Transcript AP Biology Plant evolution notesx

Charophytes
 Green algae closest to plants
Plant Diversity
Plant Evolution
 Evolution of structures for better survival on land
 Bryophytes – mosses
 Seedless Vascular Plants – ferns
 Gymnosperms – conifers
 Angioserms – flowering plants
Bryophytes
 Examples of bryophytes are mosses
 No vascular tissue
 Must remain moist to survive
 Waxy cuticle to prevent dehydration
 No lignin – they do not stand tall, but cover the
ground like a mat
Reproduction Review
 Gametes – sperm (pollen) and egg
 Gametes have half the chromosome number which we
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call being haploid
Gametes become haploid through a process called
meiosis.
Normal body cells are called somatic cells. These are all
of the other cells of the plant EXCEPT gametes.
Somatic cells are diploid, which means they have the
total number of chromosomes.
A spore is NOT a gamete. Spores can grow into a whole
organism, gametes must fuse together to form a zygote.
Bryophyte Reproduction
 In mosses, there are two parts of the body
Gametophyte – soft, green, sponge-like portion of
the moss
2. Sporophyte – stalk growing out of the gametophyte
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Bryophyte Life Cycle
Life cycle
 Start with male and female haploid (n) gametophytes.
 Antheridium contain the sperm – at the tip of the leaf
 Archegonium contain the egg – at the base of the leaf
 Fertilization occurs via water transport – diploid (2n)
zygote is formed and grows into a mature sporophyte
 Spores undergo meiosis and are now haploid (n).
 Spores fall to the ground and bud new male and female
haploid (n) gametophytes.
Ferns
Ferns
 Ferns have vascular tissue – next level of adaptation
 However, their sperm still swim like mosses
 12,000 different species
 Found in the tropics and temperate forests
 Date back to 360 MYA – carboniferous period
 The remains of these plants create peat and through the
years heat and pressure turn the peat into coal.
 Coal is a fossil fuel used to generate much of our
electricity.
 The most extensive coal beds are from the carboniferous
period.
Fern Life Cycle
Fern Reproduction
 Sorus on the underside
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of the leaf hold spores
Spores germinate into
haploid gametophyte
Antheridium holds the
sperm and archegonium
holds the egg.
Fertilization occurs
through water
New diploid sporophyte
begins to grow.
Gymnosperms
Gymnosperms
 Near the end of the Carboniferous period, the climate
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became cool and dry.
Lots of ferns and mosses began to die
Gymnosperms become very successful because of seed
production
Conifers are the most diverse gymnosperms – pines,
spruces, firs, and redwoods
Thick cuticle on the leaves, stomata in pits to prevent
water loss
Reduction of gametophye, pollen in cases, and seeds are
also adaptations to life on land.
Pine Cones
Gymnosperm Reproduction
Gymnosperm Reproduction
 Male pollen - microspore
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undergo meiosis (n)
Megaspore mother cell is
in the pine cone and
undergoes meiosis (n)
Pollen fertilizes egg in
the archegonium
Creates embryo which is
the young sporophyte
(2n).
Sporophyte grows into
mature tree.
Coniferous Forests
 190 million acres are designated national forest
 Loss of forests due to grazing, lumber industry,
mining, and public recreation.
Conifers of Yosemite
Incense Cedar
Angiosperms
 Flowering plants
 Dominate most of the Earth
 250,000 species
 Wheat, corn, oats, barley
 Citrus, fruit, vegetables
 Cotton, flax
 Cherry and walnut furniture
 Vascular adaptations make it easier for angiosperms
to live on land
 Flowers are why they are so successful.
Structure of a flower
 A flower is composed of
four whorls
1. Sepals – green parts
that enclose the flower
before it opens
2. Petals – attractive part
of the plant that attracts
birds and bees
3. Stamen – anther and
filament
4. Carpel – stigma, style
and ovary
Angiosperm Life Cycle
Angiosperm Life cycle
 Mature sporophyte (2n)
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contains pollen and egg.
Pollen and egg undergo
meiosis and become haploid
(n).
Pollen is released and carried
to the stigma (sticky)
2 Pollen travels down the style
to the ovary.
Double fertilization occurs
creating a zygote and
endosperm
Endosperm is the food for the
growing diploid embryo (2n).
Fruit
 Now the ovary is called
the fruit and the ovule is
called the seed.
 The seed will grow into a
new mature sporophyte
(2n).
Examples of seed dispersal
Medicines derived from plants
CAM plants
 Succulents – pineapple, cacti, jade plant
 CAM plants open their stomata only at night to let
CO2 in and O2 out.
 CO2 is packaged in a 4-Carbon compound and
released to calvin cycle during the day.
 Only open the stomata at night to prevent water loss.
Jade Plant