Now we get to seed plants - what this course is all about! Know the gymnosperm and angiosperm life cycles and how alternation of generations is still present but in a very different form! Get a detailed understanding of cones and flowers and what takes place in and around them! Also pay attention to where mitosis happens and where meiosis happens and keep track of diploid vs haploid!
A wonderful artistic view of flowers...enjoy!
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
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
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!
Enjoy the Time Lapse!
diagram for gymnosperms if it helps
diagram for angiosperm if it helps
diagram for angiosperm if it helps