BIO 10 2009 .pdf
Nom original: BIO-10_2009.pdf
Titre: BIO-10 2009.ppt
Auteur: Olivier Peulen
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From Unicellular Organisms…..
…To pluricellular Organisms
Advantages of multicellularity
Specialization of cells
More resistant to aggressors
Functions to be sustain:
ZOOM ON THE PLANT CELL
ZOOM ON THE PLANT CELL
Primary cell wall
Secondary cell wall
Cellulose is probably the single most abundant
organic molecule in the biosphere.
It is the major structural material of which plants
are made. Wood is largely cellulose while cotton
and paper are almost pure cellulose.
Potassium Flux as a regulator of turgency
The plant kingdom contains multicellular
phototrophs that usually live on land. The earliest
plant fossils are from terrestrial deposits, although
some plants have since returned to the water. All
plant cells have a cell wall containing the
carbohydrate cellulose, and often have plastids in
The plant life cycle has an alternation between
haploid (gametophyte) and diploid (sporophyte)
generations. There are more than 300,000 living
species of plants known, as well as an extensive fossil
Cooksonia is a typical early vascular
plant. It was less than 15 cm tall, with
stems that dichotomously branched.
Dichotomous branching (where the stem
divides into two ewqual branches)
appears a primitive or ancestral trait in
terminated in sporangia that produced a
single size of spore.
Evolution of the Haplo/Diplophasic Cycle
Bryophytes are small, nonvascular
plants that first evolved
approximately 500 million years ago.
The earliest land plants were most
Bryophytes lack vascular tissue and
have life cycles dominated by the
gametophyte phase. The lack of
conducting cells limits the size of the
plants, generally keeping them under
5 inches high. Roots are absent in
bryophytes, instead there are rootlike structures known as rhizoids.
The group includes the hornworts,
liverworts, and mosses.
The vascular plants have specialized transporting cells
xylem (for transporting water and mineral nutrients) and
phloem (for transporting sugars from leaves to the rest of
the plant). When we think of plants we invariably picture
Vascular plants tend to be larger and more complex than
bryophytes, and have a life cycle where the sporophyte is
more prominent than the gametophyte.
Vascular plants also demonstrate increased levels of
organization by having organs and organ systems.
The plants most
evolved and adapted
to live on Earth.
The ovary contains one or more ovules, which in turn
contain one female gametophyte, also referred to in
angiosperms as the embryo sac. Some plants, such as
cherry, have only a single ovary which produces two
ovules. Only one ovule will develop into a seed.
Pollen grains (from the greek palynos for dust or pollen) contain the
male gametophyte (microgametophyte) phase of the plant. The outer
part of the pollen is the exine, which is composed of a complex
polysaccharide, sporopollenin. Inside the pollen are two (or, at most,
three) cells that comprise the male gametophyte.. Division of the
germ cell can occur before or after pollination.