systems of a new plant)
• Seed plants

  • Seed plants are the most abundant plants
  • Three major parts:
  • The seed coat
  • Protection
  • The stored food supply
  • Energy & protection
  • The embryo
  • Future plant
• Seed plants have two types of spores that produce two types of microscopic gametophytes

  • Pollen grain
  • Male gametophyte
  • Produces sperm
  • Ovule
  • Produces egg
  • Female gametophyte
• In gymnosperms, the ovule is not completely enclosed by sporophyte tissue at pollination

  In angiosperms, the ovule is completely enclosed by sporophyte tissue(the ovary) at pollination
• Gymnosperms

  • "naked seed"
  • The ovules and seeds of gymnospermsare exposed on a modified leaf called ascale
  • Ex. Conifers, Cycads
  • Thrive in mild climates
• Conifers

  • Produce cones
  • Cones contain the reproductive structures of the plant
  • Adapted to cold and dry weather
  • Produce resins to protect the tree from insect or fungal attack
• Angiosperms(Covered Seed)

  • Flowering Plants
  • Found in nearly all climates and can vary in size
  • Have 2 main structures
  • Flowers: Allows plants to form cooperative evo relationships
  • Fruits: Protects the developing embryo
• The Flower

  • Sepals: Protects the flower bud before it opens
  • Petals: Attracts particular pollinator
  • Stamen(Male) Consists of 2 components
  • Filaments: holds the anthers out
  • Anther: where the pollen is
  • Pistils/Carpels(Female)
  • Ovary
  • Style
  • Stigma
• Angiosperms are thought to have arisen much earlier
• Flower produces seeds enclosed by fruits
• Each of these eventually holds an egg-bearing female gametophyte called embryo sac
• Angiosperm success


  • Attributed largely to Flowers
  • Fruits
• Angiosperms are the flowering plants
• Fruit

  • The seed forms in the ovary - ovules mature to seeds after fertilization
  • As the seed develops, the walls of the ovary thicken and form the fruit
  • In botany, a fruit is fertilized & fully grown, ripened ovary
  • Many foods commonly called vegetables are technically fruits
• The carpel may contain several ovules
• Within the ovule, female megaspores undergo mitosis to produce the egg cell as part of the embryo
• Flowering Plant Life Cycle

  1. During pollination, a pollen grain is transported to the stigma

  2. The pollen tube germinates and extends a pollen tube to the ovule

  3. The pollen tube delivers two sperm to the female gametophyte to carry out double fertilization
• Adaptations and Uses of Angiosperms

  1. The fruit serves two primary purposes: Protect the seeds, Aid in the dispersal of the seed

  2. Fleshy fruits can be eaten by animals, transporting seeds to new locations
• Flowering Plant Life Cycle

  1. In some angiosperms, the embryo uses the seed endosperm as nourishment during germination

  2. In other angiosperms, the endosperm is fully absorbed into the cotyledons (seed leaves)

  3. A fruit is a matured ovary, Sometimes other parts of the flower contribute to the fruit
• Flowering Plant Life Cycle


  1. Flower produces seeds enclosed by fruits

  2. The carpel may contain several ovules

  3. Each of these eventually holds an egg-bearing female gametophyte called embryo sac

  4. Within the ovule, female megaspores undergo mitosis to produce the egg cell as part of the embryo sac
• Flowering Plant Life Cycle

  1. The flower anther produces male microspores

  2. Pollen has 2 main cells: Generative cell, Tube cell

  3. The pollen is released from the anther
• Flowering Plant Life Cycle

  1. The sperm are involved in two fusion events: One sperm fuses with an egg to form a diploid zygote

  2. The other sperm fuses with two polar nuclei to form the triploid endosperm

  3. The ovule develops into the seed, bearing the embryo and the stored nutrients (endosperm)
• Plants release oxygen (via photosynthesis)


  Oxygen is needed for cellular respiration
• Land plants are dependent on pollinators


  Only if pollinators are present and pollination occurs can these plants produce fruits
• Many pollinators (honeybees especially) are declining worldwide
• Plants absorb CO2 from the atmosphere


  Excess atmospheric CO2 contributes to global climate change