Gymnosperms, Angiosperms, & Life Cycles 

A wonderful artistic view of flowers...enjoy!

Vascular Plant Reproduction & Introduction to Flowers

• ferns (spores) - won't mention again here

• gymnosperms (pollen, naked seeds - no flowers), angiosperms (pollen, seeds, flowers, fruits)

• sporophyte dominant - grows from a seed!

• pollen or ovules

• does not need water to reproduce, wind pollinated or vector (insect, etc. - mutualism) pollinated

• Flowers contain gametophytes (pollen and ovum)

• perfect flowers - contains male and female parts on same flower

• parts of the flower - sepal, petal, anther, pollen, filament, stamen, ovules, ovary, style, stigma

• after fertilization - ovule swells, ovule wall hardens (will be a seed), and ovary envelops it and becomes a fruit

• fruits move seeds far from parents...unlike gymnosperms

Gymnosperm Plant Reproduction - Detailed

• know the detailed life cycle

• pollen cone - sporophyte generation - meiosis - haploid microspore (seed plants are heterosporous - not homosporous like bryophytes)

• female cone - sporophyte - ovule - Megaspore mother cell - meiosis - 4 haploid cells - only two survive - one is the Megaspore (grows via mitosis) - another cell will give rise to endosperm (endosperm mother cell)

• windblown pollen (pollen is vehicle for haploid sperm) fertilizes egg in female cone - haploid Megaspore combines with haploid microspore to create diploid zygote -- endosperm mother divides via mitosis and becomes endosperm (haploid)

• Zygote = embryo, endosperm = food for embryo --> both contained with seed

Flowering Plant Reproduction - Detailed

• parts of the flower:  sepals, petals, anther + filament = stamen, stigma + style + ovary = carpel

• what is meant by a perfect flower? What other types are there?

• male parts

  • • anther - microspore mother cells (not spores) - diploid cell - must undergo meisosis to become haploid microspores to become pollen 

    • pollen (male gametophyte) - two cells - tube cell and generative cell (generates sperm cells)

• female parts

  • • inside carpel - inside ovary - ovules are egg producing structures - diploid cell - diploid megaspore mother cell undergoes meiosis forming haploid megaspores - all but one disintegrates - one survives and is our female gametophyte

    • 3 rounds of mitotic divisions - but only 7 cells produces (one cell has 2 nuclei)

    • we have the egg (haploid), endosperm mother cell (n+n, cell with two nuclei) and the rest are synergids (will disintegrate)

• Pollination

  • • pollen needs to get from anther to stigma (wind, water, biotic vector)

      • • petals, nectar, fragrance evolved for biotic vectors

    • coevolution between flowers and pollinators

    • pollen lands on stigma...this is pollination!

• Fertilization

  • • tube cell creates a tube down through the style to the ovary

    • generative cell generates two sperm that travel down the tube

    • double fertilization event

      • • one sperm fuses with egg to make zygote

        • other sperm fuses with endosperm mother cell to make a triploid cell - beginning of endosperm (nutritive tissue for embryo)

        • synergids disintegrate

• Embryo and Seed development

  • • zygote divides by mitosis (grows) - embryo has lobes of meristematic tissue (think meristems like apical-at the tips, intercalary-in the middle, and lateral-at the sides) called cotyledons

    • embryo matures, ovule becomes detached from the ovary and outside thickens - ovule becomes the seed

    • Seed is covered by fruit 

• Fruit Development

  • • ovule = seed, ovary = fruit

    • what is the function of fruit?

      • • aid in seed dispersal - this is achieved in lots of different ways!

Double fertilization in detail - get to know it!

Enjoy the time lapse!

Enjoy the time lapse!

Flowers and dinosaurs...

I. Introduction

• Orchids are masters of deception, mimicking the appearance and scent of insects to attract pollinators.

• This strategy is known as sexual deception.

II. The Mimicry

• Orchids imitate the specific shapes, colors, and textures of female insects.

• They precisely mimic the scent of a single insect species, further enhancing the deception.

III. The Pollinator's Deception

• Male insects are lured by the orchids' false signals, believing they have found a mate.

• The insect attempts to mate with the orchid, unknowingly collecting pollen in the process.

• On visiting another orchid, the insect deposits the pollen, facilitating pollination.

• Some orchids make the deception more convincing by offering a fake pollen reward or even providing a "landing platform" for the insect.

IV. Evolutionary Advantages

• Sexual deception increases pollination efficiency for the orchid, especially in areas where their specific pollinator may be scarce.

• It may reduce competition with other flowering plants that rely on more generalist pollinators.

V. Disadvantages

• Reliance on a limited number of pollinator species makes orchids vulnerable if the pollinator population declines.

• Pollinators can learn the deception over time, decreasing the effectiveness of the strategy.

VI. Extreme Examples

• Some orchids produce a substance similar to the female insect's sex pheromone, driving male insects into a frenzy.

• In a few cases, male insects have been observed ejaculating on the orchid, wasting valuable sperm and harming their own reproductive potential.