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CHAPTER 30: PLANT
DIVERSITY II
the evolution of seed plants
Common to all seed plants:
- Reduced (miniature) Gametophytes
- protects egg-containing gametophytes from environmental
stress
- enables dependent gametophytes to obtain nutrients from
sporophyte
- Heterospory
- megasporangia -> single, functional megaspore ( female
gametophyte)
- microsporangia -> vat numbers of microscpores (male
gametophyte)
Heterospory
.
Common to all seed plants:
- Ovules
- feamle gametophyte is
developed
- Pollen
- male gametophyte
Gymnosperm evolution
-dominance when drier climate favored spread of
gymnosperms (Carboniferous ecosystem)
-needle-shaped leaves
- angiosperm structure specialized for sexual reproduction
- carpel: megasporphyllis (female)
- stamen: microsporophyllis (male)
Fruits
- Typically consists of ovary, may include other parts
- Develops after pollination triggers hormonal changes, causes
ovary to grow
- wall of ovary: pericarp
- seed dispersal:
wind, water, animals (cling to fur), edibility (feces)
Angioperm Life Cycle
- Double fertilization
- 2 sperms : one fertilizes egg, other fuses with two nuclei in the
large central cell of the female gametophyte
- Divide into endosperm, tissue rich in food reserves
- Function:
1)synchronizes development of food storage with development
of embryo
2) prevents flowering plants from wasting nutrients on infertile
ovules
ovule -> seed -> embryo -> root and seed leaves (cotyledons)
Angioperm Life Cycle
.
Angiosperms . . . . .
Evolution:
Archaefructus liagoningenis - closest relative
of all angiosperms
- mostly male hypothesis: ovules developed on
microsporophyllis from mutations in the (separate)
pollen producing and ovule producing structures
Diversity:
Monocots (1 cotyledon) and Eudicots ("true dicots", 2 cotyl.)
-basal angiosperms, magnoloids
Plant-pollinator relationships
- coevolution, both benefit
Human welfare
-Use seed plants for food, fuel, wood
and medicine
-Reliance makes preservation of plant diversity critical
-Growing population: threat to plant diversity
works cited
http://2.bp.blogspot.com/-edIn4Ts63G4/TcBnANxXX1I/AAAAAAAAAR0/Hw11XL4vTlE/s1600/seed%255B1%255D.jpg
http://www.historyoftheuniverse.com/images/gymnosperm.gif
http://www.botany.hawaii.edu/nlc_biology/1411/lab/flfr/slide7.jpg
http://www.botany.com/img/plants/dictionary-plants-flowers.jpg
http://thumbs.dreamstime.com/thumblarge_394/12413715384jg7WS.jpg
http://fruitsbenefits.com/wp-content/uploads/2011/08/apple_logo_rainbow_fruit.jpg
http://4.bp.blogspot.com/_2Ak7yKAs5dI/S8SrxbLQuhI/AAAAAAAAAPY/s8nksopZnsw/s400/walnutssaidaonline.gifhttp://www.rci.rutgers.edu/~uzwiak/GBSummer11/GB101Summer11Lect/GB101Summer_Lect7_files/image011.jpg
http://thelotuscafe.com/images/p1.jpg
http://images.nationalgeographic.com/wpf/media-live/photos/000/008/cache/carboniferous-landscape_869_600x450.jpg
http://www.bbbseed.com/hummingbird2.jpg
works cited cont'd
http://www.astrobio.net/articles/images/lib/ho_archaefructus_c.jpg
http://www.pickardfarm.com/index_files/Wood_Pile12.jpg
http://healthkp.com/wp-content/uploads/2010/05/Herbal-Remedies.jpg
http://i.telegraph.co.uk/multimedia/archive/01007/england-population_1007441c.jpg
http://media-1.web.britannica.com/eb-media/41/91641-004-842864B7.jpg
http://samson.kean.edu/~breid/lect20/lect_20am.jpg
http://images.tutorvista.com/content/flowering-plants-reproduction/pollen-grains-structure.jpeg
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/lifecycles_2.gif
Role of Ovaries and Ovules in
flowering plants
- The ovary is the structure where seed plants hold their
megaspores. A plant can have only one ovary but many
ovules as ovules account for the covering of the
megaspores within the ovary.
The megaspore is protected by tissues called
integuments.
What appears as a membrane around the megaspore is
called a megasporangium.
The entire structure protects, and provides nutrients for
the megasporum until it is fertilized. The ovary provies an
environment where the ovule can thrive as well as mature
into a seed.
How many sperm are in a mature
pollen grain in the flowering plants?
16,17,18
Each pollen grain has two haploid cells or sperm cells.
During fertilization, the sperm nuclei have two fates :
Sperm 1- fertilizes egg and forms a diploid zygote
Sperm 2- fuses into the large central cell of the female
gametophyte
This process is called double fertilization which actually only
occurs in angiosperms.
What is the chromosome ploidy of
the endosperm? and How does it
come about? 19
Two endosperms enter the ovule the nuclei endosperm enters
the egg- they are haploid cells.
Process?
Microsporangium are found within the anthers of a flower.
Microspores are held in the microsporangium until they are
dispersed.
The microspores then form pollen grains (which contain the
endosperms)
Each pollen grain has one endosperm which undergoes
meiosis creating two sperm for every generative pollen grain
cell.
So, what is the function of an
endosperm? 20
Endosperms fertilize the egg of a flower allowing the zygote to
grow into a seed.
The seed is then able to germinate and grow into a sporophyte
plant.
Without the sperm, there is a break in the cycle and new
generation of sporophyte plants cannot exist.
http://www.google.com/imgres?imgurl=http://hcs.osu.edu/hcs300/gif/flower.gif&imgrefurl=http://hcs.osu.edu/hcs300/angio1.htm&usg=__CQ5Ls33d5Aix6AJkPvSsgRs4Vo=&h=279&w=300&sz=13&hl=en&start=2&sig2=_0kSCJPZUm779N7NuY6w9w&zoom=1&tbnid=KJ8G_1P4MltOwM:&tbnh=108&tbnw=116&
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