Transcript Plants - Coastalzone

Plant Evolution
Adaptations
• Cuticle
• alternation of generations
• specialized tissues
Cuticle
• Waxy coating on surfaces
• resists drying out
• stomata exist to allow necessary gas
exchange
Alternation of generations
• Plants live part of their life in a haploid
stage and part in a diploid stage
• haploid portion is called the gametophyte
generation because it produces the
reproductive cells
• diploid portion called sporophyte generation
because it produces spores
Alternation continued...
• The gametophyte plant produces male and
female sex organs (male and female
gametangium)
• eggs are fertilized by sperm to form a
zygote
• embryo development (seed) occurs within
the female gametangium (see fig 23-1 on p
421, 23-5 on p 426 and 23-8 on p 430)
Specialized tissues
• Other than bryophytes all other plants have
vascular tissues
• xylem - conducts water and minerals
• phloem - conducts food
Bryophytes
• Only nonvascular plants (mosses,
liverworts)
• no ability to internally transport water and
materials
• require moist environment
• live in colonies, has rhizoids to anchor it
• important in soil formation
Ferns
• Seedless, flowerless, vascular plants
• have xylem and phloem
• has alternation of generation, the common
familiar leafy plant is the sporophyte
generation
• has a rhizome and leaves
Ferns II
• Spore production occurs on places on the
fronds, sporangia are formed in which
meiosis occurs to form spores.
• Spores are often born in clusters called sori
• spores are released and if they germinate
will grow into the gametophytes
• method of fertilization is primitive like
bryophytes
Ferns
• Whisk ferns - extinct, no roots, no leaves
but did have vascular system above and
below ground!
• Horsetails - roots, rhizomes and vertical
stems
Heterospory
• Homospory - one type of spore produced by
bryophytes and many ferns
• Heterospory - some ferns have two types of
spores produced microspores (male
gametophytes) and macrospores (female
gametophytes)
• the development of heterospory leads two
the two most successful kinds of plants
Gymnosperms
• Vascular, seed bearing, flowerless plants
• means “naked seed”
• largest division is conifers - woody cone
bearing gymnosperms
• leaves are called needles
• most have male and female parts on same
plant. Reproductive parts in cone.
Gymnosperm reproduction
• Microspores and macrospores formed in
separate cones
• Male cones smaller than female, on lower
branches
• meiosis in male cone produces a male
gametophyte, also called a pollen grain
• carried by air current to female
gametophyte
Angiosperms
• Flowering, vascular plants
• most successful plants
• fertilization in flowering plants called
double fertilization
• 2 sperm involved - 1 fertilizes the egg, the
other fuses with 2 cells in female
gametophyte to form endosperm
2 classes of Angiosperms
• Monocots - mostly herbaceous, long,
narrow leaves,
• parallel veination,
• flower parts occur in threes,
• single cotyledon (embryonic leaf),
• endosperm present in seed
• vascular bundles scattered
2 classes of Angiosperms
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Dicotyledons - herbaceous or woody,
leaves variable in shape,
netted veination,
flower parts occur in 4 and 5,
2 cotyledons,
endosperm usually absent in mature seed
vascular bundles arranged in a circle
Plant Evolution
• Bryophytes - no roots, leaves or stems, no
vascular system, simple reproduction
relying on water, gametophyte (haploid)
dominant generation
• Ferns - first vascular system, rhizomes
(horizontal stems), fronds, sporophyte
(diploid) dominant generation
Plant Evolution
• Gymnosperms - first leaves (needles),
vascular system, stems and roots, naked
seeds
• Angiosperms - vascular system more
organized, leaves, ability to shed leaves,
seed provided with nutritive tissues,
flowers, more sophisticated reproductive
methods